Research Document 1997/109
The 1997 assessment of pollock (Pollachius virens) in NAFO Divisions 4VWX and Subdivision 5Zc
By J. Neilson and P. Perley
Abstract
Landings of pollock in the management unit 4VWX5Zc were 9,280 t in 1996, compared with a TAC of 10,000 t. Most gear sectors were unable to catch their allocations. Most fishermen report that pollock were abundant in 1996 and the first half of 1997, in some cases limiting fisheries for cod or haddock. However, some expressed concern that landings are becoming increasingly concentrated in the western portion of NAFO Div. 4X.
The stock status evaluation was based on an analytical assessment employing landings statistics, sampling for size and age composition of the commercial catch and trends in commercial fishery catch rate. The abundance index series was expanded to include more fishery components than in previous assessments. Initial VPA results indicate that if the TAC of 15,000 t is taken in 1997, the resulting fully recruited fishing mortality will be about 0.23. The beginning of year age 5+ biomass will increase from 71,338 t in 1997 to 85,639 t in 1998. The F0.1 catch in 1998 is 24,698 t. An alternative VPA attempted to adjust for apparent trends in catchability for younger ages in recent years by downweighting the corresponding age-specific abundance indices. In that scenario, the resulting fully recruited fishing mortality will be about 0.27. The beginning of year age 5+ biomass will increase slightly from 65,411 t in 1997 to 66,373 t in 1998. The F0.1 catch in 1998 is 20,212 t. Some of the more important sources of the uncertainty include the large management unit, and the schooling semi-pelagic nature of the resource which make traditional approaches to groundfish stock assessment difficult.
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