Hatchery Production Research Articles

The Effects of Larval Cryopreservation on the Epigenetics of the Pacific Oyster Crassostrea gigas.

High mortalities and highly variable results during the subsequent development of post-thaw larvae have been widely considered as key issues restricting the application of cryopreservation techniques to support genetic improvement programs and hatchery production in farmed marine bivalve species. To date, few studies have been undertaken to investigate the effects of cryodamage at the molecular level in bivalves. This study is the first to evaluate the effect of larval cryopreservation on the epigenetics of the resultant progenies of the Pacific oyster Crassostrea gigas. The results show that the level of DNA methylation was significantly (p < 0.05) higher and lower than that of the control when the trochophore larvae were revived and when they developed to D-stage larvae (day 1 post-fertilization), respectively, but the level returned to the control level from day 8 post-fertilization onwards. The expression of the epigenetic regulator genes DNMT3b, MeCP2, JmjCA, KDM2 and OSA changed significantly (p < 0.05) when the trochophore larvae were thawed, and then they reverted to the control levels at the D- and later larval developmental stages. However, the expression of other epigenetic regulator genes, namely, MBD2, DNMT1, CXXC1 and JmjD6, did not change at any post-thaw larval developmental stage. For the newly thawed trochophore larvae, the amount of methylated H3K4Me1 and H3K27Me1 significantly changed, and the expression of all Jumonji orthologs, except that of Jumonji5, significantly (p < 0.05) decreased. These epigenetic results agree with the data collected on larval performances (e.g., survival rate), suggesting that the effect period of the published cryopreservation technique on post-thaw larvae is short in C. gigas.

Hatchery capacity needed to support large‐scale Atlantic surfclam fishery enhancement

AbstractFishery enhancement methods are being explored globally to sustain commercial and recreational fisheries through improving the productivity and management of marine populations impacted by anthropogenic stressors. It is expected that access to important Atlantic surfclam fishing grounds will be limited or lost due to growing overlap with offshore wind energy development. This study explores the economic viability of large‐scale hatchery production to improve fishery access and potentially offset additional costs, reduced revenues and potential job losses associated with the displacement of the fishing fleet. Reports and primary literature were used to understand the growth and survival of Atlantic surfclams in hatchery and nursery settings to calculate the scale of hatchery efforts needed to support one million (1M) bushels of fishery‐sized clams (&gt;120 mm). Data on labour, energy, construction and material inputs and costs for hatchery and nursery production were gathered by analysing available literature and information provided by hatchery managers, researchers and others knowledgeable about shellfish hatchery production. A techno‐economic cost model and Monte Carlo analyses were employed to explore average costs and their variability. This study suggests that 374M–2.1B Atlantic surfclams are needed at the end of the hatchery stage to produce 1M bushels of market‐sized product. Total production costs range from $3.7 to $15.1M, including $2.9–$13.3M in hatchery costs and $800K–$1.9M in nursery costs. Under current market conditions, where Atlantic surfclams regularly sell for $14–$17/bushel, this analysis suggests that hatchery production could be considered a viable fishery enhancement method that supports human access to the fishery, though several additional questions remain.

Fluctuating asymmetry patterns of common carp (Cyprinus carpio) in fish hatchery center of Kabat, Banyuwangi, Indonesia

A decrease in common carp (Cyprinus carpio) fry quality has occurred in many hatcheries indicated by fry abnormality increase, which causes low survival and growth rates. This research aims to obtain quantitative information of asymmetry level on common carp fry in the Fish Hatchery Centre (FHC) of Kabat as a reference for the breeding program. A total of 200 common carp fries with a total length of 5-7 cm were obtained from FHC of Kabat. The observed magnitude (FAm) and number (FAn) are fluctuating asymmetry. To calculate both of them; bilateral meristic characteristics were measured are pectoral fins radii, ventral fins radii, and scales on the lineal lateralis number. We found that there was an incidence of asymmetric fluctuations in FHC of Kabat with the highest FAm and FAn were obtained in lateral line scales. This implies inbreeding which causes a decrease in hatchery productivity, so the introduction of brood stock from other areas is required.

