Hatchery Stocks Research Articles

Contemporary Population Structure in Klamath River Basin Chinook Salmon Revealed by Analysis of Microsatellite Genetic Data

AbstractChinook Salmon Oncorhynchus tshawytscha exhibit substantial population genetic structure at multiple scales. Although geography is generally more important than life history, particularly migration and run timing, for describing genetic structure in Chinook Salmon, there are several exceptions to this general pattern, and hatchery supplementation has altered natural genetic structure in some areas. Given that genetic structure of Chinook Salmon is often basin‐specific, we assessed genetic variation of 27 microsatellite loci in geographically and temporally distinct natural populations and hatchery stocks in the Klamath River basin, California. Multiple analyses support recognition of three major genetic lineages from separate geographic regions in the Klamath River basin: the lower basin, the Klamath River, and the Trinity River. The lower basin group was sharply distinct, but populations in the Klamath and Trinity river lineages were connected by processes that can be described by a one‐dimensional, linear, stepping‐stone model where gene exchange occurred primarily, but not exclusively, between adjacent populations. Genetic structure by migration timing was also evident, although divergences among populations that differed by migration timing only were fewer than those observed between geographic regions. Distinct run‐timing ecotypes in the Klamath River basin thus appear to have evolved independently through a process of parallel evolution. Introgressive pressure from the hatchery stocks into natural populations was attenuated by distance from the hatchery, but comparison of historical population genetic structure to contemporary patterns would be needed to fully evaluate the extent to which hatchery stocks may have altered natural genetic structure.

Steelhead vulnerability to climate change in the Pacific Northwest

Summary Steelhead (Oncorhynchus mykiss) and other Pacific salmon are threatened by unsustainable levels of harvest, genetic introgression from hatchery stocks and degradation or loss of freshwater habitat. Projected climate change is expected to further stress salmon through increases in stream temperatures and altered stream flows. We demonstrate a spatially explicit method for assessing salmon vulnerability to projected climatic changes (scenario for the years 2030–2059), applied here to steelhead salmon across the entire Pacific Northwest (PNW). We considered steelhead exposure to increased temperatures and more extreme high and low flows during four of their primary freshwater life stages: adult migration, spawning, incubation and rearing. Steelhead sensitivity to climate change was estimated on the basis of their regulatory status and the condition of their habitat. We assessed combinations of exposure and sensitivity to suggest actions that may be most effective for reducing steelhead vulnerability to climate change. Our relative ranking of locations suggested that steelhead exposure to increases in temperature will be most widespread in the southern Pacific Northwest, whereas exposure to substantial flow changes will be most widespread in the interior and northern Pacific Northwest. There were few locations where we projected that steelhead had both relatively low exposure and sensitivity to climate change. Synthesis and applications. There are few areas where habitat protection alone is likely to be sufficient to conserve steelhead under the scenario of climate change considered here. Instead, our results suggest the need for coordinated, landscape‐scale actions that both increase salmon resilience and ameliorate climate change impacts, such as restoring connectivity of floodplains and high‐elevation habitats.

Coding Gene Single Nucleotide Polymorphism Population Genetics of Nonnative Brook Trout: The Ghost of Introductions Past

Fish have been translocated throughout the world, and introductions often have been executed repeatedly and have used mixtures of different strains from the native range. This history might have contributed to their invasive potential by allowing introduced and invading populations to circumvent expected reductions in genetic diversity from founder effects in a scenario termed the “genetic paradox” of invasions. We characterize patterns of genetic diversity in nonnative Brook Trout Salvelinus fontinalis, which have been introduced across the western United States for over a century but have also invaded broadly and pose a primary threat to native trout. We analyzed 155 coding gene single nucleotide polymorphisms (SNPs) in 34 nonnative Brook Trout populations sampled across eight large river systems as well as samples from the only four hatchery strains with documented use in Idaho. We uncovered similar within-population genetic diversity and large effective population sizes in naturalized populations compared with hatchery samples. Naturalized populations also showed substantial genetic structuring (maximum pairwise FST = 0.23) across and even within watersheds and indicated suggestions of admixture in certain regions. Assignment probabilities confirmed two main hatcheries as the origin of most fish collected in the field; however, the four hatcheries were excluded as being the origin for 8% of individuals, mirroring results from clustering analyses and suggesting the influence of an additional unsampled hatchery source or sources. Simulated admixtures of hatchery samples produced genetic patterns similar to those observed in field samples, further supporting an influence of multiple historic hatchery stocks on the contemporary genetic structure of Brook Trout in Idaho. Our study highlights the potential contribution of historic hatchery and introduction practices in creating genetically variable and structured naturalized Brook Trout populations across Idaho, which may have allowed these fish to defy the “genetic paradox” early on in their nonnative history and set the stage for successful establishment and subsequent invasion.

