Research Document - 2016/063

Background and data inputs for models evaluated as part of the 2015 southern Gulf of St. Lawrence fall-spawning herring assessment framework review

By Hugues P. Benoît, Claude LeBlanc, Tobie Surette and Alain Mallet

Abstract

Herring in the southern Gulf of St. Lawrence (sGSL; NAFO 4T) are comprised of two stocks, one that spawns in the spring and the other in the fall. The March 2014 peer review meeting of the assessment of sGSL fall spawning herring identified issues with the indices of abundance from the gillnet fishery and with the assessment model. A framework review of the assessment approach was recommended to address the identified shortcomings and to review alternative model formulations. The framework review, which took place April 13 to 15, 2015, also considered two suites of assessment models; ones for the NAFO 4T area as a whole, as per past practice, and ones that treated the 4T stock as being comprised of three regional stocks (North, Middle and South regions). The regionally-disaggregated assessment models were considered in response to numerous past requests by commercial fall herring gillnet harvesters and fisheries managers from Fisheries and Oceans Canada. In this report we describe the sources of information, the data, and the indices considered for both the whole area and regionally-disaggregated assessment models. These include the traditional inputs to past assessment models for sGSL fall spawning herring, such as catches-at-age and catch-per-unit-effort indices, and new indices developed for the framework meeting, including indices based on index gillnet catch rates and catches in the multi-species bottom trawl survey of the sGSL.

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