A. Talbot

Population Structure of Columbia River Basin Chinook Salmon and Steelhead Trout

The population structure of chinook salmon and steelhead trout is presented as an assimilation of the life history forms that have evolved in synchrony with diverse and complex environments over their Pacific range. As poikilotherms, temperature is described as the overwhelming environmental influence that determines what life history options occur. The different populations represent ecological types referred to as spring-, summer-, fall, and winter-run segments, as well as stream- and ocean-type, or stream- and ocean-maturing life history forms. However, they are more correctly described as a continuum of forms that fall along a temporal cline related to incubation and rearing temperatures that determine spawn timing and juvenile residence patterns. Population structure of chinook salmon and steelhead in the Columbia Basin, therefore, is the reflection of the genetic composition of the founding source or sources within the respective region, shaped by the environment, principally temperature, that defines life history evolutionary strategy to maximize fitness under the conditions delineated. The key in developing an effective recovery program for chinook salmon and steelhead is to recognize that measures taken must address the genetic and biological requirements of the population unit within the environmental template identified.

The Controversy about Salmon Hatcheries

Abstract The use of hatcheries has been a subject of lengthy debate in the management of salmon and trout resources in the Pacific Northwest. The problem has resulted in part from the wide distribution of hatchery fish in circumstances where natural populations were disadvantaged by management policy involving hatchery fish and the confusion of the effects of management with the effects of artificial propagation. Recently, the controversy has been epitomized by the recommendations to fisheries management agencies that excess hatchery fish should not be allowed to spawn in the wild, and hatchery fish should be excluded from salmon populations listed under the Endangered Species Act. The authors of the present article disagree with those recommendations and conclude that hatchery fish have an important role in recovery and supplementation of wild stocks. The present article is an attempt to help give balance to the discussion by providing a different perspective on hatchery fish and the literature pertainin...

Differential changes in gene expression in rainbow trout hepatocytes exposed to extracts of oil sands process-affected water and the Athabasca River.

The oil sands region of northern Alberta represents the worlds largest reserves of bitumen, and the accelerated pace of industrial extraction activity has raised concern about the possible impacts on the Athabasca River and its tributaries. An ecotoxicogenomic study was undertaken on Oncorhynchus mykiss trout hepatocytes exposed to extracts of water samples near the oil sand development area, as well as to oil sands process-affected water (OSPW) extracts using the quantitative reverse transcriptase polymerase chain reaction technique. The expression of the following genes (mRNA) was monitored to track changes in xenobiotic biotransformation (CYP1A1, CYP3A4, glutathione S-transferase, multi-drug resistance transporter), estrogenicity (estrogen receptor and vitellogenin), oxidative stress (superoxide dismutase and metallothionein) and DNA repair activity (DNA ligase). The extent of DNA-aromatic hydrocarbon adducts was also determined in cells by immuno-staining. A comparative analysis of gene expression between the river/lake and OSPW samples revealed that CYP3A4, metallothioneins, DNA ligase and GST genes, were specifically expressed by OSPW. Cells exposed to OSPW, commercial naphthenic acids, and benzo(a)pyrene showed increased polyaromatic hydrocarbon DNA-adducts, as determined by cell immunofluorescence analysis. Other genes were induced by all types of water samples, although the induction potential was stronger in OSPW most of the time (e.g., VTG gene was expressed nearly 15-fold by surface waters from the lake and river samples but increased to a maximum of 31-fold in OSPW). A multivariate discriminant function analysis revealed that the lake and river water samples were well discriminated from the OSPW. The CYP3A4 gene was the most highly expressed gene in cells exposed to OSPW and responded less to the lake or river water in the Athabasca River area. This study identified a suite of gene targets that responded specifically to OSPW extracts, which could serve as toxicogenomic fingerprints of OSPW contamination.

Microsatellites Reveal Population Substructure of Klickitat River Native Steelhead and Genetic Divergence from an Introduced Stock

Abstract Determining fine-scale genetic diversity and structure is critical for the conservation and management of populations, especially those under heavy anthropogenic influence. We analyzed 446 individuals at nine microsatellite loci to determine the local population structure of naturally produced steelhead Oncorhynchus mykiss and genetic differentiation from introduced hatchery strain steelhead in the Klickitat River of the Pacific Northwest. We detected significant genetic structure among steelhead in various tributaries to the Klickitat River; the most divergent population was located above a waterfall that acts as a partial upstream migration barrier (average pairwise F ST = 0.13; P < 0.0001). Analysis of mixtures indicated an estimate of six to seven genetically distinct populations of naturally reproducing steelhead in this river system. The hatchery strain appears to remain genetically distinguishable from native stocks (average pairwise F ST of 0.078 with P < 0.0001), as only 4.0% of naturall...

A Distinctive Microsatellite Locus That Differentiates Ocean-Type from Stream-Type Chinook Salmon in the Interior Columbia River Basin

Abstract Chinook salmon Oncorhynchus tshawytscha display two life history strategies that are referred to as ocean type and stream type. Ocean-type Chinook salmon typically differ from stream-type fish in juvenile migration timing, adult spawning location, and run timing. Spatial and temporal separation during spawning can lead to reproductive isolation and genetic divergence between the two life history strategies. We identified a distinctive microsatellite locus, OtsG474, capable of distinguishing ocean-type from stream-type Chinook salmon in 93% of the samples collected from various rivers within the interior Columbia River basin (east of the Cascade Mountains). Allele frequencies at OtsG474 revealed major differences in the dominant allele as well as in the number of alleles detected in each type. This distinctive marker may be highly useful as part of a suite of microsatellite loci, allowing managers to detect the two types of Chinook salmon in the Columbia River basin. Further research is necessary ...