Implications of Uncertainty in Larval Dispersal for Management with MPAs

Assessments of the effects of MPAs on population sustainability and fishery yield have shown that they depend critically on the nature of larval dispersal, as well as juvenile and adult movement and the level of fishing outside MPAs.  Adult  movement is frequently of the home range type and the sizes of home ranges are often known, and fishing rate can be controlled, leaving larval dispersal as the dominant uncertainty.  Here we catalogue the effects of various characteristics of larval dispersal in an attempt to better understand the consequences of that uncertainty.  For non-advective dispersal, the effects of larval dispersal are well known when dispersal distances are as small as the typical size of the MPAs.  At longer dispersal distances, populations become persistent when MPA coverage exceeds a certain fraction of the coastline determined by the egg-recruit relationship at low abundance.   This reduces the dependence on larval dispersal distance.  When larval dispersal has an advective component, sustainability with MPAs can be reduced, but MPAs can lead to a large increase in yield.