Genetic Monitoring of Threatened Chinook Salmon Populations: Estimating Introgression of Nonnative Hatchery Stocks and Temporal Genetic Changes

AbstractConservation efforts aimed at Pacific salmon (Oncorhynchus spp.) populations have frequently utilized artificial propagation in an attempt to increase fish abundance. However, this approach carries the risk of unwanted changes in the genetic characteristics of the target population and perhaps others that might incidentally be affected. We used genetic monitoring techniques to estimate the amount of introgression that has occurred from nonnative hatchery stocks into native populations and to determine the extent of genetic changes that have occurred in association with supplementation efforts over the past 20–50 years in Snake River Chinook Salmon O. tshawytscha populations from northeastern Oregon. A total of 4,178 fish from 13 populations were genotyped for 12 microsatellite DNA loci. Expected heterozygosity values for each sample ranged from 0.707 to 0.868. Estimates of the effective number of breeders per year in the naturally spawning populations ranged from 20.6 to 459.1, whereas in the hatchery populations they ranged from 33.8 to 1,118.8. We found that introgression from the Rapid River Hatchery stock was particularly noticeable in the early 1990s but that it appears to have had a substantial effect on only two of the native populations (Lookingglass Creek and the upper Grande Ronde River) despite the ample opportunities for introgression to occur. All seven of the native populations sampled have maintained their levels of within‐population genetic diversity throughout the sampling period. Overall, this region's supplementation efforts appear to have had a minimal effect on the genetic diversity of its Chinook Salmon populations.Received October 9, 2012; accepted March 25, 2013

A validation of parentage-based tagging using hatchery steelhead in the Snake River basin

Parentage-based tagging (PBT) is a promising alternative to traditional coded-wire tag (CWT) methodologies for monitoring and evaluating hatchery stocks. This approach involves the genotyping of hatchery broodstock and uses parentage assignments to identify the origin and brood year of their progeny. In this study we empirically confirmed that fewer than 100 single nucleotide polymorphisms (SNPs) were needed to accurately conduct PBT, we demonstrated that our selected panel of SNPs was comparable in accuracy to a panel of microsatellites, and we verified that stock assignments made with this panel matched those made using CWTs. We also demonstrated that when sampling of spawners was incomplete, an estimated PBT rate for the offspring could also be predicted with fewer than 100 SNPs. This study in the Snake River basin is one of the first large-scale implementations of PBT in salmonids and lays the foundation for adopting this technology more broadly in the region, thereby allowing the unprecedented ability to mark millions of smolts and an opportunity to address a variety of parentage-based research and management questions.

Modelling ecosystem effects of reduced prawn recruitment on the Thukela Bank trawling grounds, South Africa, following nursery loss

