Aquaculture Research

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Online ISSN: 1365-2109
Publications
Article
Diploid gynogenesis was induced in sterlet (Acipenser ruthenus) using UV-irradiated bester (Huso huso x A. ruthenus) sperm. The optimal condition for the retention of the second polar body in sterlet was investigated by altering the timing, intensity and duration of heat shock application. A total of 90 gynogens of known parentage from three different experimental treatments were screened using microsatellite DNA analysis, and uniparental transmission in meiogens was confirmed. (c) 2007 Elsevier B.V. All rights reserved.
 
Article
To investigate potential use of dietary β-1,3-glucan for health management of hybrid striped bass, juvenile fish were fed diets supplemented with yeast glucan (MacroGuard®) at 0.05%, 0.1% or 0.2% of diet for 4 weeks, followed by immune response assays and a bath challenge with Streptococcus iniae. Dietary glucan significantly (P<0.05) enhanced neutrophil oxidative radical production, and fish fed 0.1% glucan had a significant (P<0.05) reduction in mortality (10%) after bacterial challenge compared with fish fed the control diet (46.7%). However, accumulative mortality of fish fed 0.2% glucan was not significantly different from that of fish fed the control diet. To further elucidate this observation, macrophages from sub-adult hybrid striped bass were isolated and cultured in L-15 medium with 10% foetal calf serum and penicillin/streptomycin supplemented with 0.2, 0.5, 1, 2, 5, 20 and 100 μg soluble glucan (MacroGuard®) mL−1 for 24 and 48 h. Intracellular superoxide anion production was significantly (P<0.001) increased by 0.5 μg glucan mL−1, but significantly (P<0.001) suppressed by doses >5 μg glucan mL−1. It is concluded that dietary yeast glucan has potential for use in diet formulations of hybrid striped bass to limit the adverse effects of S. iniae, but dosage should be an important consideration in administration.
 
Article
For salmonid semen, the cryoprotective action of 10% methanol was compared with a 5% dimethyl sulphoxide (DMSO), 1% glycerol mixture, until now one of the most effective cryoprotectants. In Oncorhynchus mykiss (Walbaum), Salmo trutta L. f. fario, Salmo trutta L. f. lacustris and Salvelinus alpinus (L.), semen cryopreserved with both cryoprotectants yielded post-thaw fertilization rates of 90-100% of control with untreated semen at sperm-to-egg ratios of 1.8 × 106-2.4 × 106 spermatozoa per egg. However, at sperm-to-egg ratios of 0.9 × 106-1.2 × 106 spermatozoa per egg, semen cryopreserved with methanol had significantly higher fertilization rates than semen frozen with the DMSO/glycerol mixture. In other studies we obtained similar data for Coregonus sp., Salvelinus fontinalis (Mitchill), Thymallus thymallus (L.) and Hucho hucho (L.), proving that methanol is the most effective and generally applicable cryoprotectant for semen of the studied salmonid species.To facilitate the insemination of large egg batches we investigated the suitability of 1.2 ml and 5 ml straws for deep freezing of semen of Oncorhynchus mykiss, Salmo trutta f. fario, Salmo trutta f. lacustris and Salvelinus alpinus. With 1.2 ml straws the fertilization rates were similar to 0.5 ml straws when using lower freezing and higher thawing temperatures. The 5 ml straws resulted in a fertilization success of only about 40% of fresh semen control.
 
Article
Bacterial communities from the intestinal tract of rainbow trout were investigated to assess transient and resident microbial communities using both culture-based and culture-independent techniques. Viable counts attached to the intestinal mucosa were in the range of log 4.77–5.38 and log 6.67–6.79 CFU g−1 in the intestinal contents. Pseudomonas spp. and Enterobacteriaceae constituted nearly 80% of the allochthonous population but <60% of the autochthonous populations. This coincided with an elevated mucosal level of a group of Gram-positive rods from ∼2% in the digesta to 25–35% on the mucosa. This group was identified by 16S rRNA as Arthrobacter aurescens and Janibacter spp. HTCC2649. Analysis of denaturing gradient gel electrophoresis banding patterns showed complex communities in all intestinal regions. Similarity coefficients showed that mucosal communities were ∼70% similar to digesta communities and yet due to the presence of bands found uniquely either in the digesta or on the mucosa, the communities are distinctly different. Scanning electron microscopy confirmed mucosal bacterial populations and highlighted a possible localized colonization between mucosal folds. The study highlights the complexity of resident microbial communities that have not been fully explored in previous rainbow trout studies; this is especially true with probiotic/prebiotic investigations.
 
Article
Oral administration of 11 β-hydroxyandrostenedione was used to sex inverse juvenile Stizostedion lucioperca (L.) reared under intensive culture conditions. Androgen was mixed into the commercial trout food in the following doses: 0, 30, 60 and 90 mg kg−1 diet. Administration (for 21 days) of 60 mg 11 β-hydroxyandrostenedione kg−1 of the diet produced 93% males and 7% bisexual fish. In hormone-treated groups, no morphological changes were observed in the liver. No significant differences were observed in growth or in the hepatosomatic index between the androgen-treated groups and the control group.
 
Article
At Doi Inthanon Fisheries Research Unit (DIFRU), Thailand (13°N), rainbow trout were exposed to natural (13°N) and artificial (51°N) photoperiods, and natural water (NW) temperatures and cooled water (CW) 8 months before first spawning. In group I (51°N, CW), water temperatures of 18°C were never reached. In group II (51°N, NW) and group III (13°N, NW), the mean water temperatures in May exceeded 20°C, and 19°C in June and July. Eggs from 94% of all females in group I were obtained before January. This percentage diminished to 84% and 68% in groups II and III. The weight of the spawners and the size of the eggs were significantly lower in group III than in the other groups. No significant differences were observed for egg number per kg body weight of spawners between the groups. The mean fertilization rate of eggs was the highest, with 71%, in group I, and the lowest, with 50%, in group II. For hatching rates, on average 27%, 24% and 30% in groups I, II and III, respectively, differences were not significant. In group III, 37% of all batches reached fertilization rates above 80% and 16% of egg batches showed hatching rates of more than 60%.
 
