Abstract
The pun in the above title reflects two points. First, marine life cycles com- monly include a dispersive juvenile stage that is moved about by ocean currents. This stage often is the predominant, or only, means of dispersal that connects spatially disjunct pop- ulations. As a consequence, details of dispersal likely play a critical role in determining the effectiveness of marine reserves as a management and conservation tool. Curiously, however (and this is the second point of the title), although dozens of models for marine reserves now exist, few actually account explicitly for larval dispersal. Moreover, those that do include dispersal, do so almost exclusively by considering it to be a nondirectional spreading process (diffusion), ignoring the effects of directional transport by currents (ad- vection). Here we develop a population dynamical model for marine organisms with rel- atively sedentary adults whose larvae are transported in a simple flow field with both diffusive spreading and directional characteristics. We find that advection can play a dom- inant role in determining the effectiveness of different reserve configurations. Two of the most important consequences are: (1) with strong currents, multiple reserves can be mark- edly more effective than single reserves of equivalent total size; and (2) in the presence of strong currents, reserves can significantly outperform traditional, effort-based manage- ment strategies in terms of fisheries yield, and do so with less risk. These results suggest that successful reserve design may require considerable new efforts to examine explicitly the role of dispersal of young.
Published Version
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