Size and spacing rules for marine protected areas: Useful for management?

Background/Question/Methods

Can size and spacing rules provide guidelines for marine spatial planning? The complexity and temporal variability of coral reef systems make predictions for spatial planning challenging. General guidelines offer a solution if they predictably deliver benefits. However, are general guidelines, such as rules for the size and spacing of protected areas predictable and distinguishable enough to be useful? Using a population dynamics model of coral trout on the Great Barrier Reef, we simulated marine protected areas with variation across size and spacing rules. The model imitates realistic dispersal conditions using results of biophysical dispersal models. With each simulation, we track two long term outcomes: average annual catch (a fishery objective) and remaining abundance on the reef (a conservation objective).  By tracking these two outcomes over many simulations, we evaluate the experimental size and spacing guidelines.

Results/Conclusions

Our results indicate that size and spacing guidelines can reveal tradeoffs in management objectives. On average, smaller, more disperse protected area configurations perform better for fishery objectives. This pattern is observed across a range of total protected area coverage (%10-40 of reef area protected). Regardless, a large amount of variation in the measured objectives weakens the ability to delineate between expected outcomes on the tradeoff. The overall usefulness of general guidelines in this model is diminished because the noise of the system drowns out the difference in outcomes for alternate guidelines. This may provide some evidence that simple guidelines are impractical for management of complex, dynamic reef systems.