Reproductive and production performances of pearl oyster (Pinctada maxima) produced by thermal shock spawning method

Pearl oyster (Pinctada maxima) hatchery faces several problems including low larval survival and slow larval growth. This study aimed to evaluate the reproductive and production performances of pearl oyster obtained from the breeding of silver and mixed populations through thermal shock spawning method. Two breeding types applied consisted of silver and mixed population breeding. Each breeding type was conducted in two experiments as the replication. The spawning method used in this study was thermal shock spawning method. Pearl oyster larvae hatched were stocked into a container with a stocking density of 3-4 individuals m-3. Live feed administered to larvae included Chaetoceros calcitrans, Isocrysis galbana, and Pavlova lutheri. The parameters observed included Fertilization Rate (FR), Hatching Rate (HR), Survival Rate (SR), and water quality. The silver population showed a higher reproductive performance with higher FR (35.56 ± 3.29%) and HR (81.63 ± 2.87%) than those of mixed population (35.03 ± 1.72%; 54.51 ± 0.32%). The silver population (45 ± 5%) resulted in a higher SR compared to mixed population (43 ± 2%). In conclusion, the silver population breeding provided higher reproductive and production performances, so one population breeding can be applied to achieve a high production in pearl oyster hatchery.

Improving green sea urchin (Strongylocentrotus droebachiensis) hatchery production by determining effective settlement cues and post-settlement conditions

Hatchery production methodologies of Northeastern U.S. green sea urchins (Strongylocentrotus droebachiensis) have yielded low settlement success and post-settlement survival (approximately 1–5%) contributing towards high costs for producing juveniles for this emerging aquaculture species. These are likely attributed to hatchery operations needing to optimize settlement cues and post-settlement food supplies. This study examined a range of potential settlement cues using adult conspecifics or a benthic diatom biofilm (Cylindrotheca closterium or Nitzschia sp.) alone, or in combination with seawater conditioned with conspecifics or macroalga (Saccharina latissima or Ulva lactuca). This study also examined whether sea urchin post-settlement survival and growth would improve using a benthic diatom food source (C. closterium or Nitzschia sp.) alone or in combination with an additional macroalga food source (S. latissima or U. lactuca). Both trials were conducted under hatchery ambient (control 12 °C) or elevated (14 °C) temperatures to determine whether temperature elevation could enhance S. droebachiensis settlement success and post-settlement growth. This study also examined what influence biofilm age (1, 4 and 8 weeks) and seawater salinity (26, 30, 33 and 36) had on settlement success to help towards optimizing hatchery methods. This study did not improve post-settlement survival causing it to remain a significant barrier in mass producing juveniles, but it did increase juvenile growth by 30–40% and reduce growth variability when fed the benthic diatom C. closterium in combination with U. lactuca. This combination also served as an adequate settlement cue for this species. The use of a conspecific influenced biofilm substantially improved settlement success from 1 to 5% to 50–80%. Seasonal timing and age (4 weeks) of this biofilm indicated importance in yielding this success which will be location specific. The use of conspecific biofilms for improving post-settlement survival requires further investigation and is worth examining in combination with C. closterium and U. lactuca towards enhancing S. droebachiensis production in the Northeastern U.S. Elevating seawater temperature by 2 °C had no significant effect on settlement, growth, or survival in this study. Salinities of 30–33 were optimal yielding 3–7 times more settlement compared to salinities 27 and 36. This study highlights that settlement trials need to incorporate post-settlement survival measurements for at least 1–2 months to truly reflect the effectiveness of method interventions and consider extending the time before turning seawater flow back on into settlement tanks from 24 to 48 h by up to 72–96 h to facilitate greater settlement success if seawater quality parameters permit it.

