Population dynamics of pink salmon <Emphasis Type="Italic">Oncorhynchus gorbuscha</Emphasis> (Salmonidae) from the southeastern coast of Sakhalin island

The results of monitoring from 1971 to 2004 of pink salmon Oncorhynchus gorbuscha spawning in the rivers of the southeastern coast of Sakhalin are presented. It is shown that fluctuations in the value of its return more largely depend on the level of mortality of fish of the respective generations in the marine period of life than on the yield of downstream migrating juveniles, that, in turn, is weakly related to the numbers of parents, which is explained by the spawning conditions in small rivers at a dense aggregation of spawners on the spawning grounds. Stable long-term tendencies in the variation of numbers, biological indices of fish, and the dates of their return for spawning are established. It is suggested that they indicate a decisive role of globalcyclic, climatic-oceanological processes in the population dynamics of pink salmon     

Lack of parallel genetic patterns underlying the repeated ecological divergence of beach and stream‐spawning kokanee salmon

Recent progress in methods for detecting adaptive population divergence in situ shows promise for elucidating the conditions under which selection acts to generate intraspecific diversity. Rapid ecological diversification is common in fishes; however, the role of phenotypic plasticity and adaptation to local environments is poorly understood. It is now possible to investigate genetic patterns to make inferences regarding phenotypic traits under selection and possible mechanisms underlying ecotype divergence, particularly where similar novel phenotypes have arisen in multiple independent populations. Here, we employed a bottom‐up approach to test for signatures of directional selection associated with divergence of beach‐ and stream‐spawning kokanee, the obligate freshwater form of sockeye salmon (Oncorhynchus nerka). Beach‐ and stream‐spawners co‐exist in many post‐glacial lakes and exhibit distinct reproductive behaviours, life‐history traits and spawning habitat preferences. Replicate ecotype pairs across five lakes in British Columbia, Canada were genotyped at 57 expressed sequence tag‐linked and anonymous microsatellite loci identified in a previous genome scan. Fifteen loci exhibited signatures of directional selection (high F_ST outliers), four of which were identified in multiple lakes. However, the lack of parallel genetic patterns across all lakes may be a result of: 1) an inability to detect loci truly under selection; 2) alternative genetic pathways underlying ecotype divergence in this system; and/or 3) phenotypic plasticity playing a formative role in driving kokanee spawning habitat differences. Gene annotations for detected outliers suggest pathogen resistance and energy metabolism as potential mechanisms contributing to the divergence of beach‐ and stream‐spawning kokanee, but further study is required.     

Previously spawned Atlantic salmon ascend a large subarctic river earlier than their maiden counterparts

Spawning migration timing of maiden Atlantic salmon Salmo salar and previous spawners was analysed in the catches in 1989–2004 in the large subarctic River Teno in the northernmost parts of Finland and Norway. The hypothesis was that the migration timing of previous spawners and their maiden counterparts is similar, with the migration timing similar between sexes. In most cases, however, previous spawners were observed to migrate into the River Teno and its tributaries earlier than their maiden counterparts. The difference in run timing was especially evident between maiden one-sea-winter (1SW) Atlantic salmon and the corresponding group of previous spawners [1S1, 1 year at sea (1) followed by first spawning (S) and reconditioning period of 1 year (1) at sea and second spawning run] for both sexes in the River Teno and in its two tributaries. The same was also evident between 2SW maiden and 2S1 previous spawning female Atlantic salmon in the River Teno. Females showed earlier spawning migration than males both in previous spawners and maiden Atlantic salmon. Different maiden sea-age classes also showed differences in run timing as multi-sea-winter fish (2–4SW) ascended earlier than 1SW fish but the timing of 1S1 and 2S1 previous spawning females coincided. The results suggest that run timing of Atlantic salmon may not be strictly genetically fixed as previous spawners ascend earlier than they did on their first spawning migration as maiden fish, and indicated that the closeness of the reconditioning area of postspawners to the river of origin resulted in an early ascent. Run timing of different sea-age groups has major management implications if the populations are heavily exploited with numerous fishing methods in different periods of the fishing season, as in the River Teno system.     

