Spatial identification of closures to reduce the by-catch of corals and sponges in the groundfish trawl fishery, British Columbia, Canada

摘要

From 1996 to 2004, approximately 322 t of cold-water corals and sponges were observed as by-catch in British Columbia's (BC) groundfish bottom trawl fishery. We explore an efficient spatial establishment of closures in BC to significantly reduce by-catch and destruction of habitat-forming corals and sponges. Density analyses of by-catch locations indicate twelve areas of high coral/sponge species concentration, representing about 7.5% of BC's continental shelf and slope, but about 97% of all coral/ sponge by-catch by weight. These twelve areas represent the diversity of corals and sponges identified in the observer data, though site-specific verification is required due to low confidence in species identification in the dataset. These twelve areas are of average economic value to the fishery, however, because the fishery is an individual quota fishery, and due to 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. Overall, the proposed potential closure areas contain about one quarter of historic (1996-2002) trawl sets.