Preliminary report on the physiological status of striped bass in the carquinez strait die-off

Abstract

We have conducted an analysis of tissue and blood samples from moribund striped bass ( Morone saxatilis) collected during the course of the summer 1985 die-off in the Carquinez Strait. Despite the small number of specimens that were available for this study, the differences between moribund fish and controls were striking and were consistent enough to establish the basis for this preliminary report. After comparing the results of serum and tissue analyses from three moribund samples with those of four relatively healthy controls, it became apparent that liver dysfunction is an important aspect of the pathology of fish in this die-off. This conclusion was based on data of several sorts: histological indications of hepatic lesions and inflammation, hormone imbalances and accumulations of uric acid, bilirubin and alkaline phosphatase in the plasma. Abnormal variation in plasma glucose levels, at both high and low extremes, may reflect severe disruption of carbohydrate metabolism in the moribund fish. The cause or causes of this liver damage have not yet been identified. Plasma proteins, ions (Na +, K +, Ca 2+, and Cl −1) and osmolality were at virtually identical levels in the two groups, suggesting that osmoregulatory mechanisms still permitted responses to the salinity changes encountered by these fish in and around the Carquinez Strait. Although salinity changes may contribute to the problems of fish migrating through this region, simple osmoregulatory failure is not indicated.