Co‐inheritance of sea age at maturity and iteroparity in the Atlantic salmon vgll3 genomic region

Co‐inheritance in life‐history traits may result in unpredictable evolutionary trajectories if not accounted for in life‐history models. Iteroparity (the reproductive strategy of reproducing more than once) in Atlantic salmon (Salmo salar) is a fitness trait with substantial variation within and among populations. In the Teno River in northern Europe, iteroparous individuals constitute an important component of many populations and have experienced a sharp increase in abundance in the last 20 years, partly overlapping with a general decrease in age structure. The physiological basis of iteroparity bears similarities to that of age at first maturity, another life‐history trait with substantial fitness effects in salmon. Sea age at maturity in Atlantic salmon is controlled by a major locus around the vgll3 gene, and we used this opportunity demonstrate that these two traits are co‐inherited around this genome region. The odds ratio of survival until second reproduction was up to 2.4 (1.8–3.5 90% CI) times higher for fish with the early‐maturing vgll3 genotype (EE) compared to fish with the late‐maturing genotype (LL). The L allele was dominant in individuals remaining only one year at sea before maturation, but the dominance was reversed, with the E allele being dominant in individuals maturing after two or more years at sea. Post hoc analysis indicated that iteroparous fish with the EE genotype had accelerated growth prior to first reproduction compared to first‐time spawners, across all age groups, whereas this effect was not detected in fish with the LL genotype. These results broaden the functional link around the vgll3 genome region and help us understand constraints in the evolution of life‐history variation in salmon. Our results further highlight the need to account for genetic correlations between fitness traits when predicting demographic changes in changing environments.     

Stream network geomorphology mediates predicted vulnerability of anadromous fish habitat to hydrologic change in southeast Alaska

In rivers supporting Pacific salmon in southeast Alaska, USA, regional trends toward a warmer, wetter climate are predicted to increase mid‐ and late‐21st‐century mean annual flood size by 17% and 28%, respectively. Increased flood size could alter stream habitats used by Pacific salmon for reproduction, with negative consequences for the substantial economic, cultural, and ecosystem services these fish provide. We combined field measurements and model simulations to estimate the potential influence of future flood disturbance on geomorphic processes controlling the quality and extent of coho, chum, and pink salmon spawning habitat in over 800 southeast Alaska watersheds. Spawning habitat responses varied widely across watersheds and among salmon species. Little variation among watersheds in potential spawning habitat change was explained by predicted increases in mean annual flood size. Watershed response diversity was mediated primarily by topographic controls on stream channel confinement, reach‐scale geomorphic associations with spawning habitat preferences, and complexity in the pace and mode of geomorphic channel responses to altered flood size. Potential spawning habitat loss was highest for coho salmon, which spawn over a wide range of geomorphic settings, including steeper, confined stream reaches that are more susceptible to streambed scour during high flows. We estimated that 9–10% and 13–16% of the spawning habitat for coho salmon could be lost by the 2040s and 2080s, respectively, with losses occurring primarily in confined, higher‐gradient streams that provide only moderate‐quality habitat. Estimated effects were lower for pink and chum salmon, which primarily spawn in unconfined floodplain streams. Our results illustrate the importance of accounting for valley and reach‐scale geomorphic features in watershed assessments of climate vulnerability, especially in topographically complex regions. Failure to consider the geomorphic context of stream networks will hamper efforts to understand and mitigate the vulnerability of anadromous fish habitat to climate‐induced hydrologic change.     

