Hatchery Stocks Research Articles

Minimization of genetic diversity loss of endangered fish species captive broodstocks by means of minimal kinship selective crossbreeding

The loss of genetic variability in artificially bred seed populations increases the potential risk of reducing the fitness of the hatchery stock as well as that of the wild population when releasing such seed fish to the natural water. With the aid of computer simulation and the minimal kinship ( MK) selective crossbreeding model, we have examined how to minimize the loss of genetic variability in future generations, using real data of barfin flounder broodstock management, a rare fish species on the verge of becoming endangered. Two types of selective breeding scenarios were applied: i) selection of parental pairs based on MK by means of mean P s (proportion of shared alleles) as a similarity measure; and ii) random selection of parental pairs. Gene diversity (expected heterozygosity, H e) and allelic diversity (number of alleles, N a) were used as measures of genetic variability. Results showed that the MK selective breeding scenario resulted advantageous in the retention of both gene and allelic diversities.

Effects of Hatchery Fish Density on Emigration, Growth, Survival, and Predation Risk of Natural Steelhead Parr in an Experimental Stream Channel

AbstractHatchery supplementation of steelhead Oncorhynchus mykiss raises concerns about the impacts on natural populations, including reduced growth and survival, displacement, and increased predation. The potential risks may be density dependent. We examined how hatchery stocking density and the opportunity to emigrate affect the responses of natural steelhead parr in an experimental stream channel and after 15 d found no density‐dependent effects on growth, emigration, or survival at densities ranging from 1–6 hatchery parr/m2. The opportunity for steelhead parr to emigrate reduced predation by coastal cutthroat trout O. clarkii clarkii on both hatchery and natural steelhead parr. The cutthroat trout exhibited a type‐I functional response (constant predation rate with increased prey density) for the hatchery and composite populations. In contrast, the predation rate on natural parr decreased as hatchery stocking density increased. Supplementation with hatchery parr at any experimental stocking density reduced the final natural parr density. This decline was explained by increased emigration from the supplemented groups. Natural parr had higher mean instantaneous growth rates than hatchery parr. The proportion of parr emigrating decreased as parr size increased over successive experimental trials. Smaller parr had lower survival and suffered higher predation. The final density of the composite population, a measure of supplementation effectiveness, increased with the hatchery steelhead stocking rate. Our results indicate that stocking larger hatchery parr (over 50 d postemergence) at densities within the carrying capacity would have low short‐term impact on the growth, survival, and emigration of natural parr while increasing the density of the composite population; in addition, a stocking density greater than 3 fish/m2 might be a good starting point for the evaluation of parr stocking in natural streams.Received June 28, 2010; accepted December 30, 2010

Evaluation of Hypotheses for Describing Temporal Trends in Atlantic Salmon Parr Densities in Northeast U.S. Rivers

AbstractAtlantic salmon Salmo salar in the USA have declined dramatically and their persistence is heavily dependent on stocking juvenile fish, predominantly fry. The success of stocking hatchery fry is evaluated annually throughout New England by electrofishing surveys targeting age‐1 parr. The objective of this study was to examine temporal trends in Atlantic salmon parr densities throughout New England and determine how trends vary among river basins. We fit generalized additive mixed models to investigate potential linear and nonlinear temporal trends in parr density. Akaike's information criterion was used to evaluate competing hypotheses about how temporal trends vary regionally. The top‐ranked model suggested two types of trends. The first type (the Penobscot River) showed a nonlinear trend in which parr densities increased until the 1990s and then rapidly decreased through 2008. The second type (all other rivers) showed a linear decrease throughout the time series. Parr density trends reflected trends in spawning escapement for each river group. We conclude that fry stocking has not been able to overcome the decrease in spawning escapement in altered stream ecosystems in New England and that additional management strategies should be considered.Received July 2, 2010; accepted January 9, 2011

Genetic Differentiation between Natural and Hatchery Stocks of Japanese Scallop (Mizuhopecten yessoensis) as Revealed by AFLP Analysis