Article
The pharmacokinetics and bioavailabilities of 14C-astaxanthin and 14C-canthaxanthin were studied in the blood of rainbow trout following intra-arterial (i.a.) and oral (p.o.) administration. Sixteen months old 1 kg trout were cannulated in the dorsal aorta. [6,7,6′,7′-14C]-keto-carotenoids were administered i.a. and p.o. at a dose of 573.5 kBq kg−1 fish body weight for astaxanthin and 836.2 kBq kg−1 fish body weight for canthaxanthin. After i.a. distribution, total body clearance (Cltot) was 17.30±20.29 mL kg−1 of fish h−1 for 14C-canthaxanthin and 3.30±1.50 mL kg−1 of fish h−1 for 14C-astaxanthin. The volume of distribution at steady-state (Vss) was 208.32±124.79 mL kg−1 of fish and 71.84±64.15 mL kg−1 of fish for 14C-canthaxanthin and 14C-astaxanthin respectively. Less than 0.4% of the administered radioactivity was recovered in urine. Radioactivity (expressed as percent of the dose) excreted in the bile of fish that received 14C-canthaxanthin by i.a. route was 20-fold higher than that observed for fish treated p.o. This ratio was lower for 14C-astaxanthin (7.6-fold). The mean keto-carotenoid bioavailabilities calculated were 10–15% for both compounds. Findings suggest one daily astaxanthin application is preferable, while 12-h time intervals between applications are preferable for canthaxanthin.
 
Recovered energy (RE) as protein and lipid (RE as lipid was calculated as the difference between RE and RE as protein) as a function of metabolizable energy (ME) intake of rainbow trout reared at 8.5°C for 24 weeks.
Formulation and composition of the experimental diet g kg À 1
Growth, feed e⁄ciency and utilization of nitrogen (N), lipid, phosphorus (P) and energy of rainbow trout à fed the experimental diets for 24 weeks
Carcass composition of the rainbow trout à fed the experimental diet for 24 weeks 25 50 75 100 SEMw Linear Quadratic
Article
The effects of feeding level on growth and energy partitioning were studied in rainbow trout growing from 150 to 600 g. Triplicate groups of fish (initial weight 158 g fish−1) were fed a practical diet at various feeding levels (25%, 50%, 75% and 100% of near satiation) for 24 weeks at 8.5°C. The final body weights of fish were 235, 381, 526 and 621 g. Restricted feeding levels significantly reduced live weight gain. Feeding levels had less pronounced effects on feed efficiency ratio, which were 0.98, 1.08, 1.02 and 0.83, respectively, for the 25%, 50%, 75% and 100% feeding levels. The growth of fish fed to near satiation was accurately described by the thermal-unit growth coefficient. The growth data also showed that the widely used specific growth rate was not an appropriate model. Fish fed at the lowest feeding level (25%), which represented a maintenance ration (energy gain was less than 2 kJ fish−1 day−1), showed positive protein deposition but negative lipid deposition. This indicates that fish fed a maintenance ration mobilize body lipid reserve to support protein deposition. The efficiency of energy for growth (kg) was estimated to be 0.63. The factorial multiple regression approach estimated that the partial efficiencies of metabolizable energy utilization for protein deposition (kp) and lipid deposition (kf) were 0.63 and 0.72, and that maintenance energy requirement was about 19 kJ (kg BW0.824)−1, for rainbow trout held at 8.5°C.
 
Article
The growth efficiency of juvenile Atlantic halibut, Hippoglossus hippoglossus (L.), was investigated by comparing wet weight specific growth rates (SGRs) over 28 days with protein synthesis rates measured using a non-invasive stable isotope (15N) tracer technique. A diet containing 15N-labelled protein was fed at a single meal and individual feed intake was measured by X-ray radiography to allow calculation of the amount of N consumed. Excreted ammonia and urea were collected from each fish and the ratio of 15N to 14N was used to calculate rates of protein synthesis. Peak rates of ammonia excretion occurred 12 h post-feeding. Rates of urea excretion did not change after feeding and remained relatively constant over the 48-h measurement period. Urea accounted for 17% of the measured nitrogen excretion and showed no enrichment with N. Mean protein growth rates were 1.31 ± 0.06% day−1, while whole animal fractional rates of protein synthesis were 2.02 ± 0.24% day−1. The mean protein synthesis retention efficiency was 77.41 ± 9.09%, which is higher than that recorded for most other teleosts. This suggests that halibut have a relatively low cost, high growth efficiency growth strategy.
 
Article
A method for the diagnosis of nocardiosis in yellowtail (Seriola quinqueradiata), using polymerase chain reaction (PCR), was developed in this study. Primers specific for Nocardia seriolae were synthesized based on the alignment of 16S−23S rRNA internal transcribed spacer region sequences of N. seriolae. The primers did not amplify specific PCR product from other fish pathogens. However, two and three fishes could be diagnosed as infected with N. seriolae by clinical signs and bacterial isolation. PCR amplification of N. seriolae by specific primers detected six infected fishes. Thus, the primers used in this study are useful in detecting nocardiosis in fish.
 
Article
In the current study, we assessed bacterial diversity in the gut content of pond-reared grass carp (Ctenopharyngodon idellus), in the associated habitat environments (pond water and sediment) and in the ingested food (commercial feed and the reed Phragmites australis) by analysing 16S rDNA sequences from clone libraries. The highest bacterial diversity was observed in the gut content and was determined by the total number of operational taxonomic units, Shannon diversity index (H), Shannon equitability index (EH), Coverage (Cgood) and rarefaction curves calculated from the 16S rDNA gene libraries. Our data indicated that allochthonous gut microbes of grass carp were distinctively different from the corresponding environmental microbes. The pairwise similarity coefficient (Cs) for microbe communities between gut content and ingested food was higher than for those between the gut content and habitats, indicating that the allochthonous microbiota identified in the intestines of grass carp were phylogenetically closer to those in the ingested food than to those in the habitat. Based on our study and previous research, we suggest that the digesta of grass carp harbours a microbiota phylogenetic core of Proteobacteria and Firmicutes and this observation deserves further investigations with respect to a potential pool of probiotics to grass carp.
 
Article
Duplicate groups of Atlantic salmon (Salmo salar L.), kept in seawater, were fed fish meal-based cold-pelleted diets. Diets with non-starch polysaccharides (NSP), either cellulose, purified soybean NSP or extruded purified soybean NSP at a dietary level of 100 g kg−1, were compared with a diet without supplemental NSP and a diet with soybean meal in a 28-day feeding trial. Isolation and characterizations were limited to culturable bacteria and population levels of aerobic and facultative aerobic heterotrophic autochthonous (adherent) and allochthonous (transient) bacteria present in the mid and distal intestines of Atlantic salmon fed the five different diets estimated using traditional bacteriological techniques. The presence of an autochthonous microbiota was demonstrated using transmission electron microscopy. No significant effects of diet composition were observed on total population levels of culturable bacteria present in the digestive tract, but the study showed that the composition of the gut microbiota (autochthonous or allochthonous) was sensitive to dietary changes. A total of 752 culturable isolates from the intestines were characterized by biochemical and physiological properties. Of these, 188 isolates were further characterized by partial sequencing the 16S rRNA genes. Among these, 146 isolates belonged to 31 phylotypes that were >94% identical to previously described species. However, 42 isolates showed similarity <94% to species available at the National Center of Biotechnology Information. Several of the phylotypes identified in the present study have not been reported previously in the gastrointestinal (GI) tract of fish, including the Gram-negative bacteria Gelidibacter salicanalis, Pseudoalteromonas elyakovii, Psychrobacter aquimaris, Psychrobacter cibarius, Psychrobacter fozii, Psychrobacter maritimus, Psychrobacter okhotskensis and Psychrobacter psychrophilus. Among the Gram-positive bacteria identified were Arthrobacter bergeri, Arthrobacter psychrolactophilus, Arthrobacter rhombi, Bacillus pumilus, Bacillus subtilis, Exiguobacterium spp., Microbacterium oxydans, Planococcus maritimus, Sporosarcina ginsengisoli and several bacteria that have been described as unculturable previously. In addition, we identified Carnobacterium inhibens, a lactic acid bacterium that is not frequently isolated from the GI tract of fish. Psychrobacter cibarius was the dominant bacterial species and was isolated from the digestive tract of all fish investigated.
 
Sampling sites for Litopenaeus setiferus populations from Mexico (Tuxpan, and Cd. Del Carmen) and L. schmitti populations from Cuba (Manzanillo=Mz).
Alignment of 16S gene of Artemia salina, Litopenaeus vannamei, L. schmitti, L. sylirostris, Metapenaeus lamellata, Pe- naeus monodon, L. setiferus, and Farfantepenaeus notialis
Dendrogram showing the genetic relationships among populations of Litopenaeus setiferus and L. schmitti estimates for eight electrophoretic loci.
Gene frequencies at the 10 polymorphic loci screened in two populations of Litopenaeus setiferus and L. schmitti
Article
Genetic differentiation and variability data of two populations of two species of shrimp (Litopenaeus setiferus (L.) and L. schmitti (Burkenroad)) have been obtained by electrophoretic analysis and by analysis of 16S mitochondrial DNA. Using eight polymorphic enzymes, the genetic distance (GD) between the two species was 0.165. The GD between L. setiferus populations was 0.0057 and between L. schmitti populations it was 0.0034. The greatest differentiation was found within, rather than between, populations, although the differentiation value between Mexican and Cuban populations varied in accordance with the geographic distance and ecological characteristic of each. We found a high similarity between these two species with a bimodal distribution of the loci with respect to genetic identity. The homology percentages for gene 16S fragments were compared with those from six different shrimp species (L. vannamei, L. stylirostris, Farfantepenaeus notialis, Metapeneopsis lamellata) and Artemia salina. Ninety-seven percent of identity was found by analysis of a 409 bp of 16S mitochondrial DNA. With these values a phylogenetic tree was made using parsimony criteria. The GDs obtained with this method confirm the classification proposed by Pérez-Farfante & Kensley (1997).
 
Article
Morphological and histological studies demonstrated that 17 α-methyltestosterone (MT) affects sex differentiation and can be used to control the phenotypic sex of pikeperch. Stizostedion lucioperca L. Treatment (for 21 days) of pikeperch (initially 2.2 g wet weight) with MT at 30 mg kg-1 diet induced germ cells inversion in approximately 46.67% of individuals (although 96.67% of the fish were classified as males). An increase in treatment duration (60 and 90 mg kg-1) increased the percentage of female, intersex and sterile fish. Slower growth rates of all the fish treated with MT in comparison to the control groups were demonstrated. However, no significant differences in conditions and mortalities between the MT treated fish and controls were observed.
 
Article
Monosex populations can be a valuable management tool in culture of larger size largemouth bass (>400 g). In this study, we investigated the effective mode and duration of oestrogen and androgen administrations to produce monosex largemouth bass populations. The experiment consisted of nine treatments. In oral administration groups, we fed 40-day-old fry either 200 mg of an oestradiol-17β (E2) kg−1 diet or 60 mg of a 17-methyltestosterone (MT) kg−1 diet for 30, 45 or 60 days. In bath treatments, we immersed fry in a 1 mg MT L−1 solution for 5 h a day on three or six occasions. For control treatment, we fed fry an ethanol-treated diet for 45 days. The frequency of females in the control group was 53.1%. Oral administration of E2 at all durations resulted in slight increases in the frequency of females (59.8–70.5%). Both modes of androgen administration at all durations were ineffective in altering phenotypic sex. The experimental results of our study indicated that male differentiation passed the point of being completely and functionally influenced by exogenous oestrogens, while female differentiation had already taken place and was no longer responsive to exogenous androgens in 40-day-old (33.5 mm) largemouth bass fry.
 
LC 50 (mg L À1 ) of total ammonia for all the larval stages of Scylla serrata and their 95% con¢dence limits (within brackets)
Article
While the effects of ammonia on fish and prawn larvae are well documented, little is known of its effect on mud crab (Scylla serrata) (Forsskål, 1755) larvae. Two experiments were conducted in 5 L hemispherical plastic bowls, containing 3 L of ultra-filtered and settled seawater and various larval stages of mud crab to (1) determine the acute median lethal concentration (LC50) of unionized ammonia and (2) to determine the chronic effects of unionized ammonia on survival and percentage moulting to zoea and megalop stages. The larval stages that exhibited the highest tolerance to ammonia over 24 h were zoea 1 (LC50 of 4.05 mg L−1 of unionized ammonia) and zoea 5 (LC50 of 6.64 mg L−1 of unionized ammonia). The megalop stage had the lowest total ammonia LC50 at both 24 and 48 h, making it the larval stage most susceptible to total ammonia. Exposure to 6.54 mg L−1 of unionized ammonia resulted in 100% death of all larvae within 24 h. The tolerance of S. serrata larvae to total ammonia did not appear to increase with ontogenetic development. The results indicate that the concentrations at which total ammonia produces an acute or chronic response in mud crab larvae are far higher than those experienced in current larval production systems (0–0.5 mg L−1 of total ammonia) used as industry standards in Australia.
 
Article
This preliminary study assessed genotype × diet interaction in late growth of European sea bass (Dicentrarchus labrax) fed with either a fish meal (FM)- or a fish oil (FO)-based diet (M) or an all-plant-based (PB) diet. A total of 550 fish from 224 families were reared together and tagged. DNA was sampled and microsatellites were used to assign parentage. When fish weight was 192 ± 54 g, two tanks were fed with M (FM: 100%; FO: 100%) and two others with PB (FM: 0% and FO: 0%). Body weight (BW), fork length (FL) and fillet lipid content (CorrFat) were analysed with a linear model and with REML methodology. We observed no significant differences between groups, but a slightly lower (P=0.03) daily growth coefficient in sea bass fed PB than in those fed M. Heritability estimates of BW differed significantly from zero (PB: 0.37 ± 0.18; M: 0.47 ± 0.24). Sire × diet interactions were significant and genetic correlations ranged between 0.51 and 0.87, showing genotype × diet interaction for BW and CorrFat. For the first time, genetic parameters in the context of total replacement of marine fishery by-products were estimated in European sea bass, showing re-ranking of family performances with extremely contrasted diets.
 