Effects of habitat features on size-biased predation on salmon by bears

Predators can drive trait divergence among populations of prey by imposing differential selection on prey traits. Habitat characteristics can mediate predator selectivity by providing refuge for prey. We quantified the effects of stream characteristics on biases in the sizes of spawning salmon caught by bears (Ursus arctos and U. americanus) on the central coast of British Columbia, Canada by measuring size-biased predation on spawning chum (Oncorhynchus keta) and pink (O. gorbuscha) salmon in 12 streams with varying habitat characteristics. We tested the hypotheses that bears would catch larger than average salmon (size-biased predation) and that this bias toward larger fish would be higher in streams that provide less protection to spawning salmon from predation (e.g., less pools, wood, undercut banks). We then we tested for how such size biases in turn translate into differences among populations in the sizes of the fish. Bears caught larger-than-average salmon as the spawning season progressed and as predicted, this was most pronounced in streams with fewer refugia for the fish (i.e., wood and undercut banks). Salmon were marginally smaller in streams with more pronounced size-biased predation but this predictor was less reliable than physical characteristics of streams, with larger fish in wider, deeper streams. These results support the hypothesis that selective forces imposed by predators can be mediated by habitat characteristics, with potential consequences for physical traits of prey.     

Effects of Emergence Time and Early Social Rearing Environment on Behaviour of Atlantic Salmon: Consequences for Juvenile Fitness and Smolt Migration

Consistent individual differences in behaviour have been well documented in a variety of animal taxa, but surprisingly little is known about the fitness and life-history consequences of such individual variation. In wild salmonids, the timing of fry emergence from gravel spawning nests has been suggested to be coupled with individual behavioural traits. Here, we further investigate the link between timing of spawning nest emergence and behaviour of Atlantic salmon (Salmo salar), test effects of social rearing environment on behavioural traits in fish with different emergence times, and assess whether behavioural traits measured in the laboratory predict growth, survival, and migration status in the wild. Atlantic salmon fry were sorted with respect to emergence time from artificial spawning nest into three groups: early, intermediate, and late. These emergence groups were hatchery-reared separately or in co-culture for four months to test effects of social rearing environment on behavioural traits. Twenty fish from each of the six treatment groups were then subjected to three individual-based behavioural tests: basal locomotor activity, boldness, and escape response. Following behavioural characterization, the fish were released into a near-natural experimental stream. Results showed differences in escape behaviour between emergence groups in a net restraining test, but the social rearing environment did not affect individual behavioural expression. Emergence time and social environment had no significant effects on survival, growth, and migration status in the stream, although migration propensity was 1.4 to 1.9 times higher for early emerging individuals that were reared separately. In addition, despite individuals showing considerable variation in behaviour across treatment groups, this was not translated into differences in growth, survival, and migration status. Hence, our study adds to the view that fitness (i.e., growth and survival) and life-history predictions from laboratory measures of behaviour should be made with caution and ideally tested in nature.     

Independent lineages in a common environment: the roles of determinism and contingency in shaping the migration timing of even‐ versus odd‐year pink salmon over broad spatial and temporal scales

Studies of parallel evolution are seldom able to disentangle the influence of cryptic environmental variation from that of evolutionary history; whereas the unique life history of pink salmon (Oncorhynchus gorbuscha) presents an opportunity to do so. All pink salmon mature at age two and die after breeding. Hence, pink salmon bred in even years are completely reproductively isolated from those bred in odd years, even if the two lineages bred in same location. We used time series (mean = 7 years, maximum = 74 years) of paired even‐ and odd‐year populations from 36 rivers spanning over 2000 km to explore parallelism in migration timing, a trait with a strong genetic basis. Migration timing was highly parallel, being determined almost entirely by local environmental differences among rivers. Interestingly, interannual changes in migration timing different somewhat between lineages. Overall, our findings indicate very strong determinism, with only a minor contribution of contingency.     

