Research Document - 2006/061

Reducing Bycatch of Corals and Sponges in British Columbia's Groundfish Trawl Fishery through Trawl Fishery Closures

By Ardron, J.A., and G.S. Jamieson

Abstract

From 1996 to 2002, about 295 tonnes of cold–water corals and sponges were observed as bycatch in British Columbia’s (BC) groundfish bottom trawl fishery. Many damaged coral and sponge fragments likely remained on the sea floor, suggesting that gear impact on species was more extensive than indicated by bycatch quantity. Recovery from trawl damage is species dependent, and in some cases may take several decades to centuries. While cold-water structural habitat remains poorly studied in BC, it is generally accepted that its destruction has a negative impact on benthic ecosystem dynamics and fished stocks and should be minimised.

Year-round bottom trawling closures have been established in Australia, the European Union, New Zealand, Norway, Iceland, Scotland, the USA, and BC, all with the goal of protecting corals and/or sponges. This paper explores an efficient spatial establishment of closures in BC to significantly reduce bycatch and destruction of habitat-forming corals and sponges. Density analyses of bycatch locations indicates 12 areas of high coral / sponge species concentration, representing about 7.5% of BC’s continental shelf and slope. Had these areas been closed, this would have prevented 97% of all coral/sponge bycatch by weight. The regional diversity of BC’s deep water coral and sponge species appears to be represented in these twelve areas, though site-specific verification is required. Economically, these 12 areas are of average economic value to the fishery. However, because the fishery is an individual quota fishery, and because of the mobility of many groundfish species, it is difficult to estimate the potential economic cost of establishing these closures. Closing an area does not necessarily mean that mobile individuals of targeted species would not be caught elsewhere, only that they will not be caught in the closed area. Overall, the proposed potential closure areas contain about one quarter of historic (1996-2002) trawl sets.

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