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

Abstract

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 15 N 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 15 N 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. KEY WORDS: Proximate composition · Panulirus marginatus · Scyllarides squammosus · Bulk stable isotope · Compound-specific isotopic analysis · Trophic level Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 449: [211][212][213][214][215][216][217][218][219][220] 2012 extending approximately 2000 km across the subtropical Pacific (Fig. 1). Recaptures from a 2002−2008 mark/recapture study revealed spatial variability in the growth of both NWHI lobster species. Specifically, spiny lobster growth at Necker Island, located at the southeastern end of the NWHI, was approximately one-third that of spiny lobster at Gardner Pinnacles and Maro Reef, located in the middle of the NWHI (O'Malley 2009). During the same time, slipper lobsters, particularly males, grew fastest at Necker Island with growth declining in a northwestern gradient (O'Malley 2011). These results led to a revision of the NHWI lobster population dynamic theory from a single archipelago-wide population to a series of discrete species-specific meta populations separated by the deep water between banks and connected only by larval dispersal.Common drivers of crustacean growth were examined to understand the spatial variability in NWHI lobster growth. The first, density dependence (McGarvey et al. 1999, Pollock 1991, was not supported because analysis of individual-and bank-specific growth rates relative to density indicated no relationship for either species (O'Malley 2009(O'Malley , 2011. Tempera ture, the primary environmental influence on crusta cean gr...

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