Phenotypic and transgenerational plasticity promote local adaptation to sun and shade environments

Adaptive plasticity is expected to be important when the grain of environmental variation is encompassed in offspring dispersal distance. We investigated patterns of local adaptation, selection and plasticity in an association of plant morphology with fine-scale habitat shifts from oak canopy understory to adjacent grassland habitat in Claytonia perfoliata. Populations from beneath the canopy of oak trees were >90 % broad leaved and large seeded, while plants from adjacent grassland habitat were >90 % linear-leaved and small seeded. In a 2-year study, we used reciprocal transplants and phenotypic selection analysis to investigate local adaptation, selection, plasticity and maternal effects in this trait-environment association. Transgenerational effects were studied by planting offspring of inbred maternal families grown in both environments across the same environments in the second year. Reciprocal transplants revealed local adaptation to habitat type: broad-leaved forms had higher fitness in oak understory and linear-leaved plants had higher fitness in open grassland habitat. Phenotypic selection analyses indicated selection for narrower leaves and lower SLA in open habitat, and selection for broad leaves and intermediate values of SLA in understory. Both plant morphs exhibited plastic responses in traits in the same direction as selection on traits (narrower leaves and lower SLA in open habitat) suggesting that plasticity is adaptive. We detected an adaptive transgenerational effect in which maternal environment influenced offspring fitness; offspring of grassland-reared plants had higher fitness than understory-reared plants when grown in grassland. We did not detect costs of plasticity, but did find a positive association between leaf shape plasticity and fitness in linear-leaved plants in grassland habitat. Together, these findings indicate that fixed differences in trait values corresponding to selection across habitat contribute to local adaptation, but that plasticity and maternal environmental effects may be favored through promotion of survival across heterogeneous environments.     

Temporal patterns in adult salmon migration timing across southeast Alaska

Pacific salmon migration timing can drive population productivity, ecosystem dynamics, and human harvest. Nevertheless, little is known about long‐term variation in salmon migration timing for multiple species across broad regions. We used long‐term data for five Pacific salmon species throughout rapidly warming southeast Alaska to describe long‐term changes in salmon migration timing, interannual phenological synchrony, relationships between climatic variation and migratory timing, and to test whether long‐term changes in migration timing are related to glaciation in headwater streams. Temporal changes in the median date of salmon migration timing varied widely across species. Most sockeye populations are migrating later over time (11 of 14), but pink, chum, and especially coho populations are migrating earlier than they did historically (16 of 19 combined). Temporal trends in duration and interannual variation in migration timing were highly variable across species and populations. The greatest temporal shifts in the median date of migration timing were correlated with decreases in the duration of migration timing, suggestive of a loss of phenotypic variation due to natural selection. Pairwise interannual correlations in migration timing varied widely but were generally positive, providing evidence for weak region‐wide phenological synchrony. This synchrony is likely a function of climatic variation, as interannual variation in migration timing was related to climatic phenomenon operating at large‐ (Pacific decadal oscillation), moderate‐ (sea surface temperature), and local‐scales (precipitation). Surprisingly, the presence or the absence of glaciers within a watershed was unrelated to long‐term shifts in phenology. Overall, there was extensive heterogeneity in long‐term patterns of migration timing throughout this climatically and geographically complex region, highlighting that future climatic change will likely have widely divergent impacts on salmon migration timing. Although salmon phenological diversity will complicate future predictions of migration timing, this variation likely acts as a major contributor to population and ecosystem resiliency in southeast Alaska.     

Phylogenetic effects on functional traits and life history strategies of Australian freshwater fish

Understanding the biogeographic and phylogenetic basis to interspecific differences in species’ functional traits is a central goal of evolutionary biology and community ecology. We quantify the extent of phylogenetic influence on functional traits and life‐history strategies of Australian freshwater fish to highlight intercontinental differences as a result of Australia's unique biogeographic and evolutionary history. We assembled data on life history, morphological and ecological traits from published sources for 194 Australian freshwater species. Interspecific variation among species could be described by a specialist–generalist gradient of variation in life‐history strategies associated with spawning frequency, fecundity and spawning migration. In general, Australian fish showed an affinity for life‐history strategies that maximise fitness in hydrologically unpredictable environments. We also observed differences in trait lability between and within life history, morphological and ecological traits where in general morphological and ecological traits were more labile. Our results showed that life‐history strategies are relatively evolutionarily labile and species have potentially evolved or colonised in freshwaters frequently and independently allowing them to maximise population performance in a range of environments. In addition, reproductive guild membership showed strong phylogenetic constraint indicating that evolutionary history is an important component influencing the range and distribution of reproductive strategies in extant species assemblages. For Australian freshwater fish, biogeographic and phylogenetic history contribute to broad taxonomic differences in species functional traits, while finer scale ecological processes contribute to interspecific differences in smaller taxonomic units. These results suggest that the lability or phylogenetic relatedness of different functional traits affects their suitability for testing hypothesis surrounding community level responses to environmental change.     

