Wild Broodstock Research Articles

Restricted inclusion of wild broodstock at a large hatchery does not result in detectable genetic differentiation in a supplemented coho salmon (Oncorhynchus kisutch) population

Hatchery production is common in salmonid management for harvest and conservation. Many hatcheries employ integrated broodstock programs, where wild-origin fish are included as broodstock and uni- or bi-directional gene flow between wild and hatchery components of the population is encouraged. Such approaches often assume that opportunistically obtained wild fish meet the genetic goals of minimizing hatchery–wild differentiation and maintaining genetic diversity. This may be incorrect if fine-scale spatial genetic structure exists. Here we investigate the population genetic consequences of such hatchery operations in coho salmon ( Oncorhynchus kisutch) in a small river system featuring a large integrated broodstock program. We do so using 11 082 SNPs scored in wild-origin and hatchery-origin fish collected throughout the system. We found no evidence for genetic differentiation between hatchery-origin and wild-origin fish, no evidence of lowered genetic diversity in hatchery-origin fish, and no evidence for genetic differentiation among fish sampled throughout the river system. In addition, we did not detect inbreeding. Collectively, these results are consistent with current practices meeting integrated hatchery program goals of adequately sampling the genetic diversity present in wild-origin fish, although they may slightly reduce the effective population size of the combined population.

Age and length characteristics of female and male Walleye broodstock collected at a spawning operation

AbstractObjectiveThe need to augment of Walleye Sander vitreus populations may increase as these populations face challenges of changing habitats and climatic conditions. Since little has been published outside of agency reports on wild broodstocks, the intent of this study was to describe sex‐specific Walleye spawning participation from a Great Plains broodstock operation. Specific objectives will assess standardization to collect target number of broodstock effort, catch per unit effort, and length and age participation of female and male broodstock.MethodsWalleye were collected at Sherman Reservoir, Nebraska, during April spawn collection operations from 2015 to 2019. Gill nets were used to collect female Walleye, and boat electrofishing was used to collect male Walleye. Catch per effort was calculated for each sex, fish were measured to nearest 1‐cm length‐group, and a dorsal spine was taken from a subset of fish per length‐group. Mean lengths and ages were calculated for each year of the study. Data were combined for all years of the project to display percent contribution by length and age.ResultThe amount of effort to capture 100 female and male Walleye varied by 4× and 2.5×, respectively, over the 5 years of sampling. Mean lengths and ages (±SE) of female (65 ± 1 cm; 10.4 ± 0.1 years) and male (43 ± 1 cm; 6.3 ± 0.1 years) Walleye collected were consistent during this study. The female Walleye collected represented 14 different ages, but ages 9–12 comprised 66% of all captured broodstock. The collected male Walleye also demonstrated age‐compressed spawning tendencies, with ages 4–7 accounting for 74% of collected individuals that represented 13 different ages.ConclusionThese results can define the anticipated variability in catch that can be expected at broodstock collection operations along with connection to specific lengths and ages of Walleye. Additionally, recognition that female and male Walleye broodstock contributions are consistently coming from four specific ages that are not the same year‐classes may allow spawning operation staff to anticipate brood availability and ultimately improve the planning efficiency of these operations.

Culture protocols of the Metallic Shiner for ornamental aquaculture

AbstractObjectiveWhile North American fishes are often overlooked by the ornamental fish industry, there is growing interest in fishes native to the southeastern USA, a hot spot for fish diversity. The Metallic Shiner Pteronotropis metallicus, a small‐bodied leuciscid native to Florida and Georgia, is sometimes available in the ornamental fish trade through wild collection and limited captive production. This species exhibits a distinctive color pattern straddling the lateral line: a dorsal pink to red line, fading to a black to blue stripe. This group of minnows is largely unknown to ornamental aquaculture and lacks defined culture protocols. Our objective was to develop culture protocols for the Metallic Shiner.MethodsFollowing collection of wild broodstock, we used routine culture methods to experimentally determine substrate preference, egg incubation, egg disinfection, larval feeding, and larval development.ResultMetallic Shiner spawning was more successful on yarn mops compared with other media, with average output of >50 embryos per tank per day. Hatching success was similar for static incubators (24%) and upwelling incubators (20%) and was also similar among egg disinfection treatments (iodine, hydrogen peroxide, and formalin). Larval feeding regimes altered survival, with Otohime A1 exhibiting higher survival (44%) over 14 days posthatch (dph) and better growth than other feeding regimes. During the developmental trial with water temperature at a relatively constant 25°C, length increased from 5 mm notochord length (4 dph) to 8.7 mm standard length (45 dph), with significant milestones occurring at 4 dph (swim bladder inflation), 16 dph (flexion), and 23 dph (hypural plate formation).ConclusionThese data provide basic culture information for the Metallic Shiner while also providing a place of reference to begin investigating culture protocols for related species, including species of conservation concern.