Article
Formulated feeds containing a common ingredient mixture (CIM) consisting of fishmeal (anchovies), shrimp meal (Acetes), squid meal (Loligo) and soybean meal incorporated in ascending levels to obtain protein levels ranging from 180 to 560 g kg−1(18.34%, 25.35%, 36.27%, 46.61% and 56.28%) and an energy level of 19 MJ kg−1 were fed to the marine ornamental fish, striped damsel, Dascyllus aruanus <200 mg and 200–300 mg in size for periods of 35 and 63 days. The <200 mg fish accepted particles <0.5 mm in size and showed maximum growth in terms of absolute growth rate (AGR), relative growth rate (RGR) and specific growth rate (SGR) with the feed containing 380 g kg−1 CIM having a protein content of 362 g kg−1. Second-degree polynomial regression equations fitted confirmed these observations with a predicted requirement of 360 g kg−1 protein. In fish weighing 200–300 mg, growth was not significantly different (P>0.05) in fish fed with feeds containing 380 and 580 g kg−1 CIM with 360 and 470 g kg−1 protein. With these data, the second-degree polynomial regressions showed that a protein level of 464 g kg−1 would result in an RGR of 107%. The feeds were well accepted by the damselfish, showing good colour retention and health.The cost of the feeds excluding processing costs ranges from US $ 1.35 to 3.36 kg−1. This is the first report on the development of formulated feeds for damselfish that would help in rearing and aquarium keeping of damselfish worldwide.
 
Article
With a 10-week microcosm experiment, we demonstrated that the mussel Mytilus edulis could feed and grow upon zooplankton, phytoplankton and mixture of them. The group supplied with the mixture showed the highest shell growth rate, egestion rate and largest size of faecal pellets. Individuals feeding on seawater (the control group) had the lowest growth rate, egestion rate and smallest size of faecal pellets. Egestion rates and faecal sizes of all the groups decreased with experimental time. Therefore, the mussel M. edulis could derive energy from many kinds of diet particles. Most of these particles within the water column may play an important role in bivalve nutrition, feeding and aquaculture. A mixed diet of phytoplankton and zooplankton yielded better growth performance and metabolism than diets of each fed separately.
 
Article
The effects of different levels of illumination on common dentex Dentex dentex (L.) larvae have been examined. Illumination affected the relationships between total length and digestive tube length, total length and oil globule volume, and total length and yolk sac. The relationship between total length development and yolk sac utilization in dark and light conditions was found to be significant (P<0.05). However, it was determined that the relationship between digestive tube development and oil globule absorption was not significant (P>0.05). Besides, there is no effect of different light intensities on absorption of yolk sac and oil globule and digestive tube development (P>0.05). In addition, total length development was not significant (P>0.05). Survival rate was found to be not significantly different in dark conditions (P>0.05).
 
Article
Wild female catfish Silurus asotus (Linnaeus, 1758) were injected with domperidone (DOM) alone, [d-Ala6, Pro9 Net]-luteinizing hormone-releasing hormone (LHRH-A) alone once or twice, LHRH-A plus DOM once or twice simultaneously at 6-h intervals, LHRH-A plus carp pituitary extract (CPE) twice simultaneously at 6-h intervals and LHRH-A plus human chorionic gonadotropin (HCG) twice simultaneously 6 h apart respectively. The results indicated that injection of LHRH-A at a dosage of 0.01–0.02 μg g−1 body weight (BWt) alone induced a low but significant increase in serum gonadotropin (GtH) (P<0.05) and resulted in a very low ovulation rate, while DOM at a dosage of 5 μg g−1 BWt alone did not induce an increase in the serum GtH levels and ovulation; in contrast, LHRH-A at a dosage of 0.01 μg g−1 BWt plus DOM at a dosage of 5 μg g−1 BWt (termed the Linpe technique) increased the serum GtH (P<0.05) significantly and induced an ovulatory rate of 100%, while LHRH-A plus CPE or HCG resulted in an increase in the serum GtH (P<0.05) and high ovulatory rate, although the latency period was longer when fish were given LHRH-A plus HCG or CPE.
 
Pectinid larval development stages in hatchery culture
Larval and post-larval development stages in Nodipecten nodosus (L). (a) Oocytes with germinative vesicle (vg); (b) expulsion of polar body (cp); (c) early morula stage; (d) ciliate gastrule. Scale bar (sb) in A±D ˆ 16 mm. (e) Early D-larvae stage; (f ) external view of right of D-larvae, prodissoconch I (pI) and II (pII) sb ˆ 25 mm; (g) view of umbonate outline (u) and issue of asymmetry in the anterior margin (ar) at day 7, sb ˆ 37 mm; (h) eyespot larvae at day 8, sb ˆ 52 mm; (i) pediveliger-stage larvae appear before 10 days. Ciliate foot (f ), sb ˆ 48 mm; ( j) early spat. Prodissoconch ( pd), dissoconch (d) and grill filaments (gf ), sb ˆ 75 mm. (k) Post-larvae 5 days after settlement. Dissoconch byssal notch (mb).
Larval and post-larval hinge structure of Nodipecten nodosus. (a) Right (up) and left (down) shell provinculum of prodissoconch II-stage larvae. (b) Inside view of dissoconch hinge structure of post-larval stage. Right (up) and left (down) shell.  
Article
This work describes for the first time the embryonic development of the tropical scallop Nodipecten nodosus. Larval and post-larval growth parameters and some characteristics of larvae shell morphology were also ascertained. The larvae were obtained from the induced spawning of a group of broodstocks under controlled laboratory conditions. After fertilization, larval cultivation was carried out in conical tanks at a temperature of 26–27 °C. Larval density was controlled as a function of larval growth to give 10, 5 and 3 larvae mL−1 from days 1, 3 and 8 respectively. The larvae were nourished with a 1:1 mix of Isochrysis galbana (clone T-ISO) and Chaetoceros gracilis in portions varying between 30 000 and 70 000 cells mL−1. Expulsion of polar groups was observed 5 and 15 min after fertilization, whereas the first cellular division occurred after 30 min. The first gastrule ciliates and trocophore larvae were noted after 8 and 18 h had elapsed, respectively, whereas prodissoconch I, or D-larvae, were discerned after 26 h. Subsequently, larvae with prodissoconch II or veliger-conch appeared at 30 h. Larval development continued for 10–12 days, followed by metamorphosis, at an approximate length of 208–230 µm. The growth of the post-larvae was evaluated for 9 days. Larval and post-larval growth corresponded to the linear equations L = 71.85 + 10.85t, r2 = 0.99, and L = 44.09 + 17.81t, r2 = 0.94 respectively. Accordingly, larval morphology and size disparities are discussed with respect to other tropical pectinids.
 