The genetics and breeding of the Portuguese oyster, Crassostrea angulata: lessons, experiences, and challenges in Vietnam

Aquaculture mollusc production is predominantly from Asia, with more than 80% of the total biomass produced in China. Vietnam’s annual mollusc production is growing rapidly but is comparatively small given its coastal resources. A significant challenge for future mollusc production, and oysters in particular, is the supply of high-quality spat. Most mollusc spat in Vietnam comes from local wild sources or is imported from China. Particularly in the case of oysters, where wild collection is low and importation of oyster spat into Vietnam from other jurisdictions is not controlled, supply is unreliable and presents a biosecurity risk to the industry. Controlling the life cycle in hatcheries can increase the sustainability and reliability of spat supply with the advantages of genetic enhancement in the long term. Beyond well-established selection methods based on phenotypic data for pedigreed families, the rapid development of genomic technology has enabled innovation in hatchery production based on genetic programs. This technology allows greater insight into oyster genetics in intensive aquaculture production systems. Recent reviews of selection programs demonstrate that inbreeding control via mate selection is an effective strategy for oyster species. Genetic response through combinations of individual and family-based selection can enhance morphometric traits by 10% per generation and disease resistance by 15% per generation in many aquaculture species. Genomic techniques provide information for selecting candidates at an earlier stage and improve prediction accuracy. In this paper, we review the literature on popular genomic tools and breeding techniques used for molluscs, focusing on the Portuguese oyster, Crassostrea angulata. This is to better comprehend how modern quantitative and molecular genetic technologies are being applied in mollusc breeding programs. It considers opportunities for and the feasibility of using genomic-based selection as well as the challenges that are faced in breeding programs transitioning to these new methods.

Examination of Muskellunge overwinter survival and growth in an earthen extensive culture pond

AbstractObjectiveTrack cohort survival, individual growth, and PIT tag retention, as well as relative growth rate, from fall to the following spring for age‐0 Muskellunge Esox masquinongy held in an extensive culture pond.MethodsA total of 806 age‐0 Muskellunge were provided a 12‐mm PIT tag in October 2021 and placed into a 0.1‐ha pond. Individual total length (mm) was recorded for each fish. When the pond was drained in March 2022, an assessment of survival and PIT tag retention was calculated for the cohort, as well as assessment of mean individual growth and relative growth rate.ResultMuskellunge experienced high survival (91.9%) but low individual mean growth (21.7 ± 0.2 mm [mean ± SE]). The mean length of surviving Muskellunge (267.8 ± 0.9 mm) was significantly greater than nonsurviving Muskellunge (251.4 ± 3.1 mm). However, smaller surviving Muskellunge did exhibit slightly improved growth compared to individuals that were initially longer.ConclusionThe results provide an expectation for overwinter survival and growth in an extensive culture pond. This can assist managers in developing expectations on the numbers and length of Muskellunge that will be available to stock the following spring, which has largely been unreported previously.

Diet–egg relationships and equilibration of fatty acids in eggs of southern flounder, Paralichthys lethostigma

There is increasing interest in the transfer of nutrients from broodstock diets to eggs due to the consequences for egg and larval quality. Analyses were conducted with southern flounder Paralichthys lethostigma to identify which fatty acids (FAs) in eggs are influenced by broodstock diet and how long it takes for the FA composition of eggs to equilibrate to the broodstock diet. Data were obtained from a laboratory experiment and from hatchery production operations. For each source, two populations of adult flounder were given one or the other of two diet treatments. In the laboratory experiment, the diets differed markedly in FA composition. In the hatchery, a base diet was supplemented on two different schedules. Each of the four diet treatments produced eggs with significantly different mean FA compositions. Of the 27 FAs measured, 19 differed significantly between diets and had corresponding significant differences in eggs (direct diet–egg relationships). Combining results with data from a prior study showed that equilibration of eggs to a change in adult diet takes 8–16 weeks for southern flounder. These findings will be useful for improving broodstock diets and feeding protocols for captive flounder being used by stock-enhancement programs that are designed to mitigate the long-term and widespread population declines of this species.

Transcriptome-derived SNP markers for population assignment of sandfish, Holothuria (Metriatyla) scabra