Japanese scallop (Mizuhopecten yessoensis) is a cold-tolerant bivalve that was introduced to China for aquaculture in 1982. In this study, amplified fragment length polymorphism (AFLP) markers were used to investigate levels of genetic diversity within M. yessoensis cultured stocks and compare them with wild populations. Six pairs of primer combinations generated 368 loci among 332 individuals, in four cultured and three wild populations. High polymorphism at AFLP markers was found within both cultured and wild M. yessoensis populations. The percentage of polymorphic loci ranged from 61.04% to 72.08%, while the mean heterozygosity ranged from 0.2116 to 0.2596. Compared with wild populations, the four hatchery populations showed significant genetic changes, such as lower expected heterozygosity and percentage of polymorphic loci, and smaller frequency of private alleles, all indicative of a reduction in genetic diversity. Some genetic structures were associated with the geographical distribution of samples; with all samples from Dalian and Japan being closely related, while the population from Russia fell into a distinct clade in the phylogenetic analysis. The genetic information derived from this study indicated that intentional or accidental release of selected Japanese scallops into natural sea areas might result in disturbance of local gene pools and loss of genetic variability. We recommend monitoring the genetic variability of selected hatchery populations to enhance conservation of natural Japanese scallop resources.

Evaluating Surrogacy of Hatchery Releases for the Performance of Wild Yearling Chinook Salmon from the Snake River Basin

AbstractThe combined juvenile and adult detections of Snake River yearling Chinook salmon Oncorhynchus tshawytscha implanted with passive integrated transponder tags migrating through the hydroelectric facilities in the Federal Columbia River Power System were analyzed using the ROSTER statistical release–recapture model. This model was used to estimate the downriver survival of smolts, ocean survival, adult passage success, and smolt‐to‐adult ratios (SARs) for wild and hatchery‐reared Chinook salmon released as yearlings in the Snake River basin from 1996 through 2004. Estimates from wild and hatchery release groups were compared to assess the extent to which hatchery stocks may be used as surrogates for endangered wild stocks. Wild release groups included both spring and summer Chinook salmon runs, while hatchery release groups were separated by run (spring versus summer). Overall, there was a significant difference between estimates from wild release groups and hatchery spring‐run release groups for all survival measures except ocean survival but not between wild release groups and hatchery summer‐run release groups. Estimates of adult passage success and SAR were significantly higher for wild groups than for hatchery spring groups. There was high correlation (r > 0.8) between estimates from wild fish and both spring and summer hatchery fish for all measures except adult passage success within a calendar year. It appears that hatchery summer Chinook salmon stocks from the Snake River basin may be used as surrogates for wild stocks for measuring survival on large temporal and spatial scales (e.g., annual basinwide measures). Because of differences between survival estimates from wild fish and hatchery spring fish, hatchery spring Chinook salmon may be used as an index for trends in the survival of wild stocks but not as direct surrogates.

A protocol for stocking hatchery reared freshwater pearl mussel Margaritifera margaritifera

Abstract Freshwater pearl mussel (Margaritifera margaritifera L.) populations are under serious threat of extinction throughout their geographical range and only a few remnant populations are recruiting to adulthood. Consequently, M. margaritifera is classified as endangered on the International Union for Conservation of Nature Red List. Several institutions across many countries have set up Ark sites at hatcheries to culture and rear young M. margaritifera from population remnants, with the intention of stocking these juveniles into rivers. The release location must fulfill the habitat requirements for the full life‐cycle of the species, so they can contribute to the next generation and thus the long‐term recovery of the species. However, little research or advice exists about how to decide if river environments are suitable for stocking. A protocol is presented for determining whether a M. margaritifera population will benefit from stocking hatchery reared juveniles and how to identify suitable areas. Stocking locations are considered from catchment scale to microscale using water quality (reach), macrohabitat (site) and microhabitat, including physicochemical properties of the substratum (spots). A case study of the River Esk in north‐east England, is incorporated to exemplify the myriad of considerations surrounding attempts to conserve M. margaritifera, and describes how implementation of the protocol can structure and assist stocking programmes. Copyright © 2010 John Wiley & Sons, Ltd.

