Self-recruitment in coral reef fish populations

Most populations of benthic marine organisms are considered to be open, when recruitment results from dispersal of larvae from other source populations. In truth we know little about the degree of connectivity among populations. For localities such as coral reef islands, relative isolation from other island populations may increase the importance of self-recruitment to population persistence. In order to test this hypothesis, I used larval growth history and elemental composition of otoliths to classify locally and non-locally produced populations of coral reef fish larvae. Using this approach in a study of reef fish recruitment to St. Croix, US Virgin Islands, I found that periods of high recruitment in the lee of the island were coincident with environmental signatures indicative of local retention of larvae. Physical measurements of the circulation dynamics of the island wake region using a high frequency radar indicate that high recruitment events occur during periods favorable for physical retention of larvae. Coastal measurements of food resources for developing fish larvae indicate that local retention of pelagic larvae may enhance larval growth and survival, as well as increase the probability of successfully returning to reef environments at the end of the larval period. These results suggest that local processes operating in the nearshore regions of islands are important factors influencing larval recruitment to island populations of reef fishes.