Sexual differentiation was studied at the histological level using a mixture of 30 families of se... more Sexual differentiation was studied at the histological level using a mixture of 30 families of sea bass Dicentrarchus labrax. Most of the fish (93%) differentiated into males as usually observed in farmed populations. All testes were differentiated when the males reached 12 cm and no more undifferentiated fish were found from 419 days postfertilization (p.f.). In 28% of the males, among the biggest, sexual differentiation had already begun at 168 days p.f. (8.3-9.5 cm) and these fish started spermatogenesis in their first year of life. The other males differentiated later and remained immature at the end of their first year of life. Ovaries could be identified at the histological level from the age of 168 days p.f. (7.9-9.0 cm) and the females became significantly longer than the males from the age of 191 days p.f., i.e. during the process of ovarian differentiation. In the studied group, 62% of the males developed intratesticular oocytes. Such intersexuality had no consequence on growth rate. Intratesticular oocytes were also recorded in testes of wild males originating from Atlantic (Britain and Gulf of Gascogne) and West Mediterranean showing that juvenile intersexuality is not restricted to farmed populations but is a widespread phenomenon in sea bass.
Journal of the World Aquaculture Society, May 18, 2021
The Tripletail, Lobotes surinamensis, is a warm-water pelagic fish that is increasingly targeted ... more The Tripletail, Lobotes surinamensis, is a warm-water pelagic fish that is increasingly targeted by U.S. anglers. The superior quality of Tripletail flesh coupled with the lack of domestic commercial fisheries stimulated interests to develop aquaculture of this species. In this work, photothermal conditioning of captive-held broodstocks promoted maturation in females, but spontaneous spawning was not observed. GnRHa slow-release implants induced ovulation in late vitellogenic females but fertility remained below 10% when GnRHa was administered alone. However, spawns with high fertility (up to 85%) were obtained when a dopamine antagonist was administered in conjunction with GnRHa implants indicating dopamine inhibition impaired final gamete maturation, in particular sperm production in males, in aquaculture conditions. Tripletail larvae successfully initiated exogenous feeding on enriched rotifers followed by Artemia nauplii and were weaned to prepared feeds at 25 days post hatch, yet with low survival through the late phases of larval culture. Pilot grow-out trials at low density in recirculating systems revealed impressive growth rates averaging over 170 g/month through a market size M201-13-01; Perciformes Group LLC
The red snapper Lutjanus campechanus is an exploited reef fish of major economic importance in th... more The red snapper Lutjanus campechanus is an exploited reef fish of major economic importance in the Gulf of Mexico region. Studies of genome wide genetic variation are needed to understand the structure of wild populations and develop breeding programs for aquaculture but interpretation of these genome scans is limited by the absence of reference genome. In this work, the first draft of a reference genome was developed and characterized for the red snapper. P-454 and Illumina sequencing were conducted to produce paired-end reads that were assembled into reference contigs and scaffolds. The current assembly spans over 770 Mb, representing an estimated 69% of the red snapper genome in 67,254 scaffolds (N50 = 16,803 bp). The genome contigs were applied to map double digest Restriction-Site Associated DNA Tags and characterize Single Nucleotide Polymorphisms (SNPs) in five outbred full-sib families. The identified SNPs and 97 microsatellite loci were used to generate a highdensity linkage map that includes 7,420 markers distributed across 24 linkage groups and spans 1,346.64 cM with an average inter-marker distance of 0.18 cM. Sex-specific maps revealed a 1.10:1 female to male map length ratio. A total of 4,422 genome contigs (10.5% of the assembly) were anchored to the map and used in a comparative genomic analysis of the red snapper and two model teleosts. Red snapper showed a high degree of chromosome level syntenic conservation with both medaka and spotted green puffer and a near one to one correspondence between the 24 red snapper linkage groups and corresponding medaka chromosomes was observed. This work established the first draft of a reference genome for a lutjanid fish. The obtained genomic resources will serve as a framework for the interpretation of genome scans during studies of wild populations and captive breeding programs.
North American Journal of Aquaculture, Jan 2, 2014
ABSTRACT The Atlantic Croaker Micropogonias undulatus (Sciaenidae) is a candidate species for mar... more ABSTRACT The Atlantic Croaker Micropogonias undulatus (Sciaenidae) is a candidate species for marine baitfish aquaculture in the southeastern United States because of its high value and common use as live bait by recreational fishers. However, an efficient larviculture procedure has not been reported to date; development of such a procedure was the impetus for this study. Embryos were obtained from captive broodstock that were induced to spawn volitionally by using a single injection of a luteinizing hormone releasing hormone agonist. Larvae were cultured at lowdensity (initial density=6.4 larvae/L) via intensive culture methods, including the use of recirculating filtration systems and of rotifers, brine shrimp Artemia spp., and micropellets as larval foods. The trial was performed in six 1,100-L tanks at a salinity of 14–29‰, with average rearing temperatures of 23.6◦C and 24.6◦C. At the completion of the study (39 d posthatch), mean SLs were 24.7 mm (SE = 0.738) for larvae cultured at 24.6◦C and 23.0 mm (SE = 0.624) for larvae cultured at 23.6◦C. Mean survival at 39 d posthatch was 25.9% and did not differ significantly between temperature groups. This work demonstrated a successful methodology for intensive larviculture of Atlantic Croakers and can serve as a platform for the experimentation that will be necessary to develop economically viable procedures for intensive production of this species.