Morphology and metabolic traits related to swimming performance in Australasian snapper (Chrysophrys auratus) selected for fast growth.

Changes in body shape are linked to swimming performance and become relevant for selective breeding programmes in cultured finfish. We studied how the selection for fast growth could affect phenotypes by investigating the relationship between swimming performance and body shape. We also investigated how swimming might affect plasma metabolite concentrations. Critical swimming speed (UCrit), body traits (e.g., BW, body weight; BL, body length; K, condition factor), and plasma lactate and glucose concentrations were evaluated in two cohorts of Australasian snapper (Chrysophrys auratus): one derived from wild broodstock (F1), and the other selected for fast growth (F4). UCrit tests (n = 8) were applied in groups of 10 snapper of similar BW (71.7 g) and BL (14.6 cm). The absolute or relative UCrit values of both cohorts were similar (0.702 m⋅s-1 and 4.795 BL⋅s-1, respectively), despite the F4 cohort displaying a higher K. A positive correlation between K and absolute UCrit (Pearson's r = 0.414) was detected in the F4 cohort, but not in the F1 cohort, which may be linked to differences in body shape. A negative correlation between relative UCrit and body size (Pearson's r between -0.682 and -0.501), but no correlation between absolute UCrit and body size, was displayed in both cohorts. Plasma lactate and glucose concentrations were higher in the F4 cohort at UCrit. Whether a longer selective breeding programme could result in more changes in body shape, potentially affecting swimming performance, should be explored, along with the potential outcomes of the differences in metabolic traits detected.

Genetic Structure and Diversity of Hatchery and Wild Populations of Yellow Catfish Tachysurus fulvidraco (Siluriformes: Bagridae) from Korea.

Yellow catfish Tachysurus fulvidraco is an important commercial fish species in South Korea. However, due to their current declines in its distribution area and population size, it is being released from hatchery populations into wild populations. Hatchery populations also produced from wild broodstocks are used for its captive breeding. We reported 15 new microsatellite DNA markers of T. fulvidraco to identify the genetic diversity and structure of its hatchery and wild populations, providing baseline data for useful resource development strategies. The observed heterozygosity of the hatchery populations ranged from 0.816 to 0.873, and that of the wild populations ranged from 0.771 to 0.840. Their inbreeding coefficient ranged from -0.078 to 0.024. All populations experienced a bottleneck (p < 0.05), with effective population sizes ranging from 21 to infinity. Their gene structure was divided into two groups with STRUCTURE results of K = 2. It was confirmed that each hatchery population originated from a different wild population. This study provides genetic information necessary for the future development and conservation of fishery resources for T. fulvidraco.

Generational breeding gains in a new species for aquaculture, the Australasian snapper (Chrysophrys auratus)

Selective breeding for improved trait performance is a promising approach for developing new species for food production. Globally, a shortage of livestock species presents a significant bottleneck, and this is particularly pronounced for the aquaculture sector. In New Zealand, the Australasian snapper (Chrysophrys auratus) is a potential candidate for aquaculture, and a breeding programme was started in 2004. Here we assess the performance of the most recent F4 cohort in terms of growth and survival against 1) previous generations and 2) unselected offspring from wild broodstock over the first 6 months. First, we detected generational gains over the entirety of the breeding programme in growth, averaging 11.4% for length and 81.1% for weight over 3 years, and detected a strong seasonal Specific Growth Rate (SGR) increase during summer and a general decrease of growth with age. Second, when growing the F4 and F1 cohort side by side, we found a consistent pattern of superior performance, less growth heterogeneity, and a higher condition factor within the F4 population. Notably, these data revealed breeding gains of 4.9% in survival, 10.5% in length and 41.4% in weight for F4 snapper over the first 6 months from hatching. Together these results indicate that domestication gains and genetic improvement can strengthen the potential of snapper as a candidate to diversify and grow aquaculture in New Zealand.

