Should Marine Mammal Consumption be Included in Stock Assessments of Small Pelagics?

Small pelagic fish species are both commercially important to local fisheries and ecologically important as prey for many species of fish and marine mammals. Estimates of marine mammal consumption are rare, although past studies have indicated that mammal consumption can be important to improving realism and model fits of small pelagic stock assessments. This study expands on previous work to include consumption estimates of three small pelagic prey groups for the Northeast US Large Marine Ecosystem (NEUS LME): clupeids, scombrids, and sand lance by ