Research Document - 2001/089

Status of Manila Clam (Venerupis philippinarum) Stocks in Area 7, British Columbia, with a Proposal for Active Management of a Data-limited Fishery

By G.E. Gillespie, T.C. Norgard, and F.E. Scurrah

Abstract

The Area 7 intertidal clam fishery has been active since 1992, resulting in production of over 600 t of Manila clams, Venerupis philippinarum. The fishery was managed using arbitrary total allowable catches (TACs) of 113.6 t (250,000 lb) for each of Manila, littleneck, Protothaca staminea, and butter, Saxidomus gigantea, clams until review in 1999, when the TAC was reduced to 68.2 t (150,000 lb) for Manilas and the other two species were removed from the commercial fishery. An assessment program was developed in 1999 that identified important beaches within each subarea that were heavily harvested and these beaches were surveyed in both 1999 and 2000.

Four of five subareas assessed exhibited declines in biomass of legal sized clams from 1999 to 2000, as did the overall aggregate biomass of all index beaches in Area 7. This paper examines the application of the Magnussen-Stefansson feedback gain model to the first two years of data collected. Two options are discussed - adjustment of the overall Area 7 TAC based on the aggregate results, and establishment of harvest thresholds for individual subareas, which would allow opportunity to harvest the remainder of the TAC from underutilized subareas.

The paper recommends that managers consider adopting the second option (subarea thresholds), with a review of the appropriateness of index beaches currently assessed, establishment of index beaches in subareas not currently assessed, and that managers and harvesters acknowledge that continued reductions in subarea thresholds will require re-assessment of the overall Area 7 TAC.

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