Biomass estimates of Pacific herring, Clupea harengus pallasi, in California from the 1988-89 spawning-ground surveys
1989
Spratt, Jerome D.
The 1988-89 spawning biomass estimate of Pacific herring,Clupea harengus pallasi, in San Francisco Bay is 66,000 tons, a 3,000-ton decrease from the 1987-88 biomass estimate of 69,000 tons. The San Francisco Bay herring population which had been increasing since 1984, remains above the 10-year population mean of 60,000 tons.In Tomales Bay the 1988-89 herring spawning biomass wasestimated at 380 tons. This is the lowest spawning biomassrecorded and follows a poor 1987-88 season, when 2,000 tonsof herring spawned. It is believed that spawning herring arenot returning to Tomales Bay. The current drought conditionin California may be the cause of the change in spawningbehavior.January was the month of peak spawning activity in SanFrancisco Bay, with 40,000 tons of herring spawning duringthe month. In Tomales Bay, nearly all herring also spawnedin January.In San Francisco Bay, 50% of all spawning occurred along theSan Francisco waterfront, 25% occurred in the Oakland-Alameda area, and 25% occurred in the Belvedere, Tiburon, and Angel Island areas. No spawning was found near Richmond, Berkeley, Candlestick Point, Sierra Point, or Oyster Point.During the past seven seasons in San Francisco Bay, over 70%of all spawning escapement has been in the southern part ofthe bay. For the nine seasons prior to that, 94% of allspawning escapement was in the northern part of the bay.Estero Americano was included in spawning-ground surveys this season. Only trace amounts (<1 ton) of herring spawned in the estero. (35pp.)
Показать больше [+] Меньше [-]Ключевые слова АГРОВОК
Библиографическая информация
Эту запись предоставил California Department of Fish and Game