The sandfish, Holothuria scabra is a commercially important fishery and aquaculture species contributing to the high-value sea cucumber industry. Overexploited across many areas throughout its distributional range, natural populations are considered in decline. Accurate genetic assignment to population of origin is becoming increasingly important for genetics-based marine fisheries management and monitoring, especially for species experiencing depletion of natural stocks and decline in fisheries productivity due to overfishing and illegal, unreported, and unregulated (IUU) fishing. Initiatives for genetics-based applications on economically important seafood such as H. scabra have been limited by the lack of comprehensive genome or transcriptome resources. The present study developed and evaluated the use of gene-associated single nucleotide polymorphism (SNP) markers to assign sandfish to three locations in the Philippines, in the proximity of existing and emerging hatchery production centers. In silico SNP discovery pipeline using pooled RNA-Seq libraries and medium-throughput genotyping approach generated a dataset comprising 115 individuals genotyped at 88 SNPs. Population assignment using machine-learning analysis and Bayesian approach revealed that the 88 transcriptome-derived SNPs allowed the assignment of sandfish individuals to population of origin, with an overall assignment accuracy of >80%. The novel SNPs developed could find their utility in facilitating the development of geographic traceability tools applicable in the context of sandfish aquaculture, fisheries management and conservation.

Effects of ethylenediaminetetraacetic acid on growth and survival of long‐spined sea urchin Diadema antillarum larvae

AbstractObjectiveThe presence of heavy metals in seawater is a major challenge for hatchery culture of sea urchin larvae due to their sensitivity to metal pollution. The impact of heavy metals in seawater for sensitive marine larviculture could be minimized via chelation of metals using chemical compounds such as ethylenediaminetetraacetic acid (EDTA).MethodsIn this study the effects of EDTA were tested for the long‐spined sea urchin Diadema antillarum during larviculture at two concentrations (10 μM and 50 μM) and two exposure durations (6 and 24 days postfertilization). Growth and survival of larvae were evaluated as response variables.ResultSignificant differences in growth and survival of larvae were found among the treatments at different EDTA concentrations and exposure durations. The 10‐μM EDTA treatment enhanced growth and survival of larvae relative to control for both exposure durations. The 50‐μM EDTA treatment was unsuitable for long‐spined sea urchin larviculture due to reductions in growth and survival.ConclusionThe use of 10 μM EDTA during embryo incubation and larviculture is expected to improve long‐spined sea urchin larval fitness, leading to improved hatchery production.

Effect of ploidy on salinity and temperature tolerance in early life stages of the eastern oyster (Crassostrea virginica)

The U.S. Gulf of Mexico contains the largest remaining wild oyster fishery in the world, but populations have declined in recent decades. A growing interest in off-bottom aquaculture that relies on triploid eastern oysters (Crassostrea virginica) has emerged in the Gulf region, yet these faster growing oysters suffer high mortality as adults during low salinity (<5) events in warmer summer months. The combined effects of low salinity and high temperature stress on early life stages of triploid oysters are unknown. Early life stages are particularly crucial to understand because triploid oysters do not occur naturally and must be reared in hatchery settings, requiring appropriate water conditions to yield the greatest survival and growth. Thus, we tested the effects of different temperatures (28 ºC and 32 ºC) and salinities (5, 10, and 15) on diploid and triploid oysters at three critical production stages: veliger, pediveliger, and spat. Veliger survival was significantly lower for triploids relative to diploid oysters at all experimental conditions, but triploid veligers had faster growth than diploids at 32 ºC and salinity of 15. Pediveliger settlement was not affected by ploidy type and was reduced only at high temperature (32 ºC) and the lowest salinity (5). Diploid spat showed highest survival at 28 ºC and 15 salinity, while triploids survived best at 32 ºC and 15 salinity. Triploid spat attained greater shell height compared to diploids in our 6-day exposures, but growth decreased for both ploidies at lower salinities. At the salinity and temperature levels examined, diploid early life stages performed best at 28 ºC and 15 salinity, whereas triploids were more successful at 32 ºC and 15 salinity. A broader understanding of the combined effects of environmental stressors will improve the success of hatchery production yields and the resulting economic and environmental benefits of the oyster industry.

