Incidental catch and mortality of striped bass, Morone saxatilis, in the commercial bay shrimp trawl fishery in the San Francisco estuarine complex

Abstract

The commercial bay shrimp fishery was monitored from April 1989 to September 1990 in south San Francisco Bay, and from September 1989 to September 1990 in San Pablo Bay and Carquinez Strait, to estimate incidental catch and mortality of young-of-the-year (YOY), juvenile and adult striped bass. Of the total estimated by-catch of 44,000 to 52,000 YOY bass, 98.5% were taken in San Pablo Bay. Of the total estimated bycatch of 3160 to 3570 older bass, approximately 75% were taken in San Pablo Bay. Estimated mortality from shrimp tows was 22% for YOY and 2% for older bass. More than 99% of mortalities occurred in San Pablo Bay. July and August 1990, when YOYs were smallest and most vulnerable to trawling, was considered a critical period. A reduction in tow duration as well as effort in San Pablo Bay during this period may be effective in significantly reducing total mortality. (42pp.