Article
We examined the effects of cyclic fasting in red porgy (Pagrus pagrus) fed different dietary carnitine levels. Juvenile fish (23.58 ± 3.49 g) were divided into eight groups – four groups were fed every day to apparent satiation, while the other four were fasted for 7 days every 2 weeks. In each feeding regime, two replicates were fed an l-carnitine non-supplemented diet (46 mg kg−1) and the other two groups were fed an l-carnitine supplemented diet (630 mg kg−1). Fish fed 630 mg l-carnitine accumulated two times more l-carnitine in muscle than fish fed 46 mg l-carnitine. Cyclic fasting reduced the growth performance and lipid content in the liver. Carnitine supplementation did not affect performance and body composition, but decreased the n-6 PUFA content. Moreover, the combined effects of fasting and carnitine supplementation were observed on reducing the n-3 fatty acid content. Areas of steatosis were found in the livers of red porgy, but the results revealed that supplementation of l-carnitine in cyclic fasted fish contributed towards a lower degree of vacuolization than in fish fed to apparent satiation. Regardless of the feeding regime applied, the spleen of fish fed the l-carnitine-supplemented diet was haemorrhagic and hyper activation of melanomacrophage cells was observed.
 
Article
The physico-chemical characteristics of particulate wastes of Sparus aurata and Dicentrarchus labrax were investigated. Changes in the dimensions, settling velocity and total ammonia nitrogen (TAN) leached from commercial feed pellets were investigated after soaking. Also, the settling velocity and TAN leached from faecal pellets of these fish were assessed at 15 and 25 °C. The settling velocity of feed pellets was influenced positively by pellet weight and negatively by immersion length as a result of changes in pellet dimensions after soaking. The settling velocity of faecal pellets was determined by pellet weight. The experimental design did not allow identification of any consistent effect of water temperature on settling velocity. Total ammonia nitrogen leaching over time from feed and faecal pellets was successfully explained by means of a first-order kinetic equation. For feed pellets, water temperature significantly affected the speed of the process and the time at which the maximum TAN leached was reached, but did not influence the maximum TAN leached. Leaching was related to feed pellet size, and so the smaller the pellet, the higher the leaching. Total ammonia nitrogen leaching from faecal pellets was greater per unit weight than in feed pellets. However, neither water temperature nor fish species influenced TAN leaching from faeces.
 
Basic statistics for selected water quality variables from water samples taken in tank positions 1^4 and 5^7
Article
To quantify the effects of serial-use of water on abalone growth and feed conversion, this study describes water quality in a serial-use raceway with seven passes. A flow index of 7.2–9.0 L h−1 kg−1 was estimated as the minimum value at which to grow 60–70 mm Haliotis midae, as weight gain (analysis of variance; F6, 14=13.9, P<0.0001) and feed conversion ratio (Kruskal–Wallis test; H6, 21=16.3, P=0.012) were significantly reduced at lower values. pH and dissolved oxygen concentration were positively correlated with the flow index (pH, r2=0.99; P<0.001; dissolved oxygen, r2=0.99; P<0.001), while free ammonia nitrogen (FAN) and nitrite were negatively correlated with the flow index (FAN, r2=0.99, P<0.001; Nitrite, r2=0.93, P<0.001). The concentration of nitrite increased throughout the experiment and may reflect the colonization of Nitrosomonas bacteria as water re-use increased. Based on comparisons with growth and toxicity tests, it is suggested that low pH combined with growth-limiting levels of FAN were the first variables limiting abalone growth in the serial-use raceway.
 
Article
The effects of handling on haematocrit, haemoglobin, plasma glucose, lactate and total amino acids, liver glycogen and hepatic activity of fructose 1,6-bisphosphatase (FBPase) and alanine aminotransferase (AAT) were investigated in common dentex (Dentex dentex Linnaeus, 1758). A total of 42 fish (50-g weight) were subjected to handling (netting and shaking in the air for 45 s). Six fish were sampled at 0, 0.5, 1, 2, 4, 8 and 12 h after handling. Six unstressed fish were also sacrificed at each time and used as controls. Handling resulted in a rise in plasma glucose and lactate levels, as well as in enhanced hepatic FBPase and AAT activities. In most cases values returned to control levels 8 h after handling. There were no significant changes in haematocrit, haemoglobin, plasma total amino acids and liver glycogen levels as a consequence of handling. The results suggest that dentex is rather tolerant to handling; apparently, sensitivity to handling is not the main factor responsible for the low survival exhibited by this species in aquaculture.
 
Physical parameters of blue¢n tuna
Water quality parameters in sampling areas
Blood biochemical parameters of wild and captive blue¢n tuna
Article
Northern bluefin tuna (NBT) are a prominent marine pelagic fish species. There are few reference values for their blood chemistry and this is the first report to demonstrate blood biochemical values in the Eastern Mediterranean. The study was carried out with 60 captive (penned) and 60 wild NBTs from Ildir Bay (Izmir) and Antalya Bay in the Eastern Mediterranean, from winter to early summer 2003. The aim of this research was to determine the biochemical parameters of wild male/female and captive male/female NBTs. According to the present results, the blood biochemical values of the captive NBTs were significantly higher than those of wild NBTs (P<0.05) except albumin, globulin, total protein and very low-density lipoprotein levels. Moreover, many of the biochemical parameters were detected at high levels in captive and wild male NBTs than those of the females. Especially, the values of glucose, lactate dehydrogenase, creatine phosphokinase, γ-glutamyl transferase, cholesterol, triglyceride, low-density lipoprotein, ferritin, transferrin and iron levels were significantly higher, although high-density lipoprotein values were significantly lower in wild and captive male samples than those of both groups of females (P<0.05).
 
Sample of red colour Oreochromis niloticus breeders from the base population.
Sample of red colour Oreochromis niloticus breeders from the fifth selection generation.
Proportion of red colour and wild type Oreochromis niloticus specimens in ¢ve selection generations for red col- our and number of fry collected during reproduction season
Male and female colour, number and red fry per- centage in eight pairs of Oreochromis niloticus
Article
Mass selection in Oreochromis niloticus, Stirling strain, was used to obtain a red colour homozygous dominant population from a base population containing wild type and red fish with black blotches. Each selection generation included 28–80 breeders in a 1:1 male:female ratio and a density of 1 pair m−2.First selection for red colour was done when fry reached 3 g, discarding those exhibiting wild type colouring or with a high black blotch incidence. Second selection was done before fish began the reproduction stage. To determine if red-coloured fish were homozygous, a progeny test was done with the fifth selection generation using eight individual crosses of red males with wild type females and wild type males with red females. Red colour proportion increased from 5.6% in the first generation to 100% in the fifth generation. All fry in the progeny test were red colour, inferring that the population was homozygous dominant (RR). Accumulated inbreeding rate in the fifth selection generation was 1.79%. The selection process did not affect fecundity as fry production in red colour females was similar to that in wild type females. Mass selection to obtain a red homozygous population in O. niloticus, Stirling strain, was appropriate and was also effective in reducing black blotch incidence in the same species.
 
