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Reproductive behaviour and early development in yellowtail kingfish (Seriola lalandi Valenciennes 1833)
Abstract
The spawning behaviour of wild caught brood stock as well as early egg and larval development were studied in yellowtail kingfish (Seriola lalandi). Spawning occurred naturally in the austral spring/summer (November–February) when the seawater temperature was above 17 °C. Courtship behaviour involved one male and female, and consisted of a high-speed pursuit punctuated by stalling, nipping and touching. This lasted for approximately 0.5–1.5 h until, immediately prior to spawning, the male would nip at the female gonoduct, presumably to induce spawning. At this stage, in 50% of spawns, a second male would become involved. The release of gametes involved frenzied circling behaviour near the bottom of the tank and lasted approximately 22 s. Spawning occurred in the early daylight hours at the start of the spawning season, but shifted to around dusk in the latter part. Spawned eggs were positively buoyant, had a high fertilisation rate (> 99%), ranged 1.33–1.50 mm in diameter with a single oil droplet 0.30–0.33 mm diameter, and developed in a similar manner to that described in congenerics. Egg viability within the floating fraction was visually determined to be 74% ± 17% over the entire reproductive season. Indistinct cell margins and asymmetrical cleavage were the most common blastomere deformities observed. Egg and oil droplet volume were found to decrease by 15–20% over the spawning season, though no relationship was found between visually assessed egg viability and date. Egg incubation trials between 16 and 24 °C indicated that temperature accelerated the time to hatch by a Q10 of 5.0. While larvae were found to hatch at a smaller length with a larger yolk sac and oil droplet at warmer incubation temperatures, there was little difference in the maximum larval length reached at the onset of first feeding among the rearing temperatures used. It is proposed that the reason for this was that higher incubation temperatures accelerated the hatching process faster than the rate of tissue deposition. The findings from this study are discussed in terms of the biological significance and implications for the larviculture of this species.
... En estanque se da un comportamiento reproducti- vo entre hembra y macho, que consiste nadar a gran velocidad, donde el macho pellizca y toca a la hembra, acción que dura entre 0,5-1,5 horas, hasta inmediatamente antes del desove, donde el macho pellizcaría el gonoducto de la hembra para inducir el desove (Moran et al., 2007). ...
... El desove se produce en las primeras horas del día al comienzo de la temporada de desove y se desplaza hacia el anochecer en la última parte. Durante el desove, un segundo macho se involucra y sería el responsable del 50% de los huevos fecundados (Moran et al., 2007). ...
... Los huevos son flotantes, con una alta tasa de fecundación (> 99%), el diámetro promedio varía entre 1,33-1,50 mm de diámetro, con una sola gota de aceite de 0,30 a 0,33 mm de diámetro, con una viabilidad de los huevos flotantes de un 74 ± 17% durante toda la temporada reproductiva (Moran et al., 2007). En Chile, los valores de diámetro de huevos reportados para la especie van de 1,27-1,50 mm, y para la gota oleosa los valores reportados son de 0,34-0,36 mm (Wilson, 2013), similares a los reportados en otras latitudes. ...
Compendio sobre especies de peces cultivados el Iberoamérica.
... Therefore, the acquisition of buoyancy through hydration at the final stages of oocyte maturation represents a key step in the reproduction of pelagic fish, given that only floating eggs display normal embryo development [15]. Same as in the natural process, a positive buoyancy of embryo (i.e., embryos floating to the surface) is considered a quality indicator in hatchery reared pelagic fish, such as the Sea bream, Sparus aurata [16]; Japanese anguilla, Anguilla japonica [17]; Atlantic cod, Gadus morhua [18]; Common dentex, Dentex [19]; and Yellowtail kingfish, Seriola lalandi [20]. ...
... The hatching rate (HR) of each spawning batch used in this study was quantified after 70 h of incubation of embryos in the egg collector tank (22-23 °C) using the morphological criteria described in this species [20,24,25]. The floating rate (FR) of each batch in the different developmental stages was registered in a 20 mL sub-sample obtained from the egg collecting tank, which was deposited in a 50 mL beaker where floating samples were isolated and their fraction recorded after 10 min. ...
... Additionally, to ensure that the data obtained in this study corresponded to the proposed developmental stage, a subsample of 20 eggs or embryos of each stage was fixed in 4% formaldehyde for evaluation under phase microscopy using a Leica DME phase contrast microscope (Leica Microsystems, Wetzlar, Germany). Only batches with morphological homogeneity [20,24,25], i.e., ≥70% of the individuals at the same stage of development (n = 14), were used for this study. Sample characterization also included the assessment of the diameters of individuals and their oil globules in floating and low-floating samples at each stage of the development. ...
The buoyancy of eggs and embryos is associated with successful development in pelagic fish. Buoyancy is the result of oocyte hydration, which depends on the osmotic force exerted by free amino acids (FAA) generated by yolk proteolysis, and cathepsins are the main enzymes involved in this process. Seriola lalandi is a pelagic fish whose farming has been hampered by development failure that have been partially attributed to decreased buoyancy of embryos. Therefore, the aim of this study was to compare the mRNA expression and activity of cathepsins B, D, and L, as well as the FAA content in floating and low-floating embryos at different developmental stages. The chosen stages were eggs, morula, blastula, gastrula and 24 h embryos. Complementary assessments showed that there were no differences attributed to buoyancy status in embryo and oil droplet diameters, as well as the transcriptional status at any developmental stage. Cathepsin B did not show differences in mRNA expression or activity related to buoyancy at any stage. Cathepsin D displayed higher transcript and activity levels only in low-floating eggs compared with those floating. Cathepsin L showed higher expression in floating eggs and 24 h embryos compared with that of low-floating, but the activity of this enzyme was higher in floating eggs and morula. Total FAA content constantly decreased throughout development in floating embryos, but it was always higher than low-floating embryos until gastrula stage. In 24 h embryos floating and low-floating embryos share similar quantities of FAA. In summary, differences in the expression and activity of cathepsins between floating and low-floating embryos could be revealed at specific embryonic stages, suggesting different functions of these enzymes throughout development. Besides 24 h embryos, FAA content seems to be a decisive factor for buoyancy of embryos during early development of S. lalandi. Overall, considering the main role of cathepsins and FAA in buoyancy acquisition process and therefore in both embryo quality and viability, our study identifies good marker candidates to evaluate embryo quality in the farming of this species.
... In addition to being commercially and recreationally targeted, kingfish are highly palatable and consequentially part of an expanding aquaculture industry in Japan and southern Australia [44]. Access to kingfish in a captive aquaculture environment has permitted the description of their reproductive behaviours [11,31]. Spawning most often occurs between dawn and dusk (A Miller; pers. ...
... Spawning most often occurs between dawn and dusk (A Miller; pers. comms, [31]) and typically involves long periods of high-speed pursuit of a female by one male, interspersed with stalling, nipping, and touching of bodies followed by the male nipping the female gonoduct, presumably to induce spawning [31]. Kingfish movement and body position during these events should, therefore, be suitably different to other behaviours, providing a unique opportunity to use accelerometers to characterise acceleration profiles of spawning behaviours [51] and develop a RF model to predict these behaviours of freeranging kingfish.. ...
... Spawning most often occurs between dawn and dusk (A Miller; pers. comms, [31]) and typically involves long periods of high-speed pursuit of a female by one male, interspersed with stalling, nipping, and touching of bodies followed by the male nipping the female gonoduct, presumably to induce spawning [31]. Kingfish movement and body position during these events should, therefore, be suitably different to other behaviours, providing a unique opportunity to use accelerometers to characterise acceleration profiles of spawning behaviours [51] and develop a RF model to predict these behaviours of freeranging kingfish.. ...
Background
Tri-axial accelerometers have been used to remotely describe and identify in situ behaviours of a range of animals without requiring direct observations. Datasets collected from these accelerometers (i.e. acceleration, body position) are often large, requiring development of semi-automated analyses to classify behaviours. Marine fishes exhibit many “burst” behaviours with high amplitude accelerations that are difficult to interpret and differentiate. This has constrained the development of accurate automated techniques to identify different “burst” behaviours occurring naturally, where direct observations are not possible.
Methods
We trained a random forest machine learning algorithm based on 624 h of accelerometer data from six captive yellowtail kingfish during spawning periods. We identified five distinct behaviours (swim, feed, chafe, escape, and courtship), which were used to train the model based on 58 predictive variables.
Results
Overall accuracy of the model was 94%. Classification of each behavioural class was variable; F 1 scores ranged from 0.48 (chafe) – 0.99 (swim). The model was subsequently applied to accelerometer data from eight free-ranging kingfish, and all behaviour classes described from captive fish were predicted by the model to occur, including 19 events of courtship behaviours ranging from 3 s to 108 min in duration.
Conclusion
Our findings provide a novel approach of applying a supervised machine learning model on free-ranging animals, which has previously been predominantly constrained to direct observations of behaviours and not predicted from an unseen dataset. Additionally, our findings identify typically ambiguous spawning and courtship behaviours of a large pelagic fish as they naturally occur.
... Seriola lalandi is a globally distributed marine pelagic fish with growing importance worldwide for the aquaculture industry (Stuart and Drawbridge, 2013;Orellana et al., 2014;Sanchís-Benlloch et al., 2017). However, there are major knowledge gaps regarding its reproductive physiology and early embryo development that hamper scaling of production (Moran et al., 2007;Yang et al., 2016). A major distinctive reproductive strategy of pelagic fishes is the floatability (buoyancy) of eggs and embryos during the early stages of development. ...
... The hatching rate of each spawning batch used in this study was quantified after 70 h of incubation of embryos in the egg collector tank (22-23 • C) using the morphological criteria described by Moran et al. (2007). Thus, the fraction of newly hatched larvae approximately 4.8 mm in length was registered in a 50 mL sub-sample. ...
... Additionally, in order to ensure that data obtained in this work corresponded to the developmental stage proposed, a sample of 20 embryos was fixed in 4% formaldehyde for evaluation under phase contrast microscopy with a Leica DME microscope (Leica Microsystems, Wetzlar, Germany). Batches used met criteria for morphological homogeneity (Moran et al., 2007;Yang et al., 2016), where at least 70% of the individuals corresponded to the same stage of development (n = 14). Sample characterization also included the assessment of the diameters of individuals and their oil globules in floating and low-floating embryos at each developmental stage. ...
In pelagic fish, embryo buoyancy is a noteworthy aspect of the reproductive strategy, and is associated with overall quality, survival, and further developmental success. In captivity, the loss of buoyancy of early embryos correlates with high mortality that might be related to massive cell death. Therefore, the aim of this study was to evaluate under captivity conditions the expression of genes related to the apoptosis process during the early embryonic development of the pelagic fish Seriola lalandi, and its relationship to the buoyancy of embryos. The relative expression of bcl2, bax-like, casp9, casp8, and casp3 was evaluated by RT-qPCR and FasL/Fas protein levels by western blot in five development stages of embryos sorted as floating or low-floating. All genes examined were expressed in both floating and low-floating embryos up to 24 h of development. Expression of the pro-apoptotic factors bax, casp9, casp8, and casp3 was higher in low-floating as compared with floating embryos in a developmental stage-specific manner. In contrast, there was no difference in expression of bcl2 between floating and low-floating embryos. Fas protein was detected as a single band in floating embryos without changes in expression throughout development; however, in low-floating embryos, three higher intensity reactive bands were detected in the 24-h embryos. Interestingly, FasL was only detected at 24-h in floating embryos, whereas in low-floating samples this ligand was present at all stages, with a sharp increase as development progressed. Cell death, as evaluated by the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay, was highly increased in low-floating embryos as compared to floating embryos throughout all developmental stages, with the highest levels observed during the gastrula stage and at 24 h. The results of this study suggest that an increase in cell death, probably associated with the intrinsic and extrinsic apoptosis pathways, is present in low-floating embryos that might explain their lower developmental potential under captivity conditions.
... The oocyte development of yellowtail kingfish is similar to that of yellowtail, with slight differences. For example, in yellowtail kingfish the diameter of fully vitellogenic oocytes is larger at 850 lm (Poortenaar et al. 2001), and the diameter of spawned eggs ranges from 1.2 to 1.5 mm (Moran et al. 2007;Setiawan et al. 2016), while it is around 1.2 mm in yellowtail (Vassallo-Agius et al. 2002). In addition, the oocyte size-frequency distribution of yellowtail kingfish shows that the spawning batch is more clearly distinct from other oocytes in the mature ovary, showing one or two group-synchronous modes (Gillanders et al. 1999;Poortenaar et al. 2001). ...
... In farming in Australia, the age at puberty was found to be accelerated to 1 year in male yellowtail kingfish, but females take 4-5 years to reach sexual maturity (Sanch ıs-Benlloch et al. 2017). A rearing study demonstrated that a water temperature above 17°C is required for the spawning of yellowtail kingfish (Moran et al. 2007) and the spawning period ranges from November to February (austral spring to summer) in waters around Australia and New Zealand (Gillanders et al. 1999;Poortenaar et al. 2001). Gonadal analysis of the reproductive cycle of wild yellowtail kingfish in northern New Zealand showed that the GSI was maintained at high values between October and January, in association with the appearance of fish in OM/ovulation and spermiation (Poortenaar et al. 2001). ...
... In contrast, spawning in captivity occurs spontaneously in yellowtail kingfish and longfin yellowtail, showing different spawning characteristics (Tables 5 and 6). The rearing of wild-caught yellowtail kingfish in New Zealand demonstrated that multiple spawning occurred at water temperatures above 17°C (Moran et al. 2007), with a spawning interval of two-four days. The fish spawned in the early daylight hours before 06:00 h at the start of the period, while they spawned around dusk between 20:00 and 22:00 h towards the end. ...
The family Carangidae contains several species of aquaculture interest, including the amberjacks, yellowtails and trevallies. Among them, the greater amberjack (Seriola dumerili), the Japanese amberjack or yellowtail (Seriola quinqueradiata) and the yellowtail kingfish (Seriola lalandi) are considered the species with the highest potential for commercial aquaculture. Understanding the reproductive physiology–biology, spawning kinetics and production characteristics in captivity are of utmost importance for the domestication of any animal, and developing broodstock management methods and therapies to optimize egg production and overcome potential reproductive dysfunctions are essential. The present article reviews the available literature on the reproductive biology of the Carangidae species of interest for the aquaculture industry, both in the wild and under farming conditions. The reproductive traits of wild and farmed fish, whenever available, were compared in order to improve the understanding of the reproductive dysfunctions occurring in captivity. Finally, the hormonal maturation and spawning induction protocols examined so far to ameliorate the reproductive dysfunctions and obtain fertile gametes are summarized, and their effectiveness in the different rearing conditions is discussed.
... This species had a viable range of egg incubation from 20 to 30°C, where the thermal-dependent development rate of embryos to hatch doubled with a Q 10 of ~ 2.4. A smaller value when compared to the yellowtail kingfish (Seriola lalandi Valenciennes) with a Q 10 of 5 and a viable range of egg incubation from 16 to 24°C (Moran et al., 2007) suggests that longfin yellowtail has possibly a higher F I G U R E 8 Bifactorial analysis of total length ± SD of larvae at hatch. (a) comparison between spawn # 2 (S2) and spawn # 4 (S4) at constant temperatures (20 to 30°C). ...
... Therefore, hatching morphology was not a result of a differential timing because of temperature. These phenotypes agreed to a previous study in yellowtail Kingfish, where warmer temperatures provoked an acceleration of hatching, resulting in smaller larvae with a bigger YSV (Moran et al., 2007). On the other hand, colder temperatures allowed embryos to grow inside the egg while spent more time to break the chorion, resulting in larger larvae with a smaller YSV, being these phenotypes the result of a differential temperature timing on hatch (Moran et al., 2007). ...
... These phenotypes agreed to a previous study in yellowtail Kingfish, where warmer temperatures provoked an acceleration of hatching, resulting in smaller larvae with a bigger YSV (Moran et al., 2007). On the other hand, colder temperatures allowed embryos to grow inside the egg while spent more time to break the chorion, resulting in larger larvae with a smaller YSV, being these phenotypes the result of a differential temperature timing on hatch (Moran et al., 2007). ...
Constant and oscillating egg incubation temperatures on embryonic development and early larval morphology were studied in longfin yellowtail (Seriola rivoliana Valenciennes). We investigated the effects of constant temperatures from 16 to 32°C on embryo development and larval morphology at hatch, and whether oscillating temperature during embryogenesis could lead to larval morphological variations. After hatching, larval morphology and development during yolk sac (YS) utilization were examined in larvae at constant temperatures and larvae at 25°C that had oscillating temperature during egg incubation. Hatching rates were > 75%, only decreasing to ~ 50% at 30°C. At constant temperatures, the largest larvae occurred at 22 and 24°C. The oscillating temperature did not affect the timing of embryo development but resulted in larger and smaller larvae with a smaller and bigger YS, respectively, with a similar hatching time. Therefore, a growth response occurred in embryos during a window of development before hatching, depending on the adaptive response to temperature (spawn‐specific). After hatching, most of the YS was absorbed within 24 hr in all treatments, and the growth of the larval head was a priority with an optimal development at 26°C. There was compensatory growth in smaller larvae resulting in similar sizes after YS utilization, but larvae showed variations in body structure that could be important in further aquaculture research.
... 78 and 79). Spawning in captive YTK held under ambient temperatures and photoperiods in New Zealand by Moran et al., 2007 was consistent with that of wild fish being temperature limited to the range 17 -24°C and occurred either just prior to dawn during the first half of the spawning season and 1 h either side of dusk in the latter half. No mass spawning events (those involving more than one female) were recorded, although two or three individual females spawned within an hour of each other on several occasions. ...
... For the most part broodstock, larval and nursery rearing equipment and operating protocols already described for mulloway in this document (see Chapter 2), and for snapper in good detail by Partridge et al., 2003 also apply to YTK. What follows is an account of variations on equipment and operating protocols that apply generally to kingfish (Seriola spp.,) and in particular to YTK (Seriola lalandi lalandi) as described in Moran (2007), Poortenaar et al., (2001) and PIRSA (2002). ...
... However after December spawning tends to occur at night, precluding the immediate collection of eggs. Moran et al., 2007;Benetti et al., 2002;Carton 2005;Kolkovski, 2005 andKolkovski andSakakura, 2004.) ...
This manual was commissioned by the Aquafin CRC and Fisheries Research and Development Corporation (FRDC) and is the first consolidated and documented information on successful techniques for culturing juvenile Australian bass (Macquaria novemaculeata), mulloway (Argyrosomus japonicus) and yellowtail kingfish (Seriola lalandi) in NSW. This manual provides specialised instruction on:
how to collect and reproductively condition Australian bass, mulloway and yellowtail
kingfish to spawn;
how to induce them to spawn;
how to hatchery-rear their young through the larval and early juvenile stages to an age
and size suitable for on-farming or for stocking to enhance fisheries.
The reader will notice that the chapters are a blend of practical (hands-on) instruction and
supporting scientific information. This approach is intended, to develop a manual that can be understood by the layman, while at the same time provide background and references for those who require further reading and elaboration of the concepts and methods described.