ABSTRACT Twenty one microsatellite markers were isolated from two enriched genomic libraries of t... more ABSTRACT Twenty one microsatellite markers were isolated from two enriched genomic libraries of the gray triggerfish, Balistes capriscus. The number of alleles detected varied between 4 and 27, and expected heterozygosity estimates ranged from 0.502 to 0.967 (n = 35). Genotypic proportions conformed to Hardy–Weinberg expectations for all but two of the loci. The microsatellite markers developed in this work will be precious to conservation genetics studies of the gray triggerfish.
An intensive, large-scale batch culture system to produce the calanoid copepod, Acartia tonsa. Aq... more An intensive, large-scale batch culture system to produce the calanoid copepod, Acartia tonsa. Aqua (2018),
Twenty nuclear-encoded microsatellites from a genomic DNA library of cobia, Rachycentron canadum ... more Twenty nuclear-encoded microsatellites from a genomic DNA library of cobia, Rachycentron canadum , were isolated and characterized. The microsatellites include two tetranucleotide, one trinucleotide, three combination tetranucleotide/dinucleotide, nine dinucleotide, and five imperfect (dinucleotide) repeat motifs. Gene diversity ranged between zero to 0.910; the number of alleles among a sample of 24 fish ranged from one to 15. Cobia support an important recreational fishery in the southeastern United States and recently have become of interest to aquaculture. The microsatellites developed will be useful tools for studying both population genetics (e.g. stock structure, effective population size) and inheritance of traits important to aquaculture.
The quality of red snapper eggs is highly variable and unpredictable in aquaculture, leading to h... more The quality of red snapper eggs is highly variable and unpredictable in aquaculture, leading to high mortality during early larval rearing. In this work, the viability of red snapper eggs was monitored from fertilization until unfed larvae expired because of exhaustion of vitelline reserves to determine egg quality traits in this species. The spawns were obtained via strip spawning wild-caught females following hormonal induction with chorionic gonadotropin. Females were induced immediately after capture (wild group, n = 17) or held captive for the entire maturation period prior to induction (captive group, n = 7). Candidate predictors of egg quality measured on the female parent at the time of induction or on the spawn at ovulation were evaluated using correlation and multiple regression analysis. The fertilization rate, the hatching rate, and the duration of survival of unfed larvae post hatch were weakly correlated to each other (-0.23 < r < −0.08), revealing occurrence of distinct and independent components of egg quality. Spawns from captive females were characterized by a longer latency interval between hormonal induction and ovulation, lower fecundity, and lower hatching rates, as compared to those from wild females. Among the wild brood fish, a positive correlation was observed between the age of the female and the hatching rate. The best model optimized during stepwise multiple regression analysis of hatching rate data only explained 34% of the variance for this trait and no model could be optimized for the prediction of fertilization rate or the duration of survival post hatch. These results highlight the need to develop alternative egg quality measures to predict the viability of fry with confidence.
Highlights ► In aquaculture, incubation of eggs under high density leads to hypoxia and elevated ... more Highlights ► In aquaculture, incubation of eggs under high density leads to hypoxia and elevated ammonia concentration. ► Knowledge of the effects of these stressors on the viability of marine species is very limited. ► Red snapper embryos and newly hatched larvae were exposed to different levels of hypoxia and elevated ammonia concentrations. ► The minimum dissolved oxygen level and maximum ammonia concentration compatible with short term survival indicate high sensitivity to these stressors and warrant further study. ► The tolerance to hypoxia and elevated ammonia concentration is variable among spawns highlighting the possible occurrence of parental effects and the need to characterize multiple spawns when determining safe levels for hatchery production.