Influence of ploidy, genetic and environment on production traits of the Pacific oyster Crassostrea gigas

Pacific oysters, Crassostrea gigas, are one of the most widely farmed shellfish. To meet demand, the advantages of growth and increased sterility are currently being exploited in the commercial culture of triploid C. gigas. However, the extent of the triploid advantage can vary, environmental conditions and rearing methods. In the present study, the performance of diploid and triploid oysters was compared at two sites (Rongcheng and Rushan) to determine whether the triploidization would result in any advantage on production traits that could be utilized for aquaculture of this species. Triploid oysters were also produced using the wild broodstock and selected line to verify whether selectively bred oysters maintain their improved traits after triploidization. In this study, we found that the survival advantage of triploid is “site-dependent” and that Rongcheng's triploids did not exhibit significantly higher cumulative survival than diploids. Notably, incremental survival of triploid oysters was consistently higher than that of diploids during the second summer, which may be related to gonad development and spawning in diploids. At both sites, growth traits (shell height and individual weight) were always higher for triploids than in diploids in both the selected and control groups, which is strong evidence of a superior growth advantage for triploids. In addition, we found that the production performance (growth, survival and yield) of the selected group was consistently better than that of the control group (either diploid or triploid), suggesting that the superior traits of diploids can be converted to triploids through ploidy manipulation. Our results support the notion that yield can be further optimized by reducing mortality through a selective breeding program coupled with triploid production to increase growth rates. This study provides meaningful information on the potential of triploid C. gigas for oyster culture in northern China.

Characterization and Expression of Cytochrome b5 Gene and Protein in Ovaries of Giant Tiger Shrimp Penaeus monodon

The full-length transcript of cytochrome b5 (PmCytb5) in the giant tiger shrimp (Penaeus monodon) was characterized. It was 1539 bp with an open reading frame (ORF) of 432 bp deducing to 143 amino acids. The deduced PmCytb5 protein contained predicted cytochrome b5-like heme/steroid binding domain (Cytb5, positions 17-91) and a transmembrane domain (positions 120-139). In non-ablated wild adults, PmCytb transcript was significantly increased in mature ovaries while it was earlier upregulated in late vitellogenic stage in eyestalk-ablated shrimp (P&lt;0.05). Progesterone injection (0.1 μg/g) induced the expression of PmCytb5 at 48 hours post injection (hpi, P&lt;0.05) but serotonin (50 μg/g) did not alter its expression (P&gt;0.05) in domesticated adults. The cytoplasmic PmCytb5 protein was upregulated from immature ovaries in the early vitellogenic stage and comparably expressed in subsequent stages in non-ablated wild broodstock. In eyestalk-ablated wild broodstock, a similar expression profile was observed but its expression was further increased in late vitellogenic, and mature stages. The membrane PmCytb5 protein was upregulated in late vitellogenic and mature stages in the former but expressed at a similar level in different ovarian stages in eyestalk-ablated broodstock. Results suggested the important role of PmCytb5 in ovarian development of P. monodon.