The reader will also notice that the chapters are presented with information furnished for
Australian bass followed by mulloway and then yellowtail kingfish. This reflects the amount of published information and the history of culture of each species. Hatchery production of Australian bass has been developing for three decades and methods for culture are now proven reliable and sustainable. On the other hand, yellowtail kingfish is considered a ‘new’ species, having only been cultured for the last ten years and is currently the subject of much research effort to refine culture methods.
There are many culture methods including live feed production and equipment design and
management that are common to all three species. To avoid replication in each chapter, these have been dealt with in leading chapters with reference to the applicable section provided in Chapters where information has not been expanded upon.
This manual is not intended as a stand-alone text but rather as a companion to other publications listed in the references section. In particular, we encourage the reader to acquire Partridge et al. (2003) “Hatchery Manual for the Production of Snapper (Pagrus auratus) and Black Bream (Acanthopagrus butcheri), which we refer to widely in this manual, which provides an excellent account of many culture techniques common to those used for Australian bass, mulloway and yellowtail kingfish.
... The yellowtail kingfish (Seriola lalandi) is a marine pelagic fish with a worldwide distribution (Moran et al., 2007), including the Pacific Ocean and South Atlantic Ocean (Patel et al., 2016;Sepulveda and Gonzalez, 2017). Due to the commercial value of yellowtail kingfish, this species is cultured by fishery industries in several locations, including in northern Chile (Ottolenghi et al., 2004). ...
... After a series of analyses, to ensure cross-amplification, and accounting for the presence of null alleles, 12 (out of 25 analysed) microsatellites markers were used in the study of genetic contribution and population structure analysis (see Fernandez et al., 2015, for details on the markers used). For each microsatellite marker, forward and reverse primers were designed in our laboratory or were previously published (Miller et al., 2011;Moran et al., 2007;Patel et al., 2016;Sepulveda and Gonzalez, 2017). Primer sequence and allele representation are presented in Supplementary Table 1. ...
... We observed an asymmetric contribution of the broodstock within the breeding units of yellowtail kingfish, for the different spawning seasons analysed, in which a few males and females dominate. This is consistent with the courtship behaviour described for yellowtail kingfish from Australia (Moran et al., 2007). Therefore, it is likely that many of the broodstock would not contribute offspring, nor contribute to the number of reproductive partners within the reproductive season (de Oliveira et al., 2016;Renshaw et al., 2007). ...
The yellowtail kingfish (Seriola lalandi) is a marine endemic fish, and a key species in the national programme for the diversification of Chilean aquaculture. Since it has been recently developed from wild fish, the biology of this species under production is to a large extent unknown. For example, the structure of the different populations used to create the national breeding programme is not well characterised. Moreover, due to the fact that it is not possible to perform stripping of broodstock in yellowtail kingfish, the genetic contributions of individuals are affected by the reproductive behaviour of this species. To increase our knowledge of the biology of this species under aquaculture conditions, the objectives of this study were: (i) to identify the population structures of wild and commercial populations of yellowtail kingfish obtained from different fisheries off the Chilean coast, and compare these to those of Mexican and Australian specimens and (ii) to study the reproductive behaviour of commercial yellowtail kingfish broodstock through paternity testing, to estimate the genetic contributions of individuals throughout the artificial spawning season in captivity. We used a set of 12 highly informative microsatellite markers optimised for paternity testing. The analysis of the population structure showed at least two clusters of yellowtail kingfish, including a single metapopulation from Chile and Australia (possibly explained by the migratory behaviour of this species in the Pacific Ocean), and the other from Mexico (which is most likely composed of California yellowtail, S. dorsalis). Some degree of admixture, albeit small, was observed between the populations from Mexico and Australia. Paternity analysis showed that the average ratio (male/female) contributing in a spawning event was 2.6, confirming the spawning behaviour observed in other species in this genus. Additionally, we observed that males participated in matings regularly during the whole spawning season. Using the results of this research, we recommend modifying the current implementation of yellowtail kingfish breeding programmes to reduce the effects of random genetic drift. This can be achieved by managing the genetic contributions of broodstock in a two-step breeding programme. This study provides useful genetic information for the long-term development and management of the Chilean yellowtail kingfish industry, which involves a species of high importance for the diversification of Chilean aquaculture.
... Bobe & Labbé (2010) analyzed the molecular and cellular characteristics that affect the quality of male and female gametes, before, during and after fertilization in fish. 'Before' fertilization, they can be affected by mechanisms that are responsible for the initiation of sperm motility, morphology and quality of the plasmatic membranes of spermatozoa; the physical and chemical parameters of the ovary or coelomic fluid, and the appearance of the oocyte during its first stages of development (Kjørsvik et al., 1990;Bromage et al., 1994;Penney et al., 2006;Pavlov & Emel´yanova, 2008); the volume of the egg and the lipid droplets of species like Seriola lalandi (Moran et al., 2007), the composition of lipids and fatty acids in fish eggs and semen of species (Giménez et al., 2006) and Ictalurus punctatus (Sink & Lochmann, 2008) and post-ovulatory ageing of oocytes under in vivo or in vitro conditions (Mommens et al., 2015). 'During' embryonic development, the characteristics and abnormalities of the first blastomeres have been used as criteria for discrimination between good and bad quality embryos (Kjørsvik et al., 1990(Kjørsvik et al., , 2003Bromage et al., 1994;Shields et al., 1997;Penney et al., 2006;Pavlov & Emel´yanova, 2008;Avery et al., 2009;Bobe & Labbé, 2010;Vásquez et al., 2010;Valdebenito et al., 2012;Effer et al., 2012). ...
... The beginning of the development in this species is similar to characteristic processes for marine fish. They have telolecithal eggs with partial cleavage and form a small perivitelline space similar to that observed by Bustos & Landaeta (2005) in the early development of hake south (Merluccius australis) in Chile, Cuartas et al. (2003) for corocoro rayao (Haemulon bonarienses) of mangroves in Venezuela, Horie et al. (2002) in common Japanese conger (Conger myriaster) and Moran et al. (2007) in yellowtail kingfish (Seriola lalandi). In the central region of the egg there is a lipid conspicuous drop similar to that observed by Ebanks (2013) in cobia (Rachycentron canadum), Pavlov & Emel'yanova (2008) in Zebrasoma scopas and Moran et al. (2007) in Seriola lalandi. ...
... They have telolecithal eggs with partial cleavage and form a small perivitelline space similar to that observed by Bustos & Landaeta (2005) in the early development of hake south (Merluccius australis) in Chile, Cuartas et al. (2003) for corocoro rayao (Haemulon bonarienses) of mangroves in Venezuela, Horie et al. (2002) in common Japanese conger (Conger myriaster) and Moran et al. (2007) in yellowtail kingfish (Seriola lalandi). In the central region of the egg there is a lipid conspicuous drop similar to that observed by Ebanks (2013) in cobia (Rachycentron canadum), Pavlov & Emel'yanova (2008) in Zebrasoma scopas and Moran et al. (2007) in Seriola lalandi. ...
There is no information about the characteristics of early cleavage in the Patagonian blennie ( Eleginops maclovinus ), which can be used as a diagnostic tool for embryo quality. The purpose of this investigation, therefore, was to characterize the first blastomeres of E. maclovinus morphologically. Of a ‘pool’ of incubated eggs at 10.7 ± 0.5°C, 100 microphotographs of blastodiscs were extracted at different incubation periods from 0.25 to 5 h after fertilization and analyzed. Blastodiscs taken at 3.5, 4.0 and 5.0 h were characterized and classified into symmetric or asymmetric groups according to their morphology. The proportions of length (L) and width (W) of each blastomere were determined to establish its symmetry. Additionally, 20 microphotographs of blastodiscs of normal appearance were analyzed morphologically (control blastodisc: CB) and compared other blastodiscs (4.0 and 5.0 h). The results showed that before fertilization oocytes presented a somehow turgid aspect (maximum average diameter of 987 ± 41 µm) and after fertilization and hydration, their diameter increased to 1001.5 ± 11 µm (but not statistically significant) and presented a spherical shape. First cleavage ends after 3.5 h of development, forming two blastomeres 467 ± 45 μm length (L) and 328 ± 21 μm width (W) with a L/W ratio of 1.43 ± 0.19. The second cleavage ends after development at 4.5 h forming four blastomeres 238 ± 65 μm length and 227 ± 65 μm width with a ratio L/W of 1.06 ± 0.09. Five categories were identified during the blastomere characterization: 70% normal or symmetric; 8% with odd numbers of blastomeres; 6% unequal; 6% ‘pie shaped’ and 10% amorphous.
... Jaw malformations comprise an important portion of the abnormalities that appear during the larval culture of Seriola lalandi [6,9,41], and are one of the concerns for the commercial production of the species [2]. The proportion of cultured larvae with jaw abnormalities reported for S. lalandi are quite variable, for example, Crobcoft et al. found a 7% at day 4 and 38% at day 16, whereas Jara et al. found 44-47% at day 4 and 33-55% at day 9. ...
... Jaw malformations comprise an important portion of the abnormalities that appear during the larval culture of Seriola lalandi [6, 9,41], and are one of the concerns for the commercial production of the species [2]. The proportion of cultured larvae with jaw abnormalities reported for S. lalandi are quite variable, for example, Crobcoft et al. found a 7% at day 4 and 38% at day 16, whereas Jara et al. found 44-47% at day 4 and 33-55% at day 9. ...
Jaw malformations imply an important problem during the commercial production of Seriola lalandi larvae and juvenile fish in Chile and New Zealand. Since the rate of malformations in other fish species has been associated with the content of long-chain PUFA (LC-PUFA) in neutral lipids of the diet, the relationship between body LC-PUFA and the rate of malformations, together with a transcriptomic analysis of genes related to the metabolism and transport of lipids in commercially produced S. lalandi larvae have been investigated in the present work. A total of 10 batches of S. lalandi larvae were obtained and cultured at about 22 °C following the protocols of a Chilean commercial hatchery during the spawning season. There were three larval batches that were collected in August (austral winter), three batches that were obtained in October (spring), and finally four spawning events that were obtained in December-January (spring-summer). The rate and type of jaw malformations, the profile of long-chain PUFA (LC-PUFA) of total lipids during larval culture, and the distribution of LC-PUFA were analyzed. Additionally, a transcriptome analysis related to lipid metabolism in 40-day-old larvae was performed. As a result, a decrease in the rate of malformations was recorded from August to December. DHA showed a steep decrease between days 1 and 10 of culture, probably due to the consumption of yolk sac lipids, but a higher proportional change was noted in larvae that hatched during August. The DHA content in polar lipids (PL) and neutral lipids (NL) of 40-day-old larvae increased from August to December, so that the abundance of DHA was higher in PL in larvae that hatched in December, but it was higher in NL in those larvae that hatched in October. In conclusion, the rate of jaw malformations was associated with the rapid decline in DHA during early larval life and the highest abundance of DHA in neutral lipids at the end of the larval life.
... The first 100 larvae were scored within 48 h of test completion, and the proportion with normal development was determined. Normal larval development was defined as having reached the pluteus stage with good symmetry, well-developed skeletal rods, and a differentiated gut (Doyle et al., 2003;USEPA, 1995 (Moran et al., 2007). Twenty embryos were placed into one of five replicate 200-ml glass vessels per treatment, and exposed either continuously or for 2 h, then transferred to clean seawater by pipetting as described in Gissi et al. (2021). ...
... We exposed fish embryos to crude oil starting in the gastrula stage, before the onset of organogenesis (Moran et al., 2007). The timing of the exposure could affect the response of fish embryos to oil. ...
Following an oil spill, accurate assessments of the ecological risks of exposure to compounds within petroleum are required, as is knowledge regarding how those risks may change with the use of chemical dispersants. Laboratory toxicity tests are frequently used to assess these risks, but differences in the methods for preparation of oil in water solutions may confound interpretation, as may differences in exposure time to those solutions. In this study, we used recently developed modifications of standardised ecotoxicity tests with copepods (Acartia sinjiensis), sea urchins (Heliocidaris tuberculata) and fish embryos (Seriola lalandi) to assess their response to crude oil solutions and assessed whether the oil‐in‐water preparation method changed the results. We created a water‐accommodated fraction (WAF), chemically enhanced water‐accommodated fraction (CEWAF) and a high‐energy water‐accommodated fraction (HEWAF) using standard approaches using two different dispersants, Corexit 9500 and Slickgone NS. We found that toxicity was best related to total polycyclic aromatic hydrocarbon (TPAH) concentrations in solution, regardless of the preparation method used, and that the HEWAF was the most toxic because it dispersed the highest quantity of oil into solution. The TPAH composition in water did not vary appreciably with different preparation methods. For copepods and sea urchins, we also found that at least some of the toxic response could be attributed to the chemical oil dispersant. We did not observe the characteristic cardiac deformities that have been previously reported in fish embryos, most likely due to the use of unweathered oil, and, as a consequence, the high proportion of naphthalenes relative to cardiotoxic PAH in the overall composition. This study highlights the need to characterise both the TPAH composition and concentration in test solutions when assessing oil toxicity. This article is protected by copyright. All rights reserved.
... As it has been previously reported, egg incubation between 22 • C and 24 • C provided larger larval lengths (Pacheco-Carlón et al., 2021). Indeed, Moran et al. (2007) demonstrated that larval initial length is inversely proportional to the yolk sac and the oil droplet volumes. In many fishes, it has been demonstrated that, at colder temperatures, hatching enzymes present lower activity and extend the time of embryos inside the egg. ...
... In many fishes, it has been demonstrated that, at colder temperatures, hatching enzymes present lower activity and extend the time of embryos inside the egg. This allows them to grow and reduce consequently the yolk sac and oil droplet reserves for energy demand (Moran et al., 2007;Yamagami, 1988). As a logical consequence, larvae incubated at temperatures from 25 • C to 30 • C had a significantly higher growth rate Table 1 Total protein (mg⋅g − 1 ) and total lipids (mg⋅g − 1 ) in larvae of Seriola rivoliana cultured at different temperatures ( • C) at 0 and 48 h after hatching (hah). ...
The longfin yellowtail Seriola rivoliana is an emerging commercial species in aquaculture. However, there is little information regarding environmental conditions and their influence on early larval development that come from natural spawning. Temperature is one of the main factors affecting embryo and larval development. Therefore, the purpose of this research was to determine the impact of different temperatures (16-32 • C) on S. rivoliana hatching rate, larvae quality (survival, growth, yolk sac and oil droplet consumption, protein and lipid contents) and early developmental events (eye pigmentation and mouth opening). Eggs incubated at 23 • C showed the highest hatching rate (75.5%), but the larvae died 24 h after hatching (hah). Nonetheless, larvae cultivated at 24 • C had the highest survival rates at 48 hah and survived without being fed for over 100 hah. The temperature exhibits a direct effect on protein and lipid content, notochord size and oil droplet volume. In S. rivoliana, the larvae notochord size decreased after the oil droplet was more than half consumed, and at the higher temperature the faster the embryo and larvae depleted their endogenous reserves for growth. Finally, after 96 hah, the optimal mouth opening to ingest adequate rotifers for first feeding has been observed at 22 • C, while best eye pigmentation has been obtained at 24 • C. Therefore, we recommend incubating S. rivoliana eggs at 23 • C. After hatching, we suggest adjusting the temperature to 24 • C to increase the survival percentage and start eye development. Ultimately, after 48 h we encourage to low down the temperature at 22 • C to preserve notochordal length and allow faster mouth formation for further feeding. These optimal temperatures could be operated in the aquaculture industry to improve the management of larval development of S. rivoliana in captivity.
... Several carangid species closely related to C. ignobilis have been bred successfully either through natural spawning or administration of synthetic hormones. Successful spawning was observed in Caranx melampygus Cuvier, 1833 (Moriwake et al., 2001); Trachinotus carolinus (Linnaeus, 1766) (Hoff et al., 1972;Weirich and Riley, 2007); Trachinotus blochii (Lacepède, 1801) (Gopakumar et al., 2012); Seriola quinqueradiata Teminck & Schlegel, 1845 (Nagakura et al., 2003;Hamada and Mushiake, 2006); Seriola dumerili Risso, 1810 (Diaz and Garcia, 2001;Jerez et al., 2006;Fernandez-Palacios et al., 2013); Seriola rivoliana Valenciennes, 1833 (Roo et al., 2012;Fernandez-Palacios et al., 2015); Seriola lalandi Valenciennes, 1833 (Moran et al., 2007;Stuart and Drawbridge, 2012); and Trachurus japonicus Temminck & Schegel, 1844(Nyuji et al., 2013. Taking a cue from the successful development of the hatchery technology of these carangid species, the present study aims to breed captive C. ignobilis using commercially available induced spawning agents. ...
... The unsuccessful spawning in CPE treatment in this study may be because carp pituitary is highly impure, and because the number and amount of components in a given pituitary is unknown, their action is unpredictable (Harvey and Carolsfeld, 1993), thus its effectiveness may be limited to some fish species. Among the carangid fishes known in aquaculture, natural spawning in captivity have been reported for C. melampygus (Moriwake et al., 2001); S. lalandi (Moran et al., 2007;Stuart and Drawbridge, 2012); and S. dumerili (Jerez et al., 2006). However, in this study the uninjected Control C. ignobilis did not spawn naturally despite having similar ripe oocytes (0.50 ± 0.016 mm diameter and 61.84 ± 2.7 % at GVM stage) as in injected experimental fish. ...
... Failure of female broodstock to undergo final oocyte maturation, ovulation, and spawning in captivity is a common reproductive dysfunction of cultured fishes (Mylonas et al. 2004), and aquaculture of YTK largely relies on capture of wild juveniles. Despite the reproductive behavior and morphological development of embryo have been recently described in YTK (Moran et al. 2007;Yang et al. 2016), key molecular factors involved in embryogenesis such as IGFs remain to be characterized in this species. In an initial attempt to shed light on this important issue, the aims of this study were (1) to clone and sequence the full-length cDNAs for igf1 and igf2, (2) to study the tissue distribution of igf1 and igf2 mRNAs, and (3) to examine the expression profiles of igf1 and igf2 during embryonic development of YTK. ...
... The water temperature and salinity during embryo development were 21.5°C and 31‰, respectively. The embryonic stages were classified according to the methods described in detail elsewhere (Moran et al. 2007;Yang et al. 2016) and samples of eggs at various stages were directly immersed in RNAlater solution and then stored at − 80°C until RNA extraction. ...
In this study, to understand the role of the insulin-like growth factor (IGF) system in the regulation of early development in yellowtail kingfish (YTK, Seriola lalandi), an economically important marine fish species with a high potential for aquaculture, we first cloned the full-length cDNAs for igf1 and igf2 from the liver. YTK igf1 cDNA was 1946 base pairs (bp) in length with an open reading frame (ORF) of 558 bp encoding preproIGF1 of 185 amino acids (aa). The preproIGF1 consisted of 44 aa for the signal peptide, 68 aa for the mature peptide comprising B, C, A, and D domains, and 73 aa for the E domain. YTK igf2 cDNA had an ORF of 648 bp that encoded a total of 215 aa spanning the signal peptide (47 aa), the mature peptide (70 aa), and the E domain (98 aa). At the protein level, both YTK IGF1 and IGF2 exhibited high sequence identities with their corresponding fish counterparts, respectively. Subsequently, quantitative RT-PCR analysis indicated that the highest level of igf1 mRNA expression was recorded in the gonad and liver, while the igf2 mRNA expression was most abundant in the gill and liver. In addition, both igf1 and igf2 were detected in all stages of embryonic development and exhibited different gene expression patterns, supporting that IGF1 and IGF2 could be functional and play important roles during YTK embryogenesis. Overall, this initial study of IGF1 and IGF2 provides an insight into the endocrine mechanism involved in the early development of yellowtail kingfish.
