Research Document - 1999/090

Status of the coastal Pacific hake/whiting stock in U.S. and Canada in 1998

By M.W. Dorn, M.W. Saunders, C.D. Wilson, M.A. Guttormsen, K. Cooke, R. Kieser and M.E. Wilkins

Abstract

The coastal population of Pacific hake (Merluccius productus, also called Pacific whiting) was assessed using an age-structured assessment model. The U.S. and Canadian fisheries were treated as distinct fisheries in which selectivity changed over time. Catch and age data from these fisheries were supplemented with survey data from the Alaska Fisheries Science Center (AFSC) triennial acoustic survey, the AFSC triennial shelf trawl survey, the Department of Fisheries and Oceans acoustic survey, and the Southwest Fisheries Science Center midwater trawl recruit survey. New data in this assessment included updated catch at age, recruitment indices from the SWFSC recruit survey, and results from the triennial acoustic and shelf trawl surveys conducted in summer of 1998.

The hake stock is at a moderate level of abundance. Stock biomass increased to a historical high of 5.7 million t in 1987 due to exceptionally large 1980 and 1984 year classes, then declined as these year classes passed through the population and were replaced by more moderate year classes. Stock size has been stable over the past four years at 1.7-1.9 million t. The mature female biomass in 1998 is estimated to be 38% of an unfished stock. The exploitation rate was below 10% prior to 1993, then increased to 17% during 1994-98. Total U.S. and Canadian catches have exceeded the ABC by an average of 12% since 1993 due to disagreement on the allocation between U.S. and Canadian fisheries. The recommended yields for 1999 range from 266 to 329 thousand t, coastwide.

Major sources of uncertainty in the assessment are the poor fit of the acoustic survey to the overall time series of abundance and the significant changes in juvenile and adult distribution that have occurred since 1994. The presence of juveniles from Oregon to British Columbia suggest that spawning and juvenile settlement has spread northwards. It is not yet clear whether these changes will be a benefit or a detriment to stock productivity and stability. For instance hake eggs and larvae may be subject to unfavorable transport, and juveniles to increased predation from cannibalism and to increased vulnerability to fishing mortality.

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