Comparative study of ovarian development in wild and captive-reared long-whiskered Sperata aor (Hamilton, 1822)

Long-whiskered catfish Sperata aor is a freshwater catfish known for its supreme flesh quality and fast growth, whose captive-reared broodstock denotes a difficult challenge for aquaculture. The reproductive dysfunctions in long-whiskered catfish raised in tank conditions were observed by comparing tissue biochemical composition and ovarian histology of wild female broodstock. Sixty (60) female broodstocks were used in the current study, consisting of 30 reared at sandy-muddy soil tank bottoms in captive conditions and 30 wild individuals collected from the haor basin during the breeding season. The fish reproductive state was investigated using the biometric and reproductive parameters, biochemical composition and levels of amino acids in the different tissues, and histological analysis of ovarian development. Results revealed that the biometrical parameters of wild and captive female broodstocks exhibited no remarkable difference (p > 0.05). Nevertheless, the wild fish had remarkably higher (p < 0.05) GSI (8.73%), oocyte weight (0.45 mg/egg), and ripeness (27.08%) in comparison with captive-reared broodstock. The total length and body weight, body weight and ovary weight, ovipositor diameter and ovary weight, and GSI and HSI displayed a positive relationship with R2 = 1, R2 = 1, R2 = 0.993, and R2 = 0.973, respectively, for wild broodstock, while R2 = 0.994, R2 = 0.806, R2 = 0.804, and R2 = 0.896, respectively, for captive broodstock. Additionally, the proximate composition in oocytes and liver tissues in both broodstocks did not differ significantly (p > 0.05). However, two essential amino acids (EAA), i.e., lysine and phenylalanine, and two non-essential amino acids, i.e., glutamic acid and glycine, were highly significant differences (p < 0.05) in the oocytes and liver of wild broodstock compared to the captive-reared broodstock. On the other hand, the EAA, e.g., isoleucine, threonine, leucine, and arginine, were highly dominated in both wild and captive female brood oocytes and liver. The ovarian histological slides from each fish group showed three oocytes developmental stages that indicated the asynchronous-reproductive ovarian oocytes of this fish. This study may be useful to fully understand the factors affecting the spawning and reproduction of S. aor broodstock, crucial for management in captive conditions as well as conservation and protection for sustainable aquaculture management of S. aor.

Comparison of genetic diversity of farmed Oreochromis niloticus and wild unidentified tilapia (Wesafu) using microsatellite markers

Abstract. Ukenye EA, Megbowon I. 2023. Comparison of genetic diversity of farmed Oreochromis niloticus and wild unidentified tilapia (Wesafu) using microsatellite markers. Biodiversitas 24: 2953-2957. Nile tilapia (Oreochromis niloticus Linnaeus, 1758) and unidentified tilapia (Wesafu) are cichlid species of important nutritional and economic value with good aquaculture potential. Assessing and comparing the genetic diversity of these cichlid species will assist in information development for conservation and management strategies to improve their overall productivity and sustainable aquaculture production. Using twenty fish specimens each from farmed O. niloticus and ecotype, Wesafu from the wild respectively, we examined the genetic diversity between these two cichlid species. Eight microsatellite loci were utilized to molecularly characterize and compare these two cichlid species from the wild and farm based on their genetic variation levels. Genetic diversity was investigated from isolated, amplified and resolved DNA of the two cichlid species obtained from the wild and farm. The microsatellite markers analysis revealed that ecotype, Wesafu from the wild exhibited higher genetic diversity than farmed O. niloticus as evidenced by the effective number of alleles (1.756), Shannon information index (0.596), observed and expected heterozygosity values (0.682 and 0.400). All genetic diversity indices were observed to have declined in farmed populations due to inbreeding. However, farmed O. niloticus recorded more polymorphism (87%) than ecotype, Wesafu from the wild (75%). Low genetic differentiation was found between the farmed and wild cichlid species according to the fixation index (-0.628) while Principal Coordinate Analysis (PCoA) demonstrated some level of variation between the two cichlid species. This finding provides more insights into the conservation of the genetic resource and better management of these species to minimize inbreeding in aquaculture. We advise that only wild broodstocks should be used for fish restocking in breeding program for sustainable aquaculture production.