North American Journal of Fisheries Management, Aug 1, 2011
Gray triggerfish Balistes capriscus is a reef fish exploited by recreational and commercial fishe... more Gray triggerfish Balistes capriscus is a reef fish exploited by recreational and commercial fisheries in the southeastern United States. Recent stock assessments indicated that the species is overfished, and a rebuilding plan is in progress. The U.S. fishery is currently managed as a single stock owing to the absence of reliable information on stock structure. We sequenced a 617‐base‐pair fragment of the ND4 mitochondrial gene in a total of 150 specimens from five localities (South Texas, Louisiana, West Florida, southeastern Florida, and South Carolina) encompassing the exploited range of the species in the USA. Analysis of molecular variance, spatial analysis of molecular variance, and spatial autocorrelation analysis did not reveal significant spatial heterogeneity in haplotype distributions within the studied range. Significant departure from neutrality was inferred from neutrality tests and may reflect the signature of a rapid population expansion following the recent glacial epochs, an inference that was supported by the results of Bayesian coalescent analysis. While the present results are consistent with management of the species as a single stock, development of additional genetic markers is needed to increase the resolution in genetic analyses and evaluate fine‐scale genetic stock structure in the region.Received January 10, 2011; accepted May 5, 2011
Twenty-five microsatellites from Atlantic bluefin tuna (Thunnus thynnus thynnus) were characteriz... more Twenty-five microsatellites from Atlantic bluefin tuna (Thunnus thynnus thynnus) were characterized. All 25 microsatellites were polymorphic; the number of alleles among up to 56 individuals surveyed ranged from two to 23. Atlantic bluefin tuna are highly exploited and major questions remain as to stock structure and abundance in the eastern and western North Atlantic. The microsatellites will be useful in testing stock-structure hypotheses and in generating estimates of effective population size. The polymerase chain reaction primer sets developed also amplified identifiable alleles in three other species of genus Thunnus : T. albacares (yellowfin tuna), T. alalunga (albacore tuna) and T. obesus (bigeye tuna).
Understanding the spatial scale of demographic connectivity in marine reef fishes dispersing pela... more Understanding the spatial scale of demographic connectivity in marine reef fishes dispersing pelagic larvae is a challenging task because of the technical difficulties associated with tagging and monitoring the movements of progeny at early life stages. Several studies highlighted a strong importance of local retention with levels of dispersal of ecological significance restricted to short distances. To date little information is available in species where pelagic dispersal lasts for long periods of time. In this work population structure and connectivity were studied in the gray triggerfish, Balistes capriscus. Gray triggerfish larvae and juveniles remain associated with floating Sargassum sp. beds for an estimated period of 4 to 7 months before settling on benthic habitats where they remain sedentary as adults. Analysis of genetic variation among populations along the continental shelf of the northern Gulf of Mexico and U.S. east coast, encompassing over 3,100 km of coastline, revealed homogeneous allele frequencies and a weak isolation by distance pattern. Moment and maximum-likelihood estimates of dispersal parameters both indicated occurrence of large neighborhoods with estimates of the dispersal distribution parameter of 914 and 780 km respectively. Simulated distributions of dispersal distances using several distribution functions all featured substantial fractions of long distance dispersal events with the 90% percentiles of travel distance prior to settlement averaging 1,809 km. These results suggest a high dependency of local recruitment on the output of non-local spawning stocks located hundreds of kilometers away and a reduced role of local retention in this species.
The process of sex differentiation in the European sea bass (Dicentrarchus labrax) has been studi... more The process of sex differentiation in the European sea bass (Dicentrarchus labrax) has been studied in the context of programs aiming to develop methods for sex control in aquaculture. European sea bass gonads remain histologically undifferentiated for about four months after hatching. Ovarian differentiation takes place in fish of 80–90 mm standard length (SL), at the same time as a small proportion of males engage in testicular differentiation and initiate spermatogenesis. The remaining males remain undifferentiated for longer periods, during the first year. Intratesticular oocytes are commonly observed in cultured and wild males, and appear to reflect the masculinization of putative females due to environmental conditions. The labile period of sex differentiation seems to correspond to the end of metamorphosis and the weeks following this developmental phase. Protocols for the complete masculinization and feminization of stocks by the oral administration of sex steroids are available. Because sex differentiation in European sea bass is influenced by environmental factors, and evidence for major sex determinants is lacking in this species, potential approaches to control the sex ratio currently under investigation involve manipulations of the rearing temperature during the labile period of sex differentiation and selective breeding. Several genes have been shown to display sex‐ and/or temperature‐specific expression and methylation patterns in developing gonads before histological sex differentiation is completed. Further studies of the gonadal transcriptome and methylome, employing current genomic approaches, are warranted in order to further understand the physiological mechanisms involved in sex differentiation of the European sea bassPeer Reviewe
Eighty-four microsatellite loci were isolated from red snapper, Lutjanus campechanus, using Illum... more Eighty-four microsatellite loci were isolated from red snapper, Lutjanus campechanus, using Illumina paired-end sequencing and a direct 'Seq-to SSR' approach. The number of alleles per locus ranged from 7 to 30 and estimates of expected heterozygosity ranged from 0.466 to 0.967 (n = 30). Genotype frequencies at 7 loci deviated significantly from Hardy-Weinberg expectations; the departure at 4 of these loci likely reflects the segregation of null alleles. The markers characterized in this work will be applied to linkage mapping and genetic studies involved in the domestication and stock enhancement of red snapper. Development of the 84 microsatellites required screening approximately 1.5 M paired-end reads, highlighting the potential of this method for rapid and costeffective development of new homologous microsatellites in emerging aquaculture species.
