Elevated concentrations of Se have been detected in cold, flowing water habitats near uranium and coal mines in Canada. Fish from these systems have concentrations of Se in their tissues that exceed toxic effect thresholds that have been established for warm-water fishes. However, the applicability of toxic effect thresholds and guidelines to cold water, lotic habitats is a matter of contention in the literature since most cases of Se toxicosis have been documented in standing, warm-water systems. To examine the possibility of impaired reproduction in wild rainbow trout (Oncorhynchus mykiss) and brook trout (Salvelinusfontinalis) near coal mining activity in the northeastern slopes region of Alberta, Canada, spawn from both species were collected from exposure and reference sites. Gametes were fertilized in the laboratory, reared to the swim-up stage, and examined for deformities. A significant relationship was observed for rainbow trout between the amount of Se in eggs and the incidence of developmental abnormalities, specifically craniofacial defects, skeletal deformities, and edema. These associations approximate exponential functions with probabilities that 15% of the population would be affected occurring between 8.8 and 10.5 microg Se per gram of wet egg weight, based on probit analysis. These relationships are similar to those described for centrarchids inhabiting a seleniferous warm-water lake. No such relationships were established for brook trout.

Toxicological studies are often hampered by concerns of fish residency in the industrial effluent being evaluated. Contaminants in muscle or visceral tissue are useful indicators of recent exposure, but depuration, metabolic transformation, and tissue recompartmentalization of contaminants makes their use as temporal markers tenuous. Otoliths are metabolically stable and can provide temporal resolution for exposure to some elements that are incorporated into their calcified structure, including the divalent cations Sr, Zn, and Mn. Here we provide the first determinations of selenium, an anion in biological systems, in the otoliths of rainbow trout captured from a site receiving runoff with elevated selenium from a coal mine operation. Concentrations of selenium in annual growth zones of otoliths suggest that fish from the mine-impacted system are recent immigrants from nearby reference streams not receiving selenium-bearing effluent.

Molecular genetic assays can contribute to conservation of aquatic taxa by assessing evolutionary and taxonomic distinctiveness, levels of genetic variation within and between populations, and the degree of introgression with introduced taxa. The Athabasca River drainage of western Alberta, Canada is one of only three (and the largest) drainages flowing east of the continental divide that contain native populations of rainbow trout (Salmonidae: Oncorhynchus mykiss). The ''Athabasca'' rainbow trout has been considered a preglacial relict worthy of special conservation measures. In addition, the native range of Athabasca rainbow trout has seen many instances of introductions of non-native populations since the beginning of the 20th century. We assayed rainbow trout from the Athabasca River drainage, from hatchery populations, and from representative populations in adjacent regions (N = 49 localities) for variation at 10 microsatelite loci to assess the level of evolutionary distinctiveness of Athabasca rainbow trout, and to assess the levels of introgression with non-native hatchery fish. We found that native Athabasca rainbow trout did not form a distinctive genetic assemblage and that the greatest amount of allele frequency variation was attributable to contemporary drainage systems (29.3%) rather than by a Athabasca/non-Athabasca distinction (12.6%). We found that 78% of all fish were confidently assigned to a ''wild'' rather than a ''hatchery'' genetic grouping and that most of the inferred introgression with hatchery fish was restricted to a few localities (N = 6). Our results suggest that: (i) Athabasca River rainbow trout are likely postglacial immigrants from adjacent populations of the Fraser River, and (ii) that there is no evidence of widespread introgression of hatchery alleles into native Athabasca River drainage rainbow trout.

A simple theoretical model shows that mechanisms of density-dependent survival that result in stable dynamics for populations with only intracohort interactions during the juvenile phase can produce cyclic behaviour when cohorts interact together. We compared these theoretical results with a time series (1971-1985) on juvenile bull trout (Salvelinus confluentus) from Eunice Creek, Alberta. Abundance of bull trout in Eunice Creek ranged over two orders of magnitude over the 15 years. By assigning age-classes to the abundance data (using a probabilistic length-frequency analysis), we assessed yearly survival rates for age-classes 1-3. Survival rates for age-classes 1 and 2 were negatively correlated (P < 0.05) with the effective density (an index of total consumption) of all juvenile bull trout in Eunice Creek. These observations support the hypothesis that different age cohorts of juvenile bull trout do interact. Using a stochastic version of the model and parameter values estimated from Eunice Creek, we hypothesize that even moderate levels of adult mortality (an average adult spawns during two seasons) coupled with random variation in the density-independent component of juvenile mortality can result in an apparent cyclic pattern for bull trout. Finally, stock- recruitment relationships for these populations are not represented by a single average curve.