Salmonid Physiology, Morphology, and Behavior

As a faculty research assistant at Oregon State University, I worked on a suite of studies under the Wild Chinook Surrogate Project. The aim of the project was to produce Chinook salmon Oncorhynchus tshawytscha that closely emulate wild fish (surrogates) for researchers who are studying dam passage, survival of naturally-produced fish, and fish navigation within reservoirs. Due to the ESA-listing of these fish, researchers are required to use hatchery origin surrogates. To produce these fish, we altered various factors such as density, substrate/habitat, diet, temperature, and flow and subsequently evaluated differences in physiology, behavior, and morphology throughout development.

I worked with many hatcheries across Oregon with the Fish Performance and Genetics Lab (FPGL) in Corvallis, OR and the Oregon Hatchery Research Center (OHRC) in Alsea, OR being the main two facilities. At the OHRC we were able to monitor in-stream movement of our surrogate fish in replicated artificial streams with video coverage and PIT tag array. The fish ladder at OHRC controls passage of migrating fishes to the upper basin of Fall Creek and permits collection of metric and genetic data on the fishes before assisting them upstream to spawn.

In addition to Chinook salmon, I also worked with Steelhead trout Oncorhynchus mykiss doing many similar studies and bull trout Salvelinus confluentus.

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Check out some of our most recent publications:

Egg size and emergence timing affect morphology and behavior in juvenile Chinook Salmon, Oncorhynchus tshawytscha

Abstract

Variation in early life history traits often leads to differentially expressed morphological and behavioral phenotypes. We investigated whether variation in egg size and emergence timing influence subsequent morphology associated with migration timing in juvenile spring Chinook Salmon, Oncorhynchus tshawytscha. Based on evidence for a positive relationship between growth rate and migration timing, we predicted that fish from small eggs and fish that emerged earlier would have similar morphology to fall migrants, while fish from large eggs and individuals that emerged later would be more similar to older spring yearling migrants. We sorted eyed embryos within females into two size categories: small and large. We collected early and late-emerging juveniles from each egg size category. We used landmark-based geometric morphometrics and found that egg size appears to drive morphological differences. Egg size shows evidence for an absolute rather than relative effect on body morphology. Fish from small eggs were morphologically more similar to fall migrants, while fish from large eggs were morphologically more similar to older spring yearling migrants. Previous research has shown that the body morphology of fish that prefer the surface or bottom location in a tank soon after emergence also correlates with the morphological variations between wild fall and spring migrants, respectively. We found that late-emerging fish spent more time near the surface. Our study shows that subtle differences in early life history characteristics may correlate with a diversity of future phenotypes.

Salinity effects on plasma ion levels, cortisol, and osmolality in Chinook salmon following lethal sampling

Abstract

Studies on hydromineral balance in fishes frequently employ measurements of electrolytes following euthanasia. We tested the effects of fresh- or salt- water euthanasia baths of tricaine mesylate (MS-222) on plasma magnesium (Mg(2+)) and sodium (Na(+)) ions, cortisol and osmolality in fish exposed to saltwater challenges, and the ion and steroid hormone fluctuations over time following euthanasia in juvenile spring Chinook salmon (Oncorhynchus tshawytscha). Salinity of the euthanasia bath affected plasma Mg(2+) and Na(+) concentrations as well as osmolality, with higher concentrations in fish euthanized in saltwater. Time spent in the bath positively affected plasma Mg(2+) and osmolality, negatively affected cortisol, and had no effect on Na(+) concentrations. The difference of temporal trends in plasma Mg(2+) and Na(+) suggests that Mg(2+) may be more sensitive to physiological changes and responds more rapidly than Na(+). When electrolytes and cortisol are measured as endpoints after euthanasia, care needs to be taken relative to time after death and the salinity of the euthanasia bath.

Effects of transportation timing on osmoregulation and survival in yearling hatchery Chinook salmon (Oncorhynchus tshawytscha)

Abstract

Seasonal timing of transportation and acclimation of juvenile Chinook salmon (Oncorhynchus tshawytscha) between hatcheries may affect osmoregulation and survival. We investigated the duration of time fish need to acclimate to hatchery conditions prior to being presented with a saltwater challenge. We monitored acute survival and osmoregulatory ability following a 24-h saltwater challenge of fish previously transported to a hatchery at various times throughout the year compared to fish reared at that hatchery. Fish that underwent a saltwater challenge 3 weeks after transport had significantly reduced osmoregulatory performance and increased mortality compared to fish allowed an acclimation period of 2 months.

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