Otolith chemistry of young-of-year (YOY) yellowfin tuna Thunnus albacares was examined to determi... more Otolith chemistry of young-of-year (YOY) yellowfin tuna Thunnus albacares was examined to determine whether chemical signatures are distinct across major spawning areas in the Atlantic Ocean. YOY yellowfin tuna otoliths were collected from 4 locations in the
Lane snappers (Lutjanus synagris), sampled from eight localities in the northern Gulf of Mexico (... more Lane snappers (Lutjanus synagris), sampled from eight localities in the northern Gulf of Mexico (Gulf) and one locality along the Atlantic coast of Florida, were assayed for allelic variation at 14 nuclear-encoded microsatellites and for sequence variation in a 590 base-pair fragment of the mitochondrially encoded ND-4 gene (mtDNA). Significant heterogeneity among the nine localities in both microsatellite allele and genotype distributions and mtDNA haplotype distributions was indicated by exact tests and by analysis of molecular variance (AMOVA). Exact tests between pairs of localities and spatial analysis of molecular variance (SAMOVA) for both microsatellites and mtDNA revealed two genetically distinct groups: a Western Group that included six localities from the northwestern and northcentral Gulf and an Eastern Group that included three localities, one from the west coast of Florida, one from the Florida Keys, and one from the east (Atlantic) coast of Florida. The between-groups component of molecular variance was significant for both microsatellites (U CT = 0.016, P = 0.009) and mtDNA (U CT = 0.208, P = 0.010). Exact tests between pairs of localities within each group and spatial autocorrelation analysis did not reveal genetic heterogeneity or an isolation-by-distance effect among localities within either group. MtDNA haplotype diversity was significantly less (P \ 0.0001) in the Western Group than in the Eastern Group; microsatellite allelic richness and gene diversity also were significantly less in the Western Group (P = 0.015 and 0.013, respectively). The difference in genetic variability between the two groups may reflect reduced effective population size in the Western Group and/or asymmetric rates of genetic migration. The relative difference in variability between the two groups was substantially greater in mtDNA and may reflect one or more mtDNA selective sweeps; tests of neutrality of the mtDNA data were consistent with this possibility. Bayesian analysis of genetic demography indicated that both groups have experienced a historical decline in effective population size, with the decline being greater in the Western Group. Maximum-likelihood analysis of microsatellite data indicated significant asymmetry in average, long-term migration rates between the two groups, with roughly twofold greater migration from the Western Group to the Eastern Group. The difference in mtDNA variability and the orderof-magnitude difference in genetic divergence between mtDNA and microsatellites may reflect different demographic events affecting mtDNA disproportionately and/or a sexual and/or spatial bias in gene flow and dispersal. The spatial discontinuity among lane snappers in the region corresponds to a known zone of vicariance in other marine species. The evidence of two genetically distinct groupings (stocks) has implications for management of lane snapper resources in the northern Gulf.
North American Journal of Aquaculture, Aug 19, 2021
Eggs of Acartia tonsa and Parvocalanus crassirostris were contaminated with ciliates (Euplotes sp... more Eggs of Acartia tonsa and Parvocalanus crassirostris were contaminated with ciliates (Euplotes sp.) and exposed to five concentrations of sodium hypochlorite (25, 55, 105, 205, and 405 mg/L) for durations of 15 s, 5 min, 15 min, or 30 min to assess the efficacy of household bleach for removing the ciliates. Eggs from each exposure treatment were incubated for 40 h (A. tonsa) or 12 h (P. crassirostris) to assess hatch. The presence of living ciliates was evaluated after incubation, and the egg hatch rate (%) for the copepods was estimated for each treatment and in controls. Exposure to 105 mg/L total chlorine for 15 s killed all of the ciliates and reduced the copepod hatch rate by less than 26% with respect to controls in both species. Exposure to 55 mg/L for 15 min or 25 mg/L for 30 min also killed the ciliates and achieved a mean copepod hatch rate of 38.5% and 58.1% of the control‐group hatch rate, respectively, in A. tonsa. Treatments for 5 min or longer reduced the hatch rate for P. crassirostris eggs by at least 76% at all of the concentrations that we tested.
