Genetic analysis of juvenile coho salmon (Oncorhynchus kisutch) off Oregon and Washington reveals few Columbia River wild fish

Little is known about the ocean distributions of wild juvenile coho salmon off the Oregon-Washington coast. In this study we report tag recoveries and genetic mixed-stock estimates of juvenile fish caught in coastal waters near the Columbia River plume. To support the genetic estimates, we report an allozyme-frequency baseline for 89 wild and hatchery-reared coho salmon spawning populations, extending from northern California to southern British Columbia. The products of 59 allozyme-encoding loci were examined with starch-gel electrophoresis. Of these, 56 loci were polymorphic, and 29 loci had P0.95 levels of polymorphism. Average heterozygosities within populations ranged from 0.021 to 0.046 and averaged 0.033. Multidimensional scaling of chord genetic distances between samples resolved nine regional groups that were sufficiently distinct for genetic mixed-stock analysis. About 2.9% of the total gene diversity was due to differences among populations within these regions, and 2.6% was due to differences among the nine regions. This allele-frequency data base was used to estimate the stock proportions of 730 juvenile coho salmon in offshore samples collected from central Oregon to northern Washington in June and September-October 1998−2000. Genetic mixed-stock analysis, together with recoveries of tagged or fin-clipped fish, indicates that about one half of the juveniles came from Columbia River hatcheries. Only 22% of the ocean-caught juveniles were wild fish, originating largely from coastal Oregon and Washington rivers (about 20%). Unlike previous studies of tagged juveniles, both tag recoveries and genetic estimates indicate the presence of fish from British Columbia and Puget Sound in southern waters. The most salient feature of genetic mixed stock estimates was the paucity of wild juveniles from natural populations in the Columbia River Basin. This result reflects the large decrease in the abundances of these populations in the last few decades

Genetic Identification of Chinook Salmon: Stock-Specific Distributions of Juveniles along the Washington and Oregon Coasts

We used microsatellite DNA data and genetic stock identification methods to delineate the temporal and spatial distributions of juvenile Chinook Salmon Oncorhynchus tshawytscha occupying coastal habitats extending from central Oregon to northern Washington. Juveniles were collected in trawl surveys conducted during spring, summer, and autumn over 15 years. Distributions (mean latitude and distance from shore) differed between yearling and subyearling life history types and between stocks; many of these differences were consistent across years. Yearlings were nearly all (98%) from Columbia River sources, and only 6% were naturally produced. In late May, yearlings from the lower Columbia and Willamette rivers were farther north than other yearlings, likely due to the early spring timing of their releases from hatcheries and subsequent out-migration from the Columbia River. However, yearling distributions in late June reflected known migration behaviors. Yearlings from interior Columbia and Snake River sources were farthest north by June, whereas yearlings from other stocks were more spread out in latitude. Subyearlings sampled in early summer were also largely from the Columbia River (98%), but greater percentages of subyearlings from coastal rivers were present during the fall (24%). In contrast to yearlings, natural production accounted for nearly one-third of subyearlings. Subyearlings of most stocks tended to remain relatively near their point of sea entry throughout the summer. Subyearlings from the Snake River fall-run stock and upper Columbia River summer–fall-run stock exhibited diverse distributions that included both southward and northward dispersal. Overall, distributions of Chinook Salmon stocks and life history types reflected differences in migration behavior but also reflected the influence of environmental factors and hatchery practices

Early Marine Migration Patterns of Wild Coastal Cutthroat Trout (Oncorhynchus clarki clarki), Steelhead Trout (Oncorhynchus mykiss), and Their Hybrids

Hybridization between coastal cutthroat trout (Oncorhynchus clarki clarki) and steelhead or rainbow trout (Oncorhynchus mykiss) has been documented in several streams along the North American west coast. The two species occupy similar freshwater habitats but the anadromous forms differ greatly in the duration of marine residence and migration patterns at sea. Intermediate morphological, physiological, and performance traits have been reported for hybrids but little information has been published comparing the behavior of hybrids to the pure species.This study used acoustic telemetry to record the movements of 52 cutthroat, 42 steelhead x cutthroat hybrids, and 89 steelhead smolts, all wild, that migrated from Big Beef Creek into Hood Canal (Puget Sound, Washington). Various spatial and temporal metrics were used to compare the behavior of the pure species to their hybrids. Median hybrid residence time, estuary time, and tortuosity values were intermediate compared to the pure species. The median total track distance was greater for hybrids than for either cutthroat or steelhead. At the end of each track, most steelhead (80%) were located near or north of the Hood Canal, as expected for this seaward migrating species, whereas most cutthroat (89%) were within 8 kilometers of the estuary. Most hybrids (70%) were detected leaving Hood Canal, though a substantial percentage (20%) remained near the Big Beef Creek estuary. More hybrids (7.5%) than pure cutthroat (4.5%) or steelhead (0.0%) were last detected in the southern reaches of Hood Canal.Given the similarity in freshwater ecology between the species, differences in marine ecology may play an important role in maintaining species integrity in areas of sympatry

