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Research Document - 2012/110

Identification of species and habitats that support commercial, recreational or aboriginal fisheries in Canada

By Kenchington, E., Duplisea, D.E., Curtis, J.M.R., Rice, J.C., Bundy, A., Koen-Alonso, M., and Doka, S.E.

Abstract

The changes to Article 35 of the Fisheries Act include a new phrase that contains undefined terminology, i.e., “No person shall carry on any work, undertaking or activity [w/u/a] that results in serious harm to fish that are part of a commercial, recreational or Aboriginal fishery, or to fish that support such a fishery”. An ecological interpretation of the support functions of an ecosystem are those functions which are essential for sustaining the production of commercial, recreational or Aboriginal (CRA) fishery species within the bounds of natural variability (taking into account managed changes to many populations) over short- and long-term temporal scales. Theoretical and empirical approaches can be used to identify fish that support CRA fisheries by considering the ecological functions that allow CRA fish species to carry out their life cycles. We discuss support functions in terms of direct and indirect support roles. Key prey species and biogenic habitats are considered to be direct support functions while a number of species may indirectly affect the ongoing productivity of the CRA fish species. These include keystone species, wasp-waist species, highly-connected species, apex predators and environment-modifying species all of which have important roles in maintaining ecosystem structure and functioning and therefore indirectly supporting CRA fish species. Changes to the structure of “supporting fish” populations (e.g., in terms of abundance, size structure, spatial structure, genetic structure, distribution) brought about through w/u/a must have the potential to alter the capacity for support species to fulfill their corresponding supporting function(s) in a manner which affects the ongoing productivity of the CRA fish species. Support functions and “supporting fish” populations which affect the productivity of CRA fishery species may occur in areas outside of the distribution of the CRA fishery species and be connected to the CRA fishery species through such mechanisms as food webs, source-sink dynamics or migratory behaviour. When identifying the range of key functional roles played by species supporting CRA fisheries, we describe common characteristics of species fulfilling each role and provide a few examples of such species. We also discuss vulnerability to perturbation and the most common types of human-induced perturbations that will affect support species. For each function, we provide guidance on how to make defensible and consistent decisions on which instances meet our definitions for "support".

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