Sexual differentiation was studied at the histological level using a mixture of 30 families of se... more Sexual differentiation was studied at the histological level using a mixture of 30 families of sea bass Dicentrarchus labrax. Most of the fish (93%) differentiated into males as usually observed in farmed populations. All testes were differentiated when the males reached 12 cm and no more undifferentiated fish were found from 419 days postfertilization (p.f.). In 28% of the males, among the biggest, sexual differentiation had already begun at 168 days p.f. (8.3-9.5 cm) and these fish started spermatogenesis in their first year of life. The other males differentiated later and remained immature at the end of their first year of life. Ovaries could be identified at the histological level from the age of 168 days p.f. (7.9-9.0 cm) and the females became significantly longer than the males from the age of 191 days p.f., i.e. during the process of ovarian differentiation. In the studied group, 62% of the males developed intratesticular oocytes. Such intersexuality had no consequence on growth rate. Intratesticular oocytes were also recorded in testes of wild males originating from Atlantic (Britain and Gulf of Gascogne) and West Mediterranean showing that juvenile intersexuality is not restricted to farmed populations but is a widespread phenomenon in sea bass.
Journal of the World Aquaculture Society, May 18, 2021
The Tripletail, Lobotes surinamensis, is a warm-water pelagic fish that is increasingly targeted ... more The Tripletail, Lobotes surinamensis, is a warm-water pelagic fish that is increasingly targeted by U.S. anglers. The superior quality of Tripletail flesh coupled with the lack of domestic commercial fisheries stimulated interests to develop aquaculture of this species. In this work, photothermal conditioning of captive-held broodstocks promoted maturation in females, but spontaneous spawning was not observed. GnRHa slow-release implants induced ovulation in late vitellogenic females but fertility remained below 10% when GnRHa was administered alone. However, spawns with high fertility (up to 85%) were obtained when a dopamine antagonist was administered in conjunction with GnRHa implants indicating dopamine inhibition impaired final gamete maturation, in particular sperm production in males, in aquaculture conditions. Tripletail larvae successfully initiated exogenous feeding on enriched rotifers followed by Artemia nauplii and were weaned to prepared feeds at 25 days post hatch, yet with low survival through the late phases of larval culture. Pilot grow-out trials at low density in recirculating systems revealed impressive growth rates averaging over 170 g/month through a market size M201-13-01; Perciformes Group LLC
The red snapper Lutjanus campechanus is an exploited reef fish of major economic importance in th... more The red snapper Lutjanus campechanus is an exploited reef fish of major economic importance in the Gulf of Mexico region. Studies of genome wide genetic variation are needed to understand the structure of wild populations and develop breeding programs for aquaculture but interpretation of these genome scans is limited by the absence of reference genome. In this work, the first draft of a reference genome was developed and characterized for the red snapper. P-454 and Illumina sequencing were conducted to produce paired-end reads that were assembled into reference contigs and scaffolds. The current assembly spans over 770 Mb, representing an estimated 69% of the red snapper genome in 67,254 scaffolds (N50 = 16,803 bp). The genome contigs were applied to map double digest Restriction-Site Associated DNA Tags and characterize Single Nucleotide Polymorphisms (SNPs) in five outbred full-sib families. The identified SNPs and 97 microsatellite loci were used to generate a highdensity linkage map that includes 7,420 markers distributed across 24 linkage groups and spans 1,346.64 cM with an average inter-marker distance of 0.18 cM. Sex-specific maps revealed a 1.10:1 female to male map length ratio. A total of 4,422 genome contigs (10.5% of the assembly) were anchored to the map and used in a comparative genomic analysis of the red snapper and two model teleosts. Red snapper showed a high degree of chromosome level syntenic conservation with both medaka and spotted green puffer and a near one to one correspondence between the 24 red snapper linkage groups and corresponding medaka chromosomes was observed. This work established the first draft of a reference genome for a lutjanid fish. The obtained genomic resources will serve as a framework for the interpretation of genome scans during studies of wild populations and captive breeding programs.
North American Journal of Aquaculture, Jan 2, 2014
ABSTRACT The Atlantic Croaker Micropogonias undulatus (Sciaenidae) is a candidate species for mar... more ABSTRACT The Atlantic Croaker Micropogonias undulatus (Sciaenidae) is a candidate species for marine baitfish aquaculture in the southeastern United States because of its high value and common use as live bait by recreational fishers. However, an efficient larviculture procedure has not been reported to date; development of such a procedure was the impetus for this study. Embryos were obtained from captive broodstock that were induced to spawn volitionally by using a single injection of a luteinizing hormone releasing hormone agonist. Larvae were cultured at lowdensity (initial density=6.4 larvae/L) via intensive culture methods, including the use of recirculating filtration systems and of rotifers, brine shrimp Artemia spp., and micropellets as larval foods. The trial was performed in six 1,100-L tanks at a salinity of 14–29‰, with average rearing temperatures of 23.6◦C and 24.6◦C. At the completion of the study (39 d posthatch), mean SLs were 24.7 mm (SE = 0.738) for larvae cultured at 24.6◦C and 23.0 mm (SE = 0.624) for larvae cultured at 23.6◦C. Mean survival at 39 d posthatch was 25.9% and did not differ significantly between temperature groups. This work demonstrated a successful methodology for intensive larviculture of Atlantic Croakers and can serve as a platform for the experimentation that will be necessary to develop economically viable procedures for intensive production of this species.