미토콘드리아 DNA분석에 의한 자연산 및 양식산 넙치 집단의 유전적 다양성 변화

우리나라의 주요 양식 대상 종이며, 년간 총 생산량 1위를 점하고 있는 넙치를 모델로 하여 양식 집단의 유전적 다양성의 변화를 확인하였다. 이를 위해, 한국에서 서식하고 있는 자연산 및 양식산 넙치 각 29개체를 사용하여, hypervariation 영역으로 알려진 tRNA (<TEX>$tRNA^{Thr}$</TEX>, <TEX>$tRNA^{Pro}$</TEX>) 영역과 control region의 앞부분까지의 522 bp에 대한 염기서열의 특성을 분석하였다. 23개의 haplotype에서 522 bp의 염기 중 49곳(9.4%) 에서 변이가 나타났다. 대부분의 haplotype은 자연집단에서 유일하게 나타났으며, 오직 4개의 haplotype만이 양식집단에서 나타났다. 또한, 두 집단 사이에서는 유전적으로 유의한 집단분화가 발생하였다는 사실도 확인할 수 있었다. 따라서 미토콘드리아 DNA 염기서열 분석 기법은 집단의 유전적 다양성을 평가뿐만 아니라 양식집단의 유전적 모니터링에 사용 가능 할 것으로 판단된다. We sequenced a 522 bp fragment including the <TEX>$tRNA^{Thr}$</TEX>, <TEX>$tRNA^{Pro}$</TEX> gene and the first half of the control region from 29 wild and cultured olive flounder specimens from Korea. Out of 522 nucleotide sites, 49 (9.4%) were variable, 23 haplotypes being found. Most haplotypes are unique in the wild population and only four were shared by cultured specimins. The nucleotide diversity and differences between wild and cultured populations were <TEX>$0.025{\pm}0.013$</TEX> and <TEX>$0.015{\pm}0.008$</TEX>, and <TEX>$12.94{\pm}6.00$</TEX> and <TEX>$7.83{\pm}3.75$</TEX>, respectively. Haplotype diversity was <TEX>$0.98{\pm}0.02$</TEX> and <TEX>$0.49{\pm}0.09$</TEX> in the wild and cultured populations, respectively. These results show that marked reductions of genetic variability in the hatchery strains were observed in the number of mitochondrial DNA haplotypes and haplotype diversity when compared to the wild populations. Furthermore, we detected significant population differentiation between both populations. The mtDNA sequencing technique used to evaluate the genetic variability of hatchery strains compared to that of the wild population is potential for genetic monitoring of olive flounder hatchery stocks.

PCR multiplex tool with 10 microsatellites for the European seabass ( Dicentrarchus labrax) — Applications in genetic differentiation of populations and parental assignment

The European seabass ( Dicentrarchus labrax) is a fish of high commercial value both from fisheries and aquaculture, especially in the Mediterranean countries. Population genetic studies with molecular markers have aimed at assessing the structure of wild and hatchery stocks, as well as evaluating genetic interactions between them. The increasing demand for population genetic studies in D. labrax prompts for robust and low cost genetic tagging tools for large-scale population analysis, to assist in genetic management and selection programs. The aim of this study was to develop a multiplex PCR technique adapted to automated DNA detection systems, taking advantage of the existing microsatellites from D. labrax. A 10 loci multiplex ( Dl10plex) with high allelic variability, high PIC value and no evidence of null alleles was obtained. Dl10plex was successfully applied to differentiating one Atlantic and one Mediterranean wild samples, as well as to effectively trace parents in an artificial cross, in which a large variation in parental contribution was detected. These results support its use in a standardized way, thus opening the possibility for a more reliable comparison of data from different sources and accelerating the understanding of D. labrax stock status, both in wild and cultivated populations.

