Effects of bacterial kidney disease on saltwater preference of juvenile spring chinook salmon, Oncorhynchus tshawytscha

Abstract

In March 1998, we conducted a laboratory experiment to assess the effect of bacterial kidney disease (BKD) on the saltwater preference of juvenile spring chinook salmon, Oncorhynchus tshawytscha . Experiments were done in 757-l tanks in which a vertical salinity gradient was established. Fish with external signs of BKD were designated as sick and those without external signs of disease served as controls. Two hours after saltwater introduction, 85±17.6% (S.D.) of controls held in salt water, compared to 31±20.0% of sick fish. There was a significant negative relationship between mean infection level (quantified by enzyme-linked immunosorbent assay, ELISA) and saltwater preference. Such behavior may increase the risk of avian predation for chinook salmon outmigrating through the estuary .