ABSTRACT Twenty one microsatellite markers were isolated from two enriched genomic libraries of t... more ABSTRACT Twenty one microsatellite markers were isolated from two enriched genomic libraries of the gray triggerfish, Balistes capriscus. The number of alleles detected varied between 4 and 27, and expected heterozygosity estimates ranged from 0.502 to 0.967 (n = 35). Genotypic proportions conformed to Hardy–Weinberg expectations for all but two of the loci. The microsatellite markers developed in this work will be precious to conservation genetics studies of the gray triggerfish.
An intensive, large-scale batch culture system to produce the calanoid copepod, Acartia tonsa. Aq... more An intensive, large-scale batch culture system to produce the calanoid copepod, Acartia tonsa. Aqua (2018),
Twenty nuclear-encoded microsatellites from a genomic DNA library of cobia, Rachycentron canadum ... more Twenty nuclear-encoded microsatellites from a genomic DNA library of cobia, Rachycentron canadum , were isolated and characterized. The microsatellites include two tetranucleotide, one trinucleotide, three combination tetranucleotide/dinucleotide, nine dinucleotide, and five imperfect (dinucleotide) repeat motifs. Gene diversity ranged between zero to 0.910; the number of alleles among a sample of 24 fish ranged from one to 15. Cobia support an important recreational fishery in the southeastern United States and recently have become of interest to aquaculture. The microsatellites developed will be useful tools for studying both population genetics (e.g. stock structure, effective population size) and inheritance of traits important to aquaculture.
The quality of red snapper eggs is highly variable and unpredictable in aquaculture, leading to h... more The quality of red snapper eggs is highly variable and unpredictable in aquaculture, leading to high mortality during early larval rearing. In this work, the viability of red snapper eggs was monitored from fertilization until unfed larvae expired because of exhaustion of vitelline reserves to determine egg quality traits in this species. The spawns were obtained via strip spawning wild-caught females following hormonal induction with chorionic gonadotropin. Females were induced immediately after capture (wild group, n = 17) or held captive for the entire maturation period prior to induction (captive group, n = 7). Candidate predictors of egg quality measured on the female parent at the time of induction or on the spawn at ovulation were evaluated using correlation and multiple regression analysis. The fertilization rate, the hatching rate, and the duration of survival of unfed larvae post hatch were weakly correlated to each other (-0.23 < r < −0.08), revealing occurrence of distinct and independent components of egg quality. Spawns from captive females were characterized by a longer latency interval between hormonal induction and ovulation, lower fecundity, and lower hatching rates, as compared to those from wild females. Among the wild brood fish, a positive correlation was observed between the age of the female and the hatching rate. The best model optimized during stepwise multiple regression analysis of hatching rate data only explained 34% of the variance for this trait and no model could be optimized for the prediction of fertilization rate or the duration of survival post hatch. These results highlight the need to develop alternative egg quality measures to predict the viability of fry with confidence.
Highlights ► In aquaculture, incubation of eggs under high density leads to hypoxia and elevated ... more Highlights ► In aquaculture, incubation of eggs under high density leads to hypoxia and elevated ammonia concentration. ► Knowledge of the effects of these stressors on the viability of marine species is very limited. ► Red snapper embryos and newly hatched larvae were exposed to different levels of hypoxia and elevated ammonia concentrations. ► The minimum dissolved oxygen level and maximum ammonia concentration compatible with short term survival indicate high sensitivity to these stressors and warrant further study. ► The tolerance to hypoxia and elevated ammonia concentration is variable among spawns highlighting the possible occurrence of parental effects and the need to characterize multiple spawns when determining safe levels for hatchery production.
