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Growth variation in larval Makaira nigricans
Abstract
The Atlantic blue marlin Makaira nigricans larvae were collected from Exuma Sound, Bahamas and the Straits of Florida over three summers (2000–2002). Sagittal otoliths were extracted and read under light microscopy to determine relationships between standard length (LS) and age for larvae from each year and location. Otolith growth trajectories were significantly different between locations: after the first 5–6 days of life, larvae from Exuma Sound grew significantly faster than larvae from the Straits of Florida. Exponential regression coefficients were similar among years for Exuma Sound larvae (mean instantaneous growth rate, GL = 0·125), but differed between years for larvae from the Straits of Florida (GL = 0·086–0·089). Differences in larval growth rates between locations resulted in a 4–6 mm difference in LS by day 15 of larval life. These differences in growth appeared to be unrelated to mean ambient water temperatures, and may have been caused by location‐specific differences in prey composition or availability. Alternatively, population‐specific differences in maternal condition may have contributed to these differences in early larval growth.
... The importance of daylength and SST in the timing of spawning may thus be attributed to their more direct effects on rates of larval growth and development. Many of the taxa considered in this study exhibit extremely rapid larval growth (De Vries et al. 1990;Govoni et al. 2003;Luthy et al. 2005b;Sponaugle et al. 2005a), a strategy that is likely adapted to minimize the duration of the high mortality larval stage. Spawning in higher temperature waters will positively affect rates of larval growth and development, assuming food is not limiting (Houde 1989;Pepin 1991). ...
... At the same time, it is important to recognize the limitations of the correlational approach with respect to addressing the critical questions concerning patterns of the movement and recruitment in pelagic species. Ongoing analyses of these collections with a focus on the feeding ecology (Llopiz and Cowen in review) and growth rates (Sponaugle et al. 2005a) of larvae are better suited to exploring the mechanisms that underlie recruitment variability. ...
... No sailfish larvae from this collection were aged. Alternatively a total of 66 sailfish larvae from other collections in stage I-IV had previously been aged using established techniques (Luthy et al. 2005b, Sponaugle et al. 2005a). To validate the age of first increment formation, the otoliths of further set of 8 yolk-sac sailfish were measured, and where possible, aged. ...
The objective of this dissertation was to examine sailfish ( Istiophorus platypterus) and blue marlin (Makaira nigricans ) spawning in the Straits of Florida, with a specific focus on (1) the physical and biological characteristics of the spawning environment, and (2) the role of the region within the broader spawning patterns of these two species. In order to accomplish these objectives, two years of monthly ichthyoplankton collections and physical measurements across the Straits of Florida were combined with a finer-scale Lagrangian study. Additionally, a molecular species-identification methodology was developed that was both high-throughput and suitable for use with a broad taxonomic range of species.An initial analysis considered the diversity, assemblages and associated habitat of the larvae of large and medium size pelagic species. In total 36 species and 14,295 individuals were collected during this study, with the highest diversity occurring during the summer, and in the western frontal region of the Florida Current. Sailfish were included in an assemblage with Auxis rochei, A. thazard and Euthynnus alleterattus, all species found in highest abundance during the summer along the western edge of the Straits of Florida. Blue marlin grouped most closely with Thunnus atlanticus, Ruvettus pretiosus and Lampris guttatus, all summer spawners, whose larvae tended to occur further offshore. The primary environmental factors associated with these assemblages were SST (highest summer-early fall), day-length (highest early summer), thermocline depth (shallowest on the Florida side) and fluorescence (highest on the Florida side).A Lagrangian sampling effort was then used to more specifically evaluate the role of frontal zones in sailfish spawning. The results of this sampling indicated that the highest levels of sailfish spawning occurred in a frontal zone associated with the formation of a submesoscale frontal eddy. This spawning resulted in the first-feeding larvae occupying an area rich in prey items. Given the small spatial-scale of the front, and the distribution of the eggs of adult prey items, the results of this work would suggest that sailfish are actively targeting features for spawning that are favorable to the growth and survival of their larvae.Finally the relative importance of the Straits of Florida as a spawning ground was evaluated by calculating the annual egg production of both sailfish and blue marlin within this region. In total it was estimated that 2.1% of western Atlantic sailfish spawning and 1.6% of Atlantic wide blue marlin spawning occurs in the SF. Pop-up satellite tags deployed on sailfish at the start of the spawning season revealed their short residency times in the SF, suggesting that a large (≈10%) transient portion of the sailfish population is responsible for the SF egg production. These results indicate that the SF is a migratory bottleneck for sailfish.In conclusion the results of this study indicate that a hierarchy of physical and biological processes influence the distribution of billfish spawning in space and time. The results provide insights into the movement patterns and life history strategies of these species, and ultimately may aid in the development of the spatially explicit ecosystem based management approaches that are currently being advocated.
... The feeding habits of the youngest individuals, including the first-feeding stage, and any variability with time, space and prey availability, are yet to be described. However, it is clear from previous work that larval istiophorids are piscivorous, with individuals as small as 6 mm standard length consuming other fish larvae, presumably to meet the demands of their characteristically fast growth ( Luthy et al. 2005b, Sponaugle et al. 2005). ...
... Such an effect could be large since the annual egg Without linking growth and feeding, only the potential for growth effects can be noted, but direct relationships have been shown for piscivorous Japanese Spanish mackerel larvae (Shoji & Tanaka 2006). Additionally, swordfish Xiphias gladius larvae exhibit a distinct increase in linear growth rates once piscivory begins ( , and for istiophorids, the exponential growth of blue marlin and sailfish larvae ( Luthy et al. 2005b, Sponaugle et al. 2005) is much faster at later, piscivorous lengths. ...
... This suggested the potential for growth-limiting levels of available larval fish prey. However, despite substantial growth variability in blue marlin larvae (Sponaugle et al. 2005), a link to prey availability has yet to be established. ...
The processes influencing larval fish survival in the low-latitude open ocean are poorly understood, especially with regard to feeding. As part of a large-scale study that included two years of monthly sampling in the Straits of Florida (SOF), the objectives of this dissertation were to elucidate the larval fish feeding behaviors and strategies of 1) istiophorid billfishes, 2) tunas, and 3) coral reef fishes, while also 4) characterizing the feeding environment, synthesizing the dominant trophic pathways to fish larvae, and reviewing the literature for evidence of latitudinal distinctions in larval fish trophodynamics. Larval billfishes exhibited highly selective feeding, and their diets were numerically dominated (90%) by two genera of crustaceans, Farranula copepods and Evadne cladocerans. These prey were consumed throughout early larval ontogeny, from first-feeding through piscivorous lengths (> 5 mm), until piscivory became exclusive near 12 mm. High feeding incidence (0.94) and rapid digestion (~3.5 hrs) suggests frequent and successful feeding by billfish larvae. For tunas, nearly all larvae examined (>98%) contained prey. Thunnus spp. exhibited a mixed diet, while skipjack, little tunny, and Auxis spp. nearly exclusively consumed appendicularians. All four tuna taxa co-occurred in the western SOF where prey was more abundant, while in the central and eastern SOF (where prey availability was lower), only Thunnus spp. and skipjack were present. Additionally, these two taxa exhibited significantly different vertical distributions. Estimates of predatory impact indicated the potential for depletion of resources in the absence of the spatial and dietary niches of larval tunas. Coral reef fish families examined included Serranidae, Lutjanidae, Mullidae, Pomacentridae, Labridae, Scaridae, and Acanthuridae. Feeding incidences were high (0.94 to 1.0) for all taxa except scarids (0.04), and diets were narrow and predator-specific. Cluster analysis yielded clear groupings based on the selective feeding exhibited by the taxa, while within taxa, canonical correspondence analysis illustrated the change in diet with a variety of variables. The physical and biological environment varied markedly across the SOF, largely influenced by the Florida Current. Characteristics examined included thermocline depth, fluorescence, and abundances of total plankton and copepod nauplii. The feeding ecologies of the 21 taxa of fish larvae in this work were synthesized into qualitative and quantitative webs that illustrate the variable trophodynamic strategies of larvae in the SOF and the levels of community reliance upon zooplankton prey types. A review of 170 investigations on larval fish feeding revealed notable distinctions between high- and low-latitude regions, highlighting the substantial variability across environments in the role of larval fishes within the planktonic food web.
... The early life history of billfishes is characterized by exponential larval growth, a highly selective diet, and an early transition from invertebrate to fish prey (Govoni et al. 2003;Luthy et al. 2005b;Sponaugle et al. 2005;Llopiz and Cowen 2008). These characteristics reflect a strong adaptation to a pelagic existence, particularly in the relatively oligotrophic, warm waters of the tropics and subtropics where larvae must find and capture prey at a high rate to sustain fast growth. ...
... These characteristics reflect a strong adaptation to a pelagic existence, particularly in the relatively oligotrophic, warm waters of the tropics and subtropics where larvae must find and capture prey at a high rate to sustain fast growth. There is some indication that growth rates of Atlantic blue marlin larvae are higher in some semi-enclosed basins such as Exuma Sound (Bahamas), relative to more oceanic environments such as the Straits of Florida (SOF), but it is not known whether prey abundance, composition, or other oceanographic conditions underlie this differential growth (Sponaugle et al. 2005). ...
... Further, otolith increment widths can be used to compare the daily growth. These techniques have been used previously to estimate larval growth for both blue marlin and sailfish from the Bahamas (Sponaugle et al. 2005) and the SOF (Luthy et al. 2005b). ...
Atlantic blue marlin (Makaira nigricans) and sailfish (Istiophorus platypterus) larvae were collected from 10monthly cruises (June–October 2003 and 2004) across the Straits of Florida to test (1) whether
growth differed between the more productive western region near the Florida shelf, and the less productive eastern region
toward the Bahamas, and (2) whether growth was related to prey consumption. Examination of larval sagittal otoliths revealed
that instantaneous growth and daily growth during the first 2–3weeks of life did not vary significantly between the two regions
for either species. However, recent growth during the last two full days prior to collection was greater in the west for blue
marlin larvae. Recent growth of blue marlin larvae<9mm SL (primarily zooplanktivorous) was significantly related to prey
composition (faster growth when higher proportions of Farranula copepods were consumed). Western larvae grew faster and had higher proportions of Farranula in their guts. Trends for sailfish larvae were not significant. In both species, comparison of early growth between<9 and≥9mm
SL size groups indicated that growth trajectories diverged around 5–8mm SL, the time when billfish larvae become capable
of piscivory. Significantly faster growth of larger (older) larvae suggests that mortality was selective for fast growers
and that the transition to piscivory may be a critical point in the early life of billfish.
... Age and growth of striped marlin and size in other billfish (Prince et al., 1991;Luthy et al., 2005;Sponaugle et al., 2005), and in species where daily periodicity has been validated (Campana and Neilson, 1985;Kayama et al., 2007). Using the same methods employed in this investigation, Speare (2003) reported an underestimate of daily age in an oxytetracyline-injected and recaptured black marlin. ...
... However, the growth rate of striped marlin at age 1 (1.5 mm d -1 ) was identical to that of blue marlin at the same age (Prince et al., 1991). Growth rates between 1 and 6 mm d -1 are common for pelagic fish during the first few months of life (Uchiyama et al., 1986;Megalofonou et al., 1995;Luthy et al., 2005;Sponaugle et al., 2005). Unlike most pelagic fish, however, striped marlin maintained an accelerated rate of growth in body length of 1.5-3.1 mm d -1 after 6 months. ...
Kopf, R. K., Davie, P. S., Bromhead, D., and Pepperell, J. G. 2011. Age and growth of striped marlin (Kajikia audax) in the Southwest Pacific Ocean. – ICES Journal of Marine Science, 68: 1884–1895.
