Research Document - 2014/110

Framework assessment for SFA 29 West scallop fishery

By S.J. Smith, L.E. Nasmith, A. Glass, B. Hubley, and J.A. Sameoto

Abstract

The sea scallop, Placopecten magellanicus, is a sedentary, filter feeding bivalve; as a broadcast spawner, it tends to aggregate in densely populated beds. In 2000, an exploratory survey of Scallop Fishing Area (SFA) 29 (west of 65° 30) (West) revealed the commercial potential of the area, with catch rates significantly higher than surrounding areas. The sea scallop fishery in SFA 29 West started in 2001 with a 400 t total allowable catch, fished by the Full Bay fleet. In 2002, some East of Baccaro scallop licence holders joined the fishery. Since then, the fishery has occurred every year.

For sea scallop, bottom type has been identified as a determining factor for distribution, a relationship that was demonstrated in SFA 29 West through multibeam acoustic mapping undertaken in 2002. Fisheries and Oceans Canada’s Science Branch has conducted a survey in SFA 29 West annually since 2001. Survey results were used in 2001 to subdivide the area into subareas A–E. Over time, the survey design has changed. In 2005, the results from the multibeam mapping project were used for the first time to re-stratify the survey. The survey design changed again in 2007, as a result of new information and a greater understanding of the bottom types and how those related to scallop habitat. Assessment of stock status has changed over time. Initial assessments were based on commercial catch rates, removal densities, and recruitment signals in the survey. Eventually, models were tested on the survey data. Trends in catch rate were examined using a depletion model, and exploitation estimates were derived from both survey and commercial data.

Application of a new scallop habitat suitability model demonstrating that higher fishing intensities were associated with the higher suitability areas, which in turn exhibited the higher densities based on survey estimates. A new assessment model that incorporates these habitat suitability features provided a clearer understanding of the population dynamics for scallops in this area and offers a model-based approach for assessing stock status. Harvest control rules and reference points have not been set for this fishery. Methods for determining the upper stock reference and lower reference point are proposed based on methods accepted for other inshore scallop fishing areas, but modified to take into account scallop habitat suitability in SFA 29 West.

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