Article
The aim of this study was to compare the amino acid (AA) composition of edible parts of three experimental groups of carp, i.e. a pure line of Přerov scaly carp (PS), a hybrid line of Přerov scaly carp and Northern mirror carp (PS × M72), and a hybrid line of Přerov scaly carp and Ropsha scaly carp (PS × ROP), with the quality of the edible parts of control hybrids of Hungarian and Northern mirror carp (M2 × M72) in harvest size (K3). A comparison between the controls (M2 × M72) and experimental carp (PS, PS × M72, PS × ROP) showed that their muscle tissues contained the same amounts of 10 AA [essential amino acids (EAA): Thr, Val, Leu, Phe, Lys, His; non-essential amino acids (NEAA): Asp, Gly, Ala, Tyr] of the 16 AA determined. Glu, Asp, Lys and Leu were the AA with the highest muscle concentrations. The total EAAsum and NEAAsum contents in the fastest-growing PS × ROP hybrid, in spite of specific differences found (P<0.05: Arg, Met; P<0.01: Pro), were practically identical to those found in the control group of M2 × M72 mirror carp. PS × ROP hybrid female and male muscle tissues differed (P<0.05) only in Met and Ala levels. Hard roes of experimental female carp (PS, PS × M72, PS × ROP) contained the largest quantities of Glu and Val, and that of control female carp (M2 × M72) the largest quantities of Glu and Gly. Hard roes of PS × ROP hybrids contained the largest quantities (P<0.01) of EAAsum (52.44±0.19%). Compared with hard roes, soft roes from all groups of carp contained more EAAsum (PS × ROP: 55.03±0.26%). The two most abundant AA in soft roes were Lys and Arg. The most abundant AA in the hepatopancreas in all carp groups were Glu, Asp, Leu and Arg. Hepatopancreas EAAsum levels in experimental carp (PS, PS × M72, PS × ROP) were significantly (P<0.05) lower than those in controls (M2 × M72).
 
Article
This study assessed the use of increasing levels of brown propolis extract (BPE) as a growth promoter in Nile tilapia fingerling feeds. In a complete randomized design, 75 Nile tilapia fingerlings with 60 days on average and weighing 4.1±0.1 g were assigned to 25 aquaria (60 L) and subjected to 5 treatments in 5 repetitions for 30 days. Propolis from Serra do Araripe, Cariri Region, South Ceará State – Brazil was used to produce the BPE. The treatments involved the addition of BPE to feed samples (0.91, 1.83, 2.74 and 3.65 g kg−1) and feed control (without BPE). The final mean weight and the percentage of weight gain varied quadratically with the increase in BPE (P<0.01), with a maximum of 2.22 g kg−1. The other evaluated parameters were not affected by the treatments (P>0.05). The level of best performance parameters was 2.22 g kg−1, between the levels of 1.83 and 2.74 g BPE kg−1 feed inclusion. These results indicate the potential to use the brown propolis extract as a growth promoter to Nile tilapia fingerlings.
 
Article
Common dentex larvae were reared using two culturing techniques, mesocosms and intensive rearing, to determine the principal culture parameters involved in the differences observed in growth, skeletal deformations and survival between the two rearing techniques. In growth, only dry weight of larvae of 40 days post-hatching (dph) from mesocosms was significantly higher than larvae from intensive rearing. Significant differences were observed in survival at 40 dph (6.58% in mesocosms and 1.58% in intensive rearing) and in the incidence of skeletal deformations, both for percentage of deformed larvae and for some deformation types such as those related to vertebral column and to the caudal complex. Initial larval density and initial prey density and quality are the factors suspected to affect growth and survival performance, while skeletal deformities might also be affected by tank hydrodynamics.
 
Article
Red porgies (Pagrus pagrus) of 20.6±1.5 g mean weight were reared in tanks under four delayed self-feeding conditions (0=control, 7, 30 and 90 s) after rod activation. The time intervals were chosen to simulate the time taken for a commercial pelleted feed to transit the tube linking a surface-mounted feed hopper and the depth at which a cage might be submerged. Daily feeding rate, growth, food conversion index and condition factor were quite similar but fish behaviour differed among conditions. Fish remained close to the feeding point in the first two treatments (0 and 7 s delay) but foraged more widely in the remaining treatments (30 and 90 s delay), only reconsolidating around the feeding point a few seconds before feed was released. Results are discussed in relation to learning capacity and adaptation of fish to feeding behaviour flexibility, in order to develop reliable self-feeding systems suitable for submerged cages.
 
Article
The oxygen consumption (02) and ammonia excretion (N) of juvenile and adult common wolffish was measured in culture tanks in the laboratory. The oxygen consumption and ammonia excretion were affected by temperature (C), fish size and feeding rate. For juveniles (0.5 kg; 7C) the diel oxygen consumption rate varied between 37 and 62 mg O2 kg-1 h-1 and ammonia excretion between 2.3 and 5.7 mg N kg-1 h-1. The corresponding rates for adult fish (6.9 kg; 7C) were 29-44 mg O2 kg-1 h-1 and 1.2–3.1 mg N kg-1 h-1. The weight-specific oxygen consumption (mg O2 kg-1 h-1) was described by the following formulae: O2 (7C) = 0.17* W0.83 and O2 (12C) = 0.39 * W0.73 and the corresponding ammonia excretion (mg N kg-1 h-1) by: N(7C) = 0.024 W0.75 and N(12C) = 0.073 W0.60, where W is fish weight in g.
 
Article
Red porgy, Pagrus pagrus L., is a potential candidate for marine finfish diversification on commercial Mediterranean and Atlantic coastal aquaculture. This paper described the development of a suitable larval rearing protocol for commercial application. Red porgy eggs were reared under Intensive and Semi-intensive systems until 50 days after hatching. In addition, two different weaning protocols were tested for each rearing system. The effects of these treatments were evaluated on the growth, survival and whole-body biochemical and fatty acid composition of red porgy larvae. Significant differences in growth but not in survival at 50 days after hatching were detected in trial A for the semi-intensive and intensive rearing system (23.5 ± 2.7–18.9 ± 3.4 mm; 4.4–4.9%); however, modifications in initial prey density and illumination conditions, implemented in trials B (29.5 ± 3.0–25.2 ± 1.9 mm; 21.8–5.3%) and C (26.2 ± 2.6–24.6 ± 2.6 mm; 22.7–3.8%), significantly improved survival and growth rates in the semi-intensive rearing system. Furthermore, the results in trial C confirmed the feasibility of a partial reduction in Artemia use and the significant improvement in survival rates with the new weaning protocol applied (26.4 ± 2.3–24.1 ± 3.9 mm; 28.7–12.5%) in the intensive systems. The results of this study concluded that the best larval rearing protocol for commercial production of red porgy fingerlings should include the use of semi-intensive systems.
 