This study describes the first validated model of age and growth developed for striped marlin (Kajikia audax). Daily periodicity of otolith microincrements was corroborated by back-calculated hatch dates that matched the known spawning
season in the Southwest Pacific Ocean (SWPO). Yearly annulus formation in fin-spine sections was corroborated by daily otolith
microincrements and by a marginal increment analysis. Ages of females ranged from 140 d to 8.5 years in fish between 990 mm
and 2872 mm lower-jaw fork length (LJFL), and ages of males from 130 d to 7.0 years in fish between 1120 mm and 2540 mm LJFL.
Sex-specific differences in growth were significant, with females growing to a larger asymptotic size and greater age than
males. An instantaneous growth rate of 3.1 mm d–1 at 6 months and an estimated length of 1422–1674 mm LJFL by age 1 year makes this species among the fastest growing bony
fish. Implications of these findings are discussed in relation to commercial longline and recreational fisheries management
of striped marlin in the SWPO and in relation to the biology of pelagic fish growth.
... Further, pelagic larvae from broad oceanic areas have been reported to accumulate within frontal zones (Richards et al., 1993;Bakun, 2006), making it difficult to determine where individuals spend the majority of their lives and therefore, in which feature(s) most of their early growth occurs. Estimated growth of sailfish in the Gulf (g= 0.113 to 0.127) varied temporally and rates were comparable to or slightly slower than those reported for sailfish in the Straits of Florida (g= 0.130 to 0.146; Luthy et al., 2005;Richardson, 2007;Richardson et al., 2009a) and blue marlin from the Bahamas (g= 0.098 to 0.125; Serafy et al., 2003;Sponaugle et al., 2005) and the Straits of Florida (g= 0.089 to 0.114; Sponaugle et al., 2005;Richardson, 2007). Observed differences in growth among studies are minor and similarities are not unexpected because the timing of collections and environmental conditions between the regions were comparable. ...
... Further, pelagic larvae from broad oceanic areas have been reported to accumulate within frontal zones (Richards et al., 1993;Bakun, 2006), making it difficult to determine where individuals spend the majority of their lives and therefore, in which feature(s) most of their early growth occurs. Estimated growth of sailfish in the Gulf (g= 0.113 to 0.127) varied temporally and rates were comparable to or slightly slower than those reported for sailfish in the Straits of Florida (g= 0.130 to 0.146; Luthy et al., 2005;Richardson, 2007;Richardson et al., 2009a) and blue marlin from the Bahamas (g= 0.098 to 0.125; Serafy et al., 2003;Sponaugle et al., 2005) and the Straits of Florida (g= 0.089 to 0.114; Sponaugle et al., 2005;Richardson, 2007). Observed differences in growth among studies are minor and similarities are not unexpected because the timing of collections and environmental conditions between the regions were comparable. ...
Ichthyoplankton surveys were conducted in shelf and slope waters of the northern Gulf of Mexico during the months of May-September in 2005 and 2006 to investigate the potential role of this region as spawning and nursery habitat of sailfish (Istiophorus platypterus). During the two-year study, 2426 sailfish larvae were collected, ranging in size from 2.0 to 24.3 mm standard length. Mean density for all neuston net collections (n=288) combined was 1.5 sailfish per 1000 m2, and maximum density was observed within frontal features created by hydrodynamic convergence (2.3 sailfish per 1000 m2). Sagittalotoliths were extracted from 1330 larvae, and otolith microstructure analysis indicated that the sailfish ranged in age from 4 to 24 days after hatching (mean=10.5 d, standard de-viation [SD]=3.2 d). Instantaneous growth coefficients (g) among survey periods (n=5) ranged from 0.113 to 0.127, and growth peaked during July 2005 collections when density within frontal features was highest. Daily instantaneous mortality rates (Z) ranged from 0.228 to 0.381, and Z was indexed to instantaneous weight-specific growth (G) to assess stage-specific production potential of larval cohorts. Ratios of G to Z were greater than 1.0 for all but one cohort examined, indicating that cohorts were gaining biomass during the majority of months investigated. Stage-specific production potential, in combination with catch rates and densities of larvae, indicates that the Gulf of Mexico likely represents important spawning and nursery habitat for sailfish.
... The feeding habits of the youngest individuals, including the first-feeding stage, and any variability with time, space and prey availability, are yet to be described. However, it is clear from previous work that larval istiophorids are piscivorous, with individuals as small as 6 mm standard length consuming other fish larvae, presumably to meet the demands of their characteristically fast growth (Sponaugle et al. 2005). ...
... Of the sailfish larvae collected at least 30 min after sunrise, the smallest (2 to 3 mm BL) and largest (8 to 21 mm BL) subgroups had lower feeding incidences (0.79 and 0.85, respectively) than the 0.99 value for the intermediate 3 to 8 mm BL class. Nearly all blue marlin (0.97) larvae contained food, including the 2 to 3 mm BL class, which includes first-feeding larvae as indicated by comparison with identified yolksac larvae and the 2 to 3 d ages of larvae this size (Sponaugle et al. 2005). Of 6159 prey items extracted from all larvae, the copepod Farranula and the cladoceran Evadne accounted for nearly 90% (Table 2). ...
The oligotrophic open ocean of low latitudes is larval fish habitat for a diversity of resi- dent and migratory species. It is hypothesized that these waters, relative to coastal regions, yield reduced predation mortality, but little is known regarding the feeding and feeding environment of these larvae and the extent to which a nutritional tradeoff may exist, whereby lower predation mor- tality is accompanied by poor feeding conditions. Monthly sampling of larval billfishes (Istiophoridae) across the Straits of Florida over 2 yr allowed for an investigation of the temporal, spatial and ontoge- netic variability in the feeding of sailfish Istiophorus platypterus and blue marlin Makaira nigricans. Consumed prey were numerically dominated (90%) by 2 crustaceans: a copepod (Farranula; mainly F. gracilis) and a cladoceran (Evadne; mainly E. tergestina), with relative proportions displaying marked spatial variability. These prey were consumed throughout early larval ontogeny, from first feeding through piscivorous lengths (>5 mm), until piscivory became exclusive near 12 mm. High daytime feeding incidence (0.94) and rapid digestion (~3.5 h) support generally frequent and success- ful feeding by billfish larvae. Prey selectivity was illustrated by preference for Evadne over Farranula and a near absence of calanoid copepods from diets despite high environmental concentrations. Gut fullness exhibited a distinct sunset peak and also differed significantly with larval length and year, but not with season or location. A gut evacuation rate was used to estimate a daily ration of 29 to 75% of gut-free body weight, varying greatly with model selection but also with daylight length. Although potentially unique to the Straits of Florida and larval billfishes, these results contradict the general presumption that the subtropical open ocean is nutritionally constraining for larval fish.
... A total of 121 sailfish and 187 blue marlin larvae were aged using the protocol outlined in Sponaugle et al. (2005) and Luthy et al. (2005b) [7] ...
... The implementation of the larval production method was a four-step procedure: (i) the age of each larva was estimated using a regression of age on length, (ii) an apparent mortality rate (z) (incorporates mortality and increasing net avoidance with age; Houde et al., 1979) was calculated using a regression of abundance-at-age on age, (iii) for each cruise daily egg production was calculated based on the age-specific flux of larvae across the transect and the apparent mortality rate, and (iv) a non-linear regression of daily egg production versus ordinal day of year was used to calculate P a (Fig. 1, Table 1). As with previous work with billfish larvae (Luthy et al., 2005b;Sponaugle et al., 2005), an exponential growth model was used. In contrast to those studies, length was treated as the dependent variable (equation 1, Table 1), though for consistency, and to aid interpretation, the instantaneous daily growth rate (G L ) and length at hatch (L 0 ) values are reported here, rather than the regression coefficients [i.e., 1 ⁄ G L and 1 ⁄ G L * ln(L 0 )]. ...
Much of the uncertainty in managing highly migratory pelagic species results from the scarcity of fisheries-independent data relevant to determining long-term trends in abundance, migratory movements, and the relative importance of different spawning grounds. To address these issues, we used an ichthyoplankton-based method to quantify the overall level of spawning of sailfish (Istiophorus platypterus) and blue marlin (Makaira nigricans) in the Straits of Florida (SF). We estimated that during the 2 years (2003–2004) of the study, 4.60 × 1011 sailfish eggs and 4.49 × 1011 blue marlin eggs were produced on an annual basis in this region. These egg production values, when combined with estimates of annual fecundity for each species and the most recent stock assessment estimate of total biomass, indicate that about 2.1% of Western Atlantic sailfish spawning and 1.6% of Atlantic-wide blue marlin spawning occurs in the SF. Additionally, pop-up satellite tags deployed on sailfish at the start of the spawning season revealed their short residency times in the SF, suggesting that a large (≈13%) transient portion of the sailfish population is responsible for the SF egg production. Overall, this study provides a critically needed fisheries-independent method of quantifying spatial and temporal trends in the abundance of highly migratory species. The application of this methodology in the SF indicated that above-average levels of sailfish and blue marlin spawning occur in this area and, possibly more importantly, that the SF is a migratory bottleneck for these species.
... An instantaneous growth rate of 0.0976 [16] enabled calculated age estimates to be assigned to each larva. Sponaugle et al. [17], building on Serafy et al.'s collections, but dissecting out and enumerating all otoliths, determined various instantaneous growth rates by location, year and larval age. One of the higher rates (0.1280) was used to bracket the ages of larvae in this study. ...
... A -Size classes (midpoints) for istiophorid larvae captured by towed plankton nets off the Ribbon Reefs. B -Calculated ages for the larvae based on instantaneous growth rates for blue marlin of 0.0976 (lower curve after [16]) and 0.1280 (upper curve after [17]). Dotted lines indicate the median size and corresponding calculated ages. ...
The black marlin (Istiompax indica) is one of the largest bony fishes in the world with females capable of reaching a mass of over 700 kg. This highly migratory predator occurs in the tropical regions of the Pacific and Indian Oceans, and is the target of regional recreational and commercial fisheries. Through the sampling of ichthyoplankton and ovaries we provide evidence that the relatively high seasonal abundance of black marlin off the Great Barrier Reef is, in fact, a spawning aggregation. Furthermore, through the tracking of individual black marlin via satellite popup tags, we document the dispersal of adult black marlin away from the spawning aggregation, thereby identifying the catchment area for this spawning stock. Although tag shedding is an issue when studying billfish, we tentatively identify the catchment area for this stock of black marlin to extend throughout the Coral Sea, including the waters of Papua New Guinea, the Solomon Islands, Micronesia, New Caledonia, Kiribati, Vanuatu, Fiji, Tuvalu and Nauru.
... The mean instantaneous growth coefficient K was 0.105, comparable to that of larval blue marlin (Makaira nigricans, K = 0.085-0.128) from the Bahamas and Straits of Florida [79] and to larval sailfish (Istiophorus platypterus, K = 0.144) from the nGoM [80]. In contrast, the larval growth coefficient of western Atlantic snappers such as schoolmaster (Lutjanus apodus, K = 0.047) and mutton snapper (Lutjanus analis, K = 0.044) are considerably lower [81]. ...
The invasion of the western Atlantic by the Indo-Pacific lionfish (Pterois volitans/miles) is a serious threat to the ecological stability of the region. The early life history of the lionfish remains poorly understood despite the important role that larval supply plays reef fish population dynamics. In this study, we characterized patterns in the horizontal and vertical distributions of larval lionfish collected in the western Caribbean, US Caribbean, and the Gulf of Mexico from 19 ichthyoplankton surveys conducted from 2009-2016. Using generalized additive models (GAMs), we assessed the relative effects of spatiotemporal and environmental variation on the distribution of lionfish larvae. We also examined otoliths to determine larval ages and report the first larval growth rate estimates for this species. Lionfish larvae were present at 7.8% of all stations sampled and our model suggests that lionfish presence is related to sea surface temperature and the lunar cycle. Year and location also strongly affected the larval distribution, likely reflecting the ongoing expansion of the species during our sampling timeframe. Much of the variation in larval lionfish presence remained unexplained , and future studies should incorporate additional environmental factors to improve model predictions. This study improves our understanding of the lionfish life cycle and accentuates the need for further research into the early life history of this invasive species. The design and implementation of effective long-term lionfish control mechanisms will require an understanding of their entire life history.