Reproductive performance of captive-reared Indian white shrimp, Penaeus indicus, broodstocks over two generations

Closing the complex life cycle of closed thelycum shrimp in captivity is one of the fundamental challenges in breeding programs. In the present study, we investigated the sexual maturity, broodstock development, and spawning performance of two generations of captive-reared Indian white shrimp, Penaeus indicus, over 36 months originated from a single stock of wild brooders. The post larvae (GN-1) produced from wild P. indicus (G0) and P.L. (GN-2) produced from captive-reared (GN-1) broodstocks were nursery (1000 PL m-3) and grow-out (12 shrimp m-2) reared, and subsequently raised in broodstock ponds (1 shrimp m-2). The annual salinity and photoperiod in broodstock ponds varied between 20 to 36 ppt, and 11.2 -12.5 L and 11.5-12.8 D hours, respectively. The light intensity varied between 91 ± 6 lux at dusk to 75,358 ± 1719 lux at noon. The size at first impregnation or mating was 16.45 ± 1.7 g (132 DOC) and 17.62 ± 1.9 g (90 DOC), respectively, in GN-1 and GN-2 females. By 220 DOC, 25% of the GN-1 females initiated gonad development, whereas 55% of the GN-2 females recorded developing ovaries or were in stage II at 150 DOC. The broodstock attained an average final body weight of 38.85 ± 1.5 g (GN-1) and 42.65 ± 1.8 g (GN-2) by 360 DOC. The highest (p&amp;lt;0.01) eggs per gram body weight (5137 ± 303 eggs g-1) and hatchability, H (83 ± 0.7%), was recorded in wild broodstocks (G0) followed by GN-2 (1,715 ± 162 eggs g-1; H: 69 ± 2%) and GN-1 (1,476 ± 151 eggs g-1; H: 75 ± 1%). However, captive-reared broodstock had better survival (89-92%) than wild broodstocks (71 ± 0.8%). Further, indoor maturation trial (21 days) using ablated broodstocks (GN-1) revealed 79% of the impregnated broodstocks undergo molting, resulting in the loss of sperm pack and subsequent reduction in mating efficacy to 29%. The average sperm count and percentage of normal sperm also recorded (p&amp;lt;0.05) reduction during the maturation cycle. The data generated in the present investigation can form the baseline information for developing the breeding strategy for the genetic improvement of Indian white shrimp in India.

Survival and growth of triploid eastern oysters, Crassostrea virginica, produced from wild diploids collected from low-salinity areas

Triploid Eastern oysters have been reported to suffer greater mortalities than diploids when exposed to low-salinity (<5) conditions in the U.S. Gulf of Mexico and Atlantic estuaries. As such, the effect of broodstock parentage was investigated on the low-salinity tolerance of triploid progeny produced by mating diploid females (collected from three Louisiana estuaries differing in salinity regimes) with male tetraploids at two hatcheries. Diploid crosses were also produced using the wild broodstocks to verify expected differences in low-salinity tolerance among diploid progeny and between ploidy levels. All progeny were deployed at low and moderate-salinity (averages of 9.3 and 19.4) field sites to monitor monthly growth and mortality. Sex ratio, gametogenic stage, gonad-to-body ratio, condition index, and Perkinsus marinus infection were also measured periodically at both field sites Although high triploid mortality at the low-salinity site prevented complete analysis, results indicated that diploid parentage had little effect on triploid survival at low salinity. Broodstock parentage affected diploid mortality and growth, although results did not match with predictions made based on historical salinity at broodstock collection sites. Ploidy level had the largest effect on triploid survival and growth followed by the hatchery site where the oysters were produced.

Enrichment of livefeed with very low level of docosahexaenoic acid (DHA) is enough for yellowtail sea bream (Acanthopagrus latus) larvae

