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Hexactinellid Sponge Reefs: Areas of Interest As Marine Protected Areas

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Hexactinellid Sponge Reefs: Areas of Interest As Marine Protected Areas C S A S S C C S Canadian Science Advisory Secretariat Secrétariat canadien de consultation scientifique Research Document 2002/122 Document de recherche 2002/122 Not to be cited without Ne pas citer sans permission of the authors * autorisation des auteurs * Hexactinellid Sponge Reefs: Areas of Récifs d’éponges hexactinellides : zones Interest as Marine Protected Areas in présentant un intérêt comme zones the North and Central Coast Areas marines protégées sur la côte Nord et la côte Centrale G.S. Jamieson1 and L. Chew2 1Fisheries and Oceans Canada Pacific Biological Station, Nanaimo, BC V9T 6N7 2 Fisheries and Oceans Canada Institute of Ocean Sciences, Sidney, BC V8l 4B2 * This series documents the scientific basis for the * La présente série documente les bases scientifiques evaluation of fisheries resources in Canada. As such, des évaluations des ressources halieutiques du Canada. it addresses the issues of the day in the time frames Elle traite des problèmes courants selon les échéanciers required and the documents it contains are not dictés. Les documents qu’elle contient ne doivent pas intended as definitive statements on the subjects être considérés comme des énoncés définitifs sur les addressed but rather as progress reports on ongoing sujets traités, mais plutôt comme des rapports d’étape investigations. sur les études en cours. Research documents are produced in the official Les documents de recherche sont publiés dans la language in which they are provided to the langue officielle utilisée dans le manuscrit envoyé au Secretariat. Secrétariat. This document is available on the Internet at: Ce document est disponible sur l’Internet à: http://www.dfo-mpo.gc.ca/csas/ ISSN 1480-4883 © Her Majesty the Queen in Right of Canada, 2002 © Sa majesté la Reine, Chef du Canada, 2002 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 boundries 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. 2 RÉSUMÉ On considère les quatre complexes récifaires identifiés sur la côte Centrale et la côte Nord de la Colombie-Britannique comme uniques au monde. Il sont actuellement protégés de la pêche des crevettes au chalut par le biais de fermetures volontaires et de la pêche du poisson de fond au chalut, par le biais de fermetures réglementaires imposées depuis juillet 2002. Les récifs portent des signes de dommages passés imputables aux activités de pêche, notamment le chalutage. La pêche dans les eaux où gisent ces récifs est moins intense depuis 1999, lorsque l’on a demandé aux pêcheurs de poisson de fond de les éviter, mais ils ne le font pas tous car de récents relevés visuels ont révélé de nouveaux dommages. On ne sait rien de la dynamique de la construction de ces récifs et de l’écosystème qu’ils constituent, les seules données biologiques disponibles étant des observations visuelles limitées faites de véhicules sous-marins, ainsi que des données et des observations issues de la pêche. Nous analysons ces dernières et documentons les activités de pêche sur les récifs et dans les zones d’interdiction de chalutage des crevettes établies autour de ceux-ci. Les quatre complexes récifaires diffèrent par l’abondance relative des espèces ciblées qu’ils abritent. Le récif A (le plus au nord) abrite des populations proportionnellement plus abondantes de poissons plats. Comme peu d’activités de pêche ont été pratiquées au voisinage du récif B, peu de données biologiques sont disponibles. La région dans le périmètre du récif D, le plus au sud, est la plus intensément pêchée, le sébaste y étant l’espèce davantage ciblée. Pour les zones analysées, les meilleurs rendements de la pêche ont été obtenus dans les zones immédiatement adjacentes des récifs et non sur les récifs mêmes. Nous n’avons pas évalué comment ces prises se comparent à celles obtenues plus loin des récifs, c’est-à-dire complètement à l’extérieur des zones d’interdiction de chalutage. Dans ces dernières et à l’exclusion des récifs principaux, les prises sur les quatre complexes récifaires combinés s’élevaient en moyenne à quelque 1 320 t par année et se composaient d’espèces ciblées assujetties à un quota individuel de bateau (QIB) à 80 % et d’espèces ciblées non assujetties à un QIB à 15 %. Afin que les récifs soient adéquatement protégés, nous recommandons qu’une autre zone tampon de 9 km de large soit établie sur le périmètre des zones d’interdiction de chalutage du poisson de fond récemment créées car les limites actuelles de ces dernières sont souvent trop près du récif principal. La pêche dans cette zone tampon éventuelle devrait être étroitement surveillée afin de veiller à ce que les engins ne se retrouvent pas sur les récifs. En outre, des recherches devraient être entreprises afin d’établir l’importance de ces écosystèmes et la dynamique des populations qu’ils abritent. Aux fins de leur protection à long terme et de la conservation des ressources marines vivantes qui y vivent, les récifs devraient être désignés des zones marines protégées plutôt qu’être visés par un règlement de pêche. 3 1 Introduction............................................................................................................................. 5 1.1 Objectives and Methods...................................................................................................... 7 2 North and Central Coasts General Description....................................................................... 8 2.1 Physiography....................................................................................................................... 9 2.2 Oceanography ..................................................................................................................... 9 2.3 Potential offshore oil and gas exploration activity............................................................ 10 3 Description of Sponge Reefs ................................................................................................ 10 3.1 Unique conditions for sponge reef formation ................................................................... 11 3.2 Sponge biology ................................................................................................................. 12 3.3 Biotic associations around sponge reefs ........................................................................... 15 3.4 Documented impacts of trawling on sponge reefs........................................................... 15 4 Fishery activity and species catches in the vicinities of sponge reefs .................................. 16 4.1 Groundfish trawl ............................................................................................................... 16 4.1.1 Groundfish trawl activity in the vicinities of the sponge reefs ................................. 17 4.1.2 Groundfish trawl species lists ................................................................................... 18 4.1.3 Groundfish trawl species catch data ......................................................................... 18 4.2 Groundfish hook and line.................................................................................................
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