Hatchery Stocks Research Articles

Genetic Structure of Columbia River Redband Trout Populations in the Kootenai River Drainage, Montana, Revealed by Microsatellite and Allozyme Loci

We describe the genetic divergence among 10 populations of redband trout Oncorhynchus mykiss gairdneri from the upper Columbia River drainage. Resident redband trout from two watersheds in the Kootenai River drainage and hatchery stocks of migratory Kamloops redband trout from Kootenay Lake, British Columbia, were analyzed using allele frequency data from microsatellite and allozyme loci. The Kamloops populations have significantly different allele frequencies from those of the Kootenai River drainage. Of the total genetic variation detected in the resident redband trout, 40.7% (microsatellites) and 15.5% (allozymes) were due to differences between populations from the two Kootenai River watersheds. The divergence among populations within each watershed, however, was less than 3.5% with both techniques. Our data indicate that watershed-specific broodstocks of redband trout are needed by fisheries managers for reintroduction or the supplementation of populations at risk of extinction.

Maintenance of genetic diversity of Atlantic salmon ( Salmo salar) by captive breeding programmes and the geographic distribution of microsatellite variation

The capability of Finnish Atlantic salmon ( Salmo salar L.) broodstock breeding programmes to maintain genetic diversity was assessed by comparing the levels of microsatellite diversity in wild and hatchery stocks in general, and in wild and hatchery derivatives of the same stock. The effective population sizes ( N e) of the broodstocks and the ratio of effective size to census size ( N e/ N c) as well as the rate of loss of diversity in captive breeding were assessed. Moreover, the distribution and pattern of genetic diversity among Atlantic salmon stocks in the Baltic Sea, Barents Sea and NW Atlantic were measured. Microsatellite data were also compared with allozyme data of the same salmon stocks. Nine microsatellite loci were amplified: Ssa85, Ssa171, Ssa197, Ssa202, Ssa289, SSOSL85, SSOSL 311, SSOSL417 and SSOSL438 from 11 Atlantic salmon stocks. The effective population sizes of broodstocks were estimated with the method based on temporal allele frequency change. In short-term breeding programmes, the average rate of loss of heterozygosity was 1.4% per generation and the average observed rate of loss of alleles was 4.7% per generation. The estimated N e's for the broodstocks were 32 and 238. The average N e/ N c ratio was 0.81. Changes in present-day broodstocks were not alarming and the N e/ N c ratios were higher than in wild populations in general. The genetic D A distance between continents was 0.64 ( F ST( θ)=0.22) and distances about half of that level ( D A distance 0.34, F ST=0.09) were measured between European and Baltic Sea salmon stocks. A nearly diagnostic difference was observed in the SSOSL311 of the North American stocks (Maine 0.982 and Labrador 0.957) for a single allele (SSOSL311 118) that did not occur in European populations at all. Microsatellite data showed relatively more genetic differentiation ( F ST=0.040) on a small geographical scale than did allozyme data ( F ST=0.017), indicating the higher discrimination power of this data set.

Spatial Covariation in Survival Rates of Northeast Pacific Chum Salmon

Abstract Using indices of survival rate (residuals from stock-recruitment relationships) across four decades, we examined the spatial patterns of covariation among 40 wild and 27 hatchery stocks of chum salmon Oncorhynchus keta from 15 geographical regions in Washington, British Columbia, and Alaska. We found strong evidence of positive covariation among spawner-to-recruit survival rates of wild stocks within regions and between certain adjacent regions (e.g., correlations from 0.3 to 0.7) but little evidence of covariation between stocks of distant regions (e.g., separated by 1,000 km or more). Similarly, for hatchery stocks from Washington, British Columbia, and southeast Alaska, positive covariation in the indices of fry-to-recruit survival rate occurred only within regions and between certain adjacent regions. These patterns suggest that important environmental processes affecting interannual variation in spawner-to-recruit survival rates of chum salmon operate at local or regional spatial scales rath...

Survivorship and growth rates of hatchery-reared sea urchins

The survivorship and growth rates of juvenile, hatchery rearedPsammechinus miliaris (Gmelin) were observed for seaurchins fed different diets, and maintained at varying stocking densities andlocations (tank or sea-based). In addition survivorship and growth of secondgeneration hatchery stock was also recorded. Somatic growth rates of juvenileurchins (initial test diameter 6.5 mm SD 1.26) were measured over9months. A high lipid, high protein diet supported higher somatic growth ofurchins in this size range. Higher stocking densities (4 individualsl−1 as opposed to 2 individuals l−1)adversely affected growth as did location (sea-based urchins being smaller thantank based) although survivorship in all treatments and in both first andsecondgenerations was exceptionally high. Further research is required to designdietspromoting somatic rather than gonadal growth in urchins below market size.

