HEALTH AND CONDITION OF PACIFIC HERRING CLUPEA-PALLASI FROM PRINCE-WILLIAM-SOUND, ALASKA, 1994

This study determined baseline health and condition values of Pacific herring Clupea pallasi in 1994 in Prince William Sound (PWS), Alaska. In April 1994, 134 herring were collected from 3 spawning sites in PWS , including a sequential sampling from 1 site. For each herring, morph ometric characteristics, sex and presence of gross external and intern al lesions were documented, and samples were processed for aging, viro logical, bacteriological and histological analysis. The study did not reveal trends in herring health and condition in 1994 that could reaso nably be attributed to the 'Exxon Valdez' oil spill in 1989. No viruse s or pathogenic bacteria were detected, but herring worms, a coccidian parasite and a systemic and virulent fungal infection were found in t he herring. The degree of vacuolation in liver cells, previously thoug ht to indicate exposure of fish to oil, varied significantly with the stage of reproductive development of the herring. Similarly, the liver melanomacrophage index, also believed to be correlated with environme ntal toxicant exposures, varied significantly among sample locations a nd with collection date. In this study, significant differences in age distribution of spawning herring populations occur in close geographi c proximity and collection time intervals in PWS. Based on our results , the use of condition factor, disease and indices of liver function t o indicate pollutant exposure are likely to be invalid unless other fa ctors unrelated to pollutant exposure are taken into account, such as reproductive stage of the herring, spawning behavior and location, age of herring and collection date. Thus, we conclude that various hypoth eses advanced regarding impacts of the 'Exxon Valdez' oil spill as wel l as other cases of environmental contamination cannot be supported wi thout rigorous statistical evaluation of natural variations in indices of fish health and condition.