Genetic diversity of wild and domesticated stocks of Thai abalone, Haliotis asinina (Haliotidae), analyzed by single-strand conformational polymorphism of AFLP-derived markers

Amplified fragment length polymorphism (AFLP) analysis was carried out on representative individuals of wild Haliotis asinina using 64 primer combinations. Nine polymorphic AFLPs were cloned and sequenced. Sequence-specific primers were designed from six AFLP-derived fragments. Three sequence-characterized amplified region (SCAR) markers (HaSCAR(320), HaSCAR(295), HaSCAR(327)) were selected for genotyping of 8-month-old domesticated stocks of H. asinina cultured separately at Sichang Marine Science Research and Training Station (N = 95) and at a hatchery in Trang province (N = 40) using single-strand conformational polymorphism analysis. Genotypes of wild abalone originating from Talibong Island (N = 25), Cambodia (N = 22), and the P(0) progeny established from Samet Island founders (N = 20) were also investigated. Significant genetic differentiation (P<0.0001 for the exact test and F(ST) = 0.8759-0.8919, P<0.001) between abalone from the Gulf of Thailand (Cambodia and Samet Island--east) and the Andaman Sea (Talibong Island--west) were observed. This demonstrated the strong biogeographic structure of H. asinina in Thai waters. Non-overlapping composite genotypes for wild abalone from different coastal regions allow us to determine founder contributions in domesticated abalone stocks. Almost all Sichang Marine Science Research and Training Station and the Trang province hatchery stocks exhibited the east coast genotypes (97% of the 135 samples). We suggest that abalone from the east coast population have better survival rates under cultivated conditions than those from the west coast population.

The importance of genetic cluster recognition for the conservation of migratory fish species: the example of the endangered European huchen Hucho hucho (L.)

European huchen Hucho hucho (L.) is an endangered flagship species, which is endemic to the Danube drainage in central Europe. To date, no genetic information has been available as a basis for ongoing conservation and breeding programmes for the species. It is suspected that most populations in the wild share one common gene pool and that they exclusively depend on stocking with hatchery fish. In this study, highly variable microsatellite markers were established and the genetic diversity and differentiation from four important hatchery-reared stocks were compared with that of eight H. hucho populations sampled in the wild. Overall, eight genetic clusters with a moderate to very great degree of genetic differentiation and high assignment rates were identified. Each cluster contained individuals from two to 10 different populations and 9-100% of specimens from hatchery stocks. It is proposed that genetic cluster-based management in the conservation of European huchen is advantageous compared with the consideration of single local populations. A combined approach of maintaining the evolutionary potential of wild populations and genetically variable hatchery stocks can maximize the conservation of the species' evolutionary potential.

Ancestry, population structure, and conservation genetics of Arctic grayling (Thymallus arcticus) in the upper Missouri River, USA

We genotyped Arctic grayling ( Thymallus arcticus ) at 10 microsatellite loci in 18 samples (n = 726) from Montana, Wyoming, and Saskatchewan to determine genetic relationships among native, captive, and naturalized populations in the upper Missouri River basin, to assess patterns in genetic diversity, and to infer recent demographic histories. Substantial genetic subdivision was observed among sample populations (global FST= 0.10). Canadian populations have been isolated from Missouri River populations long enough for mutation to cause genetic differences between regions (mean pairwise FST= 0.18, RST= 0.54). Within the Missouri River basin, most naturalized lacustrine populations traced their ancestry to Red Rock lakes. Two populations in headwater lakes within the Big Hole River watershed appear to be native. We found neither evidence for introgression of Canadian-origin grayling nor any effect of hatchery stocking in native populations. The native fluvial Big Hole River group was genetically distinct and most diverse (HE= 0.89), whereas native Madison River and Red Rock lakes populations exhibited lower genetic diversity (HE= 0.74 and 0.80, respectively) and evidence of recent bottlenecks. The existing Big Hole and Red Rock populations are at low abundance but do not appear to be at immediate risk of inbreeding depression (Ne= 207.7–228.2).

Genetic diversity status of White shrimp Penaeus (Litopenaeus) vannamei broodstock in Mexico