The marine fish larvae mostly rely on livefeed, with certain nutritional deficiencies such as poor long chain fatty acids, in spite of recent progress in developing artificial feed. Thus, the present experiment was conducted to evaluate a 30-day dietary effects of enriched rotifer (Brachionus rotundiformis) and Artemia nauplii (Artemia franciscana) with docosahexaenoic acid (DHA) on performance of yellowtail sea bream (Acanthopagrus latus) larvae. For this purpose, 60,000 larvae from wild broodstocks were stocked in 12 tanks (50 larvae/L) supplied with green water (0.5 ×106 cell/ml Nannochloropsis. sp). The rotifer and Artemia were enriched with four experimental emulsions contained four levels of DHA including very low (6 %, DHA-VL), low (12 %, DHA-L), medium (24 %, DHA-M) and high (37.8 %, DHA-H). Larvae were fed with rotifers from day 2–20 post hatch (DPH) and Artemia metanauplii (Instar-II, from 16 to 30 DPH). After the 30-day dietary trial, survival rate and growth performance of larvae were found not affected by different levels of DHA (P > 0.05). The activity of digestive enzymes including total proteases, lipase, amylase, alkaline phosphatase, and leucine-alanine peptidase showed some fluctuations among the experimental groups. However, in the most of the sampling intervals, except for protease activity, the activity of digestive enzymes did not change significantly among the experimental groups. The n–3 polyunsaturated fatty acids, particularly eicosapentaenoic acid (EPA) and DHA, were the highest in the whole body of larvae from DHA-M treatment. The DHA/EPA ratio in the whole body of larvae was significantly increased with increasing DHA level (P < 0.05). Based on our findings, very low levels of DHA is enough for supporting normal growth, survival and metamorphosis in developing A. latus larvae up to 30 days post hatching.

Broodstock exposure to warming and elevated pCO2 impairs gamete quality and narrows the temperature window of fertilisation in Atlantic cod.

Impacts of global warming and CO2 -related ocean acidification (OA) on fish reproduction may include chronic effects on gametogenesis and gamete quality, as well as acute effects on external fertilisation. Here, temperature thresholds and OA-sensitivity of gametogenesis and fertilisation were investigated in Atlantic cod, Gadus morhua. Three broodstock groups of farmed cod (FC 1-3) were exposed for 3 months to three maturation conditions (FC 1: control, 6°C/400 μatm CO2 ; FC 2: warming, 9.5°C/400 μatm; FC 3: warming and OA, 9.5°C/1100 μatm). In addition, a broodstock group of wild cod (WC) was kept at control conditions to compare the acute temperature window of fertilisation with that of farmed cod (FC 1). Fertilisations were conducted in a temperature-gradient table at 10 temperatures (between -1.5 and 12°C) and two CO2 levels (400/1100 μatm). In FC 1 and WC, fertilisation success was relatively high between 0.5°C and 11°C (TRange of c. 10.5°C), indicating similar gamete quality in farmed and wild broodstocks kept at control conditions. Exposure of farmed broodstocks to warming (FC 2) and the combination of warming and OA (FC 3) impaired gamete quality, causing a reduction in fertilisation success of -20% (FC 2) and - 42% (FC 3) compared to FC 1. The acute temperature window of fertilisation narrowed from FC 1 (TRange =10.4°C) to FC 2 (TRange =8.8°C) and FC 3 (TRange =5.9°C). Acute effects of CO2 on fertilisation success were not significant. This study demonstrates potential climate change impacts on gametogenesis and fertilisation in Atlantic cod, suggesting the loss of spawning habitat in the coming decades.

Improving the Reproductive Yield of Black Sea Salmon (Salmo labrax PALLAS, 1814) with a Selective Breeding Program

This study aimed to improve some culture characteristics of Black Sea salmon (Salmo labrax) culture generations through a classical selective breeding program. Thus, the success of the applied program was examined by comparing the reproduction time and proportional distribution of the wild broodstock (F0 ) individuals with the F1 , F2 , F3 and F4 generation broodstocks adapted to the culture conditions. According to the results, gamete uptake from the new generations occurred between October and February. The highest egg uptake was determined for all generations in December. While the difference between wild (F0 ) broodstock and F1 , F2 , F3 , and F4 generations was statistically significant in favor of new generations (P&lt;0.05), the difference was insignificant between hatchery origin-new generations. Mean egg diameters were low in F2 and F3 generations, and F0 , F1 and F4 generations were found to be higher than the others (P&lt;0.05). It was calculated that the fertilization rate was higher in F3 and F4 generations, similar in F1 and F2 generations, and lower in F0 generation than the others (P&lt;0.05) at the end of the study. Through the selection program, it was determined that the adaptation of the species to the culture conditions improved, the reaction to human activities declined, and homogeneous distribution in tanks/ponds was relatively achieved from the F2 generations. As a result, it has been determined that F4 generation broodstock have higher culture performance than other generations. Producers of this species should use F4 broodstock for efficient and economical production.&nbsp;

