Insight into the feeding ecology of the California spiny lobster, Panulirus interruptus, using stable isotope analysis

The California spiny lobster, Panulirus interruptus, is an abundant predator in southern California and may play important roles in dictating community structure in several coastal habitats. In kelp forests, spiny lobsters may function as keystone predators, regulating kelp biomass by consuming herbivorous sea urchins. In estuaries, spiny lobsters may help eelgrass communities resist invasion by preying upon introduced species (e.g Asian mussel). Despite the potential role that lobster predation plays in structuring communities, evidence is largely correlative and there is little quantitative information about their diets. Gut content analysis is unreliable for spiny lobsters, revealing only snapshots of feeding habits. We propose to investigate how habitat influences the feeding ecology of P.interruptus using stable isotope analysis (SIA), which integrates feeding habits over long time scales and is used to understand trophic relationships. SIA represents a novel application for this species and these data will give insight into effects habitat has on spiny lobster diet. We are quantifying the diet of adult spiny lobsters in two major habitat types where they are abundant: kelp forests and eelgrass meadows in San Diego Bay. We hypothesize spiny lobster diet will reflect the relative local abundance of potential food sources. We believe the effects of habitat on spiny lobster diet may be valuable to policymakers and may benefit lobster conservation through the California Marine Life Protection Act by informing the selection of habitats to be designated as Marine Protected Areas. Should lobster densities change within MPAs, this project may help predict subsequent trophic effects.