... Abundance estimates from early life surveys also represent important fishery independent indices that can be used to predict spawning biomass and the recruitment potential of tuna populations (Ingram et al., 2010). As a variety of biological, physical and chemical factors influence growth and survival during early life stages of pelagic fishes, recruitment success may be linked to the oceanographic conditions of the water mass inhabited (Lang et al., 1994;Sponaugle et al., 2005;Wexler et al., 2007;Simms et al., 2010;. Therefore, density and occurrence data for tunas and other pelagic fish larvae are often combined with environmental data to determine the location of highly suitable habitats or nurseries (Rooker et al., 2013, Kitchens & Rooker, 2014. ...
Summer ichthyoplankton surveys were conducted in the northern Gulf of Mexico from 2007 to 2010 to characterize the distribution and abundance of tuna larvae. Larval assemblages of tunas were comprised of four genera: Thunnus, Auxis, Euthynnus, and Katsuwonus. Thunnus were the most abundant and four species were detected; T. atlanticus [blackfin tuna], T. obesus [bigeye tuna], T. albacares [yellowfin tuna], and T. thynnus [bluefin tuna]. Intra- and inter-annual variability in the distribution and abundance of Thunnus species were observed with higher densities in 2008 and 2009, with a decline in abundance observed in 2010. Distribution and abundance of Thunnus larvae were influenced by physical and chemical conditions of the water mass, notably sea surface temperature and salinity. Distinct species-specific habitat preferences were observed and the location of mesoscale oceanographic features influenced larval abundance with higher densities of T. atlanticus, T. obesus, and T. albacares near anticyclonic (warm core) regions and the Loop Current, while T. thynnus was observed in higher densities near cyclonic (cold core) regions. This study demonstrates that spatial and temporal variability in the location of mesoscale oceanographic features may be important to partitioning nursery habitat among Thunnus species.
... Several investigators report strongly variable growth rates in field collected larvae, even among those of very similar ages. This is assumed to be mainly induced by biotic and abiotic environmental variability, although a maternal condition effect has also been proposed (Aranda et al. 2013;Sponaugle et al. 2005;Uriarte et al. 2016a). Temperature affects vital rates which, in turn, influence growth and mortality rates (Chambers and Leggett 1987;Houde 1989). ...
Tunas show a wide variety of life history strategies, spatial distributions and migratory behaviors, yet they share a common trait of spawning only in tropical and sub-tropical regions. The warm-water tuna species generally show significant overlap between spawning and feeding grounds, and longer spawning seasons of several months to near year-round. In contrast, the cool-water bluefin tunas migrate long distances between feeding and spawning grounds, and may spawn over periods as short as 2 months. Here, we examine the spatial distributions of tuna larvae in the world’s oceans, and examine interspecific differences in the light of adult behaviors and larval ecology. We discuss the links between larval tuna and their oceanographic environments and relate these to current knowledge of larval growth, feeding and trophodynamics, with a focus on the better-studied bluefin tunas. We show that larval tunas have moderate to fast growth rates and selective feeding habits, and thus appear to be adapted for survival in warm, oligotrophic seas. We also examine the challenges of sustainably managing species which migrate across multiple management boundaries to reach spatio-temporally restricted spawning grounds and discuss the previous and future anthropogenic impacts on tuna spawning areas.
... Há também a formação de uma marca de pré-nascimento ("pre-birth ring"), que pode ser facilmente distinguida das demais e cuja formação tem sido relacionada à mudança nutricional embrionária (Casey et al., 1985;Ribot-Carballal et al., 2005). Em teleósteos, a análise do crescimento nas fases larvais e juvenis tem sido realizada através da análise da microestrutura dos otólitos (anéis diários) e associados às influências das variáveis oceanográficas e disponibilidade de alimento (Brothers et al., 1983;Radtkle, 1983;De Vries, 1990;Jenkins & Davis, 1990;Berkeley et al., 2004;Sponaugle et al., 2005;Takasuka & Aoki, 2006). ...
... Early growth, expressed as the daily increase in the body mass of eggs, larvae, and juveniles, was modeled as an exponential function with a constant daily rate of increase in body mass (K ELH ). This pattern is characteristic of early life history stage growth of billfishes (e.g., Sponaugle et al., 2005) and was parameterized using the expected early stage duration D ELH and the expected weight of an age-0 fish (W(0) = 8792.7 g) under the von Bertalanffy growth curve (Fig. 1a). The expected body mass (wet weight) at an age of d days (W ELH (d)) was computed from the initial egg weight to the ending age-0 weight as ...
The resilience of a stock-recruitment relationship is a key characteristic for modeling the population dynamics of living marine resources. Steepness determines the expected resiliency of a fish stock to harvest and is fundamentally important for the estimation of biological reference points such as maximum sustainable yield. Stock-recruitment steepness was the primary uncertainty for the determination of stock status and biological reference points in recent stock assessments of Western and Central North Pacific striped marlin (Kajikia audax). We therefore applied the method of Mangel et al. to estimate probable values of steepness for striped marlin using new information on the mean batch fecundity, spawning frequency, and spawning season duration under an assumption of Beverton–Holt stock-recruitment dynamics. Results indicated that the median steepness was 0.87 with an 80% probable range of (0.38, 0.98). It is very likely that North Pacific striped marlin is highly resilient to reductions in spawning potential. Variation in reproductive and life history parameters had an important influence on the distribution of steepness. Sensitivity analyses showed that steepness was most sensitive to body girth, mean egg weight, and most importantly, early life history stage survival. Sensitivity analyses also confirmed that the effects of changes in life history parameters on steepness were consistent with expected increases or decreases in reproductive output due to changes in body weight or fecundity. Our approach can be applied to pelagic fish species to directly assess the probable distribution of stock-recruitment resiliency when sufficient information on reproductive ecology and life history parameters is available.
... Sphyraena barracuda caught in the wet season included larval fishes in their diets beginning at 8 mm SL and were exclusively piscivorous by 12 mm SL. As a result, larval S. barracuda growth in the wet season was rapid, nearing that of larval blue marlin (Makaira nigricans) and sailfish (Istiophorus platypterus) in the SOF (Sponaugle et al. 2005, which begin feeding on larval fishes at smaller sizes (5 mm SL; Llopiz and Cowen 2008). In contrast, dry season larval growth in S. barracuda was slower and similar to many marine fish larvae including tunas in the genus Thunnus that, like young S. barracuda larvae, feed largely on copepods and copepod nauplii . ...
The great barracuda (Sphyraena barracuda) is an important predator in mangrove, seagrass, and reef environments of south Florida and the Caribbean. Despite this very little is known about their early life history or population replenishment. In order to determine temporal patterns of larval supply to nearshore waters, a series of light traps was deployed over shal-low coral reefs along the upper Florida Keys every other night for six months from May-October of 2002 and 2003. Traps were also deployed monthly during peak settlement times throughout winter and spring (November-April) of 2003 and 2004. Larval growth rates and the pelagic larval duration (PLD) of barracuda were determined through otolith analysis and compared to concurrently collected hydrographic data. Barracuda appeared in the traps only during summer months, with two primary lunar-cyclic pulses occurring between the third quarter and new moons in late June-early July and late August-early September. Water temperature explained most of the variability in early larval growth, however, patterns were unclear for later larval growth. Additional data are needed to augment the four seasonal cohorts and verify these preliminary results. Crecimiento Larval, Duración, y Patrones de Oferta de Sphyraena barracuda La barracuda (Sphyraena barracuda) es un predador importante en los manglares, pastos marinos, y arrecifes de coral del sur de la Florida y del Caribe. A pesar de esto, se sabe muy poco con respecto a su historia de vida temprana y al repo-blamiento de sus poblaciones. Con el objeto de determinar patrones temporales de oferta de larvas a las aguas costeras, se usaron una serie de trampas de luz en arrecifes someros de los cayos superiores de la Florida cada noche de por medio por seis meses desde mayo hasta octubre durante el 2002 y el 2003. También se usaron trampas mensuales durante la época pico del reclutamiento durante el invierno y la primavera (noviembre a abril) del 2003 y el 2004. Así mismo, se determinó la tasa de crecimiento larval y la duración pelágica larval (DPL) de la barracuda con el análisis de otolitos y se compararon con datos hidrográficos recaudados concurrentemente. Solo se encontraron larvas de barracuda en las trampas durante los meses de verano, con pulsos relacionados al ciclo lunar, bimodales, y picos de oferta entre el cuarto menguante y la luna nueva al final de junio–principios de julio y al final de agosto–principios de septiembre. La mayoría de la variabilidad en el crecimiento larval y el DPL se pueden explicar usando la temperatura del agua. Sin embargo, factores hidrográficos tales como la presencia temporal de eddies tienen una influencia en el transporte de larvas y también pueden contribuir a varia-ciones adicionales en las características de la historia de vida temprana.
... Additionally, annual variation in growth was observed for three consecutive Julys (p = 0.008) indicating both seasonal and annual variation in larval growth rates in the northern Gulf of Mexico. The instantaneous growth rates observed here are comparable to that reported for sailfish in the Straits of Florida (0.137, Luthy et al. 2005) and larval blue marlin, Makaira nigricans, in the Straits of Florida and Exuma Sound, Bahamas (0.086 -0.128, Sponaugle et al. 2005). Similar to other studies on pelagic fishes (Wexler et al. 2007), this study showed that growth of sailfish varies both seasonally and annually. ...
Sailfish, Istiophorus platypterus, are commonly taken by anglers in the Gulf of Mexico and larvae are frequently reported in this region, indicating the Gulf's potential role as spawning and/or nursery ground. Ichthyoplankton surveys were conducted in the northern Gulf of Mexico in waters off Texas and Louisiana (27 – 28° N 89 -94° W) from 2005 – 2007 to collect larvae for age and growth investigations. During the three year survey, over 2,000 sailfish larvae were collected, and sagittal otoliths were extracted from 669 sailfish larvae, ranging in size from 2.0-24.3 mm standard length (SL). Otolith microstructure analysis indicated that sail-fish ages ranged between 3 and 18 days, and hatch-date distributions indicated fish were from early May to mid September spawn-ing events. Instantaneous growth coefficients ranged from 0.132 to 0.158 with an overall rate of 0.144. Growth rates varied by sea-son and year, indicating temporal changes in environmental conditions may influence the survival and recruitment success of sailfish in this region.
... The growth of the early life stages of blue marlin is extremely rapid with egg development times of approximately 1 day. Large variations in larval growth have been found between regions (Sponaugle et al., 2005). These differences were unrelated to water temperature, and it was speculated that they could have been driven by differences in larval prey field between regions or maternal effects if the size-structure of the spawning fish differed between regions. ...
This paper reviews the current knowledge on the ecology of widely distributed pelagic fish stocks in the North Atlantic basin with emphasis on their role in the food web and the factors determining their relationship with the environment. We consider herring (Clupea harengus), mackerel (Scomber scombrus), capelin (Mallotus villosus), blue whiting (Micromesistius poutassou), and horse mackerel (Trachurus trachurus), which have distributions extending
beyond the continental shelf and predominantly occur on both sides of the North Atlantic. We also include albacore (Thunnus alalunga), bluefin tuna (Thunnus thynnus), swordfish (Xiphias gladius), and blue marlin (Makaira nigricans), which, by contrast, show large-scale migrations at the basin scale. We focus on the links between life history processes and the environment, horizontal and vertical distribution, spatial structure and trophic role. Many of these species carry out extensive migrations from spawning grounds to nursery and feeding areas. Large oceanographic features such as the North Atlantic subpolar gyre play an important role in determining spatial distributions and driving variations in stock size. Given the large biomasses of especially the smaller species considered here, these stocks can exert significant top-down pressures on the food web and are important in supporting higher trophic levels. The review reveals commonalities and differences between the ecology of widely distributed pelagic fish in the NE and NW Atlantic basins, identifies knowledge gaps and modelling needs that the EURO-BASIN project attempts to address.