... This study examines the effects of swim bladder inflation failure in the carangid genus Seriola, which is cultured in several countries, and accounts for over 150,000 t of finfish production annually (FAO, 2018). Because of the importance of this group to global aquaculture, there has been increased demand over the past several years to optimize Seriola hatchery techniques in order to reduce aquaculture reliance upon wild seed and to promote the development and expansion of Seriola aquaculture into new regions (Moran et al., 2007;Stuart and Drawbridge, 2013;Yang et al., 2016). The timing during which swim bladder inflation occurs in Seriola is relatively narrow and appears to take place from 2 to 10 days post hatch (Stuart and Drawbridge, 2013;, giving these fish a limited window to complete this important inflation process. ...
... The timing during which swim bladder inflation occurs in Seriola is relatively narrow and appears to take place from 2 to 10 days post hatch (Stuart and Drawbridge, 2013;, giving these fish a limited window to complete this important inflation process. Although current hatchery research is continuing to improve swim bladder inflation rates and reduce other common hatchery deformities for Seriola (Moran et al., 2007;Stuart and Drawbridge, 2013;Yang et al., 2016), there are many variables that effect the ability to gulp air at the surface. These variables, in addition to the restrictive timing, still result in cohorts with inflation failure rates from 0 to 95% (unpublished data). ...
This study examines the effects of swim bladder inflation failure, a common developmental abnormality in finfish aquaculture, on the energy allocation, growth, and development of California Yellowtail (Seriola dorsalis). Health and fitness metrics including oxygen consumption, aerobic scope, critical swimming speed, feed conversion ratio, and growth rate, were monitored over a 32-week growout period in three groups of S. dorsalis: aquaculture-reared fish that failed to inflate their swim bladders (uninflated), aquaculture-reared fish with properly inflated swim bladders (inflated), and wild-caught individuals (wild). After the growout period, the uninflated fish had significantly lower body mass (636.1 ± 80.4 g vs. 758.6 ± 92.7 g inflated), shorter body length (36.5 ± 1.9 cm vs. 39.6 ± 2.0 cm inflated), and smaller girth (21.5 ± 1.2 cm vs. 23.2 ± 1.1 cm inflated) than the inflated fish. In addition, the uninflated fish had the least efficient feed conversion ratio (2.08 uninflated vs. 1.49 inflated, 1.41 wild), needing 39.8% more feed than the inflated fish, and 47.8% more feed than the wild fish to gain equivalent mass. These differences in growth and feed conversion appear to be primarily attributed to differences in energy allocation. Measures of oxygen consumption using a swim tunnel respirometer at two time points during the growout period showed that uninflated fish had significantly higher metabolic costs than both the inflated and wild groups over a large range of the swimming speeds tested. In addition, the uninflated fish were often observed swimming faster in their growout tank, likely to generate enough lift to compensate for the lack of a buoyant swim bladder. The wild-caught fish had the lowest feed conversion ratios and had significantly lower metabolic costs than both the inflated and uninflated aquaculture-reared fish at the beginning of the growout period (shortly after capture from the wild). The results of this study show that rearing S. dorsalis without a functional swim bladder is not economically feasible based on their poor growth and feed conversion ratios, and suggest that there is room for improvement in the metabolic efficiency of cultured S. dorsalis with properly inflated swim bladders.
... Ambient water temperatures ranged from 19-20 °C in the week prior to spawning, but dropped to 18.2 °C on the night of spawning. Eggs were collected on the morning of 24 January 2017, approximately 12 h after fertilization using an external egg collector as described by Moran et al. [64]. Eggs were collected in approximately equal proportions from each tank and mixed together. ...
... Ambient water temperatures ranged from 19-20 • C in the week prior to spawning, but dropped to 18.2 • C on the night of spawning. Eggs were collected on the morning of 24 January 2017, approximately 12 h after fertilization using an external egg collector as described by Moran et al. [64]. Eggs were collected in approximately equal proportions from each tank and mixed together. ...
Ocean acidification and warming are co-occurring stressors, yet their effects on early life stages of large pelagic fishes are not well known. Here, we determined the effects of elevated CO2 and temperature at levels projected for the end of the century on activity levels, boldness, and metabolic traits (i.e., oxygen uptake rates) in larval kingfish (Seriola lalandi), a large pelagic fish with a circumglobal distribution. We also examined correlations between these behavioral and physiological traits measured under different treatments. Kingfish were reared from the egg stage to 25 days post-hatch in a full factorial design of ambient and elevated CO2 (~500 µatm and ~1000 µatm) and temperature (21 °C and 25 °C). Activity levels were higher in fish from the elevated temperature treatment compared with fish reared under ambient temperature. However, elevated CO2 did not affect activity, and boldness was not affected by either elevated CO2 or temperature. Both elevated CO2 and temperature resulted in increased resting oxygen uptake rates compared to fish reared under ambient conditions, but neither affected maximum oxygen uptake rates nor aerobic scope. Resting oxygen uptake rates and boldness were negatively correlated under ambient temperature, but positively correlated under elevated temperature. Maximum oxygen uptake rates and boldness were also negatively correlated under ambient temperature. These findings suggest that elevated temperature has a greater impact on behavioral and physiological traits of larval kingfish than elevated CO2. However, elevated CO2 exposure did increase resting oxygen uptake rates and interact with temperature in complex ways. Our results provide novel behavioral and physiological data on the responses of the larval stage of a large pelagic fish to ocean acidification and warming conditions, demonstrate correlations between these traits, and suggest that these correlations could influence the direction and pace of adaptation to global climate change.
... This observed difference in spawning frequency could be attributed to seasonal spawn variation rather than broodstock diet. Inconsistent spawning frequencies were previously recorded in yellowtail amberjack (S. lalandi) whereby spawns occurring at the beginning of the spawning season were more sporadic but transitioned to a more frequent and consistent spawning, 2 to 3 weeks into the spawning season (Moran et al., 2007). This variation in spawning frequency throughout the season may also be linked to temperature, as observed in Greater amberjack (S. dumerili) and with this present study where spawning events increased in the later and warmer months of the spawning season. ...
Existing broodstock research has ascertained that eggs are heavily influenced by broodstock diet, but there is currently sparse information regarding the time it takes for nutrients to transfer into eggs after broodstock feeding. Thus, our study aimed to quantify this duration of broodstock to egg nutrient transfer by feeding two alternating diets. In 2021, nine California yellowtail (Seriola dorsalis) broodstock were fed alternating diets of commercial pellets (Vitalis Prima: Skretting, Norway) and cutbait (70% sardine and 30% squid). These diets were switched every 41 days and then repeated so each diet was provided twice during the study. Biochemical and biometric data from spawns were collected and statistically analyzed by grouping spawns based on diet type and diet duration. Between diet switches, we observed a selective retention of C18:3n-3 (α-linolenic acid) and C18:2n-6 (linoleic acid) from the Vitalis diet, and C20:5n-3 (eicosapentaenoic acid), from the cutbait diet. Our results showed overall fatty acids from both diets were incorporated by the eggs after 10 to 19 days of feeding. Knowing this timing of nutritional incorporation from broodstock diet to eggs will help significantly improve feed efficiency by providing producers with a specific timeframe to maximize egg quality through dietary modifications or supplements.
... Following the spawning event in April, the eggs were promptly gathered and incubated within 2-L beakers, with a water temperature of 21.5 °C and a salinity level of 31‰. The various stages of embryonic development were identified and classified using established methods, as detailed in previous studies (Moran et al. 2007;Yang et al. 2016). Samples representing different developmental stages were collected and immediately added RNAiso Plus and placed in liquid nitrogen for quick freezing, then stored at − 80 ℃ until further used. ...
Leptins and other related genes have been proven to play vital roles in food intake, weight control, and other life activities. While the function of leptins in yellowtail kingfish (Seriola lalandi) has not yet been explored, in the present study, we investigated the structure and preliminary function of four leptin-related genes in S. lalandi. In detail, the sequence of two leptin genes (lepa and lepb), one leptin receptor gene (lepr), and one leptin receptor overlapping transcript (leprot) gene were obtained by homology cloning and RACE methods, in which lepa and lepb have similar structure. Moreover, homologous sequence alignment and evolutionary analysis of all four genes were clustered with Seriola dumerili. The tissue distribution of these four genes in thirteen tissues of yellowtail kingfish was detected by RT-qPCR. Both lepa and leprot were highly expressed in the brain and ovary, while lepb was highly expressed in the pituitary, gill, muscle, and ovary; lepr was highly expressed in the gill, kidney, and ovary. Additionally, these four genes also played roles in embryo development and early growth and development of larvae and juveniles of yellowtail kingfish. Finally, the function of leptin and leptin-related genes was investigated during fasting and re-feeding adaption of yellowtail kingfish. The results showed that these four genes have different regulation functions in five tissues; for example, the mRNA levels of lepa, lepr, and leprot in the brain decreased during fasting and immediately increased after re-feeding, while the mRNA level of lepb did not show significant fluctuation during starvation but significantly lowered after re-feeding. However, lepa and lepb mRNA levels were significantly elevated during fasting and returned to control levels after re-feeding, and there were no significant changes in the expression of lepr and leprot in the liver during fasting and after re-feeding. Moreover, the body mass of fish in the experimental group was measured, and compensatory growth was found after the resumption of feeding. These results suggested that leptin and receptor genes play different functions in different tissues to regulate the physiological state of fish in food deficiency and gain processes.
... (2.3) Induced spawning technology: Some carangid species reach gonadal maturation and spontaneously spawn in captivity, such as blue trevally (Moriwake et al., 2001), California yellowtail (reviewed by Rotman et al., 2021), greater amberjack (Kawabe et al., 1996(Kawabe et al., , 1998, yellowtail amberjack (Moran et al., 2007;Setiawan et al., 2016) and white trevally (Nogueira et al., 2018). However, in most cases, hormonal administration is required by either injection of hCG or injection/implantation of luteinizing hormone releasing hormone analogue (LHRHa), as detailed in Table 3. Notably, some species, such as greater amberjack, do not respond well to hormone injection (Kawabe et al., 1996(Kawabe et al., , 1998, but have better fry quality when naturally spawned or induced with environmental cues, such as an increase in temperature (Watanabe et al., 1998)). ...
Article Info Importance of the work: Interest in marine fin-fish aquaculture has grown in recent decades in response to the rising demand for seafood. Objectives: To provide information and knowledge regarding aquaculture of carangid fishes and synthesize common features, followed by recommendations for development of aquaculture. Materials & Methods: The main literature sources used in this review were from SCOPUS and Google Scholar. Production data were from the Food and Agriculture Organization of the United Nations. All information and data gathered were analyzed and synthesized. Results: Of the 148 carangid fish species, 13 contribute a substantial proportion of global aquaculture production. The two most valuable species are pompano (Trachinotus ovatus), mainly produced by China and Japanese amberjack or yellowtail (Seriola quinqueradiata), mainly produced by Japan. This review provided an overview of aquacultural practices for each species and revealed that the following characteristics are common to carangid aquaculture: culture was first established using wild fingerlings; the success of hatchery production of fingerlings requires lengthy rearing of broodstock; availability of commercial artificial feed is another key success factor; diseases and parasites can be devastating and very difficult to control; and market constraints can have major adverse impacts. Main finding: The following recommendations were made: 1) development of fry production technology is a priority; 2) stocks should be genetically improved to cope with diseases and parasites; 3) cost-effective and environmental-friendly artificial diets should be developed; 4) cost-effective, land-based recirculating aquaculture systems should replace sea-cage and pen culture; and 5) new species, such as bluefin trevally, should be developed for aquaculture to diversify production.
... The eddies and upwelling regions are also productive environments that attract predatory species (Booth et al., 2007;Suthers et al., 2011) Additionally, the water temperatures during these seasonal aggregations coincide with the optimal spawning temperature of captive kingfish (Gillanders, Ferrell & Andrew, 1999;Moran et al., 2007), implying that kingfish may be using these shallow estuaries for spawning aggregations. ...
Identifying the species response to changing environments can contribute towards proactive and adaptable resource management and, although obtaining observations can be logistically challenging for aquatic species, can be postulated through monitoring.
A network of acoustic tracking receivers ( n = 93) across south‐eastern Australia was used to identify the effects of environmental conditions on the activity of the yellowtail kingfish ( Seriola lalandi , n = 63), an economically important species with a crucial role in pelagic ecosystems. Activity (measured via tri‐axial acceleration) provides an insight into the energetic expenditure of animals, which is linked to movement, behaviour, and physiological processes.
Kingfish activity was strongly influenced by sea surface temperature and hour of day, with smaller effects from distance to nearest landmass and bathymetry. Activity also decreased during higher tides and periods of greater moon fraction. Findings show that the energetic responses of kingfish are sensitive to long‐ and short‐term changes, which can regulate behaviours and physiological processes. Changes in kingfish activity and movement (residency and space use) were further investigated at a seasonal aggregation in a small temperate estuary (approx. 120 km ² ; Coffin Bay, South Australia), where individuals remained during the austral spring and summer (September–April), with a complete exodus in winter. Fifty per cent of tagged fish returned to this estuary in three consecutive years, indicating its importance for aggregating kingfish.
While residing in Coffin Bay, kingfish activity varied between interconnected areas, with temperature, hour of day, tide height, and moon fraction again identified as important explanatory variables. These findings have implications for the energetic budgets of large pelagic fish in subtropical and temperate regions, which are facing rapidly changing climates.
These results are important for understanding and accounting for the potential responses and physiological impacts of future climatic conditions on migratory pelagic species.
... (2.3) Induced spawning technology: Some carangid species reach gonadal maturation and spontaneously spawn in captivity, such as blue trevally (Moriwake et al., 2001), California yellowtail (reviewed by Rotman et al., 2021), greater amberjack (Kawabe et al., 1996(Kawabe et al., , 1998, yellowtail amberjack (Moran et al., 2007;Setiawan et al., 2016) and white trevally (Nogueira et al., 2018). However, in most cases, hormonal administration is required by either injection of hCG or injection/implantation of luteinizing hormone releasing hormone analogue (LHRHa), as detailed in Table 3. Notably, some species, such as greater amberjack, do not respond well to hormone injection (Kawabe et al., 1996(Kawabe et al., , 1998, but have better fry quality when naturally spawned or induced with environmental cues, such as an increase in temperature (Watanabe et al., 1998)). ...
Interest in marine fin-fish aquaculture has grown in recent decades in response to the rising demand for seafood.
Objectives: To provide information and knowledge regarding aquaculture of carangid fishes and synthesize common features, followed by recommendations for development of aquaculture.
Materials & Methods: The main literature sources used in this review were from SCOPUS and Google Scholar. Production data were from the Food and Agriculture Organization of the United Nations. All information and data gathered were analyzed and synthesized. Results: Of the 148 carangid fish species, 13 contribute a substantial proportion of global aquaculture production. The two most valuable species are pompano (Trachinotus ovatus), mainly produced by China and Japanese amberjack or yellowtail (Seriola quinqueradiata), mainly produced by Japan. This review provided an overview of aquacultural practices for each species and revealed that the following characteristics are common to carangid aquaculture: culture was first established using wild fingerlings; the success of hatchery production of fingerlings requires lengthy rearing of broodstock; availability of commercial artificial feed is another key success factor; diseases and parasites can be devastating and very difficult to control; and market constraints can have major adverse impacts. Main finding: The following recommendations were made: 1) development of fry production technology is a priority; 2) stocks should be genetically improved to cope with diseases and parasites; 3) cost-effective and environmental-friendly artificial diets should be developed; 4) cost-effective, land-based recirculating aquaculture systems should replace sea-cage and pen culture; and 5) new species, such as bluefin trevally, should be developed for aquaculture to diversify production.
... However, the Northern Pacific Ocean currents are colder and thus more suitable for the migration of yellowtail kingfish adults, juveniles, and larvae. Indeed, two of the main factors affecting the migratory routes of yellowtail kingfish are ocean currents and temperature [41][42][43]. Our preliminary surveys indicated that the Dasha fishing ground in the Yellow Sea (~32°00′-34°00′ N, ~122°30′-125°00′ E) is the spawning grounds of the wild Chinese yellowtail kingfish population. ...
To clarify the population genetic structure, intrapopulation diversity, and interpopulation differentiation of yellowtail kingfish (Seriola aureovittata), we sampled 143 individuals from five collections of yellowtail kingfish: farmed (n = 30) and wild (n = 33) collections in China, a wild collection in Japan (n = 20), and farmed (n = 31) and wild (n = 29) collections in Australia. Using 2b-RAD simplified genome sequencing, we obtained an average of 287,594 unique tags per population, with an average sequencing depth of 27.13×. Our final genotype dataset included 48,710 SNPs (Single Nucleotide Polymorphisms). The five collections were all in Hardy–Weinberg equilibrium, and the interpopulation differentiation varied among the sample collections. The genetic differentiation coefficients (Fst) between the Chinese and Japanese yellowtail kingfish collections were low and the gene flow (Nm) values were high. These results suggest continuous gene flow occurs frequently between the collections, indicating that they belong to the same population. In contrast, genetic differentiation was high between the Australian collections and the Chinese and Japanese populations, suggesting different evolutionary origins and belonging to different populations. The farmed and wild Australian collections fell into distinct clades in a neighbor-joining phylogeny tree, suggesting farmed fish have begun to differentiate from the wild collection. A similar level of genetic diversity between the wild collections in China and Japan suggests that they originated from the same spawning ground. This, therefore, reminds us that in future aquaculture processes attention is needed regarding implementing targeted breeding strategies. In addition, our data will contribute to Chinese yellowtail kingfish genetic breeding and the sustainable use of Chinese yellowtail kingfish germplasms.
... week since the start of the project, when the first fish was tagged, beginning from 15th August 2018) was also included as a random effect in all models to account for temporal autocorrelation. Absolute temperature values collected from receivers were used instead of temperature anomalies, as sea temperature has previously been linked to kingfish spawning behaviours (Moran et al., 2007 ;Miller et al., 2011 ), persistence across oceanographic habitats (Champion et al., 2018 ), and physiological condition (Champion et al., 2020b ). The most appropriate statistical family, transformation, and validity of the model were determined by examining the distribution of the response variable and visual inspection of residuals. ...