Sandfish generations: Loss of genetic diversity due to hatchery practices in the sea cucumber Holothuria (Metriatyla) scabra

Hatcheries are indispensable for seed production of many commercial aquaculture species. However, for mass-spawning species in particular, they can be capricious environments where genetic diversity among progeny may be lost due to small effective broodstock population sizes, variable parental contributions and differential family survival. Understanding the genetic impacts of hatchery production is therefore important for addressing these problems and optimising propagation methods. We used 6051 genome-wide Single Nucleotide Polymorphisms (SNPs) to analyse genetic diversity, parental contributions and offspring kinship during a commercial-scale hatchery production run of sandfish (Holothuria scabra), a high-value sea cucumber grown in mariculture operations across the Indo-Pacific region. Broodstock contributions were highly skewed, with up to 26% of the parent pool contributing and kinship analyses determined that just two parents sired between 44.4 and 67.5% of all offspring genotyped. Effective population sizes were reduced as expected between broodstock and offspring groups (NeLD = 1121.2 vs. 19.4, respectively), while losses of allelic diversity but not overall heterozygosity were apparent. Numbers of families surviving (13–16) to the juvenile stage were low, suggesting low effective population sizes among offspring cohorts is an issue for sandfish hatchery operations. To address variability in family compositions and broodstock contributions, pedigree tracking and batch spawning may be used to optimize broodstock management and hatchery protocols, to ensure production of genetically diverse offspring for routine culture and restocking operations. As many sandfish broodstock remain wild-sourced, maintenance of healthy wild populations as reservoirs of genetic diversity is important, along with selection for spawning of genetically diverse individuals which are as distantly-related as possible.

In vitro evaluation of probiotics and their effect on hatchery production and farming of L. Vannamei

In vitro evaluation of probiotics and their effect on hatchery production and farming of L. Vannamei

Exploring the feasibility of cryopreserving larvae of the common cockle (Cerastoderma edule) for hatchery production

The decline of natural populations of the common cockle (Cerastoderma edule) through the European coast is posing a threat to local small-scale fisheries. These declines are primarily attributed to the prevalence of several pathogens and the disseminated neoplasia in cockle populations. The institution of a biobank of cryopreserved larvae could enhance hatchery production and help the restocking. The present work aimed at the development of a cryopreservation protocol for larvae of the common cockle using the mollusk cryopreservation protocols designed in our laboratory. Toxicity bioassays and short-term cryopreservation experiments were performed for protocol optimization according with cellular tolerance. Once settled, the viability of cryopreserved larvae was studied long term. Toxicity tests evidenced high tolerance of larvae against detrimental effects of Cryoprotecting Agents (CPAs). Cryopreservation of 48 h-old D-larva showed a 100% survival when increasing the equilibrium time from 15 to 60 min and using Propylene-Glycol (PG) + 0.4 M Trehalose (TRE) in Filtered Sea Water (FSW) and 60 min of exposure to CPA solution before slow-cooling. However, when cryopreserving the older larvae, the variation in equilibrium times hardly showed any effect but 10% Ethylene-Glycol (EG) + 0.4 M TRE and 60 min of exposure yielded the best relative survivorship (100%). Cryopreservation caused a significant delay on the growth rate of the latest larval stage. However, cryopreserved larvae survived to day 4–6, while 30 ± 12.17% of control larvae developed into pediveliger stage, of which 50% settled and transformed into juvenile cockles. These results demonstrated the role of the cell-type specificity in cryopreservation and highlight the importance of studying potential long-term effects of this tool to ensure the viability of the protocols.

Return(s) on investment: Restoration spending in the Columbia River Basin and increased abundance of salmon and steelhead.

The decline in salmon and steelhead populations in the Columbia River Basin has been well documented, as have the decades-long, $9 billion restoration spending efforts by federal and state agencies. These efforts are mainly tied to Endangered Species Act (ESA) mandates for recovery of wild, naturally-spawning threatened or endangered fish species. The impact of these efforts remains poorly understood; many observers, including the federal courts, have long been concerned by the lack of evidence of recovery. Most studies evaluating restoration efforts have examined individual projects for specific species, reaches, or life stages, which limits the ability to make broad inferences at the basin level. There is a need to ask: is there evidence of an overall increase in wild fish abundance associated with the totality of these recovery efforts? To that end, the current study estimates fixed-effects panel regression models of adult returns of four species. Results indicate that restoration spending combined with hatchery production are associated with substantial increases in returning adult fish. Evidence of benefits to wild fish alone, however, require indirect approaches given the commingling of restoration spending with spending on hatchery releases, the impacts of spending on hatchery fish survival, and the density dependence effects of hatchery releases. To accomplish this, the models' predicted adult returns (both hatchery and wild fish) attributed to both spending and hatchery releases are compared to independent estimates of returning hatchery fish based on hatchery survival estimates (smolt-to-adult ratios). The comparison finds the model-predicted levels of adult returns due to spending and hatchery releases do not exceed the survival-rate based estimates for hatcheries alone, so that we are unable to reject the hypothesis of no benefits to wild fish from the restoration spending.