... The growth of the early life stages of blue marlin is extremely rapid with egg development times of approximately 1 day. Large variations in larval growth have been found between regions (Sponaugle et al., 2005). These differences were unrelated to water temperature, and it was speculated that they could have been driven by differences in larval prey field between regions or maternal effects if the size-structure of the spawning fish differed between regions. ...
This paper reviews the current knowledge on the ecology of widely distributed pelagic fish stocks in the North Atlantic basin with emphasis on their role in the food web and the factors determining their relationship with the environment. We consider herring (Clupea harengus), mackerel (Scomber scombrus), capelin (Mallotus villosus), blue whiting (Micromesistius poutassou), and horse mackerel (Trachurus trachu-rus), which have distributions extending beyond the continental shelf and predominantly occur on both sides of the North Atlantic. We also include albacore (Thunnus alalunga), bluefin tuna (Thunnus thynnus), swordfish (Xiphias gladius), and blue marlin (Makaira nigricans), which, by contrast, show large-scale migrations at the basin scale. We focus on the links between life history processes and the environment, horizontal and vertical distribution, spatial structure and trophic role. Many of these species carry out extensive migrations from spawning grounds to nursery and feeding areas. Large oceanographic features such as the North Atlantic subpolar gyre play an important role in determining spatial distributions and driving variations in stock size. Given the large biomasses of especially the smaller species considered here, these stocks can exert significant top-down pressures on the food web and are important in supporting higher trophic levels. The review reveals commonalities and differences between the ecology of widely distributed pelagic fish in the NE and NW Atlantic basins, identifies knowledge gaps and modelling needs that the EURO-BASIN project attempts to address.
... Similarly, average growth rates of dolphinfish in the Atlantic Ocean were 3.8 mm d 21 for fish less than 1-year old (Schwenke and Buckel, 2008). Rapid growth rates are common for pelagic fish during the first few months of life Sponaugle et al., 2005;Tanaka et al., 2007). Fish growth rates, particularly in larval and juvenile stages, have been suggested to increase with increasing water temperature, latitude, oxygen uptake, and food consumption (Pauly, 1979;Houde 1989). ...
Zischke, M. T., Griffiths, S. P., and Tibbetts, I. R. 2013. Rapid growth of wahoo (Acanthocybium solandri) in the Coral Sea, based on length-at-age estimates using annual and daily increments on sagittal otoliths. – ICES Journal
of Marine Science, 70: 1128–1139.
The wahoo (Acanthocybium solandri) is an economically important species incidentally caught in oceanic fisheries targeting tuna and coastal fisheries targeting
mackerels. The age and growth of wahoo was examined using whole and sectioned otoliths from 395 fish (790–1770 mm LF) sampled from the Coral Sea. Growth increments were more reliably assigned on whole otoliths than sectioned otoliths. Edge
analyses revealed that growth increments were deposited annually, primarily between October and February. Furthermore, analysis
of presumed daily microincrements showed that ∼90% of fish had deposited the first “annual” growth increment by the 365th
day, thereby indirectly validating annual increment formation. Wahoo were aged at between 108 d and 7 years, with 76% of fish
being <2-year old. The specialized von Bertalanffy growth function provided the best fit to length-at-age data, with parameter
estimates (sexes combined) of L∞ = 1499 mm LF, K = 1.58 year−1, and t0 = −0.17 years. The growth performance index for wahoo in the Coral Sea (φ′ = 4.55) was one of the highest of all pelagic fish, with their growth and maximum size most similar to dolphinfish. This
study suggests that wahoo are one of the fastest growing teleosts and provides growth parameter estimates that may facilitate
future stock assessments and guide fisheries management.
... Atlantic marlins tend to exhibit solitary behavior; however, small aggregations of white marlin have been observed (Nakamura 1985). As with all istiophorids, the marlins likely exhibit extremely rapid growth rates in early life (Sponaugle et al. 2005), but the average size of an adult blue marlin (100–175 kg) is much larger than that of a white marlin (20–30 kg) (NMFS 2007). Also, sexually dimorphic growth is common to both species (though much more pronounced in blue marlin), with females growing larger than males (Nakamura 1985; Wilson et al. 1991; Arocha and Bárrios 2009). ...
... The differences found in otolith morphometry, relative growth and ring positions clearly evidenced there is a strong geographical variation in the growth pattern of the young of the year throughout the three areas occupied by Merluccius hubbsi, even on the Brazilian coast. Many studies have shown consistent growth differences among same fish species living in Season Autumn Spring different geographical locations and distributed over large areas (Denit and Sponaugle 2004;Kingsford and Hugles 2005;Sponaugle et al. 2005;Silva et al. 2008). Therefore, distinct oceanographically and biological processes can limit egg distribution and adult exchange among areas ensuring thus that groups present even greater phenotypic and/or genetic distinctions (Bergenius et al. 2006). ...
Morphology and morphometry of the sagittae otolith were studied in young of the year Argentine hake, Merluccius hubbsi in the Southeastern Atlantic. Geographical variation in the growth pattern of the young of the year Merluccius hubbsi was correlated with the differences found in otolith morphometry, relative growth, ring positions, as well as the formation
of a new ring. The otolith development of M. hubbsi throughout its area of distribution accompanies an increasing northward temperature gradient, resulting in bigger otoliths
and greater variability of ring position from northern to southern area. The canonical discriminate analysis showed that the
otolith length and height explained most of the variation of the first discriminant function. We found significant differences
in the discriminant scores between those samples from northern and southern area. As regards the Uruguayan coast and Southern
Brazil, age groups zero shared some similarity as well as differences in growth; environmental features explain these differences
but their effect on the adult fishes growth is still unknown.
KeywordsOtoliths–Young of the year–Morphometry–
Merluccius hubbsi
–Southeastern Atlantic
... Sphyraena barracuda caught in the wet season included larval fishes in their diets beginning at 8 mm SL and were exclusively piscivorous by 12 mm SL. As a result, larval S. barracuda growth in the wet season was rapid, nearing that of larval blue marlin (Makaira nigricans) and sailfish (Istiophorus platypterus) in the SOF (Sponaugle et al. 2005, which begin feeding on larval fishes at smaller sizes (5 mm SL; Llopiz and Cowen 2008). In contrast, dry season larval growth in S. barracuda was slower and similar to many marine fish larvae including tunas in the genus Thunnus that, like young S. barracuda larvae, feed largely on copepods and copepod nauplii . ...
The great barracuda (Sphyraena barracuda) is a widespread, ecologically and socioeconomically important coastal fish, yet very little is known about its larvae. We
examined spawning and larval ecology of Western Atlantic sphyraenids using monthly ichthyoplankton samples collected over
2years along a transect spanning the east–west axis of the Straits of Florida (SOF). Samples were dominated by the great
barracuda (92.8%) and sennets (Sphyraena borealis and Sphyraena picudilla; 6.6%). While larval sennets and S. barracuda displayed similar vertical distributions (majority in upper 25m), horizontal and temporal patterns of abundance suggested
a spatial and temporal species replacement between larval S. barracuda and sennets that tracks adult ecology. The diet of both taxa consisted largely of copepods, with inclusion of fish larvae
at 8mm SL, and in S. barracuda alone, a switch in the wet season to exclusive piscivory by 12mm SL (18days post-hatch). A lack of piscivory in S. barracuda larvae captured in the dry season corresponded to slower larval growth than in the wet season. Larval growth was also related
to size-at-hatch and larval age such that larvae that were larger at hatch or larger (older) at capture grew faster at earlier
ages, suggesting faster larval growth, and indirectly larger hatch size, conveys a survival advantage. Unlike larval growth,
instantaneous mortality rate did not differ with season, and no lunar cyclic patterns in spawning output were identified.
Our results provide insight into the pelagic phase of sphyraenids and highlight the importance of both diet and hatch size
to the growth and survival of fish larvae in low latitude oceanic environments.
... Larval encounter with other features can be positive: Cod larvae collected in the vicinity of a hydrographic front in the North Sea exhibited faster growth than larvae collected farther away (Munk 2007). On a larger spatial scale, Atlantic blue marlin larvae from two neighboring but distinct oceanographic areas-Exuma Sound, Bahamas, and the Straits of Florida-had different patterns of growth rates (faster in the Exuma Sound), although the underlying cause of this variation among water masses was unclear (Sponaugle et al. 2005a). In another example, larval anchovy in the southwest Atlantic off Brazil had increasing growth rates in upwelling areas whereas growth rates of larvae in areas with more stable water columns decreased over time (Castello and Castello 2003). ...
Information obtained from fish otoliths has been a critical component of fisheries management for decades. The nature of this information has changed over time as management goals and approaches have shifted. The earliest and still most pervasively used data are those of annual age and growth used to calculate the demographic rates of populations in single-species management strategies. Over time, the absence of simple stock-recruitment relationships has focused attention on the youngest stages, where otolith microstructure resolved on a daily basis has become a valuable tool. As management has transitioned to more ecosystem-based approaches, the need to understand ecological and oceanographic processes has been advanced through the analysis of daily otolith microstructure. Recent field examples illustrate how otolith microstructure data have been used to reveal environmental influences on larval growth, traits that lead to higher survivorship, mechanisms of larval transport, dynamics of dispersal and population connectivity, determinants of recruitment magnitude, carry-over processes between life stages, habitat-specific juvenile survival, and identification of natal sources. Daily otolith-derived data collected at an individual level are increasingly combined with data from other disciplines and incorporated into individual-based models, which in turn can form the building blocks of complex models of ecosystem dynamics. A mechanistic understanding of the ecology of young stages is particularly necessary in light of a rapidly changing ocean environment, as we need to be able to predict individual and population responses to perturbations. Otolith microstructure analysis is an important tool in our management arsenal, contributing to a broader understanding of the oceanographic and ecological processes underlying ecosystem dynamics.
In January 2016, historic levels of rainfall in the upper Mississippi River Basin prompted the earliest opening of the Bonnet Carré Spillway, a water control structure on the Mississippi River that diverts flood-stage river water through an alternate pathway (Lake Pontchartrain) into the northern Gulf of Mexico. This unprecedented winter opening of the spillway coincided with the spawning season and larval ingress period for Gulf Menhaden, a forage fish species that supports the largest commercial fishery in the region. Oceanographic observations and plankton samples were collected in the Mississippi Bight region shortly after the Bonnet Carré Spillway winter opening to examine the impacts on larval Gulf Menhaden feeding, growth and condition. Three distinct water masses were identified based on temperature, salinity, and particle scattering (proxy for turbidity) characteristics. Larval Gulf Menhaden with the highest growth rates and body condition were collected in a water mass defined by relatively high temperature and salinity and relatively low turbidity and zooplankton (prey) abundance. In contrast, larvae with the slowest growth rates and poor body condition were collected in a water mass with the highest zooplankton abundance, but also highest turbidity and lowest temperature and salinity. This water mass was nearest the diversion outflow and most impacted by the spillway opening. Our results indicate that the anomalous freshwater discharge event resulted in hydrographic conditions that diminished otherwise favorable larval fish foraging habitat with abundant zooplankton prey. These findings suggest that the recent trend of Bonnet Carré Spillway openings may result in negative consequences for larval fish survival and subsequent fishery recruitment.
