Lisa A. Wetzel

Migratory Behavior of Chinook Salmon Microjacks Reared in Artificial and Natural Environments

Abstract Emigration was evaluated for hatchery Chinook salmon (Oncorhynchus tshawytscha) microjacks (age-1 mature males) and immature parr (age-1 juveniles, both sexes) released from both a hatchery and a natural stream (fish released as fry). In the hatchery, volitional releases (∼14 to 15 months post-fertilization) to an adjacent river occurred during October–November. The hatchery release was monitored by using an experimental volitional release that diverted fish to a neighboring raceway. Fish captured during the experimental release (range 361–4,321 volitional migrants) were made up of microjacks and immature parr. Microjacks were found only in the migrant samples, averaged 18% (range 0–52%) of all migrants, and were rarely found in non-migrant samples. In comparison, immature parr were common in both the migrant and non-migrant samples. Microjacks were significantly longer (9%), heavier (36%), and had a greater condition factor (16%) than migrant immature parr (P < 0.01). In addition, they differed ...

Differential Survival among sSOD-1* Genotypes in Chinook Salmon

Abstract Differential survival and growth were tested in Chinook salmon Oncorhynchus tshawytscha expressing two common alleles, *–100 and *–260, at the superoxide dismutase locus (sSOD-1*). These tests were necessary to support separate studies in which the two alleles were used as genetic marks under the assumption of mark neutrality. Heterozygous adults were used to produce progeny with –100/–100, –100/–260, and –260/–260 genotypes that were reared in two natural streams and two hatcheries in the states of Washington and Oregon. The latter also were evaluated as returning adults. In general, the genotype ratios of juveniles reared at hatcheries were consistent with high survival and little or no differential survival in the hatchery. Adult returns at one hatchery were significantly different from the expected proportions, and the survival of the –260/–260 genotype was 0.56–0.89 times that of the –100/–100 genotype over four year-classes. Adult returns at a second hatchery (one year-class) were similar b...

PEPA-1* Genotype Affects Return Rate for Hatchery Steelhead

Abstract Allozymes continue to be useful as genetic markers in a variety of studies; however, their utility often hinges on the selective neutrality of the allelic variation. Our study tested for neutrality between the two most common alleles (*100 and *110) at the cytosol nonspecific dipeptidase locus (PEPA-1*) in steelhead Oncorhynchus mykiss from Dworshak National Fish Hatchery in Idaho. We tested for differential growth and survival among fish with the *100/100, *100/ 110, and *110/110 genotypes rearing in a hatchery or a natural stream. We repeated the study for two year-classes, using heterozygous (*100/110) adults to make the experimental crosses. This design avoided differences in family contribution among genotypes because each cross produced all three genotypes. We divided the progeny from each family into two groups. One group was reared in a hatchery for 1 year and then released for migration to the sea and subsequent return to the hatchery as adults. The other group was released into a natura...

Juvenile coho salmon growth and health in streams across an urbanization gradient

Expanding human population and urbanization alters freshwater systems through structural changes to habitat, temperature effects from increased runoff and reduced canopy cover, altered flows, and increased toxicants. Current stream assessments stop short of measuring health or condition of species utilizing these freshwater habitats and fail to link specific stressors mechanistically to the health of organisms in the stream. Juvenile fish growth integrates both external and internal conditions providing a useful indicator of habitat quality and ecosystem health. Thus, there is a need to account for ecological and environmental influences on fish growth accurately. Bioenergetics models can simulate changes in growth and consumption in response to environmental conditions and food availability to account for interactions between an organisms environmental experience and utilization of available resources. The bioenergetics approach accounts for how thermal regime, food supply, and food quality affect fish growth. This study used a bioenergetics modeling approach to evaluate the environmental factors influencing juvenile coho salmon growth among ten Pacific Northwest streams spanning an urban gradient. Urban streams tended to be warmer, have earlier emergence dates and stronger early season growth. However, fish in urban streams experienced increased stress through lower growth efficiencies, especially later in the summer as temperatures warmed, with as much as a 16.6% reduction when compared to fish from other streams. Bioenergetics modeling successfully characterized salmonid growth in small perennial streams as part of a more extensive monitoring program and provides a powerful assessment tool for characterizing mixed life-stage specific responses in urban streams.