Biomass estimates of Pacific herring Clupea harengus pallasi, in California from the 1985-86 spawning-ground surveys

Spratt, Jerome D. (1986) Biomass estimates of Pacific herring Clupea harengus pallasi, in California from the 1985-86 spawning-ground surveys. Monterey, CA, California Department of Fish and Game, Marine Resources Region, (Marine Resources Administrative Report, 86-3)

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Abstract

The 1985-86 spawning biomass estimate of Pacific herring, Clupea harengus pallasi, in San Francisco Bay is 49,000 tons. The relatively small population increases during 1984 and 1985 indicate that the population is rebuilding slowly from the 1983-84 season when only 40,000 tons of herring spawned. Spawning-ground surveys in Tomales Bay were inconclusive. Herring normally spawn in eelgrass, Zostera marina, beds; this season herring spawned unexpectedly in deeper water, disrupting our sampling plan. A first attempt at population modeling with cohort analysis indicates that about 6000 tons of herring spawned this season. In San Francisco Bay, 74% of the herring spawned in January and only one small spawn occurred after February 7th. Late season spawning was probably affected by severe winter storms that hit central California during February. In San Francisco Bay, during the past three seasons, over 60% of the spawning escapement occurred south of Treasure Island. This season spawning escapement was split evenly between the north and south part of the bay, In San Francisco Bay, there are four major spawning areas, accounting for 78% of the average spawning escapement; they are Richardson Bay, the San Francisco waterfront, Tiburon-Belvedere complex, and Sausalito. There was a major spawn at Richmond for the first time since 1982. (31pp.)

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