The use of chemical and biological settlement cues in enhancing the larval settlement of abalone (Haliotis midae): Implications for hatcheries and ocean ranching

AbstractReducing the time to settlement and metamorphosis of abalone larvae is critical for ensuring that abalone larvae settle within the seeding site for ocean ranching or to increase production in hatcheries. This study investigated the effect of biological (planktonic Nitzschia sp.) and chemical (potassium chloride) cues in inducing settlement and metamorphosis of abalone larvae Haliotis midae on diatom‐coated plastic sheets. Larvae were exposed to different concentrations of KCl (10–20 mM), with settlement being highest at 10 mM in the first 20 h. Settlement of larvae exposed to a combined KCl and Nitzschia treatment for 24 h was highest, followed by larvae exposed to KCl for 12 h, while larvae exposed to KCl for 24 h, and both controls (12 and 24 h) had the lowest settlement. However, in both experiments, larval settlement in all treatments declined after 24 h of exposure, while that of the controls (no added settlement cues) increased and surpassed the other treatments after 24 h. Finally, the settlement was very low on uncoated sheets, compared to diatom‐coated sheets, regardless of exposure to different combinations of KCl and Nitzschia. The exposure period's results should be interpreted with caution when drawing biological conclusions for field studies. This is due to the dramatic decrease in mean settlement post‐exposure to the cue. Therefore, we hypothesize that exposure of H. midae larvae to 10 mM KCl and Nitzschia sp. will not enhance settlement in the ocean, as the inducers are primarily only effective at a KCl concentration level equal to 10 mM for 12 h. However, long‐term exposure to KCl and Nitzschia over 24 h could be used in hatcheries to improve the settlement of H. midae larvae.

Advancements in hatchery production of red snapper Lutjanus campechanus: Exclusive use of small strain rotifers as initial prey for larval rearing

AbstractThe red snapper (Lutjanus campechanus) has one of the most valued fisheries in the southeastern United States and has been largely studied for its aquaculture potential with varied results that revealed production challenges. This study focused on addressing challenges in larval rearing and juvenile production of this species. Broodstock fish were acclimated in a 60 m3 tank equipped with recirculating aquaculture system (RAS) and temperature control. After 1 year in captivity, fish volitionally spawned and larval rearing trials were conducted in replicated flow‐through seawater tanks ranging from 0.4 to 2.4 m3, at a temperature range of 24–26°C. Enriched s‐strain rotifers, Brachionus rotundiformis (lorica length of 100–210 μm), were used for first feeding. Enriched Artemia sp. were gradually introduced after 18 days post hatch (DPH). The survival rate before metamorphosis (12 DPH) averaged 66.09 ± 0.08%. Survival rate from yolk‐sac larvae to post‐metamorphic early juvenile averaged 4.43 ± 0.01%. At 40 DPH, early red snapper juveniles averaged 0.35 ± 0.02 g in weight and 28.83 ± 0.60 mm in standard length. A total of 31,849 fully weaned juveniles were harvested. This study demonstrates that small strain rotifers can be used exclusively as first feeding prey organism for red snapper larvae, representing a significant advancement for red snapper juvenile production.

Effects of n-3 HUFA-enriched Artemia on growth, biochemical response, skeletal morphology and stress resistance of Asian sea bass (Lates calcarifer) larvae reared at high temperature