Cols bleus : hebdomadaire de la Marine française

31 octobre 19811981/10/31 (N1682)-1981/10/31

Genetic diversity in the Snake River sockeye salmon captive broodstock program as estimated from broodstock records

Snake River sockeye salmon spawning in Redfish Lake, Idaho are one of the most endangered taxa of Pacific salmon. The wild population nearly went extinct in the 1990s, and all surviving fish were incorporated into a captive broodstock program at that time. We used pedigree analysis to evaluate the effectiveness of the breeding program in retaining genetic variation from 1991 through 2008. Broodstock records document which males were crossed with which females, but fish from multiple crosses were frequently raised in the same tank so the exact pedigree of the population is unknown. Therefore, a simulation- based approach was used to estimate how much genetic diversity was retained by this breeding program. Results indicate that in 2008, after 5.5 generations of breeding, the average inbreeding coefficient was probably about 0.056. We estimated the inbreeding effective population size to be 41 over the entire program and 115 for the most recent generation. This amount of inbreeding is substantially less than has occurred in many high-profile captive breeding programs. Our results depend on several assumptions regarding the relatedness of fish in the breeding program, but simulations suggest our main results are relatively insensitive to these assumptions

Genotypes for genetic diversity analyses

Sample numbers and genotypes for juvenile steelhead trout analyzed for measures of genetic variability. Brood year = year in which juvenile O. mykiss was produced based on scale age. Sample ID = unique sample identifier. Remaining 30 columns = 15 microsatellite loci (i.e, Locus_1 = allele 1) Locus_2 = allele 2

Gene flow between sympatric life history forms of Oncorhynchus mykiss located above and below migratory barriers.

Oncorhynchus mykiss have a diverse array of life history types, and understanding the relationship among types is important for management of the species. Patterns of gene flow between sympatric freshwater resident O. mykiss, commonly known as rainbow trout, and anadromous O. mykiss, commonly known as steelhead, populations are complex and poorly understood. In this study, we attempt to determine the occurrence and pathways of gene flow and the degree of genetic similarity between sympatric resident and anadromous O. mykiss in three river systems, and investigate whether resident O. mykiss are producing anadromous offspring in these rivers, two of which have complete barriers to upstream migration. We found that the population structure of the O. mykiss in these rivers appears to be influenced more by the presence of a barrier to upstream migration than by life history type. The sex ratio of resident O. mykiss located above a barrier, and smolts captured in screw traps was significantly skewed in favor of females, whereas the reverse was true below the barriers, suggesting that male resident O. mykiss readily migrate downstream over the barrier, and that precocious male maturation may be occurring in the anadromous populations. Through paternity analyses, we also provide direct confirmation that resident O. mykiss can produce offspring that become anadromous. Most (89%) of the resident O. mykiss that produced anadromous offspring were males. Our results add to the growing body of evidence that shows that gene flow does readily occur between sympatric resident and anadromous O. mykiss life history types, and indicates that resident O. mykiss populations may be a potential repository of genes for the anadromous life history type

Measures of genetic diversity in the Hamma Hamma River.

<p>(A) Values of allelic richness (circles) and expected heterozygosity (squares) from Hamma Hamma River juvenile <i>O</i>. <i>mykiss</i> samples produced pre-, during-, and post-supplementation, and (B) estimates of the effective number of breeders (<i>N</i>_<i>b</i>), with 95% confidence intervals, for Hamma Hamma River <i>O</i>. <i>mykiss</i> brood years representing pre-, during-, and post-supplementation periods.</p

Map of the study area.

<p>Locations of the supplemented population (Hamma Hamma), the four non-supplemented populations (Tahuya, Little Quilcene, Union, and North Fork Skokomish), and the location of the captive rearing facility.</p

Results of the test for the effects of supplementation on redd abundance.

<p>ANOVA results testing the effects of the conservation hatchery program on the abundance of redds. The main effects were category (supplemented or not) and period (before or after supplementation). The response variable of interest was the interaction between period and category. Significant effects (P <0.05) shown in bold.</p