Publikationsdatum:
2021-06-28
Beschreibung:
Hydroacoustic monitoring and sampling of San Francisco Bayherring stocks were conducted from December 1981 to March 1982. Major schools usually were located in central San Francisco Bay between 30 and 90 ft deep prior to spawning. The largest school observed had an estimated volume of 1.5 billion ft3. There was some consistency between the maximum calculated volume of a school prior to spawning and the subsequent spawning biomass estimate, based on egg counts, by Marine Resources Region personnel.Herring samples were obtained with variable mesh gill nets, a midwater trawl and from commercial purse seine and lampara vessels. Eight discrete spawns were sampled for size and age composition, although data from December and early January samples were biased due to selectivity of the gill net mesh array. In general, a trend was observed of decreasing mean size and age as the season progressed.Ages of herring ranged from 2 to 9 years. From 87 to 94% of the fish sampled with a midwater trawl, 1.5- to 2.5-in mesh array gill net, and from commercial roundhaul samples consisted of 2-, 3-, and 4-year-olds.Calculation of desired sample size for future work indicatesthat 17 fish per 10-mm size interval need to be aged to determine age composition of each spawning population. (51pp.)
Schlagwort(e):
Management
;
Fisheries
;
Pacific herring
;
Clupea harengus pallasii
Repository-Name:
AquaDocs
Materialart:
monograph
Format:
application/pdf
Format:
application/pdf
