Richard M. Kocan—Research

Yukon Kings/Yukon Queens

Support: U.S. Fish and Wildlife Service

This study is designed to address the effects of Ichthyophonus on the survival, fecundity, and quality of Yukon king salmon (Oncorhynchus tshawytscha). Fish tissues will be collected at the mouth of the Yukon River at Emmonak (Alaska), and at Galena, Tanana, Nenana, Circle, Dawson and Whitehorse (Yukon Territories). By directly examining the tissues on-site, culturing tissues, and examining them histologically, disease progression can be determined as the fish move upstream. Preliminary results show that diseased fish increase from 4% to >50% by the time they reach Tanana.

Salmon eat large quantities of herring (Clupea pallasi), which are known to be infected with Ichthyophonus. If the Ichthyophonus that occurs in herring is genetically identical to that found in Yukon kings, then it is highly probable that herring are the source of infection.

Hatchery-reared fish will be experimentally infected with an isolate of the parasite from the Yukon River and reared over a range of temperatures to assess the effects of temperature on the progression of Ichthyophonus infections in chinook salmon. We will develop a non-lethal method for identifying infected fish—either immunodiffusion or ELISA. Using these techniques we can determine the difference in survival between infected and uninfected fish.

Ichthyophonus–Chinook Study

Support: State of Alaska

Yukon River Panel Recent observations have identified Ichthyophonus as a pathogen of Yukon River king salmon and have implicated the organism as a potential cause of mortality in adults prior to reaching their spawning streams. Unexplained decreases in numbers of upriver migrants reported in the past may be due to Ichthyphonus-related mortality. If this can be demonstrated, then management strategies could be modified to account for the loss of spawning adults. This study is a continuation of a pilot study initiated in 1999-2000 and will determine (1) the prevalence of infection and disease in Yukon River king salmon, (2) whether Ichthyphonus is responsible for chinook mortality, (3) how extensive the mortality is, (4) whether infection affects the fecundity of surviving spawners, and (5) what river conditions affect the course and severity of this diseases.

Final Report (MS Word, Excel)

Herring Embryo-Larval Success Evaluation at Cherry Point, Washington: Comparison of In Situ Exposures with Laboratory Controls

Collaborators: Washington Departments of Natural Resources and Fish & Wildlife, Applied Biomonitoring
Support: Washington Dep. Natural Resources

The Cherry Point herring (Clupea pallasi) stock is a distinct population, distinguishable from other Puget Sound stocks by its age distribution, geographic limits of spawning and late (e.g., May) spawning. For some time, the stock has been shrinking for unknown reasons and it has reached a critically low level. Consequently, a program has been initiated to study the spawning success, embryo survival, and larval survival of this stock. This will be done by examining spawning success at various locations along the Cherry Point shoreline and comparing this to laboratory-reared controls. Natural spawn will also be evaluated to determine whether substrate and mixed female spawning events affect the success of embryos and larvae. End points for success include (1) percent fertilization, (2) percent hatch, (3) morphologically normal larvae, (4) cytogenetic damage, and (5) condition factor of newly hatched larvae.

Disease Factors Affecting Herring Populations in Prince William Sound

Collaborators: J. Sullivan (Alaska Dep. Fish & Game), J. Winton (USGS-BRD), G. Marty (Univ. California Davis), and C. Kennedy (Simon Fraser University, British Columbia), P. Hershberger (graduate student)
Support: Alaska Dept. Fish & Game (Exxon Valdez Trustee Council)

Studies involve rearing specific pathogen-free herring (Clupea pallasi) from egg to adult and using them to evaluate the effects of oil exposure on the course of disease and immune function in Pacific herring. Also examines the stress effects induced by current fishing practices on the spread of infectious diseases and the natural history of viral diseases in forage fishes of Prince William Sound and Puget Sound.