Life on the ocean's surface connects worlds. From shallow waters to the deep sea, the open ocean to rivers and lakes, numerous terrestrial and marine species depend on the surface ecosystem and the organisms found therein. Organisms that live freely at the surface, termed "neuston," include keystone organisms like the golden seaweed Sargassum that makes up the Sargasso Sea, floating barnacles, snails, nudibranchs, and cnidarians. Many ecologically and economically important fish species live as or rely upon neuston. Species at the surface are not distributed uniformly; the ocean's surface harbors unique neustonic communities and ecoregions found at only certain latitudes and only in specific ocean basins. But the surface is also on the front line of climate change and pollution. Despite the diversity and importance of the ocean's surface in connecting disparate habitats, and the risks it faces, we know very little about neustonic life. This Essay will introduce you to the neuston, their connections to diverse habitats, the threats they face, and new opportunities for research and discovery at the air-sea interface.
Blue marlin, Makaira nigricans, are seasonal residents in pelagic waters of the northern Gulf of Mexico (nGOM) where they support an active catch-and-release and trophy recreational fishery. However, little is known about the biology of the species in the nGOM. We collected ovaries from 62 blue marlin (size range 253.4 – 351.3 cm LJFL) captured during fishing tournaments in the nGOM from 1999-2007 to examine their reproductive condition during the May through September resident period. Gonadosomatic Index was low during all months; mean values never exceeded 0.59 ± 0.07. Histological analysis found no females captured in the nGOM that were spawning capable, although several females captured in July 2006 and September 2007 had regressing ovaries with vitellogenic and/or hydrated oocytes undergoing atresia. Furthermore, a fish captured in June 2007 with early developing ovaries had a mass of hardened, hydrated oocytes interspersed throughout the ovary, suggesting a failed or incomplete spawning event dur-ing the 2006 season. While histological evidence suggests blue marlin do not spawn in the nGOM, we have collected blue marlin larvae < 7 d old along the western edge the Loop Current in the nGOM in July/August but not in other regions of the nGOM during the same months. Possibly, the larvae were spawned in the southern GOM or Caribbean Sea and transported to the nGOM by the Loop Current. The status of blue marlin spawning in the nGOM remains uncertain pending additional data collection.
This study describes the first validated model of age and growth developed for striped marlin (Kajikia audax). Daily periodicity of otolith microincrements was corroborated by back-calculated hatch dates that matched the known spawning season in the Southwest Pacific Ocean (SWPO). Yearly annulus formation in fin-spine sections was corroborated by daily otolith microincrements and by a marginal increment analysis. Ages of females ranged from 140 d to 8.5 years in fish between 990 mm and 2872 mm lower-jaw fork length (LJFL), and ages of males from 130 d to 7.0 years in fish between 1120 mm and 2540 mm LJFL. Sex-specific differences in growth were significant, with females growing to a larger asymptotic size and greater age than males. An instantaneous growth rate of 3.1 mm d – 1 at 6 months and an estimated length of 1422 – 1674 mm LJFL by age 1 year makes this species among the fastest growing bony fish. Implications of these findings are discussed in relation to commercial longline and recreational fisheries management of striped marlin in the SWPO and in relation to the biology of pelagic fish growth.
Of the Atlantic istiophorid billfishes, larval age-size relationships and growth rates have been examined only for blue marlin (Makaira nigricans). Using otolith microincrement analysis, we describe age-length and age- weight relationships for larval sailfish (Istiophorus platypterus) collected from the Straits of Florida. Sagittae and lapilli were dissected from 70 larvae ranging from 2.8 to 15.2 mm in (notochord or standard) length. Comparisons between otolith images obtained by light microscopy and scanning electron microscopy indicated that increment widths were well within the resolving power of light microscopy. Indirect evidence and published descriptions of larval blue marlin otoliths suggest daily increment deposition. Estimated ages of specimens ranged from 3 to 18 days. Length data were fitted to age estimates with an exponential model (R2 = 0.85). The estimated size-at-hatch for sailfish was 1.96 mm notochord length, and the daily instantaneous growth coefficient was 0.14. A power curve with exponent 3.05 described the length-dry weight relationship for sailfish. The instantaneous growth coefficient for an exponential regression of dry weight, converted from length, versus estimated age was 0.41. Growth in the length of sailfish larvae from the Straits of Florida was very similar to that described for blue marlin larvae from Exuma Sound, Bahamas.
In order to test the temporal stability within and the reproducibility of larval fish assemblages between years, the larval
fish assemblage at Helgoland Roads, North Sea (NE Atlantic) was quantitatively sampled almost daily from January 2003 to December
2005. The survey resulted in a total of 462 samples containing 50,632 larval fish of at least 42 taxa. In winter the larval
fish assemblage was mainly dominated by larvae emerging from demersal eggs. This changed gradually to larvae hatching from
pelagic eggs. Larvae from pelagic eggs dominated the ichthyoplankton assemblage in summer. A remarkably stable seasonality
in terms of dominance patterns with recurring, season-specific fish assemblages was observed over the 3years, despite substantial
variation in environmental conditions such as a temperature difference of almost 20°C between summer and winter. The lesser
sandeel (Ammodytes marinus), was the only species which showed significant fluctuations in abundance between the years. After removal of this species
from the analysis, the dominance patterns of the remaining fish species were almost identical between years.
Fronts and eddies are widely hypothesized to be critical spawning habitat for large pelagic fishes, due to increased larval and/or adult feeding opportunities at these features. We examined sailfish (Istiophorus platypterus) spawning around a cyclonic, submesoscale (∼13 × 7 km) Florida Current frontal eddy. The temporal progression of eddy dynamics over a 65 h period was determined using ocean color satellite imagery, continuous surface measurements along the cruise track, and non-linear least-squares fitting of the positions of three drifters deployed within the eddy. A peak in larval sailfish densities (n = 2435, stations = 49), composed primarily of yolk-sac and first-feeding larvae, occurred at the eddy frontal zone. A majority of these larvae were estimated to have been spawned during the formation of the eddy. A comparison between the distribution of similar-age sailfish and scombrid larvae indicated that the peak in larval sailfish density likely resulted from spawning directly at the front, rather than transport by convergent flow. The first-feeding prey items of larval sailfish (Farranula and Corycaeus copepods) were most abundant at the frontal zone and to a lesser extent inside the eddy. Egg distributions were used to indirectly assess the distribution of adult sailfish prey items. Euthynnus alleteratus and Auxis spp. eggs were in highest abundance outside the eddy, while the eggs of small carangids were in highest abundance at the eddy frontal zone. Overall, this study indicates that sailfish spawn at small-scale oceanographic features that provide a favorable feeding environment for their larvae and potentially also for the adults.
Critical gaps in our understanding of the distributions, interactions, life histories and preferred habitats of large and medium-size pelagic fishes severely constrain the implementation of ecosystem-based, spatially structured fisheries management approaches. In particular, spawning distributions and the environmental characteristics associated with the early life stages are poorly documented. In this study, we consider the diversity, assemblages, and associated habitat of the larvae of large and medium-sized pelagic species collected during 2 years of monthly surveys across the Straits of Florida. In total, 36 taxa and 14,295 individuals were collected, with the highest diversity occurring during the summer and in the western, frontal region of the Florida Current. Only a few species (e.g. Thunnus obesus, T. alalunga, Tetrapturus pfluegeri) considered for this study were absent. Small scombrids (e.g. T. atlanticus, Katsuwonus pelamis, Auxis spp.) and gempylids dominated the catch and were orders of magnitude more abundant than many of the rare species (e.g. Thunnus thynnus,Kajikia albida). Both constrained (CCA) and unconstrained (NMDS) multivariate analyses revealed a number of species groupings including: (1) a summer Florida edge assemblage (e.g. Auxis spp., Euthynnus alleterattus, Istiophorus platypterus); (2) a summer offshore assemblage (e.g. Makaira nigricans, T. atlanticus, Ruvettus pretiosus, Lampris guttatus); (3) an ubiquitous assemblage (e.g. K. pelamis, Coryphaena hippurus, Xiphias gladius); and (4) a spring/winter assemblage that was widely dispersed in space (e.g. trachipterids). The primary environmental factors associated with these assemblages were sea-surface temperature (highest in summer-early fall), day length (highest in early summer), thermocline depth (shallowest on the Florida side) and fluorescence (highest on the Florida side). Overall, the results of this study provide insights into how a remarkable diversity of pelagic species spatially and temporally partition spawning within a region that is characterized by dynamic oceanography and strong habitat gradients.
Lengths and ages of swordfish (Xiphias gladius) estimated from increments on otoliths of larvae collected in the Caribbean Sea, Florida Straits, and off the southeastern United States, indicated two growth phases. Larvae complete yolk and oil globule absorption 5 to 6 days after hatching (DAH). Larvae <13 mm preserved standard length (PSL) grow slowly (∼0.3 mm/d); larvae from 13 to 115 mm PSL grow rapidly (∼6 mm/d). The acceleration in growth rate at 13 days follows an abrupt (within 3 days) change in diet, and in jaw and alimentary canal structure. The diet of swordfish larvae is limited. Larvae <8 mm PSL from the Caribbean, Gulf of Mexico, and off the southeastern United States eat exclusively copepods, primarily of one genus, Corycaeus. Larvae 9 to 11 mm eat copepods and chaetognaths; larvae >11 mm eat exclusively neustonic fish larvae. This diet indicates that young larvae <11 mm occupy the near-surface pelagia, whereas, older and longer larvae are neustonic. Spawning dates for larvae collected in various regions of the western North Atlantic, along with the abundance and spatial distribution of the youngest larvae, indicate that spawning peaks in three seasons and in five regions. Swordfish spawn in the Caribbean Sea, or possibly to the east, in winter, and in the western Gulf of Mexico in spring. Elsewhere swordfish spawn year-round, but spawning peaks in the spring in the north-central Gulf of Mexico, in the summer off southern Florida, and in the spring and early summer off the southeastern United States. The western Gulf Stream frontal zone is the focus of spawning off the southeastern coast of the United States, whereas spawning in the Gulf of Mexico seems to be focused in the vicinity of the Gulf Loop Current. Larvae may use the Gulf of Mexico and the outer continental shelf off the east coast of the United States as nursery areas. Some larvae may be transported northward, but trans-Atlantic transport of larvae is unlikely.
Using an individual-based model approach we consider trophodynamic effects on the growth and survival of larval cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) on Georges Bank during late winter/early spring. These studies represent an extension of results described in Werner et al. (1996; Deep-Sea Res. II), wherein the effect of turbulence-enhanced larval-prey contact rates increased the effective prey concentration resulting in growth of cod larvae consistent with observed rates in the field. We reformulated the feeding of the larvae to include existing relationships between maximum prey-length and larval-length and we examined: (i) larval search behaviour and its effect on encounter with prey, (ii) the ability of larvae to pursue and capture prey in a turbulent environment, and (iii) the effect of turbulence on the dispersion of larvae in the vertical. We find that search behaviour, the effect of turbulence on pursuit and capture, and vertical dispersion decrease the predicted larval growth rates compared to those observed in the earlier study. These results suggest that larval feeding behaviour, and especially the ability of larvae to pursue encountered prey, could be an important input to larval growth and survival models. The inclusion of turbulence in determining the position of passive larvae in the water column allows the larvae to sample the entire water column, contributing to a decrease in the variance of the size of the larvae over time. The ability of larvae to swim and aggregate in the vertical will be necessary to reproduce distributions observed in the field.