Penaeid prawns are targeted in the Thukela Bank shallow-water trawling grounds in south-eastern Africa. Based on previous studies, these targeted prawns are assumed to primarily use 2 large estuaries (St. Lucia and Richards Bay/Mhlathuze) as nurseries on the KwaZulu-Natal (KZN) coast, which comprise over 80% of the estuarine habitat in the region. However, St. Lucia has been closed to the Indian Ocean since 2002 due to continued separation from the Mfolozi River, cessation of dredging required to open the inlet, reduced freshwater flow and drought con- ditions. To study the effects of prawn trawling and prawn nursery loss on the ecosystem, Ecopath with Ecosim models of the Thukela Bank were constructed. Models were fitted to total catch (t) for 1990 to 2009, and biomass trends were estimated by scaling Ecosim feeding interaction parame- ters to prey trophic level. Prawn trawling was modelled using fishing effort data. Prawn recruit- ment was modelled via the 'hatchery stocking' function in Ecosim simulating nursery loss along the KZN coast. Various prawn recruitment and trawling effort levels were simulated from 2010 to 2040. Decreasing prawn recruitment positively affected benthic fish and carnivorous benthos bio- mass and negatively affected prawn, commercial crustacean and benthopelagic fish biomass. Negative effects were exacerbated and positive effects were decreased by high versus low trawl- ing effort. The results suggest that indirect anthropogenic and environmental factors, such as recruitment from estuarine nursery areas, can impact offshore fisheries catches. Therefore, when modelling and managing marine ecosystems, it is important to couple processes between adjacent systems, particularly for critical life-history stages.

Genetic and ecological assessment of population rehabilitation: walleye in Lake Superior

Sustainable management of exploited species is an ongoing challenge, particularly where populations have collapsed or been depleted by overharvest and habitat alteration. The walleye (Sander vitreus) population in Lake Superior's Black Bay historically supported more than 90% of the commercial walleye harvest from the entire lake, but collapsed in 1968 and has still not recovered despite long-term closure of the fishery. In an effort to rehabilitate this population, hatchery-origin walleye from exogenous sources were released into Black Bay between 2003 and 2005. We used individual-based analysis of genetic data collected between 2007 and 2010 to examine the contributions of different wild sources and hatchery stocking events to the contemporary walleye population in Black Bay. We found that 75% of the walleye in Black Bay originated from above- and below-barrier native populations in the Black Sturgeon River. The hatchery stocking events differed considerably in their effectiveness: the 2003 release of fry had no measurable contribution, whereas the 2004 and 2005 releases of fingerlings contributed 71% and 45% of the fish in their respective age classes. Hatchery and wild fish were similar in size, but hatchery fish rarely utilized the river habitat where Black Bay walleye historically spawned, and there was little genetic evidence of interbreeding or natural recruitment of stocked fish. Overall, our results suggest that restoring habitat connectivity to facilitate wild recruitment has greater potential than further exogenous stocking to contribute to the recovery of walleye in this system.

Genetic monitoring by rapd markers for repopulation programs of Salminus brasiliensis (Pisces, Characiformes)

The preservation of the genetic variability of hatchery stocks used to supplement natural populations is a priority. Current study employed RAPD markers to examine the genetic diversity of dourado samples from the middle Paranapanema river and from the broodstock used in the stock enhancement program of the Aquaculture and Hydrobiology Station at the Salto Grande Hydroelectric Power Plant. Nineteen RAPD primers were analyzed, which generated 299 bands and the latter were used for genetic analysis. The percentage of polymorphic fragments was higher in stock captured in the Paranapanema river than from fry stocks. The genetic diversity was lower in the broodstock than in natural population. Amova results showed that most inter-population genetic variation lay within stocks (83.9%) and not between them (16.1%). Moderate genetic differentiation (FST = 0.16) was reported. Nevertheless, differentiation decreased when the four fry stocks were mixed and analyzed as a single population (FST = 0.07). Instead of releasing each lot separately into the water, mixing specimens produced in the various fry stocks before releasing them in the river would be more feasible. The restocked population will have a genetic structure closer to natural populations.

