Research Document - 2011/123
Update to the assessment framework for the Pink and Spiny scallop (Chlamys rubida and C. hastata) dive fishery in waters off the west coast of Canada
By A.M. Surry, K.H. Fong, D.T. Rutherford, and H. Nguyen
Abstract
The framework for pink and spiny scallop assessment has been updated. Scallop biomass surveys are now conducted using a remote operated vehicle (ROV) equipped with a high resolution digital still camera in place of a video drop camera. The new methodology is documented, and the results of recent surveys using the new methodology are presented. Analytical procedures for biomass estimation have been revised, resulting in updates to previously published biomass estimates. Revised estimates are lower than those previously published, with implications for existing total allowable catch. Updated estimates of natural mortality and scallop growth rates are provided, based on revised and new data since the last assessment.
Pink and spiny scallop dive fisheries remain data limited, with no consistent time series of assessment surveys or biological data. Despite new estimates of mortality and biomass, the currently used 4% harvest rate remains consistent with best available estimates of MSY. The current assessment framework, if implemented on an annual basis, will facilitate the development of provisional reference points compliant with the DFO Precautionary Approach which can then be evaluated to test for robustness to various stock size scenarios.
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