Klamath River Salmonid Emigrant Trapping Catch, Mortality, and External Health Indicators - 2004

Several field investigations conducted in spring and early summer of 2004 resulted in concurrent operation of young-of-year and age 1+ salmonid emigrant traps at six mainstem and three Klamath River tributary sites. Mortality sharply increased starting April 29 at the Bogus, I-5, and Kinsman frame trap sites. By early May, mortality approached 50% for wild young-of-year Chinook salmon captured at Kinsman, Happy Camp, and Persido Bar. From June 2 to June 18, mortality observed in daily catches of Chinook salmon at Kinsman ranged between 51% and 88%. Overall mortality of young-of-year Chinook salmon observed at lower mainstem trap sites (Persido Bar and Big Bar, 6% each) were paltry compared with those observed at Kinsman and Happy Camp (34% and 25%, respectively). In mid-May, a systematic external examination was incorporated into fish sampling as more than half of the live fish captured at Kinsman and Happy Camp exhibited external signs of disease and/or stress. High and low incidence of pale gills and other external abnormalities coincided with sites and time periods having high and low mortality. Based on external examinations, Kinsman was a “hotspot” of symptomatic young-of-year Chinook salmon (at 82%), declining downstream to Happy Camp (56%), Persido Bar (40%), and Big Bar (14%). Common external abnormalities noted in examinations of Chinook salmon included pale gills (pink or grey in color rather than a healthy red appearance), distended abdomen, gill rot, and lamprey wounds. Abnormality rates were highest at Kinsman and Happy Camp for all salmon species and age classes. Mortality was low at tributary traps operated at Horse Creek, Seiad Creek, and Elk Creek and captured fish were healthy in appearance. This agrees well with previous fish health investigations and two studies conducted on the Klamath River in 2004.