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Diet and nutrition of western rock lobsters, Panulirus cygnus, in shallow coastal waters: the role of habitat
Citation:
MacArthur, L., G. Hyndes, C. Hanson, D. L. PHILLIPS, M. Vanderklift, AND R. Babcock. Diet and nutrition of western rock lobsters, Panulirus cygnus, in shallow coastal waters: the role of habitat. Presented at 6th International Conference on Applications of Stable Isotope Techniques to Ecological Studies, Honolulu, HI, August 25 - 29, 2008.
Impact/Purpose:
Generalist consumers often have diets that vary considerably over time and space, which reflects changes in resource availability.
Description:
Generalist consumers often have diets that vary considerably over time and space, which reflects changes in resource availability. Predicting diets of consumers can therefore be difficult. The western rock lobster, Panulirus cygnus, is an omnivorous generalist consumer that uses limestone patch reefs as shelter during that day but adjacent habitats to forage at night. These patch reefs and adjacent habitats such as seagrass beds, sand and macroalgae-dominated pavement form a heterogeneous landscape in shallow (<20 m) coastal waters of the lower west coast of Australia. Potentially, the habitat surrounding these patch reefs may be a good predictor of diet for these lobsters. The aim of this study therefore was to determine if surrounding benthic habitat influenced the diet of P. cygnus from shallow water reefs. We used stable isotopes (δ13C and δ15N) to enable us to elucidate long-term trends in diet and also to reveal information on the nutritional role of food sources. Using distance-based redundancy analysis, we compared habitat related variation in diet with the influences of site, month, sex and size (carapace length). We used a modified mass balance mixing model (IsoSource) incorporating the concentration weighting principles of IsoConc to investigate important food sources from a number of potential sources. Habitat explained a significant level of variation in the diet of P. cygnus (>50%), far greater than any of the other potential influences examined (<20%). The diet of lobsters from macroalgae-dominated pavement and sand habitat differed from that of lobsters from seagrass (Amphibolis spp. or Posidonia spp.) habitat. Articulated coralline algae were more prominent in the diet of lobsters from macroalgae-dominated pavement and sand habitat. The assimilation of coralline algae nutrients into muscle tissue suggests that this food source can be used for muscle maintenance as well as for supplying Ca for shell maintenance. Mixing model data suggested that mobile invertebrate prey in particular were important for tissue maintenance in P. cygnus. Seagrass is unlikely to be an important food source but is an important habitat for invertebrate prey. Previous research has shown growth to be positively linked to increased consumption of invertebrate prey by P. cygnus. Thus lobsters from seagrass habitat may grow faster than those from macroalgae-dominated pavement and sand habitat, where coralline algae appear to be more important to diet.