Publication Date:
2021-06-28
Description:
Herring schools were surveyed hydroacoustically and sampled in San Francisco Bay from late October 1987 to March 1988. Nine large schools (greater than 1000 tons) and four smaller ones were detected. Total acoustic biomass estimate, using a combination of echo integration and "visual integration" methods, was 71,110 tons. Improved acoustic calibration parameters resulted in this estimate being close to the spawn escapement-plus-catch estimate of 68,881 tons. However, the two biomass survey methods ere complementary and, when used together, provide a more accurate estimate of the spawning population than either method alone.Eighty-two samples, containing a total of 16,316 herring, were collected with variable-mesh gill net, midwater trawl, or obtained from the roundhaul fishery. Mean body length decreased by more then 20 mm from the beginning to the end of the spawning season. Sex ratios favored males in November and December, while females were more abundant in February and March.The 1982 through 1986 year classes (6- through 2-yr olds) contributed approximately 98% by weight and number to the total 1987-88 spawning biomass in San Francisco Bay. Herring year classes aged 7 and older each comprised no more then 1% of any school.Above average recruitment occurred for the 1986 year class.Recruitment may not be complete for some year classes until age 3 yr. This was particularly evident for the 1985 year clear. (72pp.)
Keywords:
Management
;
Fisheries
;
Biology
;
Pacific herring
;
Clupea harengus pallasi
Repository Name:
AquaDocs
Type:
monograph
Format:
application/pdf
Format:
application/pdf
