|Title:||Static seawater challenge test to measure relative stress levels in spring chinook salmon smolts|
|Author/Editor:||Gene M. Matthews, Donn L. Park, Steve Achord, T. E. Ruehle|
|Institution:||National Marine Fisheries Service, Northwest and Alaska Fisheries Science Center. Seattle, Washington|
A static seawater challenge test was successfully developed and used in 1982 to establish a profile of the relative stress levels of spring chinook salmon smolts Oncorhynchus tschawytscha within the smolt collection and transport system at Lower Granite Dam on the Snake River in Washington State. A major feature of the test was the development of water-to-water transfer techniques designed to assure minimal stress interference associated with sampling and transferring test fish from the freshwater sample sites to the seawater test chambers. We used the test to isolate stresses associated with movement of smolts through the system, with our handling and marking procedures, and with holding spring chinook salmon smolts in the presence of predominately hatchery steelhead Salmo gairdneri smolts.
The test results clearly indicated a pattern of increasing stress levels as smolts moved through the system. The bypass system, the fish and debris separator complex, and transport by truck were areas where stress levels increased. Dip netting smolts with a standard (netted) dip net was implicated as the major contributor to the overall stress increase associated with our handling and marking procedures. The stress level of spring chinook salmon smolts appeared to be influenced by the presence of predominately hatchery-reared steelhead smolts.
Procedures used in this test series provided reliable but somewhat variable results. Recommended changes for reducing this variability include reducing the test time and using a different method of replication.