Research Document - 2007/036
Ocean Quahog (Arctica islandica) Survey and Yield Estimates for Sable Bank
By Roddick, D., R. Kilada, and K. Mombourquette
Abstract
A survey for ocean quahogs (Arctica islandica) was conducted on Sable Bank, Nova Scotia in 2003. 293 stations were sampled with a hydraulic clam dredge. A selectivity study of the survey dredge was conducted, and samples for morphometrics, ageing, and age and size at sexual maturity were collected. Survey biomass estimate was 1,262,628 t, and a preliminary dredge efficiency estimate (91.8% efficiency) produced an efficiency corrected biomass estimate of 1,373,913 t. Natural mortality was estimated as 0.03. Size of sexual maturity (30.96 mm) was below the size at 50% selectivity (69.6 mm). Sustainable yield estimates were produced for a range of models from MCY to F0.1. Constant mortality models such as F0.1 produced much higher yield estimates (54,957 t) than constant yield models such as MCY (13,602) as the biomass is presently in a virgin state. With such a long lived species (oldest aged from survey was 210 years old) and little knowledge of the temporal dynamics of the life history parameters or effects of the fishery on the benthos, it is advised to stay at a conservative end of the choices of yield models.
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