Identification of the origin of an Atlantic salmon (Salmo salar L.) population in a recently recolonized river in the Baltic Sea.

The founder event in a recently recolonized salmon population in the Baltic Sea (Gulf of Finland) was investigated. To identify the origin of the founders, four wild populations and two hatchery stocks were analysed using six microsatellite loci. The results of assignment tests and factorial correspondence analysis suggest that the initial recolonizers of the river Selja originated from the geographically nearest (7 km) wild population (river Kunda) but as the result of stocking activities, interbreeding between recolonizers and hatchery individuals has occurred in subsequent years. Although the hatchery releases are outnumbering the wild salmon recruitment in the Baltic Sea at present, our results suggest that the native populations may still have an important role in colonization processes of the former salmon rivers.

Growth and Long-Range Dispersal by Wild Subyearling Spring and Summer Chinook Salmon in the Snake River Basin

Abstract Wild juvenile spring and summer chinook salmon Oncorhynchus tshawytscha typically pass downstream in the Snake River as yearling smolts when migrating seaward. A small number of these fish disperse downstream from natal streams into the Snake River as subyearlings and then continue moving seaward. We estimated that the naturally produced subyearling spring and summer chinook salmon that dispersed into the Snake River in 1993, 1994, and 1997 originated from both wild (67%) and naturalized hatchery (33%) stocks. These fish were large in terms of mean fork length (range, 78–87 mm) during shoreline rearing. While moving seaward, they grew rapidly (range of means, 1.0–1.3 mm/d) to yearling smolt fork lengths (range of means, 122–128 mm). The estimated dispersal distances from natal streams to the first two dams encountered during seaward movement ranged from 172 to 810 km. Although we could not demonstrate seawater entry, we believe that the wild spring and summer chinook salmon had met the growth and...

Dinucleotide microsatellites isolated from the European flat oyster, Ostrea edulis

AbstractApproximately 5000 clones from a partial genomic library of Ostrea edulis DNA were screened with (CA)15 and (GA)15 probes. Fifty‐six positive clones were sequenced, with 24 containing a microsatellite sequence. Primers were designed for 14 loci, and the five most reliably amplifying were developed further. Four of these showed high levels of variability and only one locus (HA21) showed a significant deviation from Hardy–Weinberg expectations, with an excess of homozygotes. These microsatellite DNA markers will be powerful tools for the study of wild and hatchery stocks of this commercially important species.

The Northwest U.S. Dam Breaching Decision: Factors, Costs and Benefits

Northwestern United States' salmon populations have fallen precipitously. Attempts at salmon restoration are going on and dam breaching is being considered. Costs associated with the continued restoration attempts including hatchery stocking, barging and trucking salmon around the dams are high while benefits are unclear. Those costs may be greater than dam breaching. An additional impetus for dam removal is the revival of the commercial salmon fishing industry. This may not occur for both ecological and economic reasons. Ecologically complete restoration may not be feasible. Economically, the rise of competitively priced salmon aquaculture will reduce the value of any future commercial catch. A statistical relationship between falling prices for wild salmon and rising salmon aquaculture output is shown.

Single rays as indicators of fin vestigialization in coho salmon: patterns and perspectives

Although finrays in salmon normally contain a pair of elements (biramous), finrays with a single element (uniramous) occasionally develop. Exposure to chronic stress during character development has been shown to increase fluctuating asymmetry, suggesting the occurrence of single finrays may be stress-induced. On the other hand, single finrays may be evolutionary atavisms, reflecting fin vestigialization caused by reduced selection pressure. To assess the merits of these hypotheses, cleared and stained paired and median fins were examined for single finrays in juvenile coho salmon (Oncorhynchus kisutch Walbaum) from two compatible hatchery stocks and their reciprocal hybrids which had been exposed to different patterns of chronic temperature fluctuation throughout embryogenesis. In the median fins, uniramous secondary finrays predominated, and single primary finrays were infrequent. Single finrays in the median fins did not respond to thermal treatment or cross, suggesting the fins were evolutionarily stable and under strong developmental control. The paired fins were observed to contain only primary finrays. Frequencies of single pelvic finrays increased under thermal stress, as did fluctuating asymmetry, suggesting increased sensitivity to stress due to reduced developmental control in this fin. However, the presence or absence of single finrays in the paired fins did not alter the statistical significance of the conclusions regarding levels of fluctuating asymmetry, the number of asymmetric fish, or the contribution to meristic variation from asymmetry. Locations of single finrays in the paired fins were unaffected by thermal treatment or cross. Single finrays were most commonly observed in the trailing margins of both paired fins, a finding consistent with vestigialization theory. Frequency histograms of single pectoral finray locations revealed a second peak in the leading quarter of the fin. The esults support the hypothesis that single primary finrays are evolutionary atavisms, and that reduced selection pressure is differentially influencing the paired fins.