North American Journal of Fisheries Management, Aug 1, 2011
Gray triggerfish Balistes capriscus is a reef fish exploited by recreational and commercial fishe... more Gray triggerfish Balistes capriscus is a reef fish exploited by recreational and commercial fisheries in the southeastern United States. Recent stock assessments indicated that the species is overfished, and a rebuilding plan is in progress. The U.S. fishery is currently managed as a single stock owing to the absence of reliable information on stock structure. We sequenced a 617‐base‐pair fragment of the ND4 mitochondrial gene in a total of 150 specimens from five localities (South Texas, Louisiana, West Florida, southeastern Florida, and South Carolina) encompassing the exploited range of the species in the USA. Analysis of molecular variance, spatial analysis of molecular variance, and spatial autocorrelation analysis did not reveal significant spatial heterogeneity in haplotype distributions within the studied range. Significant departure from neutrality was inferred from neutrality tests and may reflect the signature of a rapid population expansion following the recent glacial epochs, an inference that was supported by the results of Bayesian coalescent analysis. While the present results are consistent with management of the species as a single stock, development of additional genetic markers is needed to increase the resolution in genetic analyses and evaluate fine‐scale genetic stock structure in the region.Received January 10, 2011; accepted May 5, 2011
Twenty-five microsatellites from Atlantic bluefin tuna (Thunnus thynnus thynnus) were characteriz... more Twenty-five microsatellites from Atlantic bluefin tuna (Thunnus thynnus thynnus) were characterized. All 25 microsatellites were polymorphic; the number of alleles among up to 56 individuals surveyed ranged from two to 23. Atlantic bluefin tuna are highly exploited and major questions remain as to stock structure and abundance in the eastern and western North Atlantic. The microsatellites will be useful in testing stock-structure hypotheses and in generating estimates of effective population size. The polymerase chain reaction primer sets developed also amplified identifiable alleles in three other species of genus Thunnus : T. albacares (yellowfin tuna), T. alalunga (albacore tuna) and T. obesus (bigeye tuna).
Understanding the spatial scale of demographic connectivity in marine reef fishes dispersing pela... more Understanding the spatial scale of demographic connectivity in marine reef fishes dispersing pelagic larvae is a challenging task because of the technical difficulties associated with tagging and monitoring the movements of progeny at early life stages. Several studies highlighted a strong importance of local retention with levels of dispersal of ecological significance restricted to short distances. To date little information is available in species where pelagic dispersal lasts for long periods of time. In this work population structure and connectivity were studied in the gray triggerfish, Balistes capriscus. Gray triggerfish larvae and juveniles remain associated with floating Sargassum sp. beds for an estimated period of 4 to 7 months before settling on benthic habitats where they remain sedentary as adults. Analysis of genetic variation among populations along the continental shelf of the northern Gulf of Mexico and U.S. east coast, encompassing over 3,100 km of coastline, revealed homogeneous allele frequencies and a weak isolation by distance pattern. Moment and maximum-likelihood estimates of dispersal parameters both indicated occurrence of large neighborhoods with estimates of the dispersal distribution parameter of 914 and 780 km respectively. Simulated distributions of dispersal distances using several distribution functions all featured substantial fractions of long distance dispersal events with the 90% percentiles of travel distance prior to settlement averaging 1,809 km. These results suggest a high dependency of local recruitment on the output of non-local spawning stocks located hundreds of kilometers away and a reduced role of local retention in this species.
The process of sex differentiation in the European sea bass (Dicentrarchus labrax) has been studi... more The process of sex differentiation in the European sea bass (Dicentrarchus labrax) has been studied in the context of programs aiming to develop methods for sex control in aquaculture. European sea bass gonads remain histologically undifferentiated for about four months after hatching. Ovarian differentiation takes place in fish of 80–90 mm standard length (SL), at the same time as a small proportion of males engage in testicular differentiation and initiate spermatogenesis. The remaining males remain undifferentiated for longer periods, during the first year. Intratesticular oocytes are commonly observed in cultured and wild males, and appear to reflect the masculinization of putative females due to environmental conditions. The labile period of sex differentiation seems to correspond to the end of metamorphosis and the weeks following this developmental phase. Protocols for the complete masculinization and feminization of stocks by the oral administration of sex steroids are available. Because sex differentiation in European sea bass is influenced by environmental factors, and evidence for major sex determinants is lacking in this species, potential approaches to control the sex ratio currently under investigation involve manipulations of the rearing temperature during the labile period of sex differentiation and selective breeding. Several genes have been shown to display sex‐ and/or temperature‐specific expression and methylation patterns in developing gonads before histological sex differentiation is completed. Further studies of the gonadal transcriptome and methylome, employing current genomic approaches, are warranted in order to further understand the physiological mechanisms involved in sex differentiation of the European sea bassPeer Reviewe
Eighty-four microsatellite loci were isolated from red snapper, Lutjanus campechanus, using Illum... more Eighty-four microsatellite loci were isolated from red snapper, Lutjanus campechanus, using Illumina paired-end sequencing and a direct 'Seq-to SSR' approach. The number of alleles per locus ranged from 7 to 30 and estimates of expected heterozygosity ranged from 0.466 to 0.967 (n = 30). Genotype frequencies at 7 loci deviated significantly from Hardy-Weinberg expectations; the departure at 4 of these loci likely reflects the segregation of null alleles. The markers characterized in this work will be applied to linkage mapping and genetic studies involved in the domestication and stock enhancement of red snapper. Development of the 84 microsatellites required screening approximately 1.5 M paired-end reads, highlighting the potential of this method for rapid and costeffective development of new homologous microsatellites in emerging aquaculture species.
