Spatial variability in growth and prey availability of lobsters in the northwestern Hawaiian Islands

Proximate composition, bulk tissue and amino acid compound-specific nitrogen isotopic analyses (CSIA) were used to determine whether dietary differences were responsible for the spatial variability in growth of spiny lobster and slipper lobster in the Northwestern Hawaiian Islands (NWHI). Abdominal tissues were collected and analyzed from both species at Necker Island and Maro Reef from 2006 to 2008. Protein and lipid levels did not differ significantly between locations in either species. Bulk tissue 15N of both species was significantly negatively correlated with growth for both species; however, the analysis assumed constant isotopic composition of autotrophs across this region. CSIA, which accounts for 15N variability at the base of the food web, indicated that spiny lobsters at both locations occupied the same trophic position whereas the slower-growing Maro Reef slipper lobsters fed at a lower trophic position relative to Necker Island slipper lobsters. Spatial variability in the abundance or diversity of preferred prey items appears to be responsible for the spatial variability in growth and the specific morphology and behavior of these species dictated how they coped with dietary restraints. These findings increase the understanding of NWHI coral reef ecosystem processes as well as highlight dangers of using consumer bulk tissue isotopic data without considering variation in the nitrogen isotopic composition at the base of the food web.