Pacific herring, Clupea harengus pallasi, studies in San Francisco and Tomales Bays, April 1988 to March 1989

Herring schools were surveyed hydroacoustically and sampled in San Francisco Bay from early November 1988 through mid-March 1989. Seven large schools (> 1000 tons) and three smaller ones were detected. The total acoustic biomass estimate, using a combination of echo integration and visual integration methods, was 65,080 tons. An independent spawn escapement-plus-catch estimate of 66,380 was remarkably similar. Seventy-five samples, containing 12,784 herring, were collected with variable-mesh gill nets, a midwater trawl, or obtained from the roundhaul fishery. Mean body length decreased by almost 14 mm from November to March. Sex ratios favored males in November and December, while females were dominant in February and March. The 1983 through 1987 year classes (6- through 2-yr-old herring) contributed approximately 99% by weight and number to the total 1988-89 spawning biomass in San Francisco Bay. However, the 1987 year class may be relatively weak, contributing the smallest percentage of 2-yr-olds since at least the 1983-84 season. The 1988 year class appears to be somewhat stronger than the 1987 year class was as young-of-the-year herring. A final assessment of year class strength for both the 1987 and 1988 year classes cannot be made until they return as 3-yr-old herring and recruitment into the fishery is complete. (Document has 71 pages.)