Science Response 2018/042

Indirect Effects of Bottom-Contact Fishing Activities (By Trap Gear) on Sponge Reefs in the Strait of Georgia and Howe Sound

Context

Glass sponge reefs have intrinsic, ecological, and economic value. They provide a link between benthic and pelagic environments, play an important role in carbon and nitrogen processing, and act as a silica sink. Nine glass sponge reef complexes have been mapped by the Canadian Hydrographic Service and Natural Resources Canada in the Strait of Georgia and Howe Sound. The protection of sponge reefs is a key component to a number of international commitments made by Canada through the United Nations Convention on Biological Diversity and the United Nations Food and Agriculture Organization (FAO) Code of Conduct for Responsible Fisheries.

In 2015, DFO protected these nine complexes via formal bottom-contact fishing closures extending 150 m beyond simplified polygons delineating the reef footprints. There is evidence that sediment deposition (following re-suspension from human activities) impacts sponge reef communities, including glass sponges (Leys 2013; Conway et al. 2001; Whitney et al. 2005; Conway et al. 2007; Yahel et al. 2007; Tompkins-MacDonald and Leys 2008). DFO Science has been asked to determine the risk of exposure to each of the presently protected nine sponge reef complexes in the Strait of Georgia and Howe Sound to the remobilized sediment from bottom-contact fishing activities (such as prawn and crab by trap) following the methods used to assess fisheries-induced re-suspended sediment impacts on Hecate Strait glass sponge reefs from bottom-contact trawl fishing (Boutillier et al. 2013).

This Science Response Report results from the Science Response Process March 2018 on the Review of the Indirect effects of bottom-contact fishing activities (by trap gear) on sponge reefs in the Strait of Georgia and Howe Sound.

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