Instantaneous daily growth and mortality rates each increased c0.01 per °C increase in temperature, but there was no significant regression of gross growth efficiency on temperature (mean K1=0.29), indicating no latitudinal relationship. The large increases in growth rate at high temperatures must be supported by increased food consumption, not increased growth efficiency. Oxygen uptakes also increased significantly in relation to temperature, but relatively slowly compared to growth rates. Larval stage duration was inversely related to growth rate. Potential variability in growth rate increased with temperature; the opposite trend was observed for stage duration, which tended to be both long and potentially variable in high latitudes. Early life, density-dependent regulation is thus more probable in high than in low latitudes. The required ingestion to support average growth rate increased 3-fold in the 10-30°C range, indicating that fish larvae in warm seas may be more likely to starve than larvae in cold seas. Spawning in low latitudes often is protracted with frequent batches in contrast to spawning in high latitudes, where seasons are brief with one or a few batches. -from Author
Understanding the functional linkages between the pelagic and demersal stages of marine organisms is a central goal in ecology. To better understand events that occurred during the larval period as well as their initial influence on juvenile traits, we examined individual level variation in early life-history traits (larval and early juvenile otolith growth rates, size-at-age, and larval duration) of 3 seasonal cohorts of the common coral reef fish Thalassoma bifasciatum (Bloch) (Labridae). Juveniles were collected at regular intervals (every second day) for 2 wk following their first appearance on the nearshore reefs of Barbados, West Indies. Otolith analysis indicated that each cohort exhibited a broad range of larval traits. Individuals with shorter larval durations had faster otolith growth and settled at relatively smaller sizes (based on otolith length and standard length) than larvae with longer larval durations, which exhibited slower otolith growth rates. Despite the range in larval durations for T. bifasciatum, otolith growth records revealed no evidence for delay of metamorphosis. Instead, the range in larval durations is likely to be the result of a variable pelagic environment influencing growth rates. Because metamorphosis in this species is an energetically costly non-feeding (3 to 5 d) period, we propose that successful metamorphosis requires a minimum energy reserve. Slower growers may need to remain in the plankton longer (consequently attaining larger sizes) to obtain this minimum condition. Variability in early life-history traits also occurred among the seasonal cohorts. Despite differences in patterns of larval otolith growth, mean larval duration was similar for the 2 fall cohorts (57 and 55 d), but much shorter for the spring cohort (42 d). Such inter-cohort variability in early life-history traits suggests a variable pelagic environment. In contrast to the larval period, juvenile growth rates were much less variable within and among cohorts, reflecting a more constant physical and biological environment on the reef.
Otolith microstructure of larvae of southern bluefin tuna, Thunnus rnaccoyii (Castelnau, 1872), collected from the east Indian Ocean in January/February 1987 was examined using Light and scanning electron microscopy. Daily formation was verified by examining the growth of the marginal increment on otoliths of larvae collected on 6 successive days. Most of the larvae sampled came from a single cohort which spawned over 2 d. The daily progression of increment number for this cohort was further evidence that increments were formed daily. Larvae ranged from ca 7 to 18-d-old; the larval stage appeared to last ca 20 d. Growth curves could not be fitted to plots of size-at-age due to a large variance in size-at-age and violation of assumptions for parametric tests. Back-calculation of individual growth trajectories was possible because growth of sagittae was exponential relatlve to body length, and there was a strong linear relationship between log otolith radius and standard length (R ~ = 0 91) Growth trajectories of larvae were approximately linear, R' ranging from 0.972 to 1.0, with a med~an value of 0.996. The lstribution of lndiv~dual growth rates was approximately normal, ranging from 0.20 to 0.47 mm d-' and a mean of 0 32 mm d-l. Over the range examined, the growth of T. maccoyii larvae was relatively slow and linear, although the growth trajectories of oldest larvae exhibited a c u ~ l i n e a r Increase in the days immediately preceding collection. The fast growth often attributed to young stages of tuna must occur in the late larval/early juvenile stage rather than the early larval stage of this species.
Otolith microstruc ture analysis was applied to sagittae from 18 larvae (5-10mm notochord length) and 77 juvenile, young adult, and adult (4.3-212 em lower jaw fork length, LJFL) Atlantic blue marlin Makairanigrica:ns for estimation of age and growth rate. Contingency table analyses indicated that a peri odicity of one increment per day was most consistent with the seasonal distribution and peaks of back-calcu lated spawning dates of the aged samples (May to November), and with information on spawning re ported in the literature. Microstruc tural features of larval blue marlin sagittae were indistinguishable from those in the otoliths ofother tropical pelagic species where conclusive age validation has verified daily incre ment deposition rates. Average per cent error of the counting method (precision) for the aged samples of juveniles and young adults/adults was 1.6%. Estimated ages of larvae ranged from 9 to 12 days while estimated ages of juveniles, young adults, and adults ranged from 21 to 495 days (1.4 years). Otolith microstructure analysis could not be applied with confidence to blue marlin older than 1.4 years. Allometric equations for the length-weight relationship of im mature « 140cm LJFL) and mature male and female blue marlin (>140 em) are presented. Sexual dimorphic growth (weight only) in Atlantic blue marlin appears to begin at 140cm LJFL. Both the maximum (t\l16mmlday at 50 days) and sustained (t\l10rnm/ day) growth rates in length during the first 100 days indicate that At lantic blue marlin are one ofthe fast est growing of all teleosts in the early stages of development. An at tempt to determine the periodicity of presumed annual marks on otoliths from adult blue marlin (213-367cm LJFL) by evaluating microstructural characteristics and increment counts between annuli was unsuccessful.
Theory states that small-scale turbulence decreases pursuit success of planktonic predators by advecting the encountered prey from the reactive zone of the predator during the pursuit event. We tested the quantitative pre- dictions of a previously published model describing this phenomenon in larval cod by videorecording particle motion and feeding behavior of larval cod (8.7-12.3 mm) preying on copepods in a laboratory tank. Fluid motion shared characteristics with that in the ocean, i.e., intermittent, logarithmically distributed, average particle-particle velocity difference proportional to separation distance 1/3 . Estimated bulk dissipation rates were 0-2 3 10 28 m 2 s 23 and similar to those commonly experienced by larval cod in nature (e.g., located at 30 m during winds of ca .7ms 21 ). Owing to the intermittent nature of turbulence, we related individual predation events to local, instantaneous relative velocities instead of bulk averages. Pursuit success decreased significantly with relative velocity and the observations approximated the predicted effect of turbulence on pursuit success. Nonlinear and counteracting effects of turbulence on pursuit success and encounter may partly explain the contradictory observations of how turbulence affects larval fish feeding, growth, and survival in the sea.
Otolith microstructure analysis was applied to sagittae from larvae (5-10 mm notochord length) and juvenile, young adult, and adult (4.3-212 cm lower jaw fork length, LJFL) Atlantic blue marlin for estimation of age and growth rate. A periodicity of one increment per day was most consistent with the seasonal distribution and peaks of back-calculated spawning dates of the aged samples (May-November), and with information on spawning reported in the literature. Otolith microstructure analysis could not be applied with confidence to blue marlin older than 1.4 yr. Allometric equations for the length-weight relationship of immature (≤140 cm LJFL) and mature blue marlin (>140 cm) are presented. Sexual dimorphic growth (weight) appears to begin at 140 cm LJFL. Both the maximum (c16 mm/day at 50 days) and sustained (c10 mm/day) growth rates in length during the first 100 days indicate that Atlantic blue marlin are one of the fastest growing of all teleosts in the early stages of development. -from Authors
We conducted a 2-year study off Miami, Florida, to verify the presence and seasonality of larval billfish, particularly sailfish (Istiophorus platypterus) and swordfish (Xiphias gladius), and, to examine the feasibility of obtaining laboratory observations on feeding, behavior, and growth. The Gulf Stream's western edge was sampled from April to October 1994, and from March to October 1995, with a 1-mm-mesh plankton net. A total of 315 samples yielded 288 larval sailfish and 2 larval swordfish. Sailfish larvae were present from May to October with a May to July peak, while the two swordfish were captured in May and July. Highest sailfish catches were made from 07:00 to 08:00. No swordfish survived capture at sea. Of the 288 sailfish larvae captured, 87 were alive immediately after capture and these were transported to the University of Miami's experimental hatchery. Of the sailfish captured alive, 23 survived 24 h, 7 survived 48 h, and I survived 72 h. Dissection confirmed that one larval sailfish ingested Artemia introduced as food. This is the first reported observation of larval sailfish feeding.
This paper presents a comprehensive summary of development, mortality, and survival rates of fish eggs, yolk-sac larvae, and postlarvae in relation to temperature and size. The general temperature- and, where applicable, size-dependent models explained 30-81% of the variance in vital rates. Daily development and mortality rates generally increased with increasing temperature. Temperature had an equal but opposite effect on stage-specific cumulative mortality rates of eggs and yolk-sac larvae. Stage-specific (length-dependent) cumulative mortality rates of postlarval fish were independent of temperature due to equal effects of temperature on daily growth and daily mortality rates. Size had no significant effect on daily or cumulative mortality rates of egg and yolk-sac stages. Daily mortality rates of postlarval fish were significantly influenced by mean size (i.e. length). The compensation of temperature effects between stages and/or vital rates may reduce the impact of environmental uncertainty on survival rates. It is suggested that the general temperature- and/or size-dependent relationships described in this study can serve as basic frameworks to assess whether there are significant effects resulting from species/stock-specific characteristics or environmental factors on the vital rates of the early life history stages of fish.
Istiophorid billfishes are highly migratory species that inhabit the tropical and subtropical, epipelagic waters of the world's oceans, a large, relatively homogeneous environment that lacks significant physical barriers. Based on these observations alone, one would not expect marlins, sailfish and spearfishes to exhibit substantial stock structure. This assumption has been evaluated with a variety of techniques, including analyses of morphological characters, adult distribution, tag and recapture data, the spatial and temporal distribution of spawning and, recently, molecular genetic characters. This paper focuses on inferences of istiophorid billfish stock structure derived from investigation of several different classes of molecular markers, and reviews our current understanding of the genetic basis of stock structure of striped marlin, white marlin, blue marlin, sailfish and black marlin. Significant genetic differences exist between Atlantic and Indo-Pacific populations of blue marlin and sailfish, and the presence of distinct mitochondrial DNA lineages suggests that ocean populations were isolated in the past. However, the occur-rence of identical genotypes in both oceans is evidence of recent genetic contact. The genetic data do not support recognition of separate Atlantic and Indo-Pacific species of blue marlin or sailfish. White and striped marlin are separated by about the same level of genetic divergence as Atlantic and Indo-Pacific populations of blue marlin and sailfish, but preliminary analysis of the mitochondrial DNA control region suggests that, unlike Atlantic and Indo-Pacific populations of blue marlin and sailfish, white marlin and striped marlin represent independent evolutionary units. If white and striped marlin are valid species, they are of very recent origin. Significant intraspecific genetic heterogeneity was found among collections of striped marlin and sailfish within the Indo-Pacific; both species exhibited a clear spatial partitioning of genetic variation among geographically distant collection locations. There was no genetic evidence for within-ocean population structuring for other istiophorids examined. Inferences of billfish stock structure derived from studies of molecular markers complement those obtained using other methods of analysis, and together these studies demonstrate substantial differences in the level of population structuring among istiophorid billfishes, information critical for effective management of these highly migratory species.
Using vertically stratified data of the abundance of silver hake (Merluccius bilinearis) larvae and concen-trations of copepods collected in the field, we examine relationships among the vertical distribution of larval fish, their potential prey, feeding success and water column turbulence. Water column turbulence and associated stratification parameters were estimated from: (i) in situ measures of turbulent kinetic energy dissipation (e) provided by an EPSONDE profiler; (ii) in situ wind speed; (iii) the Richardson number (Ri); and (iv) the buoyancy frequency (N 2). Small (< 5 mm total length) silver hake were more abundant in the least turbulent waters (i.e. at a minimum in the rate of dissipation of turbulent kinetic energy, e < 10 –7 W kg)1 ; Ri > 0.25; N 2 > 0.001 (rad s –1) 2). Partial correlations amongst e, N 2 and small hake larvae were significant only for N 2 . The abundance of larger (> 5 mm total length) hake larvae was positively cor-related with depth and was not associated with either e or N 2 . Vertical distributions of three potential prey (classified by stage) were variable. Early stage cope-podids were positively correlated with N 2 and negat-ively correlated with e. We found no evidence of diel distribution patterns for small (< 5 mm total length) hake larvae or for any of the developmental stages of the copepods examined. Neither estimate of water column turbulence inferred from wind speed nor from Ri was meaningfully related to in situ estimates of e or to larval fish abundance. Feeding success, measured either as prey items (gut) –1 , average prey length, or total prey volume (gut) –1 , was not related to predicted encounter rates between days. However, the average prey length (gut) –1 was significantly (P < 0.01) related to water column turbulence. These conflicting results suggest that the relationship between larval feeding and the environment is more complicated than assumed. We conclude that without substantial high resolution in situ examination of the relationship between the vertical distributions of turbulence, larvae and their prey, the growing acceptance in the secondary literature that turbulence has a positive and biologically meaningful effect on trophic interactions between fish and their zooplankton prey (a generalization based largely on modelling and laboratory experiments) is premature.