Wildlife tourism can have adverse effects on the behaviours and movements of animals, with implications for the health and fitness of individuals and populations. We used acoustic-tracking to show that food-based attractants used in shark-tourism increases activity (15%) and burst behaviours (60%) in yellowtail kingfish (Seriola lalandi, n = 18). Increased activity was restricted to periods when kingfish were on the same side of the island group as berleying tourism vessels, but decreased after operators left the site. Despite the raised activity and frequency of burst swimming events, the physiological condition of kingfish (n = 39, 6 tagged, and 33 untagged) measured using bioelectrical impedance analysis remained consistent with kingfish from control sites not exposed to tourism. This suggests that kingfish were able to compensate raised energy expenditure by feeding on bait and berley used by operators or through natural foraging. We highlight that the effects of provisioning from wildlife tourism can extend beyond changes in behaviours and movements and can additionally influence the energetic condition of non-focal animals through increased activity. However, supplemental food-sources provided through wildlife tourism may be sufficient to compensate for the increased energy expenditure and lessen the effects of tourism on individual fitness and health.
... In culturing L. crocea, a balance must be maintained between the hatching rate and the quality of the hatched larvae. High temperatures can accelerate hatching but can also reduce larval quality due to thermal stress (Ojanguren et al., 1999;Moran et al., 2007). Fluctuations in temperature are known to affect fertilized egg hatching time and rate; however, the impact of such fluctuations on malformation rates in hatched larvae was previously unknown (Koo and Johnston, 1978;Kurokawa et al., 2008). ...
Seawater temperatures have increased with global climate change. Coolant water discharged from coastal nuclear power-generating and coal-powered plants, coupled with already increasing seawater temperatures, can adversely affect local fish communities. A sudden drop in temperature caused by the winter shutdown of power plants can also affect fish health and behavior. To assess the effects of temperature change on fish populations, we subjected early life stages of the once commercially important large yellow croaker (Larimichthys crocea) to various water temperature experiments. Fertilized eggs showed the highest hatching rate at 23.4°C and the lowest rate of deformity in hatched larvae at 23.0°C. We determined the incipient lethal temperature for each life stages using derivation models. Ranges between the upper and lower incipient lethal temperatures increased during development from yolk-sac larvae to juveniles, especially in response to cold shock, indicating that later developmental stages in this species are more tolerant of temperature fluctuations. However, thermal tolerance is not solely determined by life stage. Our results suggest that rapid changes in seawater temperature caused by power plant coolant water discharges may significantly affect early developmental stages of fish. Critical thermal maximum tests indicate that the seawater heating rate is significantly negatively correlated with survival time and affects the critical thermal maximum value of L. crocea. On the basis of our determination of incipient lethal temperatures, emergency measures could be taken to avoid adverse economic and ecological impacts due to changes in seawater temperature caused by coolant water discharges.
... Spawning was allowed to occur naturally without hormonal stimulus, with spawns produced at 28.5 °C. Spawning occurred late at night, and eggs were collected in an overflow egg collector (Moran et al. 2007). For this experiment, four adult tanks were used (n = 32 adults total), as they spawned simultaneously during December 2019-January 2020. ...
The success of individuals during the pelagic larval phase is critical to maintaining healthy and viable populations of coral reef fishes; however, it is also the most environmentally sensitive and energetically demanding life stage. Climate change is increasing the frequency and intensity of marine heatwaves, which could have significant effects on the development and survival of larval coral reef fishes. However, little is known about how the larvae of pelagic-spawning coral reef fishes will be affected due to the difficulty of spawning and rearing these species in captivity. In this study, we tested how elevated temperatures, similar to those occurring during a marine heatwave, affected the yolk utilization, growth, and survival of larval, Lutjanus carponotatus , a common mesopredatory fish on Indo-west Pacific coral reefs. Eggs and larvae were reared at a current-day average summer temperature (28.5 °C) and two elevated temperatures (30 °C and 31.5 °C) until 14 d post-hatch (dph). Larvae in the elevated temperatures depleted their yolk reserves 39% faster than at the control temperature. The standard length of larvae was 55% (30 °C) and 92% (31.5 °C) longer in the elevated temperature treatments than the control temperature at 14 dph. Conversely, survival of larvae was 54% (30 °C) and 68% (31.5 °C) lower at elevated temperatures compared with the control temperature. This study provides new insights as to how the early life stages of coral reef fishes could be affected by ocean warming and marine heatwaves, with implications for their population dynamics.
... For this reason, it can be necessary to use increased numbers of males to produce a sufficient quantity of spermatozoa for fertilization. Furthermore, some female fishes exhibit systemic reproductive deficiencies during yolk deposition and ovulation, in some cases leading to barren female fish [100]. Improper domestication and an unfavorable environment during oogenesis contribute to such failures. ...
Fish represent an excellent source of animal protein as well as a biomedical research model as a result of their evolutionary relatedness and similarity with the human genome. Commercial and ornamental fish culture has achieved popularity, but reproductive dysfunctions act as a limiting factor for quality fry production, interfering with the sustainability of the aquaculture industry. Fish reproduction is crucial for any species’ existence, and reproductive performance can potentially be improved through applications of epigenetics and probiotics. Epigenetics is a highly sensitive molecular approach that includes chromatin structure and function alteration, DNA methylation, and modification of non-coding RNA molecules for the transfer of desired information from parents to offspring. DNA methyltransferase improves reproductive cyp11a1, esr2b, and figla gene expression and feminizes zebrafish (Danio rerio). Moreover, epigenetics also contributes to genome stability, environmental plasticity, and embryonic development. However, methylation of specific genes can negatively affect sperm quality, resulting in poor fertilization. Probiotic administration is able to induce responsiveness of incompetent follicles to maturation-inducing hormones and can change oocyte chemical composition during vitellogenic development. The positive role of probiotics on testicular cells is validated by upregulating the transcription levels of leptin, bdnf, and dmrt1 genes facilitating the spermatogenesis. This review not only discusses the effects and mechanism of epigenetics and probiotics for improving fish reproduction, but also presents an overview of the causal factors and current techniques used to eradicate dysfunction. Moreover, key genes and hormones related to fish reproduction along with research gaps and future prospects are also considered. This review provides an overview of necessary information for students, scientists, researchers, and breeders to resolve fish reproduction-related problems to ensure profitable and sustainable aquaculture.
... Stuart and Drawbridge (2011) experimentally demonstrated that under high light intensity the larvae of S. lalandi were larger and had a higher survival rate compared with larvae that were subjected to low light intensity. In addition, Moran et al. (2007) found that for this same species spawning occurred in the early daylight hours. These characteristics of S. lalandi could explain why its density and frequency of occurrence were higher during daytime in La Azufrada. ...
The description of the daily and seasonal variation of the species composition and abundance on the early stages of fishes in coral reefs can lead to a better understanding of fish population dynamics in these ecosystems, because settlement and recruitment processes depend on larval fish supply. Daytime and nighttime samples of ichthyoplankton were collected through circular surface tows using a bongo net between October 2010 and November 2011 at La Azufrada, the largest coral reef on the Colombian Pacific coast, located in Gorgona Island. A total of 2,171 fish larvae representing 87 species in 42 families were identified. The most important species by their frequency of occurrence and density were Anisotremus sp., Cetengraulis mysticetus, Bregmaceros bathymaster, and Gobiidae sp.4. Daytime and nighttime samples showed variations in the composition of the assemblage, with a greater number of species at night, evidencing short-scale variations over a diel cycle. On the other hand, environmental parameters such as oxygen, salinity, pH, temperature, and zooplankton biomass were also measured; however, none of them had a strong relationship with the larvae assemblage structure throughout the year. In conclusion, this study suggests that night conditions had a higher effect over the ichthyoplanktonic species found in La Azufrada coral reef than the observed changes in the environmental parameters.
... Yellowtail kingfish (Seriola lalandi) is an economically important marine fish species with a high potential for aquaculture due to its fast growth, high flesh quality and suitability for farming in both sea cages and recirculating aquaculture intensive systems (Sanchís-Benlloch et al., 2017). Although the reproductive behavior and morphological development of embryo, larvae and juvenile have been described (Moran et al., 2007;Wang et al., 2019a;Yang et al., 2016), no information is available regarding the ontogeny of the LPXRFa system in this species. Accordingly, the current study aimed to (1) obtain the cDNA sequences of lpxrfa and lpxrfa-r in yellowtail kingfish, (2) examine the temporal expression profiles of these two genes during early development, and (3) investigate the potential biological effects of LPXRFa in the expression of pituitary reproduction-and growth-related genes. ...
Despite its functional significance in mammals and birds, the biological role of gonadotropin-inhibitory hormone (GnIH) in reproduction is still far from being fully understood in teleosts. In the current study, we have identified LPXRFa, the piscine ortholog of GnIH, and its cognate receptor (LPXRFa-R) in yellowtail kingfish (YTK), which is considered as a promising species for aquaculture industry worldwide. The YTK cDNA sequence of lpxrfa was 534 base pair (bp) in length and encoded a 178-amino acids (aa) preprohormone. The LPXRFa precursor comprised three putative peptide sequences that included –MPMRF, –MPQRF, or -LPERL motifs at the C-termini, respectively. The YTK lpxrfa-r cDNA sequence was composed of 1265 bp that gave rise to a LPXRFa-R of 420 aa, encompassing the characteristic seven hydrophobic transmembrane domains. In males, both lpxrfa and lpxrfa-r transcripts could be detected at high levels in the brain and testis. In females, a noteworthy expression of lpxrfa was observed in the brain and ovary, while the expression of lpxrfa-r was especially evident only in the brain. To study the ontogeny of LPXRFa system, transcript levels were also investigated during early life stages. Variable expression of the LPXRFa system was observed during all stages of YTK embryogenesis. The highest expression of lpxrfa and lpxrfa-r were noticed at 7 dph and 15 dph, respectively. Furthermore, LPXRFa peptides stimulated growth hormone (gh), luteinizing hormone (lhβ) and follicle-stimulating hormone (fshβ) gene expression from the pituitary. Taken together, our results provide initial evidence for the existence of the LPXRFa system in yellowtail kingfish and suggest its possible involvement at early development and reproductive functions.
... However, reproductive contributions were skewed, particularly among females. Skewed contributions have been reported from a wide range of captive fish populations, including closely related species such as the yellowtail kingfish (Dettleff et al., 2020) and geographically co-occurring species such as the (Dettleff et al., 2020;Moran et al., 2007) where only one female and one male mated at any given time. Any of these factors, or a combination of them, could explain the skewed parental representation. ...
Aquaculture is the fastest growing food production sector worldwide, yet industry has been slow to implement genomic techniques as routine tools. Applying genomics to new breeding programmes can provide important information about pedigree structure and genetic diversity; key parameters for a successful long‐term breeding programme. It can also provide insights on potential gains for commercially important, yet complex, quantitative traits such as growth rate. Here we investigated a population of 1,100 captive‐bred F1 silver trevally (Pseudocaranx georgianus), a promising new species for New Zealand aquaculture. We used whole‐genome information, coupled with image‐based phenotypic data collected over two years, to build the pedigree of the population, assess its genetic diversity, describe growth patterns of ten growth traits and estimate their genetic parameters. Successful parentage assignment of 664 F1 individuals showed that the pedigree consisted of a complex mixture of full‐ and half‐sib individuals, with skewed reproductive success among parents, especially in females. Growth patterns showed seasonal fluctuations (average increase across all traits of 27.3% in summer, and only 7% in winter) and strong inter‐family differences. Heritability values for growth traits ranged from 0.27 to 0.76. Genetic and phenotypic correlations between traits were high and positive, ranging from 0.57 to 0.94 and 0.50 to 1.00 respectively. The implications of these findings are threefold: first, the best on‐growing conditions are in warmer months, where highest growth peaks can be achieved; second, size‐ and family‐based selection can be used as early selection criterion if pedigree structure and inbreeding risks are closely monitored; third, selection for body length results in concomitant increases in height and weight, traits of paramount importance for aquaculture. It is concluded that there is substantial potential for genetic improvement of economically important traits, suggesting that silver trevally is a promising species for selective breeding for enhanced growth.
... Embryos were collected as soon after fertilization as feasible (typically < 6 h) and separated for viability gravimetrically. Viability of the brood was confirmed microscopically, and toxicity tests started when embryos were at the gastrula stage (Moran et al. 2007). Seawater used in test setup and control/diluent water was collected from the Indian Ocean Marine Research Centre in Perth, passed through sand filters, and stored at 4°C in the dark. ...
Petroleum hydrocarbons can be discharged into the marine environment during offshore oil and gas production or as a result of oil spills, with potential impacts on marine organisms. Ecotoxcicological assay durations (typically 24 to 96 h) used to characterise risks to exposed organisms may not always reflect realistic environmental exposure durations in a high energy offshore environment where hydrocarbons are mixed and diluted rapidly in the water column. To investigate this, we adapted three sensitive toxicity tests to incorporate a short‐term pulse exposure to three petroleum‐based products: a produced water (PW), the water‐accommodated fraction (WAF) of a condensate, and a crude oil WAF. We measured 48‐h survival of the copepod Acartia sinjiensis, 72‐h larval development of the sea urchin Heliocidaris tuberculata, and 48‐h embryo survival and deformities of yellowtail kingfish Seriola lalandi, after exposure to a dilution series of each of the three products for 2 h, 4−12 h, 24 h and for the standard duration of each toxicity test (continuous exposure). Effects on copepod survival and sea urchin larval development were significantly reduced in short‐term exposures to PW and WAFs compared to continuous exposures. Fish embryos, however, showed an increased frequency of deformities at elevated concentrations regardless of exposure duration, although there was a trend towards increased severity of deformities with continuous exposure. The results demonstrate how exposure duration alters toxic response and how incorporating relevant exposure duration to contaminants into toxicity testing may aid interpretation of more realistic effects (and hence an additional line of evidence in risk assessment) in the receiving environment. This article is protected by copyright. All rights reserved.
... In general, species of the carangid genus Seriola are high priority targets for continued aquaculture development due to their fast growth rates and high market value (Nakada, 2008). In recent years, there has also been a push to optimize rearing protocols to reduce dependence on wild seed to meet the growing demand and expansion of culturing this desirable genus (Kolkovski and Sakakura, 2004;Moran et al., 2007;Stuart and Drawbridge, 2013;Yang et al., 2016). Recent work on S. dorsalis indicates that although this species grows well in land-based aquaculture (Stuart and Drawbridge, 2013), cultured fish often show reduced fitness in comparison to wild-caught conspecifics. ...
Five cohorts of cultured California Yellowtail (Seriola dorsalis) were used in exercise training experiments to assess the duration of exercise necessary to induce a positive growth and fitness response, quantify the variability and replicability of this response between cohorts, and track the longevity (persistence) of exercise-induced benefits following removal from the exercise stimulus. Custom-designed raceways were used to continuously exercise juvenile yellowtail at their optimal swimming speed for two, three, or four weeks following which several fitness metrics including measures of somatic growth, white muscle fiber area, metabolic rate, and feed conversion were tracked for up to 20 weeks post exercise in comparison to non-exercised controls. Within a cohort, the longest duration of exercise (4 weeks) generally had the largest and longest-lasting impact on growth, followed by the 3-week, and then the 2-week exercise regimes. However, all exercise treatments showed substantial variability in the magnitude and longevity of the response between cohorts. For example, the positive growth response (increase in mass above that of controls) of the 4-week swimming group ranged from 9.8% to 37.8% between cohorts. This variability in the exercise response between cohorts is similar in magnitude to that associated with other experimentally manipulated variables in the exercise regimes of previous studies, and thus highlights the need for additional species-specific experiments to quantify replicability of positive exercise results. In addition, the longevity of exercise-induced benefits was highly variable between cohorts and generally not retained for prolonged periods post exercise. Most notably, the exercise-induced growth response which may result from muscle hypertrophy (increase in white muscle fiber size) during exercise, subsided within weeks. Taken together, these results indicate that exercise can play an important role in the growth and fitness of S. dorsalis and other species, however the duration of the exercise, as well as the timing of exercise in the rearing process likely have important implications for optimizing exercise training for aquaculture enhancement.
... To maximize genetic variation in the experiment, eggs were collected from both brood stock tanks in even proportions. Eggs were collected using an external egg collector as described by Moran et al. (2007), with a 500 μm mesh net to retain eggs from the surface overflow of each tank. An equal proportion of floating eggs from both contributing tanks were mixed, rinsed with oxygenated sea water for 5 min, and disinfected with Tosylchloramide (chloramine-T) at 50 ppm for 15 min. ...
Rising water temperature and increased uptake of CO2 by the ocean are predicted to have widespread impacts on marine species. However, the effects are likely to vary, depending on a species’ sensitivity and the geographical location of the population. Here, we investigated the potential effects of elevated temperature and pCO2 on larval growth and survival in a New Zealand population of the Australasian snapper, Chrysophyrs auratus. Eggs and larvae were reared in a fully cross-factored experiment (18 °C and 22 °C/pCO2 440 and 1040 μatm) to 16 days post hatch (dph). Morphologies at 1 dph and 16 dph were significantly affected by temperature, but not CO2. At 1dph, larvae at 22 °C were longer (7%) and had larger muscle depth at vent (14%), but had reduced yolk (65%) and oil globule size (16%). Reduced yolk reserves in recently hatched larvae suggests higher metabolic demands in warmer water. At 16 dph, larvae at elevated temperature were longer (12%) and muscle depth at vent was larger (64%). Conversely, survival was primarily affected by CO2 rather than temperature. Survivorship at 1 dph and 16 dph was 24% and 54% higher, respectively, under elevated CO2 compared with ambient conditions. Elevated temperature increased survival (24%) at 1 dph, but not at 16 dph. These results suggest that projected climate change scenarios may have an overall positive effect on early life history growth and survival in this population of C. auratus. This could benefit recruitment success, but needs to be weighed against negative effects of elevated CO2 on metabolic rates and swimming performance observed in other studies on the same population.
... comm). Juvenile yellowtail kingfish are relatively robust (Moran, Smith et al. 2007). Fish are transferred to sea cages from about 5 g in weight (Kolkovski and Sakakura 2007). ...
... Based on the wide use of well seawater -of usually much higher pCO 2 and lower pH-in marine aquaculture hatcheries, the subject is worth further examination. Interestingly, when the congeners yellowtail kingfish, longfin yellowtail Seriola rivoliana and Japanese yellowtail were reared in tanks supplied with surface seawater they did complete vitellogenesis (Fernández-Palacios et al., 2015a;Mushiake et al., 1998;Roo et al., 2014) and even spawned spontaneously (Moran et al., 2007;Quiñones-Arreola et al., 2015). Similarly, greater amberjack broodstocks reared in tanks that were supplied with surface seawater completed vitellogenesis and at times also spawned spontaneously (Jerez et al., 2006;Jerez et al., 2018;Sarih et al., 2018). ...
Members of the genus Seriola have been notable species for aquaculture production worldwide, with the greater amberjack Seriola dumerili being a prominent species, partly due to its cosmopolitan distribution. A prerequisite to sustainable aquaculture production is controlling reproduction in captivity, which has been lacking for greater amberjack. The objective of the present study was to develop broodstock management and spawning induction methods using gonadotropin releasing hormone agonist (GnRHa) implants for greater amberjack reared in tanks and sea cages, and evaluate spawning performance. The advantages of sea cage rearing and spawning include optimal environmental conditions and welfare, and low cost of fish maintenance; while the advantages of tank rearing and spawning include biosecurity, ease of management and handling operations, and control of egg collection. Females reared in tanks supplied with well seawater throughout the year exhibited a significant reproductive dysfunction, such as limited gametogenesis, lower oocyte diameter at the peak of the reproductive season, low female eligibility for spawning induction and almost 0% fertilization success. On the contrary, females in three different broodstocks reared in sea cages for three consecutive years underwent vitellogenesis completely, and almost all females were eligible for spawning induction. Males reared under both conditions exhibited reduced sperm production compared to the wild, but unlike the situation in the females, tank rearing did not seem to have any negative effects on sperm quality parameters compared to rearing in sea cages. Spawning performance (eggs collected and fertilization) was best when fish were reared in sea cages during the year and then moved to land-based tanks for spawning after GnRHa treatment, resulting in the production of large numbers of eggs of adequate quality for commercial larval rearing of the species.
... To maximize genetic variation in the experiment, eggs were collected from both broodstock tanks in even proportions. Eggs were collected using an external egg collector as described by Moran et al. (2007), with a 500 µm mesh net to retain eggs from the surface overflow of each tank. An equal proportion of floating eggs from both contributing tanks were mixed, rinsed with oxygenated seawater for 5 min, and disinfected with Tosylchloramide (chloramine-T) at 50 ppm for 15 min. ...
As climate change advances, coastal marine ecosystems are predicted to experience increasingly frequent and intense heatwaves. At the same time, already variable CO2 levels in coastal habitats will be exacerbated by ocean acidification. High temperature and elevated CO2 levels can be stressful to marine organisms, especially during critical early life stages. Here, we used a fully cross-factored experiment to test the effects of simulated heatwave conditions (+ 4 °C) and elevated CO2 (1000 µatm) on the aerobic physiology and swimming performance of juvenile Australasian snapper, Chrysophrys auratus, an ecologically and economically important mesopredatory fish. Both elevated temperature and elevated CO2 increased resting metabolic rate of juvenile snapper, by 21–22% and 9–10%, respectively. By contrast, maximum metabolic rate was increased by elevated temperature (16–17%) and decreased by elevated CO2 (14–15%). The differential effects of elevated temperature and elevated CO2 on maximum metabolic rate resulted in aerobic scope being reduced only in the elevated CO2 treatment. Critical swimming speed also increased with elevated temperature and decreased with elevated CO2, matching the results for maximum metabolic rate. Periods of elevated CO2 already occur in the coastal habitats occupied by juvenile snapper, and these events will be exacerbated by ongoing ocean acidification. Our results show that elevated CO2 has a greater effect on metabolic rates and swimming performance than heatwave conditions for juvenile snapper, and could reduce their overall performance and potentially have negative consequences for population recruitment.
... Yellowtail kingfish, Seriola lalandi, is a pelagic, piscivorous, marine finfish, distributed globally in subtropical and temperate latitudes (Bowyer et al., 2012;Moran et al., 2007). The species is valuable for commercial aquaculture due to its high growth rate and adaptability to sea-cage conditions (Fowler et al., 2003;Poortenaar et al., 2001;Stuart and Drawbridge, 2013). ...
Monogenean parasites pose a considerable threat to the aquaculture of yellowtail kingfish, Seriola lalandi. Current chemotherapeutic treatments are expensive, labor intensive and can cause mortality if incorrectly administered. Many medicinal herbs possess anti-parasitic properties and therefore have potential as an alternative or supplement to current treatment methods. The anthelminthic effects of garlic, rosemary, and commercially manufactured herbal products were trialed both in vitro and in vivo against two species of monogeneans, Neobenedenia girellae and Zeuxapta seriolae, to assess their suitability for use in yellowtail kingfish aquaculture. The survival of adult N. girellae and Z. seriolae and larval N. girellae (i.e. oncomiracidia) were assessed in vitro, by exposure to seawater solutions containing the herbal products. All herbal-seawater solutions significantly reduced the survival of mature N. girellae and Z. seriolae and N. girellae oncomiracidia relative to the controls. Two in vivo trials were then conducted to examine the preventative and curative treatment effects of rosemary and garlic against Z. seriolae infections, by supplementing these products into their feed. The first trial fed supplemented diets for 30 days prior to exposure with Z. seriolae oncomiracidia. The second trial examined the potential curative effects of these extracts by feeding supplemented diets to yellowtail kingfish already infected with Z. seriolae for 10 and 20 days. The effect of these curative treatment diets on recruitment of juvenile Z. seriolae was also assessed. Supplementation of rosemary and garlic products into feed 30 days prior to experimental exposure significantly reduced Z. seriolae infection success, while supplementation of garlic powder, rosemary extract, and rosemary oil onto pellets significantly reduced Z. seriolae abundance on yellowtail kingfish after 20 days of feeding. Recruitment of juvenile Z. seriolae was also significantly reduced.
... Based also on reports from greater amberjack in Japan, it seems clear that an increased male to female ratio is preferable for this species, since more than one male appears to fertilize the eggs of one female (Tachihara et al., 1993). In the congener yellowtail kingfish, it has been shown that in a communal tank with 14 breeders, in 50% of the recorded spawning events two males fertilized the eggs of one female, resulting in > 99% fertilization success, suggesting also that a higher male to female ratio is preferable for that congener as well (Moran et al., 2007). In the same species, a high male contribution (60% in all egg batches) in the fertilized eggs was found after parentage analysis of the eggs spawned in a communal tank with 14 females and 10 males (Setiawan et al., 2016). ...
The greater amberjack (Seriola dumerili) is one of the most promising finfish species for aquaculture, due to its cosmopolitan distribution and acceptability, high growth rates and large size. However, lack of reproduction control has been one of the main bottlenecks for its commercialization. The study examined two endocrine methods for the induction of oocyte maturation/ovulation and spawning, which are based on the induction of endogenous Luteinizing Hormone (LH) release from the pituitary, through the use of Gonadotropin Releasing Hormone agonist (GnRHa) either in the form of sustained-release delivery systems (implants) or injections (acute release). The stock (n = 28) consisted of wild fish captured in 2011 and each GnRHa administration method was conducted in two replicates, with 6 and 8 fish per tank, respectively, at a 1:1 sex ratio. Fish were given a GnRHa injection once a week (three administrations), or a GnRHa implant every 2 weeks (two administrations). Mean daily relative fecundity was significantly higher (t1.3 = −5.24, P = 0.012) in the implanted fish (15,170 ± 2,738 eggs kg⁻¹ female day⁻¹) compared to the injected fish (6,119 ± 2,790 eggs kg⁻¹ female day⁻¹). Total relative fecundity was also significantly higher (t1.3 = −9.93, P = 0.003) in the implanted fish (102,402 ± 20,337 eggs kg⁻¹ female) compared to the injected ones (26,517 ± 9,938 eggs kg⁻¹ female), but there were no differences in the quality of eggs in terms of fertilization, 24-h embryo survival, hatching and 5-d larval survival. The number of females with fully vitellogenic oocytes eligible for induction of spawning decreased from the initial to the final sampling, from 7 to 6 females for the GnRHa implant treatment and from 7 to 3 females for the GnRHa injection treatment. In addition to apparently promoting the proper endocrine changes leading to multiple cycles of oocyte maturation, ovulation and spawning, and thus producing larger numbers of eggs; the use of GnRHa implants may be more appropriate in greater amberjack than multiple injections because (a) it also stimulates vitellogenesis and (b) involves less handling of the fish.
... Temperature in the broodstock tanks must be maintained at an optimum as the temperature can accelerate or retard the development rate of the embryo. (Bermudes & Ritar, 1999;Das et al., 2006;Kazuyuki, Hisashi, & Shogoro, 1988;Miranda, Cal, & Iglesias, 1990;Moran, Smith, Gara, & Poortenaar, 2007). Epinephelus coioides, which have very small larvae similar to those of N. nemurus, was successfully reared in a hatchery having water quality parameters: water temperature 26.0 ± 0.8°C, ammonia concentration 0.18 ± 0.05 mg/L, nitrite concentration 0.021 ± 0.003 mg/L, and pH 7.8 ± 0.4 (Yousif, Kumar, Balamurugan, Hozifa, & Sagir, 2016). ...
Steps taken for broodstock development of Neopomacentrus nemurus, Coral demoi-selle (Bleeker, 1857) in a hatchery, its spawning and development of egg to the juvenile stage are described. Among the three treatments tried, only the trial using Parvocalanus crassirostris nauplii as the first diet helped in the development of larvae. Larval and post-larval growth was studied for a period of 65 days post hatch. The larva measured 2-2.4 mm in total length at the time of hatching. The mouth size of larva at the time of hatching measured 237.92 µm. By the 5th day, the width of the larval body had significantly increased. All the fins were conjoined, except for the caudal fin which had begun its appearance on the 2nd day itself. The digestive system was functional by the 5th day and the copepod remains were seen in the digestive tract. The larva metamorphosed by the 15th day with fully developed fins and fin rays. On the 20th day, the larval body had begun to display signs of fin pigmentation. The larva assumed adult pigmentation by the 35th day. By the 65th day, the larva grew to a total length of about 27 mm and weighed about 0.56 g. K E Y W O R D S broodstock development, Damselfish, larval rearing, Neopomacentrus nemurus, Pomacentridae
... The challenges are even greater for mass spawning fish species, where a number of individuals spawn simultaneously leading to mass spawning, rather than single pair mating, and so there are a large number of maternal and paternal half-sib families produced; it is not possible to identify and tag the family of origin at hatching even if larvae were suitable for physical tagging. Mass spawning is a common phenomenon for a range of farmed fish species including barramundi Lates calcarifer (Frost et al., 2006), Japanese flounder Paralichthys olivaceus (Hara and Sekino, 2003), yellowtail kingfish Seriola lalandi (Moran et al., 2007;Yang et al., 2016) and common sole Solea solea (Blonk et al., 2009). Therefore, pedigree reconstruction with DNA-based parentage tests holds increasing interest in aquaculture, because it enables the rearing of mixed families communally. ...
Single nucleotide polymorphisms (SNPs) have been used for quantitative traits and evolutionary studies, but only recently have they been applied to identify family relationships and construct pedigrees. Pedigree assignments can be challenging for mass spawning, polygamous marine species due to the large number of half-sib families arising from mass spawning, and small size of larvae, so genetic markers are required in order to achieve a highly accurate pedigree assignment. In the present study, sibship and parentage in yellowtail kingfish (Seriola lalandi) were obtained from SNPs and the results were compared with those obtained from DNA microsatellite data. The accuracies of pedigrees formed using COLONY and a more recently developed program, Sequoia, the latter designed to optimize speed of processing large data sets, were compared. We also considered the impact of choosing SNPs with varying minor allele frequencies (MAF from 0.05 to 0.50), varying the actual numbers of SNPs used in a given analysis (from 50 to 1000+) and varying assigned SNP genotyping error rates (0% to 10%). Accuracy of assignment, relative to DNA microsatellites, tended to increase with increasing MAF, and increased, up to a point, with increasing SNP number, but did not change with assigned genotyping error rates up to 10%. Both COLONY and Sequoia analyses, with moderate number of SNPs (500 SNPs) and MAF values (0.20–0.30), were able to predict full-sib pairs of which >95% were also predicted by DNA microsatellites, i.e. the concordance between SNP and microsatellite pedigrees was high; processing speeds were faster with Sequoia albeit with some minor reductions in accuracy. When parental data were included in the analyses, 98% of the individuals assigned to parents using SNPs were also assigned to the same parents using DNA microsatellites. Overall, the present study provides guidance as to the parameters (minor allele frequencies, number of SNPs, SNP genotyping error rates) that optimize accuracy, and once optimized, SNPs can be used efficiently for sibship and parentage assignments for polygamous species such as yellowtail kingfish in comparison to pedigrees obtained from traditional microsatellite markers.
... Kingfish eggs were collected using an external egg collector as described by Moran, Smith, Gara, and Poortenaar (2007), with a 500 lm mesh net to retain eggs from the surface overflow of each tank. Eggs were sampled in the morning, approximately 12 hr post fertilisation. ...
Ocean warming and acidification are serious threats to marine life; however, their individual and combined effects on large pelagic and predatory fishes are poorly understood. We determined the effects of projected future temperature and carbon dioxide (CO2) levels on survival, growth, morphological development and swimming performance on the early life stages of a large circumglobal pelagic fish, the yellowtail kingfish Seriola lalandi. Eggs, larvae and juveniles were reared in cross‐factored treatments of temperature (21 and 25°C) and pCO2 (500 and 985 μatm) from fertilisation to 25 days post hatching (dph). Temperature had the greatest effect on survival, growth and development. Survivorship was lower, but growth and morphological development were faster at 25°C, with surviving fish larger and more developed at 1, 11 and 21 dph. Elevated pCO2 affected size at 1 dph, but not at 11 or 21 dph, and did not affect survival or morphological development. Elevated temperature and pCO2 had opposing effects on swimming performance at 21 dph. Critical swimming speed (Ucrit) was increased by elevated temperature but reduced by elevated pCO2. Additionally, elevated temperature increased the proportion of individuals that responded to a startle stimulus, reduced latency to respond and increased maximum escape speed, potentially due to the more advanced developmental stage of juveniles at 25°C. By contrast, elevated pCO2 reduced the distance moved and average speed in response to a startle stimulus. Our results show that higher temperature is likely to be the primary driver of global change impacts on kingfish early life history; however, elevated pCO2 could affect critical aspects of swimming performance in this pelagic species. Our findings will help parameterise and structure fisheries population dynamics models and improve projections of impacts to large pelagic fishes under climate change scenarios to better inform adaptation and mitigation responses.
... Captive spawning of multiple Seriola species has been demonstrated in tanks of different volumes ranging from 12 to 500 m 3 depending on the study species (Sakakura and Tsukamoto 1999;Jerez et al. 2006;Verner-Jeffreys et al. 2006;Moran et al. 2007;Hilton et al. 2008;Rodríguez-Barreto et al. 2014;Setiawan et al. 2016;Yang et al. 2016). Specifically, the Yellowtail Jack S. lalandi, the closest Seriola species to Yellowtail, has been shown to spawn volitionally and with hormone induction in tank volumes as small as 12 m 3 (Hilton et al. 2008;Moran et al. 2011;Setiawan et al. 2016). ...
Marine finfish require long-chain (LC) polyunsaturated fatty acids (PUFAs) for normal physiological function, and because these LC-PUFAs cannot be synthesized by the fish, they must be obtained from the diet. Three LC-PUFAs—arachidonic acid (ARA; 20:4[n-6]), eicosapentaenoic acid (EPA; 20:5[n-3]), and docosahexaenoic acid (22:6[n-3])—are especially important for growth and development of marine fish embryos and larvae. We supplemented ARA in the diet of Yellowtail Seriola dorsalis to determine whether ARA levels have an effect on egg and larval quality. Two experimental diets were offered to replicate groups of Yellowtail held in 10-m³ tanks under ambient water temperature and photoperiod conditions. The reference diet (REF-D; 1.4 g of ARA per 100 g of total fatty acids) was a commercial premix (BioVita Starter Mash; Bio-Oregon) without ARA supplementation; the ARA diet (ARA-D; 4.7 g/100 g total fatty acids) was the commercial premix with 1.0% concentrated ARA oil (40% ARA, weight/weight) added. Fish in the REF-D treatment spawned 53 times during the spawning season for a total of 18.0 million eggs. Fish in the ARA-D treatment tanks spawned 30 times during the spawning season for a total of 13.0 million eggs. Viability, hatch rates, and egg diameter were all significantly higher in the ARA-D treatment. Fatty acid analysis of the diets showed a significant increase in ARA in the ARA-D diet, and that same increase was seen in the resulting eggs. Correspondingly, ARA-D eggs had a lower EPA : ARA ratio than REF-D eggs. The supplementation of ARA generated increases in key performance indices, which might have biological significance in a production setting. We additionally demonstrated that Yellowtail will spawn without hormone induction in small (10-m³) breeding tanks, which facilitates manipulative studies of broodstock nutrition as reported here. These data represent an excellent starting point for dietary refinements in the future.
Changes in water quality significantly shape fish behavior, a crucial index reflecting the growth and welfare status of fish. Given the centrality of this relationship to aquaculture practices, a comprehensive understanding of how water quality dynamics influence fish behavior is imperative. While there have been some summaries of the effects of water quality parameters on fish physiology and growth, few reviews on their effects on fish behavior have been reported yet. This article reviews several water quality parameters which are of great concern in aquaculture from multiple facets of actual production, including physical parameters (water temperature and turbidity), chemical parameters (dissolved oxygen, salinity, pH, and inorganic nitrogen), and chemical pollutants (microplastics and crude oil), which have gained increasing attention from the researchers and aquaculture practitioners over the past decades. Variations in these water quality parameters can exert profound effects on fish physiology, metabolism, internal tissues and organs, and sensory perception, which influences fish behaviors such as swimming, schooling, feeding, predation, anti‐predation, aggression, courtship, as well as adaptive and stress‐related behaviors such as exploration, avoidance response, and anxiety‐like behavior. By synthesizing the behavioral changes caused by specific water quality parameters, this review aims to provide strong support for further water quality‐related research, thereby fostering environments conducive to both fish welfare and aquaculture productivity.
Egg specific gravity is of relevance for fish recruitment since the ability to float influences egg and larvae development, dispersal and connectivity between fishing grounds. Using zootechnics, histological approaches, optical and electronic transmission microscopy, this study describes the morphogenetic mechanism of adhesion of the oil-drop covering layer (OCL) to the oil droplet (OD) in embryos of Merluccius merluccius under physical conditions reflecting the marine environment. The herein described primordial (p)OCL is a substructure of the inner yolk syncytial layer which contains egg organella aimed to mobilize lipidic reserves from the oil drop (OD) towards the embryo blood. It is shown that the timely OD-OCL assembly is a critical morphogenetic process for embryo and larvae survival. Such assembly depends on egg buoyance because of its influence on the embryo capacity to rotate within the perivitelline space. Therefore, oil droplet adhesion (ODA) eggs are capable to complete their development while oil droplet non-adhesion eggs (ODNA) dye soon after hatching. We show that gravity-dependent egg buoyance categories exhibit different ODA/ODNA ratios (0–77%) and that relationship diminishes under incubation systems such as sprayers, that do not assure a dynamic seawater surface mixing to avoid egg desiccation. As an adaptive trait, egg gravity strongly depends on oceanic properties such as current dynamics, turbulence, oxygen, rainfall, and salinity, whose rapid changes would likely challenge the sustainability of fisheries recruitment.
A partir de la conformación de la Red LarvaPlus financiada por el CYTED (Convocatoria 2016), se colaboró en la edición de un libro que muestre los avances de especies de peces nativas de interés comercial para la acuicultura en diversos países de Iberoamérica, con la colaboración de todos los miembros pertenecientes a la Red. El libro muestra los avances en producción e investigación de 18 especies de peces marinos y 16 especies de peces dulceacuícolas.