Improving the growth and health status of marine fish larvae to adapt to climate change, is crucial for commercial hatchery production in tropical regions. This study evaluated the effects of dietary essential fatty acids used for Artemia enrichment on growth, biochemical responses, skeletal morphology, and stress resistance of Asian sea bass larvae, reared at high temperatures of 30 °C and 34 °C. Starting 11 days after hatch, Asian sea bass larvae, were fed Artemia, enriched with a commercial emulsion of n-3 HUFA for 14 days, at four concentrations (0, 100, 300, and 500 ppm), at two rearing temperatures (30 °C and 34 °C). The results showed that enriching Artemia with n-3 HUFA significantly improved the final weight and specific growth rate of the larvae fed n-3 HUFA enrichment at 300 ppm, at 34 °C (P < 0.05). Moreover, n-3 HUFA enriched Artemia significantly increased the essential fatty acids of the larvae in parallel with the dose of enrichment. Fish fed unenriched HUFA Artemia resulted in significantly higher ratio of skeletal deformities and lower survival rate following an air exposure test than the larvae fed the n-3 HUFA enriched diets. Overall, the findings showed that n-3 HUFA-enriched Artemia diets had benefits on body weight, specific growth rate, and stress tolerance in Asian sea bass fed HUFA enriched diets, even at high temperatures.

Identification and Characterization of Infectious Pathogens Associated with Mass Mortalities of Pacific Oyster (Crassostrea gigas) Cultured in Northern China.

The Pacific oyster (Crassostrea gigas) aquaculture industry increased rapidly in China with the introduction and promotion of triploid oysters in recent years. Mass mortalities affecting different life stages of Pacific oysters emerged periodically in several important production areas of Northern China. During 2020 and 2021, we conducted a passive two-year investigation of infectious pathogens linked to mass mortality. Ostreid herpesvirus-1 (OsHV-1) was detected to be associated with mass mortalities of hatchery larvae, but not juveniles and adults in the open sea. Protozoan parasites, such as Marteilia spp., Perkinsus spp. and Bonamia spp. were not detected. Bacterial isolation and identification revealed that Vibrio natriegens and Vibrio alginolyticus were the most frequently (9 out of 13) identified two dominant bacteria associated with mass mortalities. Pseudoalteromonas spp. was identified as the dominant bacteria in three mortality events that occurred during the cold season. Further bacteriological analysis was conducted on two representative isolates of V. natriegens and V. alginolyticus, designated as CgA1-1 and CgA1-2. Multisequence analysis (MLSA) showed that CgA1-1 and CgA1-2 were closely related to each other and nested within the Harveyi clade. Bacteriological investigation revealed faster growth, and more remarkable haemolytic activity and siderophore production capacity at 25 °C than at 15 °C for both CgA1-1 and CgA1-2. The accumulative mortalities of experimental immersion infections were also higher at 25 °C (90% and 63.33%) than at 15 °C (43.33% and 33.33%) using both CgA1-1 and CgA1-2, respectively. Similar clinical and pathological features were identified in samples collected during both naturally and experimentally occurring mortalities, such as thin visceral mass, discolouration, and connective tissue and digestive tube lesions. The results presented here highlight the potential risk of OsHV-1 to hatchery production of larvae, and the pathogenic role of V. natriegens and V. alginolyticus during mass mortalities of all life stages of Pacific oysters in Northern China.

Short‐term storage of sperm in common carp from laboratory research to commercial production—A review

AbstractShort‐term storage of fish sperm is a simple and cost‐effective process in fishery research from basic to applied perspectives. It has been used to elucidate and evaluate gamete biology and quality, perform in vitro fertilization, develop sperm cryopreservation. Sperm short‐term storage is used in selective breeding, hatchery production and advanced molecular investigations such as disease detection of commercial species in aquaculture as well as biological conservation of threatened or endangered fishes. Several studies have demonstrated that the quality of common carp Cyprinus carpio sperm can be influenced by their health, age, nutritional status, the dose of administered hormone and environmental factors. When sperm is stored for short time, spermatozoa motility and viability as key determinants of fertility affected by storage parameters including the composition of natural seminal plasma, duration of exposure, temperature, dilution ratio if the extender is used, and additives in addition to the factors that affect sperm quality such as the age of male and spawning period. This is due to damage to the integrity of the plasma membrane, production of reactive oxygen species (ROS) causing oxidative stress and epigenetic modification. This review highlights and investigates the recent data regarding worldwide aquaculture production, short‐term storage of common carp sperm and the effects of storage on spermatozoa function with consideration to factors that affect sperm quality during storage. It also highlights the knowledge gap that must be filled in the future for designing methods from laboratory into practical applications of short‐term storage in the breeding program of common carp.