Larval ontogeny enhances resilience to a patchy planktonic food supply in the American lobster (Homarus americanus)

Abstract

The American lobster (Homarus americanus) plays an integral role in the coastal Northwest Atlantic as a benthic consumer and the target of the most valuable single-species fishery in North America. In the past decade, benthic recruitment of juvenile lobster has declined, even as egg production has increased, suggesting heightening levels of larval mortality. Recent correlative studies in the Gulf of Maine further suggest early-stage larval survival may be related to the supply and composition of planktonic foods. Despite these correlative studies and the economic importance of the species, relatively little is known about how larval lobster interacts with its prey in the pelagic environment. During these early developmental stages, lobster larvae undergo significant morphological changes which influence their ability to capture and handle prey. This study used a combination of laboratory-based feeding experiments and video recordings to examine changes in feeding behavior and ingestion rates between larval stages. Calculated Ivlev-type functional response curves were used to evaluate how larval ingestion rates vary with prey density and by larval stage on a suite of prey species. We observed dramatic stage-to-stage improvements in the capacity to pursue, capture, handle, and ingest specific prey, especially after the metamorphosis to the postlarval stage. The results highlight the vulnerability of the early life stages to low food densities. They also elucidate differences in the ability of specific prey taxa to evade predation by larval lobster. Quantifying the interactions between larval lobsters and their prey enhances our understanding of how this economically important species interacts with the pelagic food web, which fraction of available zooplankton represent viable food sources, and how lobster larvae may be impacted by altered prey availability associated with climate change.