ASFB Home > 2007 > Designing optimal marine protected area networks for New Zealand’s Exclusive Economic Zone.

The New Zealand Biodiversity Strategy specifies as one of its objectives the “protecting (of) 10% of New Zealand’s marine environment by 2010 in view of establishing a network of representative protected marine areas.” I describe one approach for designing such a network for offshore waters, using a combination of recently developed data mining and reserve design tools.

To overcome the patchy geographic distribution of research trawls, we used environment-based statistical models, fitted using boosted regression trees, to interpolate the distributions of 96 demersal fish species. Predictions of species catch per unit effort were made for 1.59 million grid cells, each of 1 km² and covering all parts of the EEZ with depths between 200 and 2000 m. These predicted distributions were then analysed using reserve design software (Zonation) to explore a range of protection options. Benefits derived from the various scenarios were measured using the average degree of range protection provided for fish species, and costs were measured using a trawl intensity layer created from the start positions of commercial trawls carried out during 2005. Differential weighting was applied to endemic species to increase their levels of protection, and buffering options were used to allow for the effects of fragmentation on species of varying mobility.

Results indicate a range of options with varying benefits and costs, depending on the geographic extent of MPAs. MPAs selected without regard to current fishing patterns would deliver the greatest conservation benefits, but would reduce trawling opportunities substantially. By contrast, MPAs selected to minimise impacts on current fish harvesting would deliver conservation returns that are 85% of those achieved when selection is unconstrained. Analysis of partially protected areas proposed by the fishing industry and to be implemented during 2007, indicate that these provide less than half of the biodiversity benefits that could be achieved by alternative low-cost, configurations identified by our analyses.