Theoretical and empirical studies of plankton trophodynamics are usually based on some function of the relative density of predator-and-prey plankton. Such approaches based only on the relative density of predator and prey generally underestimate predator-prey contact rates because contact depends on both the relative density and the relative velocity of predator and prey. We estimate the components of predator-and-prey contact that are due to small-scale turbulence. The small-scale turbulence effect suggests reconsidering estimates of plankton food requirements, energy gain-and-loss from foraging and mechanisms associated with patch formation and dissipation.
Size-selective mortality decreases or increases the actual and back-calculated lengths of an age-group, while at the same time altering the shape and variance of its length frequency distribution only slightly or not at all. An index of intensity of selection (r) can be calculated from the difference in computed length (d) between the penultimate annulus at age n and the terminal annulus at age n−1, together with the standard deviation in length (s); it is r = 1.349d/s, and represents the difference in mean instantaneous mortality rate between the two halves of the frequency distribution. Instantaneous rates of increase in weight can be computed from length data by multiplying the difference between the natural logarithms of length 1 year apart by the exponent in the weight–length relationship. When there is size-selective mortality, the difference between the rate (GX) based on observed weights in successive years differs from the true rate (G) based on the terminal length differences computed from scale...
Neuston nets to sample the fishes that congregate at the sea surface have been developed at the Woods Hole Oceanographic Institution, and the characteristics of three successful designs-for use at cruising speed (9 knots) and trawling speed (6 knots)-are presented. On a cruise from 8° S to 36° S off the coast of South America, neuston nets were used at trawling speed and drifting. Eighty-five larval Makaira nigricans Lacépède were taken on the first half of the cruise (8°-25° S), when surface temperatures were around 28° C; no marlin were taken on the second half, when temperatures had fallen below 25° C.
Metabolism, growth and energy utilization of dolphin were studied at 26$\sp\circ$C during all life stages. Experimental organisms included wild and cultured adult fish (0.9-4.2 kg) and eggs, larvae and juvenile (1.5-43 g) from $F\sb1$, and $F\sb7$ generations inbred in captivity. The mean rates of oxygen consumption (VO$\sb2$ = $\mu$l O$\sb2$ indiv.$\sp{-1}$ h$\sp{-1}$) by eggs and 1-18 day-old larvae were 0.25 and 4.18, respectively. The weight-specific oxygen consumption (QO$\sb2$ = $\mu$l O$\sb2$ mg dry wt$\sp{-1}$ h$\sp{-1}$) by eggs and larvae were 1.8 and 11.34, respectively. Both VO$\sb2$ and QO$\sb2$ increased significantly with development. Respiratory quotients (CO$\sb2$/O$\sb2$) by eggs and 1-18 day-old larvae had a mean value of 0.57 and were independent of age. Specific growth rate of larvae ranged from 16-34% bw d$\sp{-1}$. Endogenous rate of nitrogen excretion was 2.11 $\times$ 10$\sp{-3}$ $\mu$mol ammonia-N mg dry wt$\sp{-1}$ h$\sp{-1}$. Ingestion rates by larvae corresponded to 166% of their body calories daily (over 80% of their body weight).The standard metabolic rate of adult dolphin (0.21 mg O$\sb2$ g$\sp{-1}$ h$\sp{-1}$) and the routine, swimming and feeding metabolism of juveniles (0.71, 0.97 and 1.5 mg O$\sb2$ g$\sp{-1}$ h$\sp{-1}$, respectively) were studied. Their hematological parameters were also determined: hematocrit (39.85%), hemoglobin (11.53 g dl$\sp{-1}$) and erythrocyte (3.1326 $\times$ 10$\sp6$ mm$\sp3$). The mean heart rate was 136 beats min$\sp{-1}$. Specific growth rates of 1-9.5 month-old fish decreased from 10 to 4.3% bw d$\sp{-1}$ within the experimental period. The rate of food ingestion by juveniles was about 4% bw d$\sp{-1}$, and their mean rate of nonfecal endogenous nitrogen excretion was 0.0052 mg/0.29 $\mu$mol ammonia-N g$\sp{-1}$ h$\sp{-1}$. Energy budgets for larvae and juvenile stages of Coryphaena hippurus were calculated as: (a) for larvae: 100 $\pm$ 21(I) = 40 $\pm$ 18(M) + 45 $\pm$ 5(G) + (1.2 $\pm$ 0.4(U) + 13.8 (F)) (E), or, in cal d$\sp{-1}$: 4.7 $\pm$ 1(I) = 1.9 $\pm$ 0.9(M) + 2.1 $\pm$ 0.2(G) + (0.05 $\pm$ 0.01(U) + 0.65(F)) (E) (b) for juveniles: 100 $\pm$ 4(I) = 47 $\pm$ 12(M) + 35 $\pm$ 11(G) + (0.02 $\pm$ 0.008(U) + 17.98(F)) (E), or, in cal d$\sp{-1}$: 3,410 $\pm$ 14(I) = 1,605 $\pm$ 445(M) + 1,210 $\pm$ 378(G) + (36.53 $\pm$ 14.6(U) + 558.5(F)) (E); where I = ingestion; M = metabolism; G = growth; U = nonfecal excretion; F = fecal excretion; and E = total excretion.The budgets suggest that dolphin larvae and juveniles have a higher energetic efficiency than other teleosts by using a proportionally larger portion of the total gross energy ingested for growth and metabolism than for excretion. Their feed conversion, assimilation and growth efficiencies were comparatively higher than for other fishes.
The goal of this dissertation was to examine the role of the Straits of Florida (SOF) as spawning habitat for billfishes (families Istiophoridae and Xiphiidae) by: (1) accurately identifying larval istiophorids; (2) developing an age-length relationship for larval sailfish; and (3) describing the spatial and temporal distribution of billfish larvae by species and age, with first approximations of potential origination points.A molecular technique was used to identify reference larvae of sailfish, blue marlin, and white marlin. Canonical Variates Analysis (CVA) revealed the extent to which the combination of morphometric measurements, lower jaw pigment patterns, and month of capture information was species-diagnostic. An identification key was constructed of characteristic jaw pigment patterns, month of capture, and linear regressions of the snout length:eye orbit diameter ratio against standard length. The key correctly identified 69.6% of 283 (blind sample) larvae used to test it, with one mis-identification. Of the 85 larvae that could not be identified by the key, 75 (88.2%) were correctly identified using CVA.Of the billfishes, larval age-length relationships exist for only blue marlin and swordfish, but larval sailfish were most abundant in the SOF. Growth increments were enumerated on sagittae of sailfish ranging in length from 2.8 to 15.2 mm. Estimated ages of larvae ranged from three to eighteen days. Length and age data were fitted with an exponential model (R2 = 0.85). Estimated size at hatch for sailfish is 1.9 mm, and the daily instantaneous growth rate coefficient is 0.14. As in the other billfishes, rapid early growth is an attribute of the sailfish.Identity was determined and age estimated for all larval billfishes captured in SOF waters. Minimum transport times through the SOF were determined for each site. If this time exceeded the age estimates of pre-flexion larvae caught at that site, it was concluded that those larvae were spawned within the SOF. The SOF is a major sailfish spawning area, with at least 52% of the pre-flexion larvae captured originating there. These results illustrate the importance of the SOF as billfish habitat, and provide a basis for further characterization of billfish spawning and nursery grounds.
Cold dense plumes have been associated with coral killoff on tropical
shelves as well as with sediment movement from banks to the deep basins
adjacent to shallow banks. This paper presents evidence that plumes of
dense, salty water generated over shallow banks entrain ambient water
rather than descending intact to a density compensation level (as has
sometimes been assumed) and that plumes can spread laterally distances
of tens of kilometers from their source. In Exuma Sound, dense, salty
water appears to be formed year-round by cooling or by evaporation over
shallow banks. The water is forced by tidal currents through the
channels between islands onto the narrow shelves of Exuma Sound where it
likely moves as gravity currents. The gravity currents entrain basin
water as they cross the shelf and cascade over the steep shelf edge into
Exuma Sound, after which they are advected by ambient currents around
the sound. A numerical streamtube model was used to explore early
details of plume evolution. The model predicts that the plumes entrain
2.6-5.0 parts ambient water, particularly as they traverse the gently
sloping shelf. The resulting loss of density contrast means that the
model plumes reach their density level in Exuma Sound at relatively
shallow depths, 50-95 m, just below the base of the mixed layer. The
final depth of modeled plumes is relatively consistent with observed
plume depths, which vary seasonally (˜75 m in early winter to
˜45 m in summer) depending on the depth and density
characteristics of the seasonal mixed layer. Over the sound, observed
plume thickness ranges from ˜40 m in winter to ˜20-30 m in
summer. Final salinity values exceed 36.8 practical salinity units;
final density ranges from sigmat ˜23.75 to ˜24.5. Plume
depth, vertical structure, and longevity are shown to depend on upper
ocean mixing processes such as convection and wind mixing.
The theory of recruitment in fishes and hypotheses pertaining to causes of recruitment fluctuation are summarized. In spite of considerable research effort over several decadesthere has been no significant improvement in identifying clear causal mechanisms of recruitment in marine fish stocks. Starvation has not been demonstrated to be a primary mechanism controlling survival of fish larvae. Studies matching food levels and year-class strength continue to provide indirect evidence that growth during the first year of life is dependent on food supply and may be important in determining survival. The hypothesis that survival is a direct function of growth provides a rational theoretical framework for recruitment research and is suggested as a basis for future work. Growth rate must be studied as a function of both ration and temperature. Studies examining the relationship of growth rate to survival should be specific to each life history stage and ideally integrated throughout the pre-recruit period. It remains to be demonstrated that survival is a direct function of growth, mediated through size-dependent predation.