Single rays as indicators of fin vestigialization in coho salmon: patterns and perspectives

Although finrays in salmon normally contain a pair of elements (biramous), finrays with a single element (uniramous) occasionally develop. Exposure to chronic stress during character development has been shown to increase fluctuating asymmetry, suggesting the occurrence of single finrays may be stress-induced. On the other hand, single finrays may be evolutionary atavisms, reflecting fin vestigialization caused by reduced selection pressure. To assess the merits of these hypotheses, cleared and stained paired and median fins were examined for single finrays in juvenile coho salmon (Oncorhynchus kisutch Walbaum) from two compatible hatchery stocks and their reciprocal hybrids which had been exposed to different patterns of chronic temperature fluctuation throughout embryogenesis. In the median fins, uniramous secondary finrays predominated, and single primary finrays were infrequent. Single finrays in the median fins did not respond to thermal treatment or cross, suggesting the fins were evolutionarily stable and under strong developmental control. The paired fins were observed to contain only primary finrays. Frequencies of single pelvic finrays increased under thermal stress, as did fluctuating asymmetry, suggesting increased sensitivity to stress due to reduced developmental control in this fin. However, the presence or absence of single finrays in the paired fins did not alter the statistical significance of the conclusions regarding levels of fluctuating asymmetry, the number of asymmetric fish, or the contribution to meristic variation from asymmetry. Locations of single finrays in the paired fins were unaffected by thermal treatment or cross. Single finrays were most commonly observed in the trailing margins of both paired fins, a finding consistent with vestigialization theory. Frequency histograms of single pectoral finray locations revealed a second peak in the leading quarter of the fin. The esults support the hypothesis that single primary finrays are evolutionary atavisms, and that reduced selection pressure is differentially influencing the paired fins.

Restoration of sturgeons: lessons from the Caspian Sea Sturgeon Ranching Programme

Depletion of sturgeon stocks world‐wide has increased interest in aquaculture‐based restoration programmes. The Caspian Sea Sturgeon Ranching Programme (SRP) of the former Soviet Union represents a unique opportunity to evaluate expense, benefits and potential ecological and genetic effects of such restoration programmes. The SRP was initiated in the 1950s to compensate for lost spawning habitat in the Volga River and elsewhere. After its completion in 1962, the Volgograd Dam reduced spawning grounds in the Volga River system, the principal spawning tributary of the Caspian Sea, by ∼80%. For two of the three commercial sturgeon species (Russian sturgeon, Acipenser güldenstädti, and stellate sturgeon, A. stellatus), yields improved after the imposition of the 1962 moratorium on sturgeon harvests in the Caspian Sea. Volga River fisheries were managed for spawning escapement. Although imprecisely known, the contribution of the millions of stocked Russian and stellate juveniles during 1962–91 was most likely important to sustaining fisheries, although less so (contributing to <30% of the adult stock) than natural recruitment. Apparently, reduced spawning grounds, supplemented with artificial spawning reefs were sufficient to support reproduction and large fishery yields of Russian and stellate sturgeons. For beluga sturgeon, Huso huso, harvests in the Volga River were nearly all dependent upon hatchery stocking. Beluga sturgeon spawning grounds were mostly eliminated with the construction of the Volgograd Dam. Without the hatchery programme, beluga sturgeon in the Volga River and Caspian Sea would in all likelihood have been extirpated. Currently, sturgeons are severely depleted in the Volga River and Caspian Sea due to poaching and lack of co‐operation between countries exploiting the species. Aquaculture‐based restoration in Russia is now viewed a chief means of rebuilding stocks of Caspian Sea sturgeons.

Analysis of microsatellite DNA resolves genetic structure and diversity of chinook salmon (Oncorhynchus tshawytscha) in California’s Central Valley

We use 10 microsatellite DNA markers to assess genetic diversity within and among the four runs (winter, spring, fall, and late fall) of chinook salmon (Oncorhynchus tshawytscha) in California's Central Valley. Forty-one population samples are studied, comprising naturally spawning and hatchery stocks collected from 1991 through 1997. Maximum likelihood methods are used to correct for kinship in juvenile samples and run admixture in adult samples. Through simulation, we determine the relationship between sample size and number of alleles observed at polymorphic microsatellite markers. Most samples have random-mating equilibrium proportions of single and multilocus genotypes. Temporal and spatial genetic heterogeneity is minimal among samples within subpopulations. An FSTof 0.082 among subpopulations, however, indicates substantial divergence among runs. Thus, with the exception of our discovery of two distinct lineages of spring run, genetic structure accords with the diverse chinook life histories seen in the Central Valley and provides a means for discrimination of protected populations.