Genetic structure of the Korean black scraper Thamnaconus modestus inferred from microsatellite marker analysis

The Korean black scraper, Thamnaconus modestus, is one of the most economically important maricultural fish species in Korea. However, the annual catch of this fish has been continuously declining over the past several decades. In this study, the genetic diversity and relationships among four wild populations and two hatchery stocks of Korean black scraper were assessed based on 16 microsatellite (MS) markers. A total of 319 different alleles were detected over all loci with an average of 19.94 alleles per locus. The hatchery stocks [mean number of alleles (N(A)) = 12, allelic richness (A(R)) = 12, expected heterozygosity (He) = 0.834] showed a slight reduction (P > 0.05) in genetic variability in comparison with wild populations (mean N(A) = 13.86, A(R) = 12.35, He = 0.844), suggesting a sufficient level of genetic variation in the hatchery populations. Similarly low levels of inbreeding and significant Hardy-Weinberg equilibrium deviations were detected in both wild and hatchery populations. The genetic subdivision among all six populations was low but significant (overall F(ST) = 0.008, P < 0.01). Pairwise F(ST), a phylogenetic tree, and multidimensional scaling analysis suggested the existence of three geographically structured populations based on different sea basin origins, although the isolation-by-distance model was rejected. This result was corroborated by an analysis of molecular variance. This genetic differentiation may result from the co-effects of various factors, such as historical dispersal, local environment and ocean currents. These three geographical groups can be considered as independent management units. Our results show that MS markers may be suitable not only for the genetic monitoring of hatchery stocks but also for revealing the population structure of Korean black scraper populations. These results will provide critical information for breeding programs, the management of cultured stocks and the conservation of this species.

Genetic improvement of tilapias in China: Genetic parameters and selection responses in growth, pond survival and cold-water tolerance of blue tilapia (Oreochromis aureus) after four generations of multi-trait selection

Genetic parameters and selection responses were obtained for growth, pond survival and cold-water tolerance of Progift blue tilapia (Oreochromis aureus) in China after four generations of multi-trait selection. Blue tilapia from four Chinese hatchery stocks and one from Vietnam were used to compose a synthetic breeding population. About 31,000 tagged fingerlings representing 519 full-sib families in five generations were tested in freshwater earthen ponds in Hainan Province of China. Individual body weights were recorded on 11,000 fish at the expected time of sexual maturation and 22,000 at harvest to estimate genetic parameters for growth rate. An additional 5000 tagged fingerlings representing all families in G3 and G4 were challenged to estimate genetic parameters for cold-water tolerance. Heritability (h2) estimates for body weight were relatively stable across time of recordings and generations, and was of similar magnitude (0.40±0.04) when analyzing all harvest data. The h2 of pond survival was considerably lower (0.05±0.01 and 0.08±0.11), while that of cold-water tolerance was intermediate (0.20±0.04 and 0.30±0.31) when estimated on the observed and underlying scales. Including all data, effects common to full-sibs other than additive genetic effects (c2) accounted for 7% and 1%, respectively, of the total phenotypic variance for body weight at harvest and the two survival traits. Genetic correlation between growth recorded at expected time of sexual maturation and at harvest was very high (0.99±0.01). The genetic correlation between growth and pond survival was positive (0.15±0.08), while that between growth and cold-water tolerance was not significantly different from zero (0.02±0.12). Breeding candidates in the base population (G0) were ranked according to their individual breeding values for growth (recorded as body weight at harvest), while those in later generations (G1–G3) were ranked according to a selection index including individual breeding values for growth and family breeding values for survival traits. A genetic trend analysis based on all grow-out data predicted an accumulated selection response of 168g (2.16 phenotypic standard deviation units) and an average selection response of 14.0% per generation of selection when using the LS mean of the G0 as a base line for the comparison. Genetic trend analyses of survival data predicted accumulated selection responses of 8.4 and 1.2%-units higher survival rates in earthen ponds and cold-water challenge tests, respectively. The average inbreeding coefficient (F) was estimated to be 2.1% in the G4 generation. The results are discussed in a practical context of adapting selective breeding technology to a new aquaculture species and it is concluded that the ongoing selective breeding of blue tilapia in China has resulted in considerable genetic improvements of both growth (about 70% larger body weight at harvest) and pond survival after four generations of multi-trait selection.

