Fisheries Research, 6 (1987) 5-16 5 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands Preliminary Report on the Physiological Status of Striped Bass in the Carquinez Strait Die-off CHRISTOPHER L. BROWN, GRAHAM YOUNG, RICHARD S. NISHIOKA and HOWARD A. BERN Department of Zoology and Cancer Research Laboratory, University of California, Berkeley, CA 94720 (U.S.A.) (Accepted for publication December 16, 1986) ABSTRACT Brown, C.L., Young, G., Nishioka, R.S. and Bern, H.A., 1987. Preliminary report on the physio- logical status of striped bass in the Carquinez Strait die-off. Fish. Res., 6: 5-16. We have conducted an analysis of tissue and blood samples from moribund striped bass (Mo- rone 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 mor- ibund samples with those of four relatively healthy controls, it became apparent that liver dys- function 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 ÷, Ca2+, and Cl ) and os- molality were at virtually identical levels in the two groups, suggesting that osmoregulatory mech- anisms 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. INTRODUCTION Striped bass (Morone saxatilis) were introduced into the San Francisco Bay-Delta system in the late 1800s and before the end of the century, a thriving fishery had been established. In recent years, this fishery has run into serious trouble. As in the Atlantic striped bass fishery, the size of the striped bass population has been gradually diminishing over many years. The adult striped bass population in the San Francisco Bay-Delta region has dropped to the lowest levels on record (Stevens et al., 1985) and it is likely that the already 0165-7836/87/$03.50 © 1987 Elsevier Science Publishers B.V.