The Mexican shrimp culture industry is based upon Penaeus (Litopenaeus) vannamei broodstock with a presumed common genetic origin and more than 10 generations of closed breeding. This has raised concerns about the low level of genetic diversity and accumulated inbreeding in these broodstock. Inbreeding depression can lead to low performance of hatchery-reared shrimp, and an evaluation of the genetic diversity can significantly enhance broodstock management. In this study, we evaluated the genetic composition and diversity of broodstock from six hatcheries from Northwestern Mexico, and estimated their inbreeding levels based on DNA microsatellite markers. A total of 658 individuals were analyzed with six microsatellite loci. Medium mean genetic diversity values (8.98 alleles per locus) and heterozygosity (0.57) were higher than anticipated. There was significant variation in the genetic composition of broodstock from different hatcheries. All the hatchery broodstock were significantly different from a wild population from the state of Sinaloa. The most common alleles were the same in broodstock from all six hatcheries. None of the hatchery stocks has uniquely distinctive alleles. Broodstock management appears to have maintained genetic diversity, because mean allele numbers were similar to the pooled values from a single hatchery sampled between 2000 and 2002. However, with an observed heterozygosity ( H o) below Hardy–Weinberg expectations and a high mean inbreeding coefficient (26.5%) it would be timely to introduce cross breeding among hatcheries to reduce the risk of inbreeding depression.

Temporal Stability of Genetic Variation within Natural Populations of Summer Steelhead Receiving Mitigation Hatchery Fish

AbstractStochastic fluctuation in allele frequencies may reflect microevolutionary processes responsible for genetic change, such as small effective population size (Ne), which is a legitimate concern for imperiled populations affected by environmental or anthropogenic factors. In salmonids, recent empirical studies have provided conflicting results regarding the consistency of within‐population genetic variation over time. In the present study, we surveyed the genetic variation at 14 microsatellite loci in two endemic populations of summer steelhead Oncorhynchus mykiss (Tucannon and Touchet) for seven consecutive years and the Lyons Ferry Hatchery stock (LFH) for 4 years. The LFH (mitigation) stock is used to enhance fishing opportunities in southeastern Washington State and not to aid in the recovery of natural populations. We observed statistically significant differences in allele frequencies between replicated collections from the same location. One of twenty‐one genic tests for the Tucannon River collections, 9 of 21 genic tests for the Touchet River collections, and all genic tests regarding LFH collections were statistically significant. Temporal variation was larger than spatial variation (0.86% and 0.44%, respectively). We also used genetic data to infer effective population sizes for natural steelhead populations and the LFH mitigation hatchery stock, with point estimates of 729.7, 599.4, and 266.7 for the Tucannon, Touchet, and LFH populations, respectively. Despite the temporal variation observed, relative genetic differentiation was stable over time, replicated collections tending to cluster together in factorial correspondence analyses of allele frequency data. However, the genetic data were consistent with the potential for gene flow between the Tucannon River and LFH populations. The potential benefits of stocking genetically differentiated hatchery fish to enhance fishing opportunities in the Tucannon River may be offset by the negative effects of hatchery introgression and the small Ne in hatchery fish.

Using an unplanned experiment to evaluate the effects of hatcheries and environmental variation on threatened populations of wild salmon

Efforts to conserve depleted populations of Pacific salmon ( Oncorhynchus spp.) often rely on hatchery programs to offset losses of fish from natural and anthropogenic causes, but their use has been contentious. We examined the impact of a large-scale reduction in hatchery stocking on 15 populations of wild coho salmon along the coast of Oregon (USA). Our analyses highlight four critical factors influencing the productivity of these populations: (1) negative density-dependent effects of hatchery-origin spawners were ∼5 times greater than those of wild spawners; (2) the productivity of wild salmon decreased as releases of hatchery juveniles increased; (3) salmon production was positively related to an index of freshwater habitat quality; and (4) ocean conditions strongly affect productivity at large spatial scales, potentially masking more localized drivers. These results suggest that hatchery programs’ unintended negative effects on wild salmon populations, and their role in salmon recovery, should be considered in the context of other ecological drivers.