Effect of pH on growth and survival in the freshwater crayfishAustropotamobius pallipes

Conservation of endangered British crayfish (Austropotamobius pallipes) involves translocation to isolated waterbodies (Ark Sites) and reintroductions from hatchery stock. The species is restricted in the wild to relatively alkaline waterbodies. The optimum pH conditions that maximise growth and survival are unknown. This information would benefit the selection of Ark Sites and hatchery water chemistry. Here we measure growth and survival of juvenile A. pallipes in the laboratory using three pH levels from within the species' natural range. Survival at pH 8.6 was high (94%), whereas that at lower pH levels was low (pH 6.5, 25%; pH 7.1, 34%). Growth (moult increment and frequency) was also higher at pH 8.6. Survival was also lower for Thelohania contejeani-infected animals, with a trend towards higher mortality in infected individuals at lower pH. Electron microscopy revealed a lower cuticle thickness at pH 6.5 than higher pH which was associated with an apparent increase in the number of endocuticle layers. We therefore recommend that high pH (ca. 8.6) be used as a target for Ark Site selection and hatchery water chemistry in order to maximise survival and growth. (

Multicompartment Gravel Bed Flume to Evaluate Swim‐Up Success of Salmonid Larvae

AbstractSwim‐up success, the proportion of fry emerging from a gravel redd, is difficult to quantify in the field, and currently available laboratory systems are limited. We used custom‐built gravel bed flumes to assess the swim‐up success of Rainbow Trout Oncorhynchus mykiss, Brook Trout Salvelinus fontinalis, and Cutthroat Trout Oncorhynchus clarkii. Flumes were built with compartments to separate individual egg batches, eggs were buried under gravel, and oxygenated water was supplied to simulate upwelling through the gravel. Temperature, dissolved oxygen, pH, and flow were constant between compartments and flumes operating in parallel. Swim‐up success was scored both by the emergence of fry relative to the number of eggs placed in the flume (59–85% depending on species) and the hatching success (proportion of eggs that hatch and resorb their yolk sac) of a sample from the same clutch reared in a vertical incubator (62–84% depending on species). The gravel bed flumes could be used to estimate the swim‐up success of salmonid egg clutches from hatchery stocks or fish from the wild or under experimental regimes of relevance to fishery or environmental assessment, including changes in pH, siltation, temperature, toxicants, or events simulating floods or droughts.Received July 12, 2012; accepted October 11, 2012

Recovery of the endangered trout cod, Maccullochella macquariensis: what have we achieved in more than 25 years?

Recovery of threatened species is often necessarily a long-term process. The present paper details the progress towards the recovery of trout cod, Maccullochella macquariensis, an iconic, long-lived fish species first listed as threatened in the 1980s. The objectives, actions and progress over three successive national recovery plans (spanning 18 years) are assessed, documenting changes to population distribution and abundance and updating ecological knowledge. Increased knowledge (especially breeding biology and hatchery techniques, movements, habitats and genetics) has greatly influenced recovery actions and the use of a population model was developed to assist with management options and stocking regimes. Key recovery actions include stocking of hatchery-produced fish to establish new populations, regulations on angling (including closures), education (particularly identification from the closely related Murray cod, M. peelii) and habitat rehabilitation (especially re-instatement of structural woody habitats). In particular, the establishment of new populations using hatchery stocking has been a successful action. The importance of a coordinated long-term approach is emphasised and, although there is uncertainty in ongoing resourcing of the recovery program, much has been achieved and there is cautious optimism for the future of this species.

POPULATION GENETIC STRUCTURE OF AN ENDANGERED KALIBAUS, Labeo calbasu (HAMILTON, 1822) REVEALED BY MICROSATELLITE DNA MARKERS