Microsatellite and mitochondrial DNA polymorphism reveals life‐history dependent interbreeding between hatchery and wild brown trout (Salmo truttaL.)

The effects of stocking hatchery trout into wild populations were studied in a Danish river, using microsatellite and mitochondrial DNA (mtDNA) markers. Baseline samples were taken from hatchery trout and wild trout assumed to be unaffected by previous stocking. Also, samples were taken from resident and sea trout from a stocked section of the river. Genetic differentiation between the hatchery strain and the local wild population was modest (microsatellite FST = 0.06). Using assignment tests, more than 90% of individuals from the baseline samples were classified correctly. Assignment tests involving samples from the stocked river section suggested that the contribution by hatchery trout was low among sea trout (< 7%), but high (46%) among resident trout. Hybrid index analysis and a high percentage of mtDNA haplotypes specific to indigenous trout observed among resident trout that were assigned to the hatchery strain suggested that interbreeding took place between hatchery and wild trout. The latter result also indicated that male hatchery trout contributed more to interbreeding than females. We suggest that stronger selection acts against stocked hatchery trout that become anadromous compared to hatchery trout that become resident. As most resident trout are males this could also explain why gene flow from hatchery to wild trout appeared to be male biased. The results show that even despite modest differentiation at neutral loci domesticated trout may still perform worse than local populations and it is important to be aware of differential survival and reproductive success both between life-history types and between sexes.

Loss of genetic variability at the transferrin locus in five hatchery stocks of tambaqui (Colossoma macropomum)

Knowledge and conservation of the genetic variability in stocks maintained as live gene banks have become a high priority task for Brazilian fish culture. The aim of the present survey was to assess the transferrin allelic diversity of five hatchery stocks of tambaqui (Colossoma macropomum). The tambaqui stock from Pentecoste, the oldest maintained in Brazilian hatchery stations, retained three of the six alleles detected in wild populations of tambaqui from the Amazon River. Other hatchery stocks, directly or indirectly derived from the Pentecoste stock, did not show transferrin allelic variability. Insufficient number of founders and genetic drift due to sampling errors seem to be the main causes leading to loss of genetic diversity in tambaqui hatchery stocks. Appropriate management strategies are required in order to improve the genetic potential of tambaqui stocks in Brazil.

Phenotypic Correlation of Juvenile Growth Rate between Different Consecutive foraging Environments in a Salmonid fish: A Field Experiment

Many organisms occupy considerably different environments during individual's lifespan. We are interested in how the phenotypic characteristics that are favourable in the earlier environment predict fitness in the later environment. High predictability of fitness between the two consecutive environments suggests that the either the same traits are favored in both environments, or that the favourable traits are genetically correlated. In this study, we ask how similarity of consecutive foraging environments affects the phenotypic correlation of juvenile brown trout growth rate. More specifically, we used a genetically narrow stock of hatchery-bred fish to contrast individual growth rates between high and low density hatchery environments, and thereafter between hatchery and natural lake environment. As expected, growth rate was highly dependent on the environment, and the fish showed considerable phenotypic plasticity. Furthermore, we found a strong positive correlation in growth rate between similar foraging environments, for example, between high and low density hatchery stocks, and between hatchery and a lake with small fish as main prey. However, hatchery growth did not predict growth rate in lakes where fish had to forage on bottom-dwelling invertebrates. Our results suggest that when the consecutive environments differed dramatically with respect to traits that fish use for foraging, relative performance of individual fish changed, earlier performance not being an accurate predictor of performance in the new environment. In this case, fitness of the fish was determined by an environment-specific set of traits that were not the same between the two consecutive environments. The result indicates that assessment of individual performance may be highly environment specific in trout.