Article
A feeding experiment was conducted to evaluate the effect of rotifers (Brachionus plicatilis) and Artemia sp. enriched differently on early growth, survival and lipid class composition of Atlantic cod larvae (Gadus morhua). Rotifers enrichments tested were: (1) AlgaMac 2000®, (2) AquaGrow® Advantage and (3) a combination of Pavlova sp. paste and AlgaMac 2000®. The same treatments were tested with Artemia as well as a combination of DC DHA Selco® and AlgaMac 2000® as a fourth treatment. After rotifer feeding, the larvae from treatment 3 [1.50 ± 0.11 mg dry weight (dw)] were significantly heavier than larvae from treatment 2 (1.03 ± 0.04 mg dw). After feeding Artemia, the larvae from treatment 1 were significantly heavier (12.06 ± 2.54 mg dw) than those from treatments 3 (6.5 ± 0.73 mg dw) and 4 (5.31 ± 1.01 mg dw). Treatment 3 resulted in the best survival through the 59 days of larviculture. After rotifer feeding, high larval concentrations of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), arachidonic acid (AA) and ω6 docosapentaenoic acid (ω6DPA) could be linked to better larval growth and survival while after feeding Artemia, high larval DHA/EPA ratios (∼3) and high DPA/AA ratios (>1) could be linked to better survival.
 
Zooplankton abundance of the three groups in Lake Kuriftu (individuals m−3) at the two sites.
Zooplankton taxa identi¢ed from Lake Kuriftu during in this study time
Percentage (%) composition of phytoplankton in Lake Kuriftu
List of phytoplankton identi¢ed from Lake Kuriftu
Article
This research was conducted to investigate the effect of stocking density on the growth performance and yield of Oreochromis niloticus in cage culture in Lake Kuriftu. The treatments had stocking densities of 50 (50F), 100 (100F), 150 (150F), and 200 (200F) fish per m−3. All treatments were in duplicate. Juveniles with an average weight of 45. 76±0.25 g were stocked in the treatments. The fish were fed a composite mixture of mill sweeping, cotton seed, and Bora food complex at 2% of their body weight twice per day using feeding trays for 150 days in powdered form. The growth performance of O. niloticus was density dependent. The final mean weight of O. niloticus ranged 147.76±0.28–219.71±1.42 g and the mean daily weight gain was 0.69±0.01–1.15±0.02 g day−1. Fish held in cages with lower density were heavier than the ones held at higher densities, and showed higher weight gain and daily weight gain. The most effective stocking density, in terms of growth parameters, was 50 fish m−3. The gross yield (4.5–20.55 kg cage−1) showed a significant difference with increasing stocking density (P<0.05). Moreover, the apparent food conversion ratio (2.48–7.22) was significantly affected by stocking density (P<0.05). However, survival rate was not affected by stocking density (P>0.05). It can be concluded that the most effective stocking densities were at 50 fish m−3 cage for larger size fish demand in a short period and 200 fish m−3 for higher gross production with supplementary feed.
 
Article
Growth and survival of the scallop Lyropecten nodosus were studied in 1997 at two sites (inner and outer Turpialito Bay) during a non-upwelling period normally occurring between August and November. Individuals had an initial shell height of 4.86 cm (SD=1.64 cm). Both experimental groups were held in suspended plastic baskets at the same depth (4 m). Measurements of shell height and dry weights of shell, gonad, digestive gland, remaining tissues and shell biofouling were taken at monthly intervals. Environmental parameters, including temperature, phytoplanktonic biomass, total particulate material (TPM) and associated organic (POM) and inorganic (PIM) fractions, were recorded simultaneously. At the end of the study, significant differences in growth and survival of scallops were observed between the two experimental sites. Scallops maintained inside the bay showed a 22% greater increase in shell height (7.41±0.27 cm) than those placed outside the bay (6.37±0.41 cm). Survival of scallops inside the bay was 31% higher compared with scallops outside. The greater availability of food of phytoplanktonic origin during the first two experimental months (July and August) together with greater POM throughout the whole experimental period except September, at the inner bay site, probably explained survival and growth differences observed between the two locations. Results suggest that, during the non-upwelling period (characterized by low primary productivity and high water temperatures), POM of sedimentary origin may play an important role as an energy source required for metabolic and reproductive activities of L. nodosus.
 
Article
The effect of temperature on the development, growth, survival and settlement of Perna viridis was studied under controlled conditions to provide information needed for the development of commercial hatchery technology for green mussel P. viridis. Total mortality of the larvae occurred after 24 h at temperatures of 33°C and 35°C. At 24°C, larvae took longer to settle than at temperatures of 27°C, 29°C and 31°C. For optimum larval development (8–13 h), growth (17.2±0.84 μm day–1) and survival (55.2±0.84%), a hatchery rearing temperature of 31°C is required. For settlement no significant difference was seen between the percentage settlement at 29°C (49.3±3.34%) and 31°C (45.8±1.76%). However, the process of settlement began and ended earlier at 29°C (from 15 to 18 days) than at 31°C (from 18 to 20 days). Thus for larval settlement a temperature of 29°C is recommended.
 
Article
Performance tests of the Pr̆erov Scaly Carp (PS), two crossbreds (PS × M72 and PS × ROP) and an internal control group (M2 × M72) were designed to assess their production and dressing out parameters at harvest size for their potential commercial utilization. The fastest growth rate (standard length (SL): 405±21.91 mm, P<0.01) and the highest final live weight (FLW: 2015.70±323.92 g, P<0.01) were recorded in the PS × ROP hybrid. The SL values in this group of carp were 12.5%, 19.12% and 11.57% higher (P<0.01) than those at M2 × M72, PS and PS × M72, respectively, and the FLW values were 21.57%, 62.83% and 24.37% higher (P<0.01) compared with M2 × M72, PS and PS × M72 hybrids respectively. Growth rate parameters of PS × M72 hybrid and control group M2 × M72 were practically identical. The lowest growth rate potential and FLW were recorded in the PS group (P<0.01). The highest (P<0.01) dressing out parameters were found in the control group of mirror carp M2 × M72 with a dressing percentage of 65.64±2.11%. There were practically no differences in this parameter between scaly carp groups (PS: 61.79±2.82%, PS × M72: 61.51±1.72%, PS × ROP: 63.60±1.96%). This study shows evidence for faster somatic growth and bigger final weight in the hybrid line PS × ROP of 3-year-old common carp compared with the pure line PS and the crossbreed PS × M72.
 