The population genetic structure of Labeo calbasu collected from four wild and a hatchery population was studied using microsatellite DNA marker analysis. Five heterologous microsatellite markers (Lr10, Lr21, Lr24, Lr26 and CcatG1) developed from rohu and catla were analyzed to test the genetic variability of L. calbasu stocks. The number of alleles observed in the loci ranged from 2-10. The loci were found to be polymorphic (<P95) in all the populations. The average numbers of possessed alleles were higher by the four wild stocks than the hatchery stock. The average number of allele was the highest in the Jamuna population (5.8) and the least in the Hatchery population (4.8). The observed average heterozygosity (Ho) in the Jamuna population (0.776) was the highest followed by the Halda (0.667), the Haor (0.661) and the Padma (0.642) populations. Except loci Lr10 and Lr24 in the Halda and locus Lr10 in the Padma and Hatchery populations, significant deviations from Hardy-Weinberg Equilibrium (HWE) were detected in all cases. The FST values and the Nm values indicated high level of differentiation and a low level of gene flow between the populations. The largest genetic distance value (D = 0.543) was measured between the Jamuna and the Hatchery populations while the least value (D =0.124) was observed between the Padma and the Halda populations. The estimated genetic population structure and potential applications of microsatellite markers may assist the proper management of L. calbasu populations in the wild.

Naturally and hatchery produced European trout Salmo trutta: do their marine survival and dispersal differ?

We tested whether marine survival and migration pattern differed between naturally and hatchery produced European trout Salmo trutta of different origins. The hatchery fish were released 150 m above the river estuary of the southwestern, Norwegian River Imsa, the home of the local population. Recaptures were used as proxy for survival. Wild and local hatchery fish survived better than transplanted hatchery stocks. Trout that were 1 year at release survived less well than 2-year olds, and small individuals less well than larger ones. Relative to their body size at release, populations that originated most distant from the River Imsa, the Baltic River Eman and the Norwegian mountain Lake Tunhovd, exhibited the poorest sea survival. At sea, trout chiefly moved less than 240 km from the river of release, but there were significant differences in dispersal among populations. Hatchery-produced River Eman and Lake Tunhovd trout moved farther from the River Imsa than the south Norwegian sea trout populations, and the marine distributions of the former were similar to that of the natural River Imsa trout. Large fish moved farther from the river than smaller ones. Straying to other rivers was low among wild and local hatchery-produced fish, and significantly lower than among most transplanted populations, and River Eman trout in particular. Thus, the River Imsa trout appeared better adapted to survival under the local conditions than non-local trout with consequences for optimal population management.

Development and multiplex PCR amplification of microsatellite markers in the commercial clam Venerupis rhomboides (Mollusca: Bivalvia)

Venerupis rhomboides is a commercial clam whose production could be enhanced through effective management of natural and hatchery stocks. This study provides the first panel of microsatellite markers for the exploitation of this species according to genetic criteria. A total of 22 polymorphic microsatellite loci were isolated and characterized from two genomic libraries enriched for different motifs. The number of alleles per locus ranged from 2 to 14 in a sample of 20 clams from Spain, and the observed and expected heterozygosity from 0 to 0.95 and 0.05-0.901, respectively. Sixteen loci were in agreement with Hardy-Weinberg equilibrium after sequential Bonferroni correction and linkage disequilibrium between loci pairs was not detected. To reduce the cost of the genotyping process, tri- and pentaplex PCRs, amplifying a total of 13 microsatellites loci were optimized. The microsatellites developed here represent the first nuclear markers described in V. rhomboides and will be useful tools for genetic studies involving assessment of genetic variation and population structure of natural and cultivated populations, assignment testing, construction of genetic linkage maps and dissection of production traits.

Molecular characterization of two populations of catfish Clarias batrachus L. using random amplified polymorphic DNA (RAPD) markers

Studies were undertaken to identify genetic relationship and diversity of Clarias batrachus L. populations collected from hatchery and wild stocks through random amplified polymorphic DNA (RAPD). 16 decamer primers were used for screening, out of which five produced amplicons. A total of 1376 RAPD bands ranging from 0.2 to 1.36 kb were amplified using five selected primers. The number of amplification products produced by a primer ranged from as low as three to a maximum of 18, with an average of 16 bands per primer. 8.1 to 13.71 polymorphic bands per primer were amplified. The polymorphic bands in these populations ranged from 56.4 to 59.6%. Polymorphic bands per lane within populations ranged from 4.88 to 5.3%. The similarity within the population from wild varied from 0.40 to 0.83 with a mean ± SE of 0.57 ± 0.08. The Jaccard’s similarity coefficient ranged from 0 to 0.27. At 0.06 similarity coefficient, two major clusters were formed, which indicates that the genotypes belonging to same clusters were genetically similar and those belonging to different clusters were dissimilar. Significant (P < 0.05) population differentiation indicated some degree of intra- and inters- population genetic variations in two populations of catfish. This might be due to difference in habitat and breeding strategies between the two populations. Key words: Random amplified polymorphic DNA (RAPD), similarity coefficient, polymorphism, Clarias batrachus, primer.

