Research Document - 2012/060

Multi-species interactions: Effects of multi-species harvesting on single species harvest rates in NAFO Division 4X

By A. Bundy, J.N. Araújo, and S. Guénette

Abstract

Canada was one of the first nations to adopt an “ecosystem approach” to oceans management, and to this end, has largely focussed on an objectives and ecosystem indicator approach. Ecosystem modelling is a complimentary approach which, until recently, has received little direct support within Fisheries and Oceans Canada. There are many advantages to using ecosystem modelling for an Ecosystem Approach to Management, and the range of established modelling approaches vary from extended single species models to multi-species minimum realistic models, food web models to whole ecosystem models with age and spatial structure. Theme III of the Maritimes Region Gulf of Maine Research Initiative explored the “Quantification of the impact of ecosystem interactions on harvest rates and dynamics of commercially targeted (and non-targeted) species” using a range of ecosystem models. Prior to this work, no multi-species or ecosystem models had been developed for Northwest Atlantic Fisheries Organization Divisions 4X/5Y. This research document presents the results of three ecosystem models of different structure, complexity and levels of aggregation, and explores how they may be used for science advice in support of fisheries management. It provides preliminary estimates of (i) single species fisheries reference points; (ii) aggregate species reference points; (iii) multi-species reference points; (iv) aggregate system reference points; and (v) the level of predation and fishing mortality on key species. These results, and others, indicate that it would be foolish to ignore the broader ecosystem in the science advice provided to fisheries management, particularly in the face of increased environmental change.

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