Managing translocations of aquatic species

The translocation of aquatic organisms is an issue of increasing concern. In assessing the genetic risks from translocations, a primary distinction should be made between translocation for the purpose of aquaculture and translocation for the purpose of stock enhancement. When translocation is for aquaculture, the question of interest is: what is the maximum level of escapes that should be permitted, beyond which there is an unacceptable probability of adverse genetic effects upon the natural population? Risk minimization should concentrate on management solutions that reduce escapes from aquaculture facilities. When translocation is for stock enhancement, the question of interest is what is the maximum level of genetic differences between hatchery and wild stock that should be permitted, beyond which there is an unacceptable probability of adverse genetic effects upon the natural population? Risk minimization should concentrate on hatchery management procedures that reduce genetic differences in fitness traits between hatchery stock and wild stock from the proposed recipient population. Where translocation poses a significant risk of adverse genetic changes, then a monitoring programme should be put in place, linked to a policy that prescribes management actions for the range of possible outcomes from the monitoring. The main limitation to our ability to develop an effective risk assessment and monitoring process is our lack of understanding of how the interaction between genetically different stocks affects the genetic basis of quantitative fitness traits that adapt organisms to their local environment.

A highly polymorphic plasma protein locus in brown trout (Salmo trutta L.) populations from Portugal.

Genetic polymorphism of an unidentified plasma protein (PX) is described for the first time in Salmo trutta (L.) by means of isoelectric focusing. The analysis of 414 individuals from different geographic origins in Portugal allowed the identification of nine alleles. Heterozygosity in natural populations is generally above 0.60, thus giving similar values to those reported for brown trout microsatellite loci. Substructuring of Portuguese brown trout is evident between northern and southern basins. Genetic affinities between the southernmost rivers and the hatchery stock were detected, suggesting the existence of recent stocking influences.

Effects of Fall-to-Winter Changes in Habitat and Frazil Ice on the Movements and Habitat Use of Juvenile Rainbow Trout in a Wyoming Tailwater

Abstract Overwinter declines in the abundance of small rainbow trout Oncorhynchus mykiss have been observed in a section of the Big Horn River that lies downstream from Boysen Reservoir, where reservoir releases prevent surface ice formation. To provide insight into the possible causes of these declines in abundance, radiotelemetry was used to determine movement and microhabitat use of juvenile (20–25 cm total length) rainbow trout during the fall and winter of 1995–1996. Throughout the fall and winter, both stocked (hatchery) and naturally spawned (wild) fish were generally found in main-channel pools with cover that reduced current velocities to less than 2 cm/s near the bottom and with nearby (<2 m) water velocities that were greater than 15 cm/s. These locations provided refuges from the current, with adjacent flowing water that could deliver drifting aquatic invertebrates. The fish were generally associated with cover that was formed by aquatic vegetation early in the fall, but they shifted to cobble...

Genetic improvement of the Pacific oysterCrassostrea gigas(Thunberg) in Australia

The Pacific oyster industry in Australia is derived from importations from Japan in the late 1940s and early 1950s to Tasmania and is almost completely hatchery based. This makes it a good target for developing and deploying genetically improved strains. An allozyme survey comparing hatchery stocks with self-recruiting Tasmanian stocks and with two collections from Japan found abundant variation and no significant evidence of allele loss. The subsequent selection programme (initiated in the summer of 1996/97) had several strands. We wanted to take advantage of the increased power that marker-assisted selection could bring and, therefore, needed to develop a linkage map and isolate flanking markers around quantitative trait loci (QTLs). Several types of markers (allozymes, microsatellites and AFLPs) were used, and single-pair crosses were set up; QTLs have been detected. Conventional selection programmes, one based on mass selection and one on family selection, have been established. Triploid Pacific oysters produced via chemical means have been available for several years, but rates of triploidy achieved by such means are usually less than 100%. In 1999, we will assess whether our tetraploid 2-year-old broodstock can be crossed with diploids to give 100% triploid offspring.

Analysis of microsatellite DNA resolves genetic structure and diversity of chinook salmon (&lt;i&gt;Oncorhynchus tshawytscha&lt;/i&gt;) in California's Central Valley

We use 10 microsatellite DNA markers to assess genetic diversity within and among the four runs (winter, spring, fall, and late fall) of chinook salmon (Oncorhynchus tshawytscha) in California's Central Valley. Forty-one population samples are studied, comprising naturally spawning and hatchery stocks collected from 1991 through 1997. Maximum likelihood methods are used to correct for kinship in juvenile samples and run admixture in adult samples. Through simulation, we determine the relationship between sample size and number of alleles observed at polymorphic microsatellite markers. Most samples have random-mating equilibrium proportions of single and multilocus genotypes. Temporal and spatial genetic heterogeneity is minimal among samples within subpopulations. An FST of 0.082 among subpopulations, however, indicates substantial divergence among runs. Thus, with the exception of our discovery of two distinct lineages of spring run, genetic structure accords with the diverse chinook life histories seen ...