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Rachel Pears,School of Marine Biology and Aquaculture, James Cook University, Townsville 4811
David McB Williams, Australian Institute of Marine Science and CRC Reef Research Centre, Townsville 4810
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This document reviews available information relevant to the possible creation of artificial reefs on the Great Barrier Reef (GBR), for extractive (fishing) or non-extractive (e.g. diving) purposes. Although the literature on artificial reefs is quite extensive, there is surprisingly little strong evidence on either socio-economic or environmental benefits or impacts, so that conclusive statements about overall costs and benefits should be treated with caution. Elsewhere in the world, against a background of degraded marine ecosystems, artificial reefs can be seen to have some socio-economic and perhaps environmental benefits. In the context of the relatively healthy systems of the GBR, any benefits will be socio-economic, not environmental, and importantly, many of the suggested benefits (e.g. enhanced fishing) are inadequately justified by available evidence, may be only short-term or may be better provided by alternative measures with less risk. Artificial reefs have proven popular for both fishing and tourism/diving uses, although reviews in Australia and overseas question their value.
In general, fished artificial reefs pose more risk than unfished artificial reefs (e.g. diving only), because in many circumstances, available evidence suggests that artificial reefs tend to aggregate existing fish stocks, rather than enhance overall fish production. In the short-term, aggregation of fish on and around artificial reefs may generally increase fishing success nearby, as expected. However, in the long-term, if increased and concentrated fishing on the artificial reef outweighs any increase in overall production, this aggregation effect may increase the vulnerability of the fish stocks, leading to over-fishing.
Creation of artificial reefs in healthy ecosystems involves a range of potential environmental costs and risks. These include the replacement of prior, natural habitat with artificial habitat, impacts on adjacent habitats (such as shifts in trophic or food-web structure), on connectivity and larval dispersal patterns between habitats, and the introduction of pollutants, diseases or marine pests.
There is a need for a careful, evidence-based, risk assessment and cost-benefit analysis, which critically considers:
- The values and motivations underlying the potential social and/or economic benefits of artificial reefs (e.g. enhanced fishing experiences);
- The likelihood of artificial reefs effectively addressing those values;
- Potential alternative solutions;
- The balance between social or economic benefits of artificial reefs and potential loss of value to other interest groups (e.g. loss of naturalness or World Heritage value);
- Evidence for other potential effects, including environmental impacts;
- Potential impacts on fisheries and fisheries management;
- Strategies to maximise benefits and minimise environmental, social and economic risks.
Unfortunately, much of the information required for this assessment is either very limited or unavailable. Key knowledge gaps are identified at the end of this document.
Download a complete copy of the report (Adobe Acrobat file 300kB).
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