The longfin yellowtail Seriola rivoliana is an emerging species for aquaculture diversification worldwide and production relies on fertilized eggs from captive broodstock. Temperature is the main factor that influences the developmental process and success during fish ontogeny. However, the effects of temperature on the utilization of the main biochemical reserves and bioenergetics are scarcely investigated in fish, whereas protein, lipid and carbohydrate metabolism have critical roles in maintaining cellular energy homeostasis. In this context, we aimed to evaluate metabolic fuels (protein, lipids, triacylglicerides, carbohydrates), adenylic nucleotides and derivates (ATP, ADP, AMP, IMP), and the adenylate energy charge (AEC) during embryogenesis and in hatched larvae in S. rivoliana at different temperatures. For this purpose, fertilized eggs were incubated at six constant (20, 22, 24, 26, 28 and 30 °C) and two oscillating (21⇄29 °C) temperatures. Biochemical analyses were made at blastula, optic vesicles, neurula, prehatch and hatch periods. Results indicated that the developmental period had a major influence on the biochemical composition at any temperature regime tested during the incubation. Protein content decreased only at hatching mainly due to the loss of the chorion, total lipids tended to increase at the neurula period and variations in carbohydrates depended on the particular spawn analyzed. Triacylglicerides were a critical egg fuel during hatching. The high AEC during embryogenesis and even in hatched larvae suggested an optimal energy balance regulation. The lack of critical biochemical changes from different temperature regimes during embryo development confirmed that this species exhibits a high adaptive capacity in response to constant and fluctuating temperatures. However, the timing of hatching was the most critical period of development, where biochemical components and energy utilization significantly changed. The oscillating temperatures tested may have physiological advantages without detrimental energetic effects that will require further research on larval quality after hatching.
This study assessed potential variability in batch fecundity and the spawning fraction of round herring Etrumeus micropus in the Pacific coastal waters of Japan. Fish were caught by a research vessel in the Kumano Nada (Kumano Sea) and Tosa Bay in February 2016, and other fish caught by commercial vessels in the Kumano Sea were collected between January 2019 and February 2020. The appearance of hydrated oocytes in the 2016 samples indicated that the fish spawned between midday and evening in the Kumano Sea, whereas they spawned from daytime to nightfall in Tosa Bay. The spawning fraction was estimated using the 2016 samples and was based on presence of post-ovulatory follicles and oocytes during oocyte maturation. The spawning fraction and spawning interval, respectively, were similar between the two areas: 0.17–0.26 and 3.9–5.9 d in the Kumano Sea, and 0.14–0.53 and 1.9–7.0 d in Tosa Bay. Batch fecundity was estimated by counting oocytes during oocyte maturation. The relationships of batch fecundity to body length varied significantly among the monthly samples. Batch fecundity at a given body length increased from January to May. This indicates that the acceleration in individual egg production would have contributed to the increase in egg abundance during the main spawning period. Relative batch fecundity (RBF) ranged from 76 to 142 eggs g⁻¹ of ovary-free female. The 2016 samples showed that RBF was higher in Tosa Bay than in the Kumano Sea. The RBF increased from January to April in the Kumano Sea. A comparison of RBF values for the same month (February) differed significantly between samples in the three years, suggesting interannual variation in RBF. Our data provide essential information for understanding the spawning ecology of round herring and for allowing the egg production method to be applied to estimates of stock biomass.
Seriola species are an important target fish for the aquaculture industry, and innovative techniques for their rearing have been developed in recent years. In Experiment 1 of this work, the growth of S. dumerili larvae (with and without a swim bladder) and diurnal changes in relative swim bladder volume were compared to elucidate the significance of swim bladder inflation success in larvae. Additional trials (Experiments 2 and 3) were conducted to elucidate the effect of “fade-in” and “fade-out” lighting conditions, in which artificial light intensity was gradually increased and/or decreased. The results indicate that larvae growth without a functional swim bladder was significantly inferior, even at the early stages of development. Suitable lighting conditions, such as “fade-in,” improved viability, and at least 30 min of “fade-out” effectively induced swim bladder inflation success in the larviculture of S. dumerili.
In pelagic fish species, studying reproductive behaviour and spawning dynamics is challenging. In culture scenarios, these parameters are difficult to investigate for broadcast spawners such as Seriola. Hubbs‐SeaWorld Research Institute has been culturing California yellowtail (S. dorsalis) since 2003 and now it is poised to become one of the first commercial offshore aquaculture marine finfish species in Southern California. Brood fish are typically kept in large tanks and spawn volitionally throughout the spawning season. This method is successful in yielding a consistent supply of eggs; however, it limits the understanding of spawning group dynamics or individual brood fish contribution, information that will be important to scaling production to commercial levels. In this study, genetic‐based offspring parentage analyses were used to evaluate captive spawning dynamics in S. dorsalis over two consecutive spawning seasons. The analyses determined that typically one female released eggs during a spawning event, compared with an average of six males who released milt during these same spawning events. Notably, the analyses revealed that a single female dominated spawning output in both years, participating in 63 spawning events and producing 49.7 million eggs. The largest single spawn contribution by a female was 2.5 million eggs, corresponding to a batch fecundity estimate of 110,000 eggs kg−1. The spawning interval for the most productive females was 5–6 days. Using genetic tools to characterize spawning events will help to improve breeding programme designs for S. dorsalis, and this information can serve as a proxy for estimating spawning capacities of this species in the wild.
The lack of knowledge in what optimizes egg and larval quality is an important limiting factor in developing culture techniques for any species. Inconsistent or poor egg quality significantly affects the production of larval and juvenile fish. Egg quality is a known predictor of subsequent larval viability, quality, and stress resistance. Without high quality eggs, it is not possible to optimize husbandry practices. Here we tracked egg quality in a population of California yellowtail (Seriola dorsalis), CYT. We used spawn events from three consecutive years and monitored basic egg quality metrics such as: spawn viability, egg diameter, oil diameter, hatch rates, larval size at hatch, and larval survival to first feeding. Along with these metrics we also ran proximate composition and fatty acid analysis of these spawn events on the viable portion of the eggs collected.
During this study we demonstrated that egg diameters for S. dorsalis decreased as the spawning season progressed and water temperature increased. We showed that larger eggs lead to higher quality hatched larvae, and that using eggs earlier in the season would lead to better overall larval and juvenile production. Our fatty acid analyses suggest that both arachidonic acid (ARA) and linoleic acid (LA) were limiting fatty acids in eggs produced, and there is potential to improve the quality of cultured CYT eggs with the addition of these fatty acids to the broodstock diet.
Spawning of snapper was observed in the public aquarium at Napier. Spawning males were characterised by a grey coloration and spawning females were the typical silvery‐pink colour. On four occasions spawning behaviour activity involved several males and one female and on one occasion it initially involved one male and one female, although other males joined in the spawning act. At each spawning event the female swam vertically towards the surface closely pursued by males. Eggs and sperms were released near the surface.
We report on the effect of temperature and egg diameter on the development rates of Atlantic cod (Gadus morhua) eggs and yolk-sac larvae from experiments in which individuals were followed from fertilization until death. Temperature was the only variable to consistently and significantly affect development rates. Egg size had no consistent effect on transition times during the egg phase, but there was a significant increase in the time to yolk absorption as well as the time until death with increasing egg diameter. Larval length at hatch was significantly greater in larger eggs, but only a small proportion of the variance in length at hatch was explained by egg size (6%). Increasing temperature resulted in a significant increase in the size at hatch and may reflect the overall metabolic load placed on the embryo as temperatures decrease below 1-2 degrees C.
Although all larval fish are small relative to adult fish, total length at hatching differs among species by an order of magnitude. As many of the factors critical to larval survival and growth are size dependent, substantially different expectations arise about which mechanisms might be most important to recruitment success. The evidence for the importance of size to feeding and starvation, to activity and searching ability, and to risk of predation is examined. Regressions based on data from 72 species of marine and freshwater species suggest that body size is an important factor that unifies many of the published observations. A conceptual framework based on body size has the potential to provide a useful integration of the available data on larval growth and survival and a focus for future studies of recruitment dynamics. -from Authors
The effect of incubation temperature (2, 4, 6, 8 and 10°C) on haddock Melanogrammus aeglefinus development and growth during the embryonic period and in subsequent ontogeny in a common post-hatch thermal environment (6°C) was investigated. Hatching times were inversely proportional to incubation temperature and ranged from 20.3 days at 2°C to 9.1 days at 10°C. Growth rates were directly proportional to incubation temperature during both the embryonic and larval periods. There was a significant decline in growth rates following hatch in all temperature groups. Compared to the endogenously feeding embryos, growth rates in the exogenous period declined by 4.4-fold at 4°C to 3.9-fold at 8°C, indicative of the demarcation between the endogenous and exogenous feeding periods. Yolk utilization varied from 17 days at 2°C to 6 days at 10°C and followed a three-stage sigmoidal pattern with the initial lag period inversely proportional to incubation temperature. Time to 50% yolk depletion varied inversely with temperature but occurred 1-1.5 days post-hatch at all temperatures. Additionally, the period between 10 and 90% yolk depletion also decreased with increased temperature. Overall developmental rate was sequential with and directly proportional (2.3-fold increase) to incubation temperature while the time spent in each developmental stage was inversely proportional to temperature. Larger embryos tended to be produced at lower temperatures but this pattern reversed following hatch, as larvae from higher temperature groups grew more rapidly than those from other temperature groups. Larvae from all temperatures achieved a similar length (c.total length 4.5 mm) upon complete yolk absorption. The study demonstrated the significant impact that temperature has upon developmental and growth rates in both endogenous and exogenous feeding periods. It also illustrated that temperature changes during embryogenesis had significant and persistent effects on growth in subsequent ontogeny.
This paper describes results on sexual maturation and natural spawning of Seriola dumerili kept in captivity on Tenerife (Canary Islands). Wild fish captured at an average weight of 8 kg, spawned naturally and reaching an average weight of 25 kg, after 6 years in captivity in 500 m3 raceway tanks, under natural conditions of light and temperature and fed on low-value fish. Spawning took place between April and October, coinciding with the increase in temperature from 19 to 24 °C. A total of 14 million eggs were collected in 38 spawns, with an average of 61.75% fertilization and 16.49% hatching. The greatest number and highest fertilization and hatching rates of eggs were obtained in the month of July. The greater amberjack eggs with 1.121±0.032 mm diameter, hatch within 34 to 45 h, producing larvae with an average length of 3.639±0.012 mm, yolk sac volume of 0.097±0.015 mm3, and oil globule diameter of 0.243±0.001 mm.
Recruitment variability is commonly associated with fluctuations in abundance of marine fish populations. Previous studies have focussed on stock-specific correlative or mechanistic models or on comparisons of recruitment variations of several stocks or species. The purpose of this study is to determine whether recruitment variability of commercial marine fish populations is associated with either size or the duration of early life history stages. The analysis was performed with data from 86 stocks representing 21 species of commercial marine fish. Univariate analysis shows that neither egg size nor the length at hatch is significantly correlated with recruitment variability. The change in length during the larval phase, which is representative of the duration of the stage, is significantly positively correlated with recruitment variability. Multivariate analysis shows that recruitment variability increases with increasing length at metamorphosis but that recruitment variability is poorly associated with length at hatch. The degree of serial correlation is related to the relative duration of egg and larval stages. The results clearly indicate that recruitment variability is linked to characteristics of early life history stages.
We report on the effect of temperature and egg diameter on the development rates of Atlantic cod (Gadus morhua) eggs and yolk-sac larvae from experiments in which individuals were followed from fertilization until death. Temperature was the only variable to consistently and significantly affect development rates. Egg size had no consistent effect on transition times during the egg phase, but there was a significant increase in the time to yolk absorption as well as the time until death with increasing egg diameter. Larval length at hatch was significantly greater in larger eggs, but only a small proportion of the variance in length at hatch was explained by egg size (6%). Increasing temperature resulted in a significant increase in the size at hatch and may reflect the overall metabolic load placed on the embryo as temperatures decrease below 1-2 degrees C.
Developing eggs and larvae of laboratory-reared gilthead sea bream (Sparus aurata) maintained in filtered seawater (40 ppt) at 18C, were measured for oxygen uptake, ammonia excretion, contents of free amino acids (FAA), protein, fatty acids (FA) accumulated ammonia, and volumes of yolk-sac and oil globule. Absorption of the yolk coincided with the consumption of FAA and was complete ca. 100 h post-fertilisation. Amino acids from protein were mobilised for energy in the last part of the yolk-sac stage. Absorption of the oil globule occurred primarily after hatching following yolk absorption, and correlated with catabolism of the FA neutral lipids. Overall, FAA appear to be a significant energy substrate during the egg stage (60 to 70%) while FA from neutral lipids derived from the oil globule are the main metabolic fuel after hatching (80 to 90%).
Eggs collected from females of striped trumpeter (Latris lineata) that were induced to ovulate with LHRHa were inseminated and incubated at six different temperatures ranging from 8.1 to 18.1°C. Mortality was recorded for four embryonic periods (I: cell cleavage, II: epiboly, III: organogenesis and IV: organogenesis-growth). A power law was used to approximate the relationship between temperature and developmental time to four stages of embryonic development (visible peripheral periblast, yolk plug closure, heart beat and hatching). These models may have application for the ageing of striped trumpeter eggs. The time taken for 50% of embryos to hatch at 8.1, 10.5, 12.3, 14.1 and 16.2°C was 13.0, 8.7, 6.4, 5.1 and 4.1 days, respectively. Embryos incubated at 18.1°C developed abnormally and almost all died during epiboly. Embryonic mortality was high during epiboly at 8.1, 16.2 and 18.1°C and during organogenesis-growth at 8.1°C. Survival to hatch was highest at 10.5, 12.3 and 14.1°C. The standard length and body depth at vent at hatching decreased with increasing temperatures but yolk volume was largest at 12.3°C. The optimal temperature range for the incubation of striped trumpeter eggs was 10.5 to 12.3°C, which is close to the mean sea-surface temperature during the spawning season (11.42–12.66°C) and the ambient temperature experienced by the broodstock at spawning (11°C).
This chapter describes the mechanisms of hatching in fish. Hatching is a process by which an animal changes its life from an intracapsular to a free-living type and is, therefore, of great significance in animal ontogeny. Changes in histochemical stainability of hatching enzyme granules during the development of fish have been reported. The hatching-gland cells of medaka can be distinguished from other endodermal cells early in development by their relatively large size, the abundance of cisternae of endoplasmic reticulum, and a large electron-dense nucleus with a large nucleolus. At stages somewhat earlier than eye pigmentation, secretory granules appear first in the cytoplasmic matrix. In salmonid fishes, secretory granules become electron-lucent and fused together just before secretion. The gland cells discharge the granules together with some other cytoplasmic structures differently from ordinary exocytosis. The appearance of multiple hatching enzyme peaks on gel filtration chromatography has been reported also in some other fish species, such as rainbow trout and pike.
Publisher Summary This chapter describes respiratory gas exchange, aerobic metabolism, and the effects of hypoxia during early life of fish. Analytical models provide a useful framework for the study of respiratory gas exchange. The cascade model, in particular, has been widely used to describe various aspects of vertebrate respiratory function. The laminar boundary layer is a semistagnant region of water adjacent to the egg surface where oxygen is depleted and metabolic wastes accumulate. The boundary layer actually has no outer limit, but for practical purposes are usually defined as the distance from the egg surface where local conditions are equivalent to 99% of free-stream conditions. Larvae experience respiratory distress during the transition from cutaneous to branchial gas exchange. The metabolic response of larvae to declining oxygen levels appears to be more variable than in embryos. The influence of salinity on the rate of oxygen consumption of embryos and larvae has been investigated in only a few species, but results to date suggest that net ionoregulatory costs are negligible once acclimation has occurred.
Incubation time, development, and growth of individual Pacific sardine eggs and larvae were studied in relation to environmental temperatures between 11 and 21 C. Time from spawning to hatching decreased with increasing temperature from approximately 140 hr at 11 C to 34 hr at 21 C. Maximum growth occurred in yolk sac larvae between 16 and 17 C before shrinking due to starvation. A functional jaw and pigmented eyes failed to develop in sardine larvae at temperatures below 13 C. In contrast, the northern anchovy, a clupeoid inhabiting much of the same ecological range as the sardine, hatches sooner and develops normally at these low temperatures. A comparison of incubation times deduced from field studies with these experimental results showed a close correspondence at all but extreme temperatures.
1. The goal of this study was to estimate the impact of the metabolic cost of growth (COG) on the energy budget of chinook salmon (Oncorhynchus tshawytscha) during embryonic and larval development. 2. In attempting to estimate COG, it was assumed that, as with juvenile and adult fish, energy is allocated in an additive fashion with respect to routine metabolism and mass-specific COG remains constant during early life. According to this model, there should be a direct relationship between metabolic intensity and specific growth rate. 3. In chinook salmon, however, there was no significant relationship between the two variables during embryonic development, during larval development, or during the combined embryonic-larval period at any of the four test temperatures (5.0, 7.5, 10.0 and 12.5⚬C). 4. The lack of correlation between metabolic intensity and specific growth rate suggests that the assumptions underpinning the additive model of energy partitioning may not hold during early life. An alternative model in which (a) energy is allocated in a compensatory manner and/or (b) mass-specific COG varies is presented.
Several convenient metrics for quantifying the ontogenetic state of fish larvae (based on age, size, and thermal history) were assessed in terms of intrinsic variability, the influence of temperature, and variability among species. Data for 12 ontogenetic events were collected from Atlantic menhaden (Clupeidae: Brevoortia tyrannus) and 15 events from red drum (Sciaenidae: Sciaenops ocellatus). Each species was reared at two constant temperatures 4-5 C apart. Precise timing of events and the variability in timing were calculated using a method analogous to a "dose-response" relationship. The logarithm of total length had the lowest intrinsic variability of all metrics examined; dry weight and age had the highest variability. Warmer temperatures accelerated ontogenetic events on all measurement scales, especially age-based metrics. Logarithmic transformations of day·degrees and effective day·degrees were insensitive to temperature, but these metrics require information that is often not available. An ontogenetic index, which compares species on the basis of their size or age at metamorphosis, performed best in interspecific comparisons.
The spawning, embryonic development, and morphological changes of the purplish amberjack Seriola dumerili were observed using specimens reared at the Aquaculture Research Laboratory of Nagasaki Prefectural Institute of Fisheries. Spawning was induced by intra-mascular injection of pituitary homogenate of the chum salmon Oncorhynchus keta and the genital hormone. Spawning occurred 36 hours after hormone treatment and 1, 400, 000 and 7, 000, 000 eggs were obtained in 1990 and 1991, respectively. The eggs were pelagic, spherical, and 1.05-1.20mm in diameter with a single oil globule of 0.22-0.28mm. The larvae hatched out 37 hours after spawning (W. T. 24.6°C). The newly hatched larvae were 2.7-3.1mm in length with 26 myotomes and a single oil globule. The yolk was mostly absorbed on the 4th day after hatching when the larvae attained 3.9mm in length and began to feed on rotifers. In the postlarval stage (6.3mm B. L.) the rudiments of ventral, dorsal, and anal fins began to develop and the vertebra was well ossified. In the juvenile stage (11.2mm B. L.) the membranous fins disappeared and fish gathered around drifting algae. Later in the juvenile stage (35.0mm B. L.) six or seven lateral bands appeared in the trunk as well as a band from the eye to the anterior part of the dorsal fin base. At a body length of 100mm, they reached the stage of young fish, while at a size of over 170mm in body length a yellow vertical stripe appeared from behind the operculum to the caudal peduncle. The smallest size of sexual maturation was thought to be about 600mm. Notochord or standard length at each growth stage was as follows: 2.7-3.9mm (yolk sac stage), 3.9-4.7mm (preflexion stage), 4.8-8.5mm (postflexion stage), 10-100mm (juvenile stage), 100-600mm (young stage), and over 600mm (adult stage).
