Research Document - 2012/027
Biomass Reference Points for Eastern Component Pollock (4VW+4Xmn)
By H.H. Stone
Abstract
A conservation Limit Reference Point (LRP) and Upper Stock Reference (USR) were calculated for Eastern Component (4VW+4Xmn) pollock based on a proxy for Bmsy using data from the Department of Fisheries and Oceans summer research vessel survey time series (1970-2011). For the purpose of calculating reference points, it was assumed that productivity of this resource has not changed appreciably over the past four decades. A 10-year period from 1984-1993 was arbitrarily chosen to reflect a sustained period of high productivity. The bias adjusted geometric mean total biomass for this period (a proxy for Bmsy) was 50,200 t with a 95% Confidence Interval (CI) ranging from 36,70.t to 72,600 t. The LRP (40% Bmsy proxy) was calculated as 20,100 t (95% CI: 14,674 to 29,043 t) and the USR (80% Bmsy proxy) as 40,100 t (95% CI: 29,347 to 58,086 t). Total survey biomass has only been above the LRP five times since 1994, four of which have occurred since 2006, suggesting that the status of this resource is improving.
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