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Forecast of the Pacific herring biomass in Prince William Sound, Alaska, 1993. Regional Information Report 5J94-04. Alaska Department of Fish and Game, Juneau, Alaska.

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An age-structured assessment (ASA) model is used to forecast the abundance of herring expected to return to spawn in Prince William Sound in 1993. The ASA model develops 1973-92 biomass estimates by smoothing differences in abundance trends suggested by spawn deposition surveys, aerial milt surveys, and the time series of purse seine, gillnet, and spawning age composition samples. The abundance trends in the 1984, and 1988-92 spawn deposition surveys are very different from abundance trends in the other indices. In addition to estimating abundance, the ASA model also estimates natural survival, maturity, and vulnerability to fishing gear. The 1993 spawning biomass is estimated to be 121,684 tonnes. At the 20% exploitation rate under the current harvest policy, the allowable harvest for the 1993 management year is 26,827 tons of herring. Following the allocations specified in the management plan, the fall 1993 food and bait herring fishery is allocated 4,373 tons of herring, the 1993 wild spawn-on-kelp fishery is allocated 2,146 tons of herring (equivalent to 268 tons of spawn-on-kelp product), the 1993 pound spawn-on-kelp fishery is allocated 3,809 tons of herring (equivalent to 305 tons of spawn- on-kelp product), the 1993 purse seine sac roe fishery is allocated 15,586 tons, and the 1993 gillnet sac roe fishery is allocated 912 tons.
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... Herring younger than 3 years of age were collected intermittently in PWS and the sex of fish under 3 years old cannot be determined reliably due to the lack of gonad development. Though herring may live beyond 11 years, we excluded older age classes due to the uncertainty of assigning ages to fish beyond this age and because that is the maximum age used in herring assessment models (Funk, 1994). Herring assigned an age of greater than 11 year represented only 0.46 percent of all fish sampled. ...
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