Pacific rockfish experience high discard mortality when captured owing to a condition called barotrauma,which is caused by the change in pressure during capture. This condition appears to be species specific at the macroscopic level; however, little is known about the microscopic tissue-level effects of barotrauma. Determining whether tissue-level injuries are...
Although much is known about the effects of electroshock on fish physiology, consequences to the immune system and disease progression have not received attention. Our objectives were to determine the effects of electroshock on selected immune function in juvenile spring chinook salmon Oncorhynchus tshawytscha, the mechanism of any observed alteration,...
Anadromous salmonids are viewed as a prized commodity and cultural symbol throughout the Pacific coast of North America. Unfortunately, several native salmonid populations are threatened or at risk of extinction. Despite this, little is known about the behavior and survival of these fish as the juveniles transition from freshwater to...
We describe the migration distances and timing of the adult Pacific lamprey, Entosphenus tridentatus, in the Willamette River Basin (Oregon, U.S.A.). We conducted aerial surveys to track radio-tagged fish upstream of a major waterfall and hydropower complex en route to spawning areas. We detected 24 out of the 43 fish...
Twenty-two steelhead trout (Salmo gairdneri) containing coded wire tags (CWT's) were captured in gillnets fished by the Oshoro-Maru in the Gulf of Alaska and along 180 during 1982-85. These fish originated from North American streams and hatcheries in British Columbia, Idaho, and Washington. One fish was age 0.1, 16 were...
We report the incidence of male intersex in adult Pacific lamprey (Entosphenus tridentatus (Richardson, 1836)) during their pre-spawning migration in fresh water. Although “hermaphrodites” have been suggested in other adult lampreys, this is the first detailed description and discussion of this phenomenon. A total of 0.5% of our adult Pacific...
To best manage Eagle Creek National Fish Hatchery, negative interactions between hatchery salmonids and Endangered Species Act listed wild salmonids in the Eagle Creek Basin need to be minimized. Our objectives were: 1) to compare summer rearing densities in two similar streams, where one stream received a release of hatchery...
It is current practice to transport juvenile anadromous salmonids in transplantation and to help them bypass dams. Essentially nothing is known about the effects that transportation could have on the ability of the fish to outmigrate and be fit for survival in the marine environment. Procedures involved in transporation subject...
Juvenile chinook salmon Oncorhynchus tshawytscha were subjected to handling and tagging protocols typical of normal hatchery operations and monitored for their physiological response to stress. Treatments included coded-wire-tagging, counting, ventral fin clipping, adipose fin clipping, and a procedure simulating a pond split. Treatment fish were also subjected to a standardized...
Experiments were designed to determine whether and how steelhead Oncorhynchus mykiss affect chinook salmon O. tshawytscha when the two species are confined together. In a behavioral experiment, we observed groups of juvenile chinook salmon and steelhead together and groups of chinook salmon alone to determine whether the steelhead were aggressive...
The Pacific salmonid species Oncorhynchus mykiss is separated into a migratory form (steelhead trout) and a
non-migratory form (rainbow trout). A decrease in water temperature is likely a cue triggering downstream
behavior in the migratory form, and testosterone inhibits onset of this behavior. To elucidate differences in
sensitivity to water...
We evaluated the effects of the McNary Dam transportation system on emigrating fall and spring chinook smolts using physiological indices of stress (e.g., plasma cortisol, hepatic glycogen, leucocrit, interrenal cell nuclear diameter) and performance tests (e.g., saltwater challenge, secondary stress challenge, disease resistance). We also conducted controlled experiments in a...
The goal of this study was to describe the duration and magnitude of the physiological stress response in lingcod Ophiodon elongatus after exposure to brief handling and sublethal air stressors. The response to these stressors was determined during a 24‐h recovery period by measuring concentrations of plasma cortisol, lactate, glucose,...
A technique that uses hypotonic lysis of erythrocytes was optimized for the purification of leukocytes from the peripheral blood and anterior kidney (pronephros) of rainbow trout Oncorhynchus mykiss. Comparisons of initial blood dilution (1:2, 1:4, and 1:6) and the time of exposure to hypotonic conditions (10, 20, and 40 s)...
We used radio and acoustic telemetry to study the behavior and survival of wild steelhead trout (Oncorhynchus mykiss) and hatchery coho salmon (Oncorhynchus kisutch) and steelhead outmigrants in a small coastal estuary during two years. Survival was generally low for hatchery fish but more variable, both within and between years,...