Steelhead Genetic Diversity at Multiple Spatial Scales in a Managed Basin: Snake River, Idaho

AbstractWe investigated the genetic diversity of steelhead Oncorhynchus mykiss in 74 wild populations and 5 hatchery stocks in Idaho's Snake River basin at the drainage, watershed, and population spatial scales using 11 microsatellite loci. We found significant genetic diversity at multiple spatial scales. Analysis of molecular variance showed that genetic diversity was greater among watersheds within drainages (3.66%) than among drainages (1.97%). Over 94% of the genetic diversity found in the Clearwater, Salmon, and Snake River drainages occurred within individual populations. Estimated effective population sizes ranged from 213 to 486.6 at the drainage scale, from 81.2 to 610.4 at the watershed scale, and from 8.4 to 4,845 at the population scale. The Middle Fork Salmon, South Fork Salmon, Lochsa, and Selway rivers—watersheds managed for wild fish—formed distinct groups in our consensus neighbor‐joining (NJ) trees. At the watershed scale our analyses support differentiation of all hatchery and wild stocks. However, this was not the case for analyses at the population scale, where 236 FST pairwise comparisons out of 3,081 (wild and hatchery) were not significantly different. The distribution of genetic diversity across the landscape does not appear to be organized by the A run or B run management designations for anadromous steelhead. The Dworshak hatchery stock was significantly different from all but one population (O'Hara Creek, Selway River) in pairwise FST comparisons and grouped with other Clearwater River drainage populations in our NJ trees. The Oxbow, Sawtooth, and Pahsimeroi hatchery stocks were indistinguishable from each other based on FST analysis. Currently, this study represents the most comprehensive evaluation of genetic diversity in Idaho's steelhead populations across multiple scales with different management histories.

Tales from scales: old DNA yields insights into contemporary evolutionary processes affecting fishes

Salmon and trout populations are suffering declines in abundance and diversity over much of their range around the Atlantic and Pacific rims as a consequence of many factors. One method of dealing with the decline has been to produce them in hatcheries but the wisdom of this approach has been hotly debated (e.g. Hilborn & Winton 1993; Waples 1999; Brannon et al. 2004). One concern is that domesticated hatchery strains will interbreed with locally adapted wild fish; but how do we study the genetic effects if the introgression might have occurred in the past? Hansen (2002) used DNA isolated from archived scales from brown trout, Salmo trutta (Fig. 1), to show that domesticated trout had, to varying degrees, genetically introgressed with wild, native trout in two Danish rivers. Extending that study, Hansen et al. (2009) have examined DNA from brown trout scales in six Danish rivers collected during historical (1927-1956) and contemporary (2000-2006) periods and from two hatchery source populations, to assess the effects of stocking nonlocal strains of hatchery trout and declining abundance on genetic diversity. Using 21 microsatellite loci, they revealed that genetic change occurred between the historic and contemporary time periods. Many populations appeared to have some low level of introgression from hatchery stocks and two populations apparently experienced high levels of introgression. Hansen et al. (2009) also showed that population structure persists in contemporary populations despite apparent admixture and migration among populations, providing evidence that the locally adapted populations have struggled against and, to some extent, resisted being overwhelmed by repeated introductions of and interbreeding with non-native, hatchery-produced conspecifics.

STUDIES ON CLONAL DIVERSITY OF GIBEL CARP, &lt;I&gt;CARASSIUS AURATUS GIBELIO&lt;/I&gt;, FROM THE IRTYSH RIVER WATER SYSTEM IN XINJIANG PROVINCE

Gibel carp, Carassius auratus gibelio Bloch, as a subspecies of Carassius auratus, has a wide geographic distribution from northern Europe to Asia. As a new culture target, it has been used widely for aquaculture practice in recent 30 years in China, and its production capacity has increased up to 2 billion kilograms annually. Gibel carp possess several interesting characteristics: 1) It is a triploid fish with more than 150 chromosomes, 2) It exists as a bisexual population with predominantly more females (an 80 : 20 female: male ratio) in natural habitats, 3) It has dual reproductive modes of gynogenesis and bisexual reproduction, 4) Various gynogenetic clones have been identified. These features make gibel carp a promising study model for evolutionary genetics, developmental biology and selective breeding. Recently, we have detected clonal diversity of gibel carp in Fangzheng stock hatchery of Heilongjiang Province and Qihe stock hatchery of Henan Province. Up to now, however, little information had been known about the status of gibel carp populations from the Irtysh River water system in Xinjiang Province. In order to obtain a better understanding of the status of clonal diversity of the gibel carp populations, four populations of Carassius auratus were collected from the Irtysh River water system in this study. Flow cytometry was applied to analyze their blood cells, revealing that all of them were triploid gibel carp. Then, a total of eight different clones were clearly discriminated from these gibel carp populations by analysis of serum transferrin phenotypes. Among them, four clones were identical to those identified previously, whereas, the other four were new. Clones A and M were the most wide-ranging, occurring in all of the four populations. Clone J appeared in two populations. Each of the other five clones was specific to single population. These distribution patterns of different clones within populations might reflect clones being able to migrate and differences in viability of a clone among different water bodies. Among these sampled populations of gibel carp, one had the level of clonal diversity obviously lower than those in the other tree, similar to those in populations reported, probably suggesting negative effects of human activities such as hydraulic engineering construction and overharvesting. The clonal diversity revealed in this study will likely benefit evolutionary genetics and selective breeding studies. At the same time, this work also highlights the significance of protecting clonal diversity Of gibel carp in the Irtysh River water system.