Article
One of the bottleneck problems of Diplodus sargus farming is a high incidence of skeletal deformities at the vertebral column. In this study, the pattern of vertebral deformities were determined in three different larval batches from 2 to 30 days after hatching (DAH). During this period, 60 larvae per spawn were observed at 2, 8, 13, 15, 18, 21, 23, 25, 27 and 30 DAH and the different types and frequency of vertebral column malformations were registered. Deformities started from 8 to 13 DAH, when the percentage of deformed larvae rose from approximately 5% to 40%. At 15 DAH, skeletal malformations had frequencies up to 80% of the observed larvae. Serious malformations such as kyphosis, scoliosis and lordosis were observed at 18 DAH but seldom in percentages higher than 15%. Vertebral fusions and compressions especially affected the preurostyle region. Abnormal shape vertebrae were more frequent between vertebrae 15 and 21. Other malformations observed were hypertrophic vertebrae, more common in the trunk and caudal regions, reaching percentages higher than 50% in the former. This study has useful information concerning skeletal malformations at the vertebral column of D. sargus larvae, as it identifies the main deformities observed and the ages of highest incidence.
 
Article
Juveniles of the fan mussel Pinna nobilis were collected in Mali Ston Bay from October to December 2006. Cages with juveniles were placed at three depths: 1, 3 and 5 m. At the end of a 2-year growth period at 1 m depths, the average length was 244.1 ± 22.9 mm, at 3 m depths, specimens averaged 244.0 ± 25.3 mm, and at 5 m depths, the average length was 231.1 ± 22.5 mm. The average monthly growth of shell length for the total experimental period was 8.7 ± 5.3, 8.4 ± 4.5 and 7.6 ± 4.4 mm, at 1, 3 and 5 m depths respectively.
 
Article
This study was designed to determine the effect of complete substitution of fish meal (FM) by three plant protein sources including extruded soybean meal (SBM), extruded full-fat soybean (FFSB) and corn gluten meal (CGM) on growth and feed utilization of Nile tilapia Oreochromis niloticus and tilapia galilae Sarothrodon galilaeus. Four isonitrogenous of crude protein (ca. 28.0%) and isocaloric (ca. 19 MJ kg−1) experimental diets were formulated. The control diet (diet 1) was prepared with FM as the main protein sources. Diets 2–4, each FM control diet, were completely substituted with SBM (diet 2), FFSB (diet 3) and CGM (diet 4). l-lysine and dl-methionine were added to plant protein diets to cover the nutritional requirements of tilapia. Each treatment was allocated to three net pens and fed for 17 weeks. Nile tilapia fed the control diet showed significantly higher (P≤0.05) values for final body weight (FBW), feed intake (FI), weight gain (WG) and specific growth rate (SGR), whereas fish fed the diet with CGM achieved the lowest values. Tilapia galilae fed SBM diet recorded the highest (P≤0.05) values for growth performance. Better feed conversion ratio (FCR) for both Oreochromis niloticus and Sarothrodon galilaeus was observed when fish were fed SBM diet, whereas the worse FCR was recorded for FFSB diet. Feed utilization parameters including protein productive value (PPV), fat retention (FR) and energy retention (ER) showed significant differences (P≤0.05) for both the species fed different dietary protein sources. The present results suggest that, for Nile tilapia, both SBM and FFSB supplemented with dl-methionine and l-lysine can completely replace dietary FM. Meanwhile, S. galilaeus fed SBM diet exhibited comparable growth and feed utilization with those fish fed a fish-meal-based diet.
 
Article
abstractTo examine the impact of fouling organisms on the growth and survival of the scallop Euvola ziczac L., we maintained 31-34-mm juveniles in pearl nets at 8 m in depth at Turpialito, Golfo de Cariaco, Venezuela. The experiment ran for a 67-d period under four conditions: (1) shells and nets cleaned; (2) shells not cleaned and nets cleaned; (3) shells cleaned and nets not cleaned; and (4) shells and nets not cleaned. The growth of the scallop was least when fouling developed on both the pearl nets and scallop shells. The rate of growth of the shell (height and mass) was strongly affected by organisms colonizing the pearl nets and only weakly affected by organisms colonizing the shells. Fouling organisms on the shells only slightly affected rates of increase of tissue mass, but probably accounted for increased mortality. In developing commercial culture of E. ziczac, strategies need to be developed to limit the adverse effects of fouling on yield.
 
Article
This study determined biometric and weight parameters and relevant indices of diploid and triploid tench. Altogether, 137 siblings of tench were studied. The effect of ploidy level appeared in significantly better growth of triploids (P<0.001) as to biometric [total length (TL), standard length (SL), body height (BH), body width (BW)] and weight [fish weight (FW), carcass weight (CW)] parameters of T3 of both sexes and of T3+ females. The effect of ploidy level also appeared as significantly higher dressing percentage (DP; P<0.001) of triploid T3 females compared with other groups, significantly higher gonad weight (GW) and gonadosomatic index (GSI; P<0.001) of diploid T3 females, as well as GSI and hepatosomatic index of diploid T3+ females. The effect of sex appeared in significantly higher (P<0.001) biometric (TL, SL, BH, BW) and weight (FW, CW) parameters of T3 females of both ploidy levels, as well as of triploid T3+ females. The effect of sex also appeared as significantly higher DP (P<0.001) of males in diploid T3 fish, as well as of males of both ploidy levels in T3+ fish and significantly higher GW and GSI (P<0.001) of females in diploid T3 fish, as well as of females of both ploidy levels in T3+ fish. This study shows evidence for faster somatic growth and bigger final weight of triploid populations of tench compared with diploids in both age categories T3 and T3+.
 
Article
Reproductive variables from 1529 females and 168 males of Atlantic salmon Salmo salar L. 1758 were recorded individually during the 1995 spawning season at a salmon farm in the south of Chile. The spawning period occurred in autumn and lasted 43 days, with a peak occurring in the first week of May. Average mature female and male body weights were 6.4 ± 0.9 kg and 7.0 ± 1.0 kg respectively. Average total and relative fecundity of females were 5998 ± 1404 eggs and 946 ± 210 eggs kg−1 respectively. Female body weight showed a similar pattern of correlation with total and relative fecundity observed in other salmonids. Average total and relative volume of ejaculate of males were 47.7 ± 32.8 cm3 kg−1 and 7.26 ± 5.44 cm3 kg−1, respectively, with the latter being lower than the values reported in the literature. Furthermore, male weight showed a negative correlation with these variables, in contrast to a positive value reported for these correlations in the northern hemisphere. Ejaculate volume showed a positive correlation with date of stripping. Average sperm density (5.83 ± 3.75 sperm cm−3 10−9) was lower than the values found in the literature and could be explained by the higher ejaculate volumes.
 
Top-cited authors
Einar Ringoe
  • UiT The Arctic University of Norway
Delbert M. Gatlin
  • Texas A&M University System
Ashild Krogdahl
  • Norwegian University of Life Sciences (NMBU) Faculty of Veterinary Medicine
Konrad ryszard Dabrowski
  • The Ohio State University
Gibson Gaylord
  • U.S. Fish and Wildlife Service