Genetic diversity and differentiation of masu salmon (Oncorhynchus masou masou) between and within cultured populations inferred from microsatellite DNA analysis.

Masu salmon, Oncorhynchus masou masou, is one of the most valuable fishery species that has been introduced to China, though to date no studies on the genetic diversity and genetic relationship among hatchery populations has been performed with molecular markers. We undertook such a study and sampled 120 individuals from three hatchery stocks and analyzed 20 microsatellite loci. All loci were polymorphic and a total of 91 alleles were detected. A relatively low level of genetic diversity was revealed with effective number of allele of 3.1094, 3.3299 and 3.1894 and expected heterozygosity of 0.6600, 0.6648 and 0.6638 in the three stocks, respectively. Deviations from Hardy-Weinberg equilibrium were found due to heterozygote deficit. Accordingly, evidence of genetic bottlenecks were found in the three stocks. An individual assignment test demonstrated that 85% of individuals were correctly assigned into their original stocks. Pairwise Fst revealed that significant differentiation occurred between these three stocks. The results of the study indicated that disequilibrium of genetic structure and differentiation has occurred in all three stocks. This information collectively provides a basis for measures to avoid of loss of genetic diversity and introgression in Chinese aquaculture.

Differences in stability effects on the marine survival of hatchery pink salmon (Oncorhynchus gorbuscha) within the upwelling and downwelling domains of the northeast Pacific Ocean

AbstractRegional coastal conditions have a strong influence on juvenile salmon survival during their critical first months in the marine environment. Salmon (genus Oncorhynchus) survival has been thought to be favored within the high latitude downwelling domain if water column stabilities increase, whereas stability may have the opposite effect in upwelling‐dominated lower latitudes. In this study, the relationships between water column stabilities during early marine residence of pink salmon (Oncorhynchus gorbuscha) in both the upwelling and downwelling domains of the northeast Pacific Ocean and marine survival rates for hatchery stocks ranging from Vancouver Island, British Columbia, to Kodiak Island, Alaska, were explored. Contrary to expectation, there was no clear difference in the effect of stability on marine survival rates in the downwelling and upwelling domains. In both domains, marine survival rates increased for pink salmon stocks that experienced below‐average stability on the inner shelf during early marine residence. Stability effects from the outer shelf showed no consistent relationship to marine survival within the northeast Pacific.

Understanding admixture patterns in supplemented populations: a case study combining molecular analyses and temporally explicit simulations in Atlantic salmon

Genetic admixture between wild and introduced populations is a rising concern for the management of endangered species. Here, we use a dual approach based on molecular analyses of samples collected before and after hatchery fish introduction in combination with a simulation study to obtain insight into the mechanisms of admixture in wild populations. Using 17 microsatellites, we genotyped pre- and post-stocking samples from four Atlantic salmon populations supplemented with non-native fish to estimate genetic admixture. We also used individual-based temporally explicit simulations based on realistic demographic and stocking data to predict the extent of admixture. We found a low admixture by hatchery stocks within prestocking samples but moderate to high values in post-stocking samples (from 12% to 60%). The simulation scenarios best fitting the real data suggested a 10–25 times lower survival of stocked fish relative to wild individuals. Simulations also suggested relatively high dispersal rates of stocked and wild fish, which may explain some high levels of admixture in weakly stocked populations and the persistence of indigenous genotypes in heavily stocked populations. This study overall demonstrates that combining genetic analyses with simulations can significantly improve the understanding of admixture mechanisms in wild populations.