Efficacy of Endangered Pinto Abalone (Haliotis kamtschatkana) Stock Restoration in the Southern Salish Sea From a Genomic Perspective

Declines in abalone populations throughout the world have led to conservation measures including fishery closures and captive breeding programs aimed at stock restoration. Restoration of endangered pinto abalone (Haliotis kamtschatkana) in the southern Salish Sea (Washington State, USA) began in the mid-2000s, and since 2009, nearly 40,000 hatchery-produced juvenile abalone have been outplanted at 21 restoration sites. We used genotyping by sequencing to evaluate the efficacy of this restoration program from a genomic standpoint. Over 49,000 SNPs and 8,000 haplotypes were evaluated across both wild and hatchery-produced abalone. Compared to wild abalone, hatchery-bred abalone had similar heterozygosity, lower allelic richness and effective population size, and higher relatedness. However, more recently bred hatchery progeny sampled prior to outplanting showed intermediate allelic richness, lower relatedness and genomic divergence, and higher effective population size compared to older hatchery outplants sampled after outplanting. We attribute these differences to genetic drift among older hatchery outplants due to mortality and emigration as well as larger numbers of broodstock families in more recent hatchery operations. This suggests that current hatchery practices that combine higher output with larger numbers of broodstock families may more effectively overcome the effects of genetic drift. Effective population size estimates among wild Salish Sea abalone had no upper limit, indicating that these abalone have sufficient genetic diversity to support the restoration program, but also highlighting the need for large broodstock sizes to overcome potential Ryman-Laikre effects. The greatest challenge for the future of the restoration program will be finding sufficient numbers of wild broodstock in the Salish Sea, where pinto abalone remain extremely rare.

Captive Rearing of Longfin Smelt Spirinchus thaleichthys: First Attempt of Weaning Cultured Juveniles to Dry Feed.

Simple SummaryLongfin smelt Spirinchus thaleichthys is an imperiled estuarine species in California, USA. A captive culture program is currently being developed; however, prior to this study, longfin smelt have only fed on live prey in the hatchery. Here, we report on our first successful attempt to wean cultured juveniles onto a dry commercial pellet feed. A subset of F1 fish was switched to a mixed diet of reduced Artemia and dry feed for 62 days, with growth, survival, and body condition compared between feeding treatments. Our results highlight that juvenile longfin smelt can utilize dry feeds while maintaining a healthy body condition.The rapid decline of longfin smelt Spirinchus thaleichthys, a threatened euryhaline forage fish in California, is a serious concern for scientists and resource managers. To recover and conserve this species, a captive culture program was initiated, focusing on the collection, captive rearing and breeding of wild broodstock, and the rearing of their offspring. Although progress has been made in the collection of broodstock and the production and culturing of larvae, no studies have evaluated the rearing of juvenile life stages in captivity. The present study examines methodological considerations for culturing F1 juvenile longfin smelt, specifically, the first efforts toward weaning juveniles to a dry commercial pellet feed. Cultured juvenile longfin smelt were fed live Artemia only or co-fed Artemia and dry feed for 62 days, and the effects of feed type on juvenile survival, growth, body condition, and fatty acid profiles were examined. No significant differences were observed between feeding treatments, despite an 80% reduction in Artemia in the co-feeding treatment. Furthermore, examination of fish stomach contents at the end of the trial confirmed the transition to dry feed. This is the first study to indicate successful feeding by longfin smelt on dry commercial pellets, and suggests that juvenile longfin smelt can be fully weaned onto dry feeds. Results of this study are critical for closing the lifecycle of longfin smelt in captivity and developing a successful conservation culture program for this imperiled species.

