There is an urgent need to clarify how different stocks, or subpopulations of fish species, are vulnerable to fishing pressure and unfavorable ocean conditions because of the increasing demand on fisheries for human consumption. For marine fishes, the potential for high gene flow increases the difficulty in determining the number...
We investigated habitat use by juvenile Chinook salmon (Oncorhynchus tshawytscha) and coho salmon (O. kisutch) to identify environmental characteristics that may define their optimal marine habitat. We utilized physical and biological data from four cruises in the northern California Current system from Newport, Oregon, to Crescent City, California, in June...
Previous studies have shown that juvenile chinook salmon Oncorhynchus tshawytscha exposed in the field or the laboratory to polychlorinated biphenyls (PCBs), an anthropogenic stressor, are immunosuppressed. It is not known whether simultaneous exposure to natural stressors can increase this immunosuppression. To examine the effects of natural and anthropogenic stressors on...
An international multi-laboratory project was conducted to develop a standardized DNA database for Chinook salmon (Oncorhynchus tshawytscha). This project was in response to the needs of the Chinook Technical Committee of the Pacific Salmon Commission to identify stock composition of Chinook salmon caught in fisheries during their oceanic migrations. Nine...
Although the adverse impact of pathogens on salmon populations in the Pacific Northwest is often discussed and recognized, little is currently known regarding the incidence and corresponding significance of delayed disease-induced mortalities. In the study reported herein, we surveyed the presence and prevalence of selected micro- and macroparasites in out-migrant...
The diel feeding periodicity of juvenile Chinook salmon Oncorhynchus tshawytscha was determined from stomachs collected in coastal waters off Oregon in 2000 and 2003. Juvenile Chinook salmon exhibited a diurnal feeding pattern with morning and evening feeding periods. There were differences in the duration and magnitude of the dawn and...
Successfully shifting to a more piscivorous diet may be an important factor in the growth and survival of juvenile coho salmon Oncorhynchus kisutch and Chinook salmon O. tshawytscha during their first summer in the northern California Current. Nonmetric multidimensional scaling and cluster analysis of diets by size showed several distinct...
Efforts to restore depressed populations of Pacific salmon Oncorhynchus spp. are often hampered by the inability to assign population identity to individuals in an admixture. This knowledge is of particular concern in supportive breeding programs, in which misidentification of individuals to population may result in progeny of mixed heritage, which,...
One aspect of diadromy that has received little attention is buoyancy regulation in fish moving between freshwater and marine environments. Because of density differences between the two water types, fish must alter their whole-fish density (WFD) or they will become positively (float) or negatively (sink) buoyant as they change environments....
Species conservation depends on robust population assessment. Data on population abundance, distribution, and connectivity are critical for effective management, especially as baseline information for newly documented populations. I describe a pygmy blue whale (Balaenoptera musculus brevicauda) population in New Zealand waters with year-round presence that overlaps with industrial activities. This...