1 Introduction.- 2 Gonad formation.- 2.1 Seasonal changes of main constituents.- 2.2 Reproductive effort.- 3 Characteristics of fish reproductive products.- Energy content and composition of mature eggs.- 3.1 Egg size.- 3.2 Caloric value of egg dry matter.- 3.3 Egg composition.- 3.4 Methodological remarks.- 3.5 Concluding remarks.- Factors affecting fish offspring.- 3.6 Genetic factors.- 3.7 Nongenetic internal factors.- 3.8 Biotic external factors.- 3.9 Abiotic external factors.- 3.10 Effect of egg quality on fish offspring.- 4 Endogenous feeding period.- 4.1 Development.- 4.2 Yolk absorption.- 4.3 Body growth.- 4.4 Metabolism.- 4.5 Budgets of energy or matter.- 5 Mixed feeding period.- 5.1 General remarks.- 5.2 Critical periods in fish early life.- 6 Early exogenous feeding period.- 6.1 Development.- 6.2 Feeding.- 6.3 Body growth.- 6.4 Metabolism.- 6.5 Budgets of energy or matter.- 7 Feeding of fish larvae in aquaculture.- 7.1 Evaluation of effects.- 7.2 Live foods v. formulated diets.- References.- Species index.
Norwegian coastal (NC) and northeast Arctic (NA) Atlantic cod (Gadus morhua) larvae were reared on live zooplankton to investigate temperature- and size-specific growth. Larval and juvenile growth was temperature and size dependent. Growth in length and weight increased with increasing temperature from 4 to 14degrees C, with a corresponding reduced larval stage duration. Maximum growthrate occurred at a larval size of 0.1-1.0 mg dry weight, followed by a declining trend during the juvenile stage. The temperature optimum of larval cod fedin excess is estimated to be between 14 and 16 degrees C, with a maximum weight-specific growth potential exceeding 25%.day(-1). Temperature- and stock-specific growth curves of dry weight at age are well described by a generalized Gompertz model. A stock-specific difference in mean weight at age was observed, with NC growing better than NA. Neither countergradient latitudinal variation in growth capacity of the two larval cod stocks nor temperature adaptation across latitudes was indicated. A stock-specific difference in weight at length was observed in early juveniles, with NC being heavier than NA. Overall, a positive correlation between temperature and condition level was found. No distinct temperature- or stock-specific differences in survival were observed.
Egg samples were collected from captive striped trumpeter maintained under phase-shifted and simulated ambient photothermal regimes and incubated at 9, 10, 11, 12, 13, 14, 15 or 16 °C. No eggs hatched at 9 °C. Time to hatch decreased from 9.6 to 4.2 days as temperature increased from 10 to 16 °C. Survival to hatch was low at 10 and 11 °C, but similar within the range 12–16 °C. Larval length at hatching was greatest at 14 °C, with no significant difference in yolk volume or muscle depth at vent across the range of temperatures. The results of our study suggest that the optimal temperature for the incubation of striped trumpeter eggs is 14 °C, which is higher than found previously.
Patterns of gamete development, size at sexual maturity, seasonal changes in gonadal condition and reproductive endocrinology were investigated in the yellowtail kingfish Seriolalalandilalandi. Samples were collected by commercial and recreational fishers along the East and West coasts of Northern New Zealand, between September 1998 and March 2000. Changes in the size distributions and proportions of oocyte stages during ovarian development indicated multiple group synchronous oocyte development and the presence of all developmental stages of oocytes in mature ovaries indicated a capacity for multiple spawning within a reproductive season. Changes in developmental stages of gametes during testicular development and the presence of all gamete stages (excluding spermatogonia), in partially and fully spermiated males, indicated multiple group synchronous gamete development in males. The smallest mature female was 775 mm fork length (FL), 50% of females reached sexual maturity at 944 mm FL and 100% at 1275 mm FL. The smallest mature male was 750 mm FL, 50% of males reached sexual maturity at 812 mm FL and 100% at 925 mm FL. Gonadosomatic index (GSI) provided a useful basic measurement of gonadal anabolism. Seasonal changes in gonad stage and GSI indicated that S.lalandilalandi were spring–summer spawners. Blood plasma concentrations of testosterone (T) and 17β-estradiol peaked in females during vitellogenesis, and plasma concentrations of 17α20β-dihydroxy-4-pregnen-3-one (17,20βP) were significantly elevated in females with ovaries undergoing final oocyte maturation. Blood plasma concentrations of 17,20βP did not change with gonadal development in males; however, plasma concentrations of 11-ketotestosterone and T were significantly elevated in partially and fully spermiated males. Blood plasma steroid profiles from natural cycles provide a benchmark to gauge reproductive performance in captive and domesticated fish. This study provides baseline information required for successful reproductive management of S.lalandilalandi.
Effects of salinity and temperature on eggs of silver sea bream (Sparus sarba) were studied in laboratory experiments. Naturally fertilized eggs were incubated under 60 different combinations of constant temperature (13.0, 15.0, 18.5, 22.0 and 23.5°C) and salinity (8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48 and 52‰). Incubation period, hatching period, hatching rate, abnormalities and total length of newly hatched larvae were investigated. The relation between incubation period and temperature was expressed for salinity levels of 24, 28, 32, 36, 40 and 44‰. Hatching occurred between 12 and 52‰ and between 13.0 and 23.5°C. Higher hatching rates of normal larvae were observed at 18.5°C between 20 and 36‰ and at 22.0°C between 28 and 32‰. Largest larval size was observed at 22.0°C and between 28 and 36‰. Using multiple regression analysis the calculated maximum yield of normal larvae was 66.7% at 19.4°C and 31.4‰.
The greenback flounder (Rhombosolea tapirina) is considered to have potential as an aquaculture species in southern Australia. Experiments were conducted to determine the optimal salinity for fertilisation and buoyancy of eggs, the optimal temperature and salinity combination for incubation of eggs, and the optimal temperature for yolk absorption. Experiments were carried out in 25 and 200 ml beakers and 31 containers. Optimal fertilisation rates occurred at salinities of 35–45‰ and eggs were buoyant at salinities above 28‰. The optimal temperature for egg incubation was approximately 12 °C and salinity had no effect if maintained between 15 and 45‰. Yolk absorption appeared to be most efficient at 15 °C as this temperature resulted in the largest larvae at complete yolk absorption and the fastest growth rate. First feeding occurred at the end of yolk absorption but before the oil droplet was absorbed.
Under simulated natural conditions female sea bass (Dicentrarchus labrax) in eastern Spain (latitude 40° N and longitude 0°) spawned over a 6–8-week period in February and March, with each female spawning on more than one occasion. Generally, male fish began spermiation up to 2 months before, and continued for at least 1 month after the spawning period of the female fish.Exposure of fish to 1 month of long days (LD ) from either 2nd May (Group C), 3rd June (Group D) or 3rd July (Group E) in an otherwise constant short day (LD ) photoperiod regime, speeded up the rates of maturation, thus increasing the proportions of oocytes entering exogenous vitellogenesis during October and November, and also brought forward the timings of ovulation and spawning. In contrast, constant long days from 2nd May (Group B) delayed maturation and spawning time by 2–3 months. Fish maintained under constant short days throughout the experiment (Group A) spawned up to 6 weeks in advance of the control fish, suggesting that endogenous timing mechanisms may operate in this species.Spawning occurred naturally in all the experimental and control fish without the necessity for induction with pituitary or hypothalamic hormones.For the control fish, egg quality (defined as the proportion of eggs spawned which were floating and viable), hatching rate and survival to first feeding (both expressed as percentages of the numbers of floating or good quality eggs) averaged 78.3±7.7% (mean±s.e), 84.8±3.3% and 54.6±20% respectively. With the exception of the eggs and fry from Group B, these measures of quality and survival appeared unaffected by the photoperiod treatments. The eggs and fry produced by the fish maintained under long days (Group B) towards the end of their spawning period (i.e. in May), showed much more variable egg quality and survivals through hatch and first-feeding, possibly because of the higher sea water temperatures which prevailed at the time of their delayed spawning.Fecundities expressed as numbers of eggs per kg of post-spawning fish weight ranged from 247–305 000/kg for Groups A, C, D and E and the controls, but were significantly reduced in Group B fish. Egg sizes, which ranged from 1.147–1.176 mm in diameter, were unaffected by the photoperiodic manipulations of spawning time.It is concluded that artificial control of daylength can improve the supply of eggs and fry for commercial on-growing without any adverse effects on the fecundity of the broodstock or the quality and survival of the eggs and fry.
Survival of the seed of goldstriped amberjack Seriola lalandi was consistently enhanced by intramuscular injection of triiodothyronine (T3) to the broodstock fish at a dose of 20 mg/kg body weight. Survival rates at the time of transfer to net cages (35 d after hatching) were 2.6–5.0% for the T3 treatment while only 0.3–2.1% for the control. Survival rates 36 mo after hatching was estimated to be 12 times higher in the T3-treated group (1.1%) than in the control (0.09%). T3 concentration in newly spawned eggs increased from control levels of 0.3–1.0 ng/g to 68–127 ng/g 2 d after injection and subsided with successive spawns. T3 concentration in the treated larvae was about 360 times higher than in the control upon hatching (29 np/p vs 0.08 ng/g), but became indistinguishable from the control 6 d after hatching. These results indicate injection of T3 to the broodstock of S. lalndi to be of practical value in aquaculture of the species.
We performed laboratory incubations of white sucker (Catostomus commersoni) eggs to determine (i) the incubation time to organogenesis, eyed egg, hatching, and swim-up phases at eight different temperatures (8.5ñ21.2∞C), and (ii) the best model to describe the relationship between these incubation times and temperature. Seven models (degree-day, power-law, BelehrÆdekís equation, quadratic equation, first- and second-order exponentials, and a thermodynamic model) all gave comparable and highly significant fits to our data (R2 > 0.90). We thus compared the in situ and predicted incubation times by (i) the degree-day model, because of its simplicity, and (ii) the thermodynamic model, because of its theoretical foundation. The degree-day model was at least as accurate as the thermodynamic model (overall mean difference between predicted and observed incubation times of 1.4 ± 1.0 and 1.2 ± 1.2 days for the thermodynamic and degree-day models, respectively). Given its high accuracy and simplicity of use, we conclude that the degree-day model should be used to predict the incubation times of white sucker. We also observed a synchronization of hatching in situ that suggested an influence of photoperiod in addition to that of water temperature. Résumé : Nous avons procØdØ ‡ des incubations díoeufs de meunier noir, Catostomus commersoni, en laboratoire afin de dØterminer (i) la durØe díincubation jusquíaux phases díorganogØnse, díoeuf oeillØ, díØclosion et de larve pØlagique (anglais : swim-up) sous huit tempØratures diffØrentes (8.5ñ21.2∞C) et (ii) le meilleur modle pour dØcrire la relation entre ces durØes díincubation et la tempØrature. Sept modles (degrØs-jours, une fonction de puissance, líØquation de B elehrÆdek, une Øquation quadratique, des Øquations exponentielles de premier et second degrØ et un modle thermodynamique) ont tous offert
The influence of temperature on fish eggs and larvae is briefly described from an autecological viewpoint. Temperature may have lethal or sub-lethal effects as well as pacing metabolism, other physiological responses and behaviour. It influences body size, growth, differentiation of muscle and meristic characters. Increase of temperature, as would occur with global warming, will change the timing of ecological events such as the spring plankton outburst so influencing the match or mismatch of larvae with their food supply and their predators.
The mariculture of yellowtail (Seriola quinqueradiata) has developed by taking advantage of abundant supplies of wild juveniles such as seed and sardines as feed. Other indispensable elements of this development were the existence of many suitable sites, such as the geographically complex inlets along the Japanese archipelago. The Japan Fish Feed Association supported the development of economical moisture pellets, extruded pellets, and granulated feeds for yellowtail to lower production costs and improve the quality of the products. The 1998 annual production of yellowtail culture in Japan was about 147,000 tons. As the number of yellowtail farms began to increase, disease outbreaks became frequent. Trials to culture yellowtail offshore or in land-based closed systems resulted in the production of high-quality meat and low pollution, but these methods do not yet seem to be sufficiently economical. Two promising technologies for maintaining a clean environment that should be considered are an autofeeding system and an integrated approach to culture. The problem for yellowtail culture today is the declining consumption by young people. Therefore, the culture of amberjack (Seriola dumerili), goldstriped amberjack (S. lalandi), and striped jack (Pseudocaranx dentex), which enjoy great popularity among the Japanese, should be increased to substitute for 30% of yellowtail production.
Fish eggs and larvae provide a relatively untapped source of biological material, increased by improvements in the techniques for rearing marine species. Most species of fish pass through a larval stage before assuming the adult form at metamorphosis. This chapter discusses the most substantial advances that have been made in the investigations of marine eggs and larvae. Most fish eggs are round, although in the anchovy Engraulis and bitterling Rhodeus they are ovoid, and in certain gobies pear-shaped. At hatching, the larva is usually transparent with some pigment spots of unknown function. Notochord and myotomes are clear with usually little development of cartilage or ossification in the skeleton. The chapter discusses mortality, rearing and farming, yolk utilization, feeding, digestion, and starvation.
This study illustrates the embryo development of the spotted wolffish (Anarhichas minor Olafsen), an interesting candidate for cold-water aquaculture. The egg morphology (semitransparent, yellow-white with numerous oil droplets in the yolk), size (5.4–6.5 mm) and long embryogenesis (c. 800–1000 d°, depending on temperature) of A. minor are very similar to Anarhichas lupus. Cleavage is slow, and the first cell divisions take place at 12 h at 8°C. After 12 days the 2-mm embryo with the first somites is laid down and the blastopore starts closing. The fat globules in the yolk fuse into one after 22 days, and after 30 days eye pigmentation is noticeable. After 44 days, eye pigmentation is strong, the digestive tract folded and a green gall bladder can be noted in the now 11-mm-long embryo. One week later the blood is brightly red, the intestine is pigmented and the lower jaw is well developed. Premature hatching may occur from this stage. After 58 days vascularization of the yolk is complete, capillaries are noted in the fin fold, the first ray rudiments are established in the tail and pectoral fins, and the four gill arches are covered by the operculum. The preanal finfold is reduced after 72 days, stomach and gill filaments are formed, and six pigmented rows are noted on the 17-mm-long embryo body. After 86 days all fin rays are seen and the digestive tract is intensely pigmented and folded. Hatching (normal) starts after 110 days and may last for 2–3 weeks. Late embryos and early larvae of A. minor have more distinct bands of pigment along the body compared with the closely related A. lupus. An increase in both length and weight of the embryos in individual batches occurs during the hatching period.
Feeding performance (intensity and incidence) of first-feeding yellowtail kingfish larvae was evaluated under a range of light intensities and algal-induced turbidities. Larvae were fed with varying degrees of success under all light intensities tested (0–17 μmol s−1 m−2), in both clearwater and greenwater (8 × 104 cells mL−1). There was a consistent trend for feeding performance to increase with larval age and light intensity in both clearwater and greenwater conditions, demonstrating that visual proficiency increases with larval age. Feeding intensity remained low over the first 3 days of first feeding across all light intensities tested. Days 6 and 7 post-hatch larvae showed considerably higher feeding intensities particularly at 8 and 17 μmol s−1 m−2. This improvement indicates an ontogenetic shift in sensory or locomotor competence. First-feeding larvae performed equally well in both clearwater and greenwater (8 × 104 cells mL−1) conditions, although at the lowest light intensity tested (0.1 μmol s−1 m−2) feeding performance was noticeably reduced. Feeding performance was severely diminished across all larval ages at an algal cell density of 32 × 104 cells mL−1, demonstrating that for this species algal-induced turbidities >16 × 104 cells mL−1 adversely affect the ability to capture free-swimming prey during the first-feeding window.
The aim of this study was to investigate ageing of ovulated eggs retained in the ovarian lumen of captive turbot, Scophthalmus maximus L., prior to handstripping. The ovulation times of egg-batches were determined by catheterization, handstripping and plotting the percentage fertilizations and hatches of resulting eggs against time. The catheterization experiments showed that eggs age and change appearance rapidly after ovulation. The stripping method demonstrated that freshly-ovulated eggs showed greater than 90% fertilization and up to 97% hatch, but ovulated eggs retained in the ovary lumen for 1 day before stripping gave 0% hatch. The turbot showed precise ovulatory rhythms. The time between ovulations varied between individuals but was constant for any one female, making it possible to predict future ovulation times. Three of the females studied had ovulatory periods of alternating length.
Varying egg quality is one of the limiting factors for successful mass production of fish fry. It may also cause some of the variability in recruitment observed in many wild stocks, since poor egg quality may decrease the survival potential of the hatched larvae. In the literature, the term egg quality has been defined and used in various ways by different authors. Due to the limited knowledge in the field, it has been difficult to pinpoint valid quality criteria. The only definition of egg quality that has general validity is probably the egg's potential to produce viable fry. The egg's potential to produce viable fry is determined by several physical, genetic, and chemical parameters, as well as the initial physiological processes occurring in the egg. If one of the essential factors is lacking, or is incomplete, egg development will fail at some stage. Thus, egg quality should be regarded as determined when the egg has left the female fish and the fertilization process is complete. This definition is, however, of very little practical value, since fry viability obviously cannot be determined before the fry is produced. Good practical criteria for the determination of egg quality should be both possible to identify early in development, and be simple to use. The problems of egg quality have received increasing attention, in relation to cultivation as well as to the assessment of reproduction of wild fishes. This chapter discusses the possible criteria for the determination of quality of fish eggs.
The development of digestive enzymes was examined in laboratory-reared yellowtail kingfish larvae from hatching to 36 days after hatching (DAH). The specific activities of amylase, lipase, and alkaline phosphatase showed three distinct phases: a sharp increase in enzyme activity from hatching to the onset of exogenous feeding on 3 DAH, followed by a fluctuation and a general decline toward 18 DAH, and then a period of low activity from 18 to 36 DAH. The total activities of these three enzymes showed a gradual increase from hatching to 18 DAH, followed by a sharp increase toward 36 DAH. In contrast to other enzymes, the specific and total activities of trypsin reached the maximum on 15 DAH and 24 DAH, respectively, and then both activities declined to low levels toward 36 DAH. The dynamics of digestive enzymes corresponded to the anatomical development of the digestive system. The enzyme activities tend to be stable after the formation of gastric glands in the stomach on 15 DAH. The composition of digestive enzymes indicates that yellowtail kingfish is able to digest protein, lipid and carbohydrates at an early stage. However, due to the low level of amylase specific activity after 18 DAH, the carbohydrate component should remain at a low level in formulated diets for fish larvae.