Comparative proximate analysis of wild and captive lumpfish (Cyclopterus lumpus) eggs show deficiencies in captive eggs and possible egg quality determinants

The production of lumpfish (Cyclopterus lumpus) is increasing rapidly due to their use as a cleaner fish for sea lice infections in Atlantic salmon farming. The sustainable development of captive broodstocks is reliant on good egg quality however this remains unknown. The present study assessed the hatching success and nutritional composition of eggs collected from two wild groups, at the start and end of the Norwegian fishing season (2018–2019), and one captive broodstock population (2019). Eggs from the farmed broodstock, used in this study, showed significantly lower fertilisation rates, eyeing rates and survival to hatching than eggs from wild broodstock. There was significantly less overall lipid content in the captive eggs when compared to the wild group as well as significantly lower levels of lipid fractions such as total N-3 PUFAs, minerals such as sodium and phosphorus and overall egg pigment levels. A principal component analysis of all 139 measured nutritional components within fatty acids, minerals and pigments was conducted to identify those associated with egg quality in lumpfish. A total of 51 components was identified as being positively (31) and negatively (20) correlated with hatching rate including essential fatty acids such as EPA, DHA and ARA, total pigment levels and calcium levels. Overall, this study clearly showed a reduction in egg quality from captive broodstock and suggested nutritional deficiencies in the current broodstock diets. As such, this study provides a foundation for further work into the optimisation of lumpfish broodstock management with a number of nutritional factors to be further investigated.

Growth and survival rates of domesticated and non-domesticated breeding stocks of Penaeus monodon Fabricius, 1798 cultured in ponds and tanks

Sourced breeders from domesticated broodstocks have played an essential role in the steady development of shrimp culture in many countries. In the present study, two experiments were performed in Tra Vinh province, Vietnam, to compare the culturing benefits of sourced breeding stocks from domesticated and non-domesticated Penaeus monodon broodstock. The first 90-day experiment was randomly arranged with three repetitions in six earthen ponds (1,500–2,000 m2). Experimental shrimp (PL12) were stocked at a density of 20 ind. m−2. The second experiment was randomly designed with three repetitions in six composite tanks (6.0 m3). PL15 of experimental shrimp were cultured at a density of 30 ind. m−2 for 120 days. Grobest pellet feed (40 % protein) was used in both experiments. At experiment termination, the mean weight (26.09 g) and length (15.68 cm) under pond culture, as well as respective values of 15.57 g, and 13.21 cm under tank culture, for D-shrimp were significantly higher than those of W-shrimp (p&lt;0.05). Similarly, the survival rate (84.33 %), FCR (0.98), and yield (3,558 kg ha−1) under pond culture, as well as the survival rate (87.59 %) and yield (470 g m−3) under tank culture, of D-shrimp were significantly better than those of W-shrimp (p&lt;0.05). These results prove that the grow-out culture of shrimp postlarvae from domesticated broodstocks resulted in superior performance to those from wild broodstocks.

Isolation and Expression Analysis of cAMP-Dependent Protein Kinase and Adenylyl Cyclase-Associated Protein 1-like cDNAs in the Giant Tiger Shrimp Penaeus monodon

Characterization of genes exhibiting differential expression profiles during ovarian development is important for understanding reproductive maturation of the giant tiger shrimp (Penaeus monodon). Here, the partial cDNAs of P. monodon cAMP-dependent protein kinase, catalytic subunit 1 (PmPkaC1) and adenylyl cyclase-associated protein 1-like (PmCap1-l) were studied. They were more preferentially expressed in ovaries than testes of cultured juveniles and wild broodstock. PmPkaC1 mRNA in ovaries of non-ablated broodstock was significantly increased during vitellogenesis (P&lt;0.05). However, unilateral eyestalk ablation (the removal of one eyestalk) resulted in a significant reduction of its expression (P&lt;0.05). PmCap1-l was not differentially expressed during ovarian development in wild non-ablated broodstock. It was up-regulated in mature ovaries following eyestalk ablation (P&lt;0.05). The PmCap1-l transcript in each ovarian stage of the former was significantly lower than that of the latter (P&lt;0.05). The levels of ovarian PmPkaC1 and vitellogenin 1 (PmVtg1) treated in vitro with 17-20β-DHP (0.1, 1.0 and 10.0 μg/ml for 24 h) was not significantly different from the control (P&gt;0.05). Nevertheless, the expression of PmCap1-l was increased in ovaries treated with 0.1 and 10 μg/ml 17-20β-DHP at 24 hours post treatment (hpt, P&lt;0.05).