Evolution of temporal isolation in the wild: genetic divergence in timing of migration and breeding by introduced chinook salmon populations

Abstract. The timing of migration and breeding are key life-history traits; they are not only adaptations of populations to their environments, but can serve to increase reproductive isolation, facilitating further divergence among populations. As part of a study of divergence of chinook salmon, Oncorhynchus tshawytscha , populations, established in New Zealand from a common source in the early 1900s, we tested the hypotheses that the timing of migration and breeding are under genetic control and that the populations genetically differ in these traits despite phenotypic overlap in timing in the wild. Representatives of families from two populations were collected within a day or two of each other, reared in a common environment, and then released to sea from each of two different rivers, while other family representatives were retained in fresh water to maturity. The date of maturation of fish held in fresh water and the dates of return from the ocean and maturation of fish released to sea all showed significant differences between the two populations and among families within populations. The very high heritabilities and genetic correlations estimated for migration and maturation date indicated that these traits would respond rapidly to selection. Combined with the results of related studies on these chinook salmon populations, it appears that spawning time may not only evolve during the initial phases of divergence, but it may play an important role in accelerating divergence in other traits.     

Recent local adaptation of sockeye salmon to glacial spawning habitats

Salmonids spawn in highly diverse habitats, exhibit strong genetic population structuring, and can quickly colonize newly created habitats with few founders. Spawning traits often differ among populations, but it is largely unknown if these differences are adaptive or due to genetic drift. To test if sockeye salmon (Oncorhynchus nerka) populations are adapted to glacial, beach, and tributary spawning habitats, we examined variation in heritable phenotypic traits associated with spawning in 13 populations of wild sockeye salmon in Lake Clark, Alaska. These populations were commonly founded between 100 and 400 hundred sockeye salmon generations ago and exhibit low genetic divergence at 11 microsatellite loci (F _ST < 0.024) that is uncorrelated with spawning habitat type. We found that mean P _ST (phenotypic divergence among populations) exceeded neutral F _ST for most phenotypic traits measured, indicating that phenotypic differences among populations could not be explained by genetic drift alone. Phenotypic divergence among populations was associated with spawning habitat differences, but not with neutral genetic divergence. For example, female body color was lighter and egg color was darker in glacial than non-glacial habitats. This may be due to reduced sexual selection for red spawning color in glacial habitats and an apparent trade-off in carotenoid allocation to body and egg color in females. Phenotypic plasticity is an unlikely source of phenotypic differences because Lake Clark sockeye salmon spend nearly all their lives in a common environment. Our data suggest that Lake Clark sockeye salmon populations are adapted to spawning in glacial, beach and tributary habitats and provide the first evidence of a glacial spawning ecotype in salmonids. Glacial spawning habitats are often young (i.e., <200 years old) and ephemeral. Thus, local adaptation of sockeye salmon to glacial habitats appears to have occurred recently.     