Otolith chemistry of young-of-year (YOY) yellowfin tuna Thunnus albacares was examined to determi... more Otolith chemistry of young-of-year (YOY) yellowfin tuna Thunnus albacares was examined to determine whether chemical signatures are distinct across major spawning areas in the Atlantic Ocean. YOY yellowfin tuna otoliths were collected from 4 locations in the
Lane snappers (Lutjanus synagris), sampled from eight localities in the northern Gulf of Mexico (... more Lane snappers (Lutjanus synagris), sampled from eight localities in the northern Gulf of Mexico (Gulf) and one locality along the Atlantic coast of Florida, were assayed for allelic variation at 14 nuclear-encoded microsatellites and for sequence variation in a 590 base-pair fragment of the mitochondrially encoded ND-4 gene (mtDNA). Significant heterogeneity among the nine localities in both microsatellite allele and genotype distributions and mtDNA haplotype distributions was indicated by exact tests and by analysis of molecular variance (AMOVA). Exact tests between pairs of localities and spatial analysis of molecular variance (SAMOVA) for both microsatellites and mtDNA revealed two genetically distinct groups: a Western Group that included six localities from the northwestern and northcentral Gulf and an Eastern Group that included three localities, one from the west coast of Florida, one from the Florida Keys, and one from the east (Atlantic) coast of Florida. The between-groups component of molecular variance was significant for both microsatellites (U CT = 0.016, P = 0.009) and mtDNA (U CT = 0.208, P = 0.010). Exact tests between pairs of localities within each group and spatial autocorrelation analysis did not reveal genetic heterogeneity or an isolation-by-distance effect among localities within either group. MtDNA haplotype diversity was significantly less (P \ 0.0001) in the Western Group than in the Eastern Group; microsatellite allelic richness and gene diversity also were significantly less in the Western Group (P = 0.015 and 0.013, respectively). The difference in genetic variability between the two groups may reflect reduced effective population size in the Western Group and/or asymmetric rates of genetic migration. The relative difference in variability between the two groups was substantially greater in mtDNA and may reflect one or more mtDNA selective sweeps; tests of neutrality of the mtDNA data were consistent with this possibility. Bayesian analysis of genetic demography indicated that both groups have experienced a historical decline in effective population size, with the decline being greater in the Western Group. Maximum-likelihood analysis of microsatellite data indicated significant asymmetry in average, long-term migration rates between the two groups, with roughly twofold greater migration from the Western Group to the Eastern Group. The difference in mtDNA variability and the orderof-magnitude difference in genetic divergence between mtDNA and microsatellites may reflect different demographic events affecting mtDNA disproportionately and/or a sexual and/or spatial bias in gene flow and dispersal. The spatial discontinuity among lane snappers in the region corresponds to a known zone of vicariance in other marine species. The evidence of two genetically distinct groupings (stocks) has implications for management of lane snapper resources in the northern Gulf.
North American Journal of Aquaculture, Aug 19, 2021
Eggs of Acartia tonsa and Parvocalanus crassirostris were contaminated with ciliates (Euplotes sp... more Eggs of Acartia tonsa and Parvocalanus crassirostris were contaminated with ciliates (Euplotes sp.) and exposed to five concentrations of sodium hypochlorite (25, 55, 105, 205, and 405 mg/L) for durations of 15 s, 5 min, 15 min, or 30 min to assess the efficacy of household bleach for removing the ciliates. Eggs from each exposure treatment were incubated for 40 h (A. tonsa) or 12 h (P. crassirostris) to assess hatch. The presence of living ciliates was evaluated after incubation, and the egg hatch rate (%) for the copepods was estimated for each treatment and in controls. Exposure to 105 mg/L total chlorine for 15 s killed all of the ciliates and reduced the copepod hatch rate by less than 26% with respect to controls in both species. Exposure to 55 mg/L for 15 min or 25 mg/L for 30 min also killed the ciliates and achieved a mean copepod hatch rate of 38.5% and 58.1% of the control‐group hatch rate, respectively, in A. tonsa. Treatments for 5 min or longer reduced the hatch rate for P. crassirostris eggs by at least 76% at all of the concentrations that we tested.
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Papers by Eric Saillant