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Publication year : 0
Thematic : Fisheries
Language : English
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Due to the increasing pressure on marine resources, no-take marine reserves (referred to as ‘marine reserves’ in this paper) are being promoted as an ecosystem-level management tool. Evidence suggests that establishing well designed and managed marine reserves can result in the protection and maintenance of biodiversity and can produce increases in the size and abundance of once exploited species (Ward et al. 2001, Gell & Roberts 2003, Lubchenco et al. 2003). Although marine reserves are now recognized worldwide as a valuable tool in their use in fisheries management is still under question (Hilborn et al. 2004).the conservation of marine biodiversity
This study will address the question of whether marine reserves in subtropical Australia are capable of providing these ‘dual goals’. Moreton Bay, in subtropical Australia, is a multiple-use Marine Park covering an area of approximately 3400 sq km. In 1997 six marine reserves were implemented with the aim of providing for the permanent preservation of the zone’s biodiversity and natural condition to the greatest possible extent. The majority of the reserves are located within inshore coastal areas dominated by habitats such seagrass and mangroves.
Moreton Bay represents 3% of the Queensland coastline and produces 12% of the total volume of commercial fisheries landings and accounts for one-third of the recreational fishing effort for the state of Queensland. Consequently, the marine resources in Moreton Bay are under increasing anthropogenic pressure. The aim of this study is to evaluate how effective two of the marine reserves in the Moreton Bay Marine Park are in achieving their management objective (of conserving biodiversity) and whether the reserves provide any benefits to exploited fisheries species. This is the first study of its kind to assess the effectiveness of marine reserves in subtropical Australia.
Assessment was carried out on two existing reserves, Tripcony Bight reserve (5.7 sq km in area) in the northern tip of the Marine Park, and Willes Island reserve (1.9 sq km in area) located in southern Moreton Bay. As no baseline data was available prior to reserve establishment each marine reserve was compared to four similar non-reserve (fished) sites which were chosen on the basis of proximity to the reserves, habitat similarities, hydrodynamic conditions and types of fisheries.
Sampling within fully protected marine reserves needs to be non-destructive but at the same time survey methodology must be efficient, unbiased and tailored to the species and sizeclass of interest. Therefore a number of different survey methods were used in this study including: seine netting (to assess biodiversity), vegetation transects (to assess habitat composition), crab pots (to assess mud crab Scylla serrata populations) and line-fishing (to assess finfish species). Sampling was carried out over a two year period (2002-2004) during which time both summer and winter surveys were carried out.
Our results showed that both marine reserves provide protection to a range of exploited fisheries species with biomass and sizes of certain species being significantly higher than in non-reserve (fished) sites. The most significant response to protection was displayed by one of the most heavily targeted fisheries species in Moreton Bay, the mud crab (Scylla serrata). The mud crab fishery in Moreton Bay is unusual as it is managed with a sex and size limit (male-only fishery). Catch rates (three times higher), mean size (10% larger) and legal-sized crabs (bucks) were significantly greater within reserve boundaries compared to crabs caught in adjacent fished waters (Pillans et al. in press). Interestingly, the catch rates of S. serrata were almost identical between both marine reserves despite Tripcony Bight reserve being three times larger in size than the Willes Island reserve. This result is consistent with numerous studies showing benefits to exploited species despite small reserve size (see Halpern 2003).
Further surveys of fisheries species within the marine reserves reveal that the most popular angling species in Moreton Bay, the yellowfin bream (Acanthopagrus australis) and dusky flathead (Platycephalus fuscus), were significantly larger and more abundant within the reserve boundaries than non-reserve (fished) sites. Both exploited species had catch rates 3-7 times higher within the marine reserves, with individuals 10-25% larger and biomass 15-90% greater.
These results may translate into higher reproductive potential within the reserves and export of adults to adjacent fishing grounds. Due to the non-destructive methods used within this study reproductive potential was not physically examined however, movement of fisheries species through tag-recapture methods was carried out. Although recaptures were low, both A. australis and P. fuscus moved outside reserve boundaries (cross-boundary movement only) into adjacent waters where they were captured by re
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Keywords : Fastloc
Encoded by : Pauline Carmel Joy Eje
