Research Document - 2002/122

Hexactinellid Sponge Reefs: Areas of Interest as Marine Protected Areas in the North and Central Coast Areas

By G.S. Jamieson, L. Chew

Abstract

The four known sponge reef complexes in the Central and North Coasts of British Columbia (BC) are thought to be unique in the world and are presently protected in BC by voluntary shrimp trawl fishery closures, and as of July, 2002, regulatory groundfish trawl closures. There is evidence of past damage to the reefs by fishing activities, notably trawling. Fishing on them has been reduced since 1999, when voluntary avoidance by groundfish fishers was requested, but avoidance of the reefs has not been complete and recent visual surveys show continuing damage to them. The dynamics of reef-building and the ecosystem that the reefs support are unknown, with the only available biological data from limited submersible visual observations (not considered here) and fishery dependent observations and recordings. We have analysed the latter, and document fishing activity on the reefs and within the voluntary shrimp trawling closure zones established around them. The four reef complexes differ in the relative abundance's of targeted species around them, with Reef A (the most northern one) having proportionately larger flatfish populations. There has been little fishing activity around Reef B, and hence little biological data are available. The area around Reef D, the most southerly reef, has been the most intensively fished, with rockfish the most targeted species. For the areas analysed, highest fishing yields came not from the reefs themselves, but from the areas immediately adjacent to them. We did not assess how these landings compared to areas further away from the reefs, i.e. totally outside the voluntary fishery closures. Within the voluntary closure areas and excluding the reefs, landings for all four reefs combined averaged about 1320 t per year, comprised of about 80 % targeted individual vessel quota (IVQ) species and 15 % targeted non-IVQ species. Recommendations are that for effective reef protection, an additional 9 km buffer zone around the recently introduced groundfish trawl closures should be established; the existing closure boundaries are often much closer to the main reef complex borders. Fishing activity in this potential buffer zone should be closely monitored to ensure that gear is not straying on to the reefs. Research should also be initiated to determine the ecosystem importance and associated population dynamics relating to the sponge reefs. Marine Protected Area designations are preferable to fishery regulation for long-term protection and conservation of unique living resources such as these sponge reef complexes.

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