Fertilized Chondrostoma nasus eggs were incubated at 10, 13, 16 and 19° C until full resorption of the yolk sac. High survival was observed at 10–16° C (89–92% at the onset of external feeding), whereas at 19) C survival was depressed (76%). The time at which 5, 50 and 95% of individuals had hatched, filled the swim bladder, ingested the first food and fully resorbed the yolk sac was determined. An increase in temperature accelerated development and made it more synchronous. Within the period from fertilization to hatching embryonic development was theoretically arrested (t0 dev) at 8·8° C, and growth was arrested (t0gr) at 8·86° C. For the whole endogenous feeding period (from fertilization to full yolk resorption) the amount of matter transformed into tissue was temperature independent between 10° and 19° C. Respiration increased exponentially with age; the respiration increase was faster at higher temperatures, but, in general, metabolic expenditures of C. nasus were low. As a consequence, the efficiency of utilizing yolk energy for growth was high as compared with other fish species (57% during the whole endogenous feeding period); it was temperature independent. However, time was used less efficiently at low temperatures, increasing a risk of predation. Within the endogenous feeding period a shift from lower to higher temperatures for optimal yolk utilization efficiency was observed. The temperatures optimal for survival and energetic performance seem to be 13–16° C for egg incubation and 15–18° C for rearing of yolk-feeding larvae. Chondrostoma nasus is a potential candidate for aquaculture for restocking purposes.
Fertilized eggs from a brown trout Salmo trutta population in northern Spain were incubated in the laboratory at 4, 6, 8, 10, 12, 14, 16 and 18° C. Developmental stage and embryo size were monitored by taking samples at regular intervals. Survival was maximal at 8 and 10° C and decreased at higher and lower temperatures. Despite starting development, no embryo hatched at 16 and 18° C, which suggests an upper thermal limit for development between 14 and 16° C. Time required to reach a given ontogenetic stage decreased with increasing temperature. Embryos incubated at lower temperatures were larger at 50% hatching, and these differences persisted throughout the subsequent embryonic period until the start of exogenous feeding. A comparison with previously published data indicates low interpopulation variability in thermal sensitivity of embryonic development, even in consideration of the great latitudinal range of the studies.
Ontogeny is a continuous process with temporaryaccelerations. The embryonic period from eggactivation to hatching, and the larval periodthereafter, are considered. Advances in studieson the ontogeny of yolk-feeding Europeanfreshwater and Antarctic marine fish arecompared. New techniques and approaches aresummarized. A method for exact quantificationof the time to any developmental event isrecommended. Four attempts to quantify anindividual's ontogenetic advancement arereviewed, of which Fuiman's ontogenetic indexseems to be the best choice. The relationshipbetween the time to any ontogenetic event(, days) and temperature (t, C)has been quantified by exponential, power law,Blehradek's, Leiner's, and polynomialmodels, whose common weaknesses are that theparameters have no biological meaning, and theydo not allow comparison of temperaturerequirements between species. The ontogeneticrate (V = 1/, days–1) was welldescribed (r2 = 0.92 – 1.00) by a straightline V = a + bt (linear model) in 44 fishspecies over a broad low-mortality temperaturerange. The linear model produces biologicallymeaningful parameters: the temperature ofbiological zero t0 = –a/b, effectivetemperature teff = t –: t0, andeffective day-degrees Deff = (t – t0) = b–1. From t0 andDeff the time to any ontogeneticevent can be computed as: =Deff/(t – t0). In coldwaterspecies low t0 is accompanied by highDeff, whereas in warmwater speciesthe opposite is true. The linear model wasvalidated. Day-degrees (D = t)and physiological day-degrees (PD =t/q, where q is Winberg's temperaturemetabolic correction factor) are based onincorrect assumptions. Their use as temperature-independent measures of ontogeneticadvancement is not advised; by contrast,effective day-degrees (Deff)are temperature-independent and arerecommended. The remaining extrinsic factorsaffecting ontogenetic rate during yolk feedingare: oxygen, salinity, pH, light, dissolvedbiotic compounds, and anthropogenic factors.The main intrinsic factor is egg size, whichpositively affects the time to particularontogenetic steps at inter- and intra-specificlevels. Attempts to quantify the combinedeffects of temperature and salinity, and oftemperature and egg size, are reviewed.
Factors affecting egg quality are determined by the intrinsic properties of the egg itself and the environment in which the egg is fertilized and subsequently incubated. Egg quality in fish is very variable. Some of the factors affecting egg quality in fish are known, but many (probably most) are unknown. Components that do affect egg quality include the endocrine status of the female during the growth of the oocyte in the ovary, the diet of the broodfish, the complement of nutrients deposited into the oocyte, and the physiochemical conditions of the water in which the eggs are subsequently incubated. In captive broodfish, the husbandry practices to which fish are subjected are probably a major contributory factor affecting egg quality. Our knowledge of the genetic influences on egg quality is very limited indeed. We know that parental genes strongly influence both fecundity and egg quality, but almost nothing is known about gene expression and/or mRNA translation in fish oocytes/embryos. This is surprising because the products synthesized in ovoand the mechanisms controlling their expression are likely to play a central role in determining egg quality. The genetic mechanisms underpinning oocyte and embryo growth and development are a priority for research
The red sea bream, Pagrus major, which is widely distributed throughout the Far East, is the most important species of the family Sparidae for marine aquaculture in Japan (Ochiai and Tanaka, 1986). The total production of market-size red sea bream in Japan was over 72 000 tonnes (t) in 1993, with approximately 28% of the fish being derived from cultivation (Taya, 1995). In 1995 about 30 million red sea bream juveniles were produced: about 22 million being used for restocking into coastal waters, and the remainder were on-grown in commercial farms (Morita, 1997). In southern Japan, the natural spawning season starts at the end of February and lasts until early June, when water temperatures are within the range 15‐23 °C (Higuchi, 1977). In captivity, the spawning season of the red sea bream starts in April and comes to an end in June (Harada, 1969; Kitajima, 1978). Although there are several reports, published mostly in Japan, on aspects related to red sea bream culture, relatively little is known about the environmental requirements of the early life stages of this species. Some effects of temperature and salinity on the embryonic development of red sea bream eggs were described by Matsuura and Kakuda (1980) and Yoo et al. (1991), while Apostolopoulos (1976) provided some information about the combined effects of these factors on the hatching of red sea bream eggs. The current study was undertaken to provide information about the effects of salinity and temperature combinations on the length of the incubation period, hatching rate and appearance of newly hatched larvae of the red sea bream. The experiments were carried out at the Fishery Research Laboratory of Kyushu University in 1994. Naturally spawned eggs were collected from a broodstock tank of 3m 3 water capacity during the spawning season (which in Kyushu is early April to June), washed carefully with fresh filtered seawater and transferred directly to the experimental room. Water temperature in the spawning tank during the experimental period ranged from 16.5 to 20.0 °C, and salinity corresponded to the normal salinity of water in the adjacent bay (29.0‐32.5‰). Ten trials were conducted to test * Author to whom correspondence should be addressed.
A study was undertaken to establish the role of free amino acids (FAA) in aerobic energy dissipation in embryos of turbot (Scophthalmus maximus) which contain an oil globule in the egg. Laboratory-reared developing eggs and larvae (15C, 34 salinity) were measured for oxygen uptake, ammonia excretion, contents of FAA, protein, and ammonium, and volumes of yolksac and oil globule. Newly spawned eggs from different batches contained 55 to 90 nmol egg–1 of FAA. Resorption of FAA occurred in parallel with the consumption of yolk. Resorption of the oil globule, however, occurred predominantly after hatching and mainly after yolk resorption. The combined data suggest that approximately 70% of the FAA are utilized as an energy substrate, while the rest are polymerized into body proteins. FAA become a significant energy substrate in the early egg stage and account for 100% of the aerobic energy dissipation 2 d after Fertilization then decrease to ca. 60% at the time of hatching. Lipids derived from the oil globule seem to be the main fuel after hatching and account for ca. 90% of the energy dissipation at the onset of first-feeding. Thus, the energetics of fish embryos which contain an oil globule seems to be different from those that depend exclusively on the nutritional reserves of the yolk.
Regulation of river flow and the amount of winter rainfall are the major factors affecting the water temperature of the spawning grounds, for green sturgeon in the Klamath River. During the primary spawning period of green sturgeon, mid-April to June, the water temperature may vary from 8 to 21C. To estimate the potential implications of this modified thermal regime, we examined the survival and development in three progeny groups of green sturgeon embryos from zygote to hatch, at constant incubation temperatures (11–26C). Temperatures 23–26C affected cleavage and gastrulation and all died before hatch. Temperatures 17.5–22C were suboptimal as an increasing number of embryos developed abnormally and hatching success decreased at 20.5–22C, although the tolerance to these temperatures varied between progenies. The lower temperature limit was not evident from this study, although hatching rate decreased at 11C and hatched embryos were shorter, compared to 14C. The mean total length of hatched embryos decreased with increasing temperature, although their wet and dry weight remained relatively constant. We concluded that temperatures 17–18C may be the upper limit of the thermal optima for green sturgeon embryos, and that the river thermal regime during dry years may affect green sturgeon reproduction.
Cod (Gadus morhua L.) eggs may develop and hatch within temperatures of −1.5 to 12 °C, but little is known about the effects of very low temperatures
on larval characteristics. Eggs of the Northeast Arctic cod (Gadus morhua) were incubated at 1, 5 or 8 °C from Day 1 after fertilisation until hatching, and transferred to 5 °C after hatching. Histological
samples of the axial musculature were taken at hatching and 5 d after hatching, and the data on muscle cellularity from these
samples were related to survival and hatching, size, developmental data and viability of the yolk sac larvae. All larvae hatched
at the same developmental stage. Incubation of eggs at 1 °C produced shorter larvae with a larger yolk sac and more, small
deep fibres at hatching than larvae from eggs incubated at 5 or 8 °C. The larval size difference was still present 5 d after
hatching, a time at which the larvae from 1 °C-incubated eggs were less developed and less resistant to an acute viability
stress test (65 ppt salinity). Although there were no differences between temperature groups in number and size of muscle
fibres 5 d after hatching, the deep fibres of the 1 °C-group contained less myofibrils than the two other groups. The phenotype
of the larvae at hatching was thus affected within these incubation temperatures. Although all groups were transferred to
the same temperature after hatching, the lowest egg incubation temperature (1 °C) still had a negative effect 5 d after hatching,
as these larvae were both smaller, less resistant to stress and had less functional muscles at the time of first feeding.
Our conclusion is therefore that 1 °C is close to, or below, the lower thermal tolerance limit for normal functional development
of Northeast Arctic cod. The results are discussed in relation to larval viability and recruitment of this species in the
wild.
Developing eggs and larvae of European sea bass (Dicentrarchus labrax) maintained in filtered sea water (40 gl−1) at 18°C, were measured for oxygen uptake, contents of free amino acids (FAA), protein, fatty acids (FA), and volumes of yolk-sac and oil globule. Newly spawned eggs had a dry weight of 90 μg egg−1 and an egg diameter of 1.14±0.03 mm. The yolk was quickly absorbed during the embryonic and the early larval stages and was 95% depleted by 100 h post fertilisation. The depletion rates of the FAA were somewhat faster than the rate of absorption of the general yolk matter and were almost complete by 80 h post fertilisation. The oil globule was mainly absorbed after hatching following yolk absorption, and occurred concurrently with catabolism of FA from neutral lipids. Approximately 30% of the oil globule was still present at the presumed onset of exogenous feeding. Overall, FAA appeared to be a significant energy substrate during the egg stage and the early yolk-sac stage while FA from neutral lipids derived from the oil globule seemed to be the main metabolic fuel after hatching. Amino acids from protein seemed to be mobilised for energy in the last part of the yolk-sac stage. This investigation supports accumulating evidence for a common sequence of catabolic substrate oxidation in marine pelagic fish eggs that contain oil globules.
Ontogenetic development of the digestive tract and associated organs in yellowtail kingfish (Seriola lalandi, Family: Carangidae) larvae was morphologically and histologically examined using light microscopy from hatching to 36 days after hatch (DAH). The first developmental phase started from hatching when the digestive tract was a simple tube and ended with the onset of exogenous feeding. The second developmental phase was from the start of exogenous feeding to the appearance of gastric glands, in which eosinophilic supranuclear vacuoles occurred in the hindgut on 4 DAH and lipid vacuoles occurred in the anterior midgut on 5 DAH, indicating the start of protein and lipid absorption. After the stomach formation on 5 DAH, the digestive tract was distinctively divided into buccopharyngeal cavity, oesophagus, stomach, midgut and hindgut. Following the intestinal curve on 8 DAH, goblet cells, pharyngeal teeth, taste buds and the tongue also appeared. The third developmental phase started from the appearance of gastric glands on 15 DAH and continued onward. The stomach was divided into cardiac, fundic and pyloric regions when the pyloric caeca formed on 18 DAH. Gastric glands distributed in cardiac and fundic regions, but not in the pyloric region. The formation of the fundic stomach signalled the starting point of weaning. This study shows the quick development of the digestive system in yellowtail kingfish, and the results should lead to a better understanding of the ontogeny of fast-growing fish larvae and improvement of larval rearing success in hatcheries.
The purpose of this study was to find out how yolk and oil globule absorption in Siganus guttatus proceed as the digestive tract develops, in order to determine the probable causes of early larval mortality. Yolk and oil globule absorption in the rabbitfish were compared with the same processes in the more sturdy seaperch larvae during the first 10 days of larval life under identical rearing conditions in 32‰ sea water at 27°–30°C. The rapid decline of yolk in both species coincided with the rapid development of the digestive system within 24 h from hatching, indicating that most of the yolk was used for organogenesis. Whereas yolk was depleted in both fish in 3 days, the oil globule persisted in the rabbitfish only for 4 days and in the seaperch for 7 days. Oil globule depletion in the rabbitfish coincided with a negative mean length increment, implying an energy deficit even when the larvae had already started to feed. Ultrastructural observations of the gut epithelia of the rabbitfish revealed pinocytosis in the hindgut cells immediately after ingestion of rotifers, well in advance of complete yolk and oil globule absorption. Therefore, starvation due to exhaustion of the endogenous energy reserves in addition to the physical inability to feed were ruled out as major causes of larval mortality in rabbitfish.
Although much effort has been made to evaluate criteria for marine egg and larval quality, the significance of poor egg quality for the results in the final juvenile production has not been clarified. The aim of our experiments with turbot (Scophthalmus maximus) was to determine whether the initially observed egg quality affected offspring viability and normal development up to the juvenile stage.Eggs from each of six individual females were divided into three replicate groups, and the eggs in each replicate was quality evaluated according to fertilization rates and the ratio of normal cell cleavages (blastomere morphology) at the 8–32 cell stage. The condition of yolk-sac larvae was tested by an acute high salinity stress test, and the larvae were fed according to our standard feeding regime with microalgae, enriched rotifers and Artemia nauplii.Significant positive correlations were found between observed egg quality characteristics and hatching rates, larval tolerance to acute stress, and to survival, metamorphosis and juvenile pigmentation. Larvae hatching from poor quality egg groups thus had a lower viability and were less able to develop normally to the juvenile stage than larvae from good quality egg groups. Our conclusion is that egg quality observed as fertilization rate and rates of normal blastomeres at early egg stages may be a useful predictive tool for evaluation of the potential juvenile production in turbot.
For most fish species, blastomere size and shape are uniform during normal cleavage. However, abnormal blastomere morphology has been observed in a variety of studies, either induced directly by chemical or physical Stressors, or observed in eggs collected from plankton or broodstock. It has been proposed that abnormalities are indicative of low egg viability and may provide a useful predictive tool for egg assessment. However, there is little direct evidence relating blastomere morphology to egg survival. This paper reviews the literature on abnormal embryonic development in fish, and presents new findings on the significance of blastomere morphology in the Atlantic halibut, Hippoglossus hippoglossus. Several studies have reported qualitative relationships between egg batch survival and the proportion of normal embryos for a variety of fish species. In order to investigate more closely the relationship between blastomere morphology and fish egg survival, incubation experiments where carried out with eggs of Atlantic halibut. Eggs were individually assessed at the 8-cell stage for 5 blastomere characteristics and incubated to hatch in multiwell microtitre plates. For data pooled from 13 egg batches, the mean score for each blastomere characteristic showed a significant positive linear regression with the number of eggs hatched. Multiple regression analysis, incorporating all five blastomere characteristics, demonstrated a high degree of correlation between the independent variables. While the experimental procedure that was used for halibut eggs is too laborious for routine hatchery application, it is proposed that subjective observations of blastomere morphology could be readily adopted by commercial hatcheries to provide early assessment of egg viability.
Establishment of Pacific bonito (Sarda chiliensis (Cuvier) in captivity at Marineland of the Pacific, Palos Verdes, California, has made it possible to study and describe in detail their swimming, feeding, courtship, and miscellaneous behaviours.
The oval tank in which the fish were kept was 33 m long, 16·3 m wide, and 11 m deep at the deepest point. Sea water was pumped from the ocean and was held at 22°C. Fish were viewed through 170 windows in the sides of the tank. The oval tank was part of a public display, a circumstance which limited experimental manipulation of the fish.
Swimming speeds and tail-beat frequencies were measured from movie films and direct observation. Frequencies of behaviour patterns were recorded either as the numbers observed among all fish by a stationary observer over 10 min periods or the number observed for a single fish for periods of time averaging 71 sec. With the latter method, data were kept separately for individual fish.
They swam continuously against the current at an average speed of 88·2 cm/sec and at a tailbeat frequency of 1·42 beats/sec when not feeding or courting. The linear regression of speed (y) in body lengths/sec on the number of tail beats/sec (x) was y=0·4905+0·6394 x among feeding S. chiliensis.
When food (frozen osmerids) was tossed onto the surface, S. chilensis was the first species to reach and ingest it. During feeding, schooling was disrupted, and each S. chiliensis took on a vertically barred coloration and a yellowish middorsal stripe.
Courtship included temporary pairing, aggressive defense of females by males, and a sequence of behaviour leading to the simultaneous and adjacent release of gametes. A wobbling swimming motion by a female released a following by males, and likewise, if a male swam immediately behind a female, she began a wobbling type of swimming. Sexual discrimination was mediated by the wobbling and following movements. If more than one male was in the following position, agonistic behaviour occurred which included the transient vertically barred coloration observed in both sexes at feeding time. During courtship, only males assumed the coloration. Gametes were released during a circle swimming behaviour in which the female with the male in tandem swam in a circular path about three body lengths in diameter. If aggression occurred during the wobbling-following portion of the sequence, the sequence usually terminated and did not result in circle swimming and spawning.
S. chiliensis had nine miscellaneous behaviour patterns: mouth closure (long), mouth closure (short), snap, yawn, quick swim, lean, bend, jerk, and defecation. Often such movements have been considered as comfort movements, but in the present paper each was discussed separately in terms of association with some vital process of the fish. Mouth closure (long) movements may be associated with olfaction or gill ventilation; snaps following a yawn or a quick swim may be a drinking movement; leans may be a social releaser in schooling; and bends and jerks may be associated with passage of food through the alimentary canal.