Multiple marking of otoliths of brown trout,Salmo truttaL., with alizarin redS to compare efficiency of stocking of three early life stages

Abstract This study examined stocking with three early life stages of brown trout,Salmo truttaL., in the context of rehabilitating a native lineage. Experimental sections in five streams were stocked successively with three stages (I: unfed fry at the end of the reabsorption phase, II: fed fry measuring 2–3 cm and III: fed fry measuring 4–5 cm) derived from a hatchery stock bred from wild spawners. The three stages were distinguished by single or multiple fluoromarking of the otoliths with alizarin redS. The index of relative stocking efficiency was greater for stage II than for stage I in all sections and equivalent or greater than that for stage III. Stage II achieved significantly larger mean length and weight in autumn than stage III stockings.

Reproductive behavior and relative reproductive success of natural- and hatchery-origin Hood Canal summer chum salmon (Oncorhynchus keta)

Estimates of the relative fitness of hatchery- and natural-origin salmon can help determine the value of hatchery stocks in contributing to recovery efforts. This study compared the adult to fry reproductive success of natural-origin summer chum salmon ( Oncorhynchus keta ) with that of first- to third-generation hatchery-origin salmon in an experiment that included four replicate breeding groups. Hatchery- and natural-origin chum salmon exhibited similar reproductive success. Hatchery- and natural-origin males obtained similar access to nesting females, and females of both types exhibited similar breeding behaviors and durations. Male body size was positively correlated with access to nesting females and reproductive success. The estimates of relative reproductive success (hatchery/natural = 0.83) in this study were similar to those in other studies of other anadromous salmonids in which the hatchery population was founded from the local natural population and much higher than those in studies that evaluated the lifetime relative reproductive success of nonlocal hatchery populations.

Predation on emergent lake trout fry in Lake Champlain

The rehabilitation of extirpated lake trout ( Salvelinus namaycush) in the Great Lakes and Lake Champlain has been hindered by various biological and physiological impediments. Efforts to restore a lake trout fishery to Lake Champlain include hatchery stocking and sea lamprey control. Despite these management actions, there is little evidence of recruitment of naturally-produced fish in annual fall assessments. Spawning occurs at multiple sites lake-wide in Lake Champlain, with extremely high egg and fry densities, yet sampling for juvenile lake trout has only yielded fin-clipped fish. To investigate this recruitment bottleneck, we assessed predation pressure by epi-benthic fish on emergent fry on two spawning reefs and the subsequent survival and dispersal of fry in potential nursery areas. Epi-benthic predators were sampled with 2-h gillnet sets at two small, shallow sites in Lake Champlain throughout the 24-h cycle, with an emphasis on dusk and dawn hours. In total, we documented seven different species that had consumed fry, with consumption rates from 1 to 17 fry per stomach. Rock bass and yellow perch dominated the near-shore fish community and were the most common fry predators. Predator presence and consumption of fry was highest between 19:00 and 07:00. Predators only consumed fry when fry relative abundance was above a threshold of 1 fry trap − 1 day − 1 . We used an otter trawl to sample for post-emergent fry adjacent to the reef, but did not capture any age-0 lake trout. Due to the observed predation pressure by multiple littoral, species on shallow spawning reefs, lake trout restoration may be more successful at deep, offshore sites.