Plankton and other net-caught samples collected on past cruises of the National Marine Fisheries Service, Honolulu Laboratory vessels in Hawaiian and central Pacific equatorial waters were examined for billfish larvae and juveniles. Of the 342 billfish young found in 4,279 net tows, 209 were blue marlin, Mokaira nigrkans, 82 were shortbill spearfish, Tetrapturus angustirostris, 2 were sailfish, Istiophorus plutypterus, 20 were swordtish, Xiphias gladius. Twenty-nine larvae were unidentified owing to excessive damage. A preponderance of the catches was obtained from hauls made at the surface during daylight. In the equatorial central and North Pacific larvae of only three of the six billfish species nominally found in the Pacific were taken. The captures of these larvae (blue marlin, shortbill spearfish. and swordfish) fill the gaps in the known distribution of istiophorids and swordfish, and extend their distribu- tion eastward to the Hawaiian Islands in the North Pacific. The two sailfish larvae were taken in New Hebrides waters in the western South Pacific. The absence of striped marlin, Tefrupfurus uudax, larvae in Hawaiian waters was significant, since this species comprises nearly 82% of all istiophorids taken on the longline in the Hawaiian fishery. Their absence suggested that the striped marlin in Hawaiian waters probably migrate elsewhere to spawn. If this is true, then the spawning habits of this species differ significantly from those of blue marlin. A similar situation could hold for sailfish also. In recent years fishery workers have given more attention to the early life history of billfishes, owing to the increasing importance of these fishes in the commercial and sport fishing catches. The billfishes in the Pacific Ocean are represented by two families: Istiophoridae and Xiphiidae. The Is- tiophoridae includes five species: Istiophorus platypterus, sailfish; Tetrapturus angustirostris, shortbill spearfish; Z. audax, striped marlin; Makaira nigricans, blue marlin; and M. indica, black marlin. The Xiphiidae is represented by a single species, Xiphias gladius, swordfish. Larvae of all these s pecies, mainly from the western Pacific, have b een identified and reported by Japanese workers. This study, based on larvae collected on past cruises of the National Marine Fisheries Service, Honolulu Laboratory (HL) vessels in Hawaiian and central Pacific equatorial waters, verifies the iden- tifications reported by Yabe (1953), Y abe et al. (1959), Ueyanagi and Yabe (1959), and Ueyanagi
Surface currents in Exuma Sound (ES) were examined using satellite-tracked drifters. Of four drifters released on a line across central ES, the two launched on the middle of the transect moved to the northern part of the Sound while those launched nearest the edges did not. Of three drifters released near the deep opening of ES, one moved to northern ES and two launched in advance of a cold front moved into the Atlantic. Surface circulation in ES appears active with a general northwesterly flow, eddies and jets, mean current speeds of 11.2-19.8 cm sec−1, and drogue drift times of 6-35 days before grounding. Drogues exiting ES into the north Atlantic moved at times to the south and east, contrary to conventional presentations of the Antilles Current and on several occasions approached shallow water areas of the Bahamas. Current patterns indicate the potential for complete pelagic development of larvae of various benthic invertebrates and fishes within ES.
Individual variability in body size provides a template for selective mortality processes during early life history stages of teleost fishes. This size variability has generated the logically intuitive hypothesis that larger or faster growing members of a cohort gain a survival advantage over smaller conspecifics via enhanced resistance to starvation, decreased vulnerability to predators, and better tolerance of environmental extremes. This review evaluates field and laboratory studies that have examined size-based differences in survival, with emphasis on the juvenile stage of teleost fishes. The results in general support the "bigger is better" hypothesis, although a number of examples indicate non-selective mortality with no obvious size advantages. The reverse pattern, with enhanced survival of smaller individuals, is rare with the notable exception of bird predation. Major size-selective processes during the juvenile stage include overwinter mortality for temperate species, associated with either starvation or intolerance of physical extremes by smaller members of the young-of-the-year cohort, and predation, with smaller fish more susceptible to successful capture by predators. Most studies examining these processes have used indirect methods to evaluate size-selective mortality, with interpretation of results dependent on several critical assumptions. For methods that track size distributions over time, unbiased samples collected from the same population are critical, and changes in size distributions associated with mortality must be distinguished from changes due to individual growth. The latter requirement can be met with the direct, "characteristics of survivors" method, but few studies have used this approach. Experimental methods isolating specific mechanisms of size-specific mortality must appropriately represent the natural context of environmental factors. Specific predator/prey combinations, for example, can elucidate size-based prey preferences but may be irrelevant compared to the natural, multi-species predator field. The composition of the predator field and its correspondence to size-spectrum theory is crucial to the probability of size-selective predation as a cohort progresses through the juvenile stage. Distinction of selection on body size vs. selection on growth rate has received little attention. However, a number of physiological constraints and ecological trade-offs can place restrictions on growth rates and apparently override the advantages of large body size. Identifying the major sources of mortality and how they operate in the juvenile stage has valuable applications in understanding population dynamics and recruitment variability.
Plotting net reproduction (reproductive potential of the adults obtained) against the density of stock which produced them, for a number of fish and invertebrate populations, gives a domed curve whose apex lies above the line representing replacement reproduction. At stock densities beyond the apex, reproduction declines either gradually or abruptly. This decline gives a population a tendency to oscillate in numbers; however, the oscillations are damped, not permanent, unless reproduction decreases quite rapidly and there is not too much mixing of generations in the breeding population. Removal of part of the adult stock reduces the amplitude of oscillations that may be in progress and, up to a point, increases reproduction.
In the present study, we verified daily increment formation within sagittal otoliths of juvenile skipjack tuna Katsuwonus pelamis by analysis of diel changes in marginal increment width. Specimens were collected by midwater trawl in the tropical western Pacific from November to December 1995 and in February 1999. The sagittal plane of the otolith was embedded in enamel resin and polished with lapping films. The otolith-measuring system was equipped with a light microscope and was used for marginal increment analysis. The index of completion of the marginal increment increased with time of day, approximately 40% at 07 : 00–10 : 00 h, 66% at 13 : 00–16 : 00 h and 80% at 19 : 00–23 : 00 h. Therefore, growth of the marginal increment progressed from morning to evening and was completed during the night. We conclude that increments are formed daily in juvenile skipjack otoliths and these increments have a width of 15–40 µm.
Exuma Sound is a semi-enclosed body of water bounded by islands of the Bahamas. During July 2000, sampling for larval billfish was carried out throughout the Sound's surface waters as well as in adjacent open waters of the Atlantic Ocean. A total of 99 larval billfish (Istiophoridae) was collected. Ninety of the larvae were identifiable as blue marlin (Makaira nigricans) and three as sailfish (Istiophorus platypterus). The remaining larvae were also istiophorids, unidentified to species owing to damage; no larval Xiphias gladius were collected. Larval blue marlin densities ranged from 0 to 3.4 larvae/1000 m 2 ; their sizes ranged from 3.1 mm notochord length to 22.6 mm standard length. Densities tended to be highest north-east of the Sound's central axis, especially within the two regions where exchange with the Atlantic is greatest. Mean densities tended to decrease in the direction of mean flow; mean lengths increased from 8.08 mm at the Sound's mouth to 14.7 mm standard length at its upper reaches. Length-based estimates of larval age ranged from 2.2 to 17.2 days. Given these age estimates and assuming passive surface transport, the blue marlin larvae collected were likely the result of recent spawning in waters that include Exuma Sound and may extend some 200 km south-east of its mouth. This study suggests that Exuma Sound functions as a nursery area for blue marlin, and possibly other billfish species, at least during the summer. Limited sampling just outside Exuma Sound, in the Atlantic Ocean proper, also yielded blue marlin larvae. Extra keywords: age and growth, Istiophoridae, larval billfish, nursery grounds.
We tested the hypothesis that fast growing Atlantic cod Gadus morhua survived better than their population of orlgin in the winters of 1991-1992 and 1992-1993 on the Scotian Shelf (north-west Atlantic). Survivors were defined as fish >90 d of age at capture which comprised eplbenthic juveniles >20 mm sampled mainly near the bottom. The majority of larvae and juveniles aged 590 d at capture were sampled with a midwater trawl and were assumed to be representative of the pelagic population (survivors + non-survivors) from which epibenthic survivors originated. Standard length corrected for shrinkage was linearly correlated to lapillar radius (r2 = 0.97). lndividual growth histories were reconstructed from the width of lapillar increments. Selection for fast growth was weak in the winter of 1991-1992 and back-calculated growth and length a t a g e of survivors were not significantly larger than that of the population (repeated-measures MANOVA). In winter 1992-1993, a strong selec-tion for fast growth was evident in late larvae 41 to 80 d old. The divergence in length a t a g e between survivors and the population reached 4 mm at an age of 70 d , corresponding to a 13 d reduction in the duration of the larval phase. Survivors in the winter of 1992-1993 had larger hatch marks than the pop-ulation, suggesting that the potential for fast growth may be reflected in traits present at hatching. Our results support the hypothc.sis that fast growth increases the surv~vorship of Atlantic cod d u n n g larval 11fe in the plankton and Indicate that the intensity of slze-selective mortality may vary considerably from year to year.
Relative body size has long been recognized as a factor influencing repro-ductive success in fishes, but maternal age has only recently been considered. We monitored growth and starvation resistance in larvae from 20 female black rockfish (Sebastes melan-ops), ranging in age from five to 17 years. Larvae from the oldest females in our experiments had growth rates more than three times as fast and survived starvation more than twice as long as larvae from the youngest females. Female age was a far better predictor of larval performance than female size. The apparent underlying mechanism is a greater provisioning of larvae with energy-rich triacylglycerol (TAG) lipids as female age increases. The volume of the oil globule (composed primarily of TAG) present in larvae at parturition increases with maternal age and is correlated with subsequent growth and survival. These results suggest that progeny from older females can survive under a broader range of environmental conditions compared to progeny from younger females. Age truncation commonly induced by fisheries may, therefore, have severe consequences for long-term sustainability of fish populations.
Eight hundred and one yellowfin tuna larvae ranging from 2.57–7.48 mm SL were collected near the Mississippi River discharge plume in the Gulf of Mexico during July and September, 1987. Larvae were most abundant at intermediate salinities (i.e. frontal waters) where chlorophylla and macrozooplankton displacement values were also highest. Using sagittal otolith microstructure, we estimated larval ages ranging from 3–14 d. These ages were used to back calculate spawning dates from 13–24 July and 22–31 August. Mean absolute individual growth rate (length age–1) was 0.47 mm d–1, with the least squares linear regression SL = 1.67 + 0.47 AGE (r2 = 0.60, Pr> F = 0.0001) representing the best growth curve. Highest growth occurred at intermediate salinities near 31%, and temperatures near 29 C. There was significant temporal variation in growth, with larvae collected in July growing slower than those from September (0.37 and 0.48 mm d–1, respectively). The pooled instantaneous daily mortality rate (Z) of the larvae was estimated to be 0.33 d–1 (0.16 d–1 in July and 0.41 d–1 in September). These results show that significant spawning of yellowfin tuna may occur in the northern Gulf of Mexico in the vicinity of the Mississippi River discharge plume, and suggest that larval growth and survival may be enhanced in the plume frontal waters.
Sagittal otoliths from 50 king mackerel 2.9–13.0 mm SL and 72 Spanish mackerel 2.8–22.0 mm SL collected off the southeast U.S. were examined whole at 400 using a compound microscope-video system. Otoliths of both species had visible, presumably daily, growth increments as well as finer subdaily increments. Otolith growth was directly proportional to growth in standard length for king (r2 = 0.91) and Spanish mackerel (r2 = 0.86). Spanish mackerel were estimated to be 3–15 d old with a mean absolute growth rate (SL/number of growth increments) and 95% confidence interval of 1.15 0.07 mm d–1. The least squares linear equation: SL = –1.30 + 1.31 (age in days), with r2 = 0.67 and p < 0.001,="" described="" the="" relationship="" between="" length="" and="" age.="" there="" was="" a="" significant="" positive="" relationship="" between="" absolute="" growth="" rate="" and="" fish="" length.="" king="" mackerel="" were="" estimated="" to="" be="" 3–15="" d="" old="" with="" a="" mean="" absolute="" growth="" rate="" of="" 0.89="" ="" 0.06="" mm="">–1. The least squares linear equation: SL = 0.37 + 0.82 (age in days), with r2 = 0.77 and p < 0.001,="" best="" described="" the="" relationship="" between="" length="" and="" age.="" the="" relationship="" between="" growth="" rate="" and="" fish="" length="" was="" not="" significant.="" the="" growth="" rate="" of="" king="" mackerel="" was="" slightly="" higher="" for="" fish="" from="" the="" mississippi="" river="" plume="" than="" from="" all="" other="" locations="" combined,="" while="" spanish="" mackerel="" growth="" rates="" were="" not="" significantly="">
Billfish larvae of the Straits of Florida. PhD Dissertation Larval fish feeding and turbulence: A case for the downside
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Evaluation of identification methods for young billfishes
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Developmental strategy of scombroid larvae: high growth potential related to food habits and precocious digestive system development
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