Impact of Larval Transport and Benthic Habitat Quality upon Recruitment Dynamics: Poor Nursery Habitat Decouples Larval Supply from Reproductive Output of Caribbean Spiny Lobster

College Of William & Mary Virginia Institute Of Marine Science, Gloucester Point VA

Investigators

Abstract

This study is based on prior research of recruitment in the Caribbean spiny lobster, couched in the theoretical framework of metapopulation and source?sink dynamics, at four widely spaced sites (over 100's of kms) in Exuma Sound,Bahamas. Those findings, which were based on field sampling, field experiments and a 2?D hydrodynamic model of physical transport, produced a conceptual model describing the collective influence of physical transport, habitat quality and adult abundance upon spiny lobster recruitment. Specifically, spatial patterns in recruitment and adult abundance across the four sites were consistent over three years, adult abundance and recruitment were decoupled spatially, and the spatial patterns in recruitment were explained largely (? 67 % of mesoscale variation) by larval and postlarval transport via gyral currents and geostrophic flow. These suggested that habitat quality and physical transport decoupled recruitment and adult abundance spatially, thereby producing a source?sink network. These findings have major implications for understanding of recruitment processes and placement of marine reserves to enhance recruitment. In particular, the results are novel in their demonstration of direct and strong control of larval supply by fundamental hydrodynamic processes, and in their applicability to the design of marine reserves. For instance, placement of a marine reserve in a sink habitat would lead to a false sense of security and would not prevent local extinction of a heavily exploited population. This investigation tests a key hypothesis derived from the earlier findings: poor habitat quality in some sites reduces recruit survival disproportionately and thereby decouples larval supply and subsequent adult abundance. It includes both mensurative and manipulative experiments, specifically to measure the absolute availability of settlement and nursery habitat, to quantify abundance and survival rates of post?settlement and young juvenile spiny lobster, and to quantify population parameters at the four sites. The study therefore constitutes a unique empirical test of the collective influence of physical transport, habitat quality and adult abundance upon the recruitment dynamics of marine species.