A field reciprocal transplant experiment reveals asymmetric costs of migration between lake and river ecotypes of three‐spined sticklebacks (Gasterosteus aculeatus)

Theory of local adaptation predicts that nonadapted migrants will suffer increased costs compared to local residents. Ultimately this process can result in the reduction of gene flow and culminate in speciation. Here, we experimentally investigated the relative fitness of migrants in foreign habitats, focusing on diverging lake and river ecotypes of three‐spined sticklebacks. A reciprocal transplant experiment performed in the field revealed asymmetric costs of migration: whereas mortality of river fish was increased under lake conditions, lake migrants suffered from reduced growth relative to river residents. Selection against migrants thus involved different traits in each habitat but generally contributed to bidirectional reduction in gene flow. Focusing particularly on the parasitic environments, migrant fish differed from resident fish in the parasite community they harboured. This pattern correlated with both cellular phenotypes of innate immunity as well as with allelic variation at the genes of the major histocompatibility complex. In addition to showing the costs of migration in three‐spined sticklebacks, this study highlights the role of asymmetric selection particularly from parasitism in genotype sorting and in the emergence of local adaptation.     

Juvenile habitat partitioning and relative productivity in allochronically isolated sockeye salmon (Oncorhynchus nerka)

Allochronic divergence, like spatial isolation, may contribute to population diversity and adaptation, however the challenges for tracking habitat utilization in shared environments are far greater. Adult Klukshu River (Yukon, Canada) sockeye salmon, Oncorhynchus nerka, return as genetically distinct "early" and "late" runs. Early and late adult spawning populations (1999 and 2000) and their subsequent fry (sampled at 7 sites in 2000 and at 8 sites in 2001 throughout Klukshu Lake and River) were genotyped at eight microsatellite loci. Bayesian assignment was used to determine the spatial distribution of early versus late fry; although intermixed, the distribution of fry significantly differed in Klukshu Lake and in the Klukshu River in 2001, based on crosstab analyses. Late-run fry predominated in Klukshu Lake at all sites, while early-run fry were most common in the north and south of Klukshu Lake and in Klukshu River. Early-run spawners had significantly higher relative productivity (early life survival) than late-run fish (2.9 times more fry produced per early-run adult in 2000, and 9.2 times more in 2001). This study demonstrates spatial habitat partitioning and differences in the contribution of allochronically isolated populations to fry abundance, and highlights annual variability that likely contributes to recruitment variation.     

Out crosses between seasonally different segments of a Pacific salmon population reveal local adaptation

In salmon populations, local adaptation to seasonally varying incubation temperature is characterized by temperature-adjusted development times [measured in degree days – accumulated temperature units (ATUs)] that differ between control and F₁ hybrid crosses that were made between temporally separated population segments, a contrast not expected in a panmictic population. We examined adaptation of embryo development time to seasonally cooling temperature in a population of pink salmon by estimating genetic components of variation in control and hybrid F₁ crosses made between members of early- and late-spawning subpopulations, and replicated our observations in independent odd- and even-year brood lines. In each brood line, both sire and dam components of variation of development time were significant and accounted for a substantially larger portion of variation than their interactions, which suggested that natural selection has acted primarily on additive genetic variation. The implications of these results are that (1) spatially or temporally proximate salmon populations may be structured by distinct adaptations; (2) artificial relaxation of local geneflow barriers may lead to depression of fitness; and (3) populations of salmon genetically structured by local adaptation may carry variation that enhances their persistence during rapid climate change.     

Strong patterns of intraspecific variation and local adaptation in Great Basin plants revealed through a review of 75 years of experiments

Variation in natural selection across heterogeneous landscapes often produces (a) among‐population differences in phenotypic traits, (b) trait‐by‐environment associations, and (c) higher fitness of local populations. Using a broad literature review of common garden studies published between 1941 and 2017, we documented the commonness of these three signatures in plants native to North America's Great Basin, an area of extensive restoration and revegetation efforts, and asked which traits and environmental variables were involved. We also asked, independent of geographic distance, whether populations from more similar environments had more similar traits. From 327 experiments testing 121 taxa in 170 studies, we found 95.1% of 305 experiments reported among‐population differences, and 81.4% of 161 experiments reported trait‐by‐environment associations. Locals showed greater survival in 67% of 24 reciprocal experiments that reported survival, and higher fitness in 90% of 10 reciprocal experiments that reported reproductive output. A meta‐analysis on a subset of studies found that variation in eight commonly measured traits was associated with mean annual precipitation and mean annual temperature at the source location, with notably strong relationships for flowering phenology, leaf size, and survival, among others. Although the Great Basin is sometimes perceived as a region of homogeneous ecosystems, our results demonstrate widespread habitat‐related population differentiation and local adaptation. Locally sourced plants likely harbor adaptations at rates and magnitudes that are immediately relevant to restoration success, and our results suggest that certain key traits and environmental variables should be prioritized in future assessments of plants in this region.     

Time scale matters: genetic analysis does not support adaptation‐by‐time as the mechanism for adaptive seasonal declines in kokanee reproductive life span

Seasonal declines of fitness‐related traits are often attributed to environmental effects or individual‐level decisions about reproductive timing and effort, but genetic variation may also play a role. In populations of Pacific salmon (Oncorhynchus spp.), seasonal declines in reproductive life span have been attributed to adaptation‐by‐time, in which divergent selection for different traits occurs among reproductively isolated temporal components of a population. We evaluated this hypothesis in kokanee (freshwater obligate Oncorhynchus nerka) by testing for temporal genetic structure in neutral and circadian‐linked loci. We detected no genetic differences in presumably neutral loci among kokanee with different arrival and maturation dates within a spawning season. Similarly, we detected no temporal genetic structure in OtsClock1b, Omy1009uw, or OmyFbxw11, candidate loci associated with circadian function. The genetic evidence from this study and others indicates a lack of support for adaptation‐by‐time as an important evolutionary mechanism underlying seasonal declines in reproductive life span and a need for greater consideration of other mechanisms such as time‐dependent, adaptive adjustment of reproductive effort.     

Straying of hatchery salmon in Prince William Sound,Alaska

The straying of hatchery salmon may harm wild salmon populations through a variety of ecological and genetic mechanisms. Surveys of pink (Oncorhynchus gorbuscha), chum (O. keta) and sockeye (O. nerka) salmon in wild salmon spawning locations in Prince William Sound (PWS), Alaska since 1997 show a wide range of hatchery straying. The analysis of thermally marked otoliths collected from carcasses indicate that 0–98% of pink salmon, 0–63% of chum salmon and 0–93% of sockeye salmon in spawning areas are hatchery fish, producing an unknown number of hatchery-wild hybrids. Most spawning locations sampled (77%) had hatchery pink salmon from three or more hatcheries, and 51% had annual escapements consisting of more than 10% hatchery pink salmon during at least one of the years surveyed. An exponential decay model of the percentage of hatchery pink salmon strays with distance from hatcheries indicated that streams throughout PWS contain more than 10% hatchery pink salmon. The prevalence of hatchery pink salmon strays in streams increased throughout the spawning season, while the prevalence of hatchery chum salmon decreased. The level of hatchery salmon strays in many areas of PWS are beyond all proposed thresholds (2–10%), which confounds wild salmon escapement goals and may harm the productivity, genetic diversity and fitness of wild salmon in this region     

Acclimatization of Pink Salmon Oncorhynchus gorbuscha Walbaum in the European North: mtDNA Restriction Data

Pink salmon spawners introduced into the White Sea basin (the Umba River) were compared to the spawners from the basin of the Sea of Okhotsk (the Ola River) using restriction analysis of two fragments of mitochondrial DNA (mtDNA). One of the fragments included genes ND5/ND6, the other, the cytochrome b gene and the D-loop. It was found that mtDNA variation and diversity at the earlier examined nuclear allozyme genes significantly decreased in the odd broodline of pink salmon 8 years after the introduction. The haplotype diversity in the even broodline was considerably lower than in the odd broodline exhibiting virtually no change two generations after the introduction. Based on the results obtained, a possible role of these changes in adaptation of White Sea pink salmon from the odd broodline to the new environment is discussed.