In concert the establishment of MPAs around the world and the current push to increase the number an size of no-take areas it has been argued that these areas may be of benefit to fisheries management. Included are moving fisheries harvests towards more sustainable yield, rebuilding depleted stocks, an insurance against stock collapse and the protection of essential habitat.
But as with all management tools, potential and real benefits need to be rigorously assessed. This knowledge base is currently lacking.
The proposed project will make a major theoretical contribution to the general understanding of MPAs for fisheries management as it will incorporate several new parameters in the model, including:- effort displacement; existing management tools (input controls and TAC); larval dispersal where possible (research on larval dispersal of rock lobster has focused on Tasmania); fleet dynamics; and spatial variation in biological parameters.
The plan to establish a National System of Marine Protected Areas in Australia has been resisted by the fishing sector because of a percieved loss of yield proportional to the area of the closure and the lack of critical evidence to support the proposed benefit to fisheries (including insurance against stock collapse, sources of eggs and larvae and improvement in yield). To resolve this conflict we urgently need to model the potential impacts and provide the empirical ground-truthing of the effects of area closure on the fishery.
Given that most commercially-exploited reef species are long lived and that MPAs require several years for the effects of closure to manifest themselves, there is a need to provide baseline information on the status of proposed sites. This information can then be used to evaluate MPA objectives in the future.
Equally there is a need to maintain adequate assessment of the changes that occur once an area has been closed. Monitoring of existing reserve sites in Tasmania has been ongoing for a period of five years. It is important to continue this work because analysis after five years of initial survey provided no indication that population changes of exploited species had stabilised. The biomass of rock lobsters within reserves, for example, continued to increase throughout the five years of the study. Clearly there is a need to continue the survey in order to properly document longer term changes that occur as a result of closure. This information is fundamental to the evaluation of MPAs as a coastal management tool.
The project chooses to focus on relatively sedentary species for several reasons:
While intuitive benefits in terms of stock recovery of sedentary species have been demonstrated, other benefits are far from predictable and the scant information on this subject yields results that are species specific and dependent on the behaviour of the species. There is a growing awareness that generalised models are inappropriate and each case needs examination on its own merit. Furthermore, the size of the no-take areas under consideration mitigates against the study of the benefits for highly migratory species, which range freely between protected and unprotected sites. Finally, empirical confirmation of models based on sedentary species is most likely to be achievable (recognising that models for migratory species are not well advanced at this stage).
To address possible funding constraints we have prioritised the tasks as follows:
1. Modelling the effects of closure on the fishery
2. Survey of the proposed reserve sites in Tasmania, including the industry proposed sites
3. Ongoing survey of established sites in Tasmania
4. Survey of proposed sites eslewhere Australia
5. Survey methods workshop
Marine Protected Areas (MPAs) are being proclaimed around the world with the stated primary purposes of enhancing fisheries stocks and/or conserving marine biodiversity. In Australia, in response to a joint State/Commonwealth agreement to establish a National Representative System of MPAs (NRSMPA) to protect marine biodiversity, the focus is on their conservation role. However, fisheries enhancement is often suggested as an additional benefit of protection, potentially offsetting the cost of area closure in some cases.
This study aimed to contribute to the debate on the positive and negative effects of the establishment of MPAs, documenting changes that have occurred in reserves following establishment, and particularly, attempting to understand more about their role as a fisheries management tool. It builds on a program initiated following the establishment of Tasmania’s first ‘no-take’ MPAs a decade ago.
Changes within the MPAs over the period indicated that fishing has had a substantial influence on the demographic structure of many species, particularly those targeted by fishers. The magnitude of change detected appeared to be dependant on the susceptibility of species to capture, the remoteness of protected locations and to the MPA configuration itself. Changes within the more remote Maria Island reserve (the largest area studied), relative to fished reference sites, included increases in the abundance of lobsters and certain fish species and increases in the mean size of rock lobsters (responses typical of protected areas studied elsewhere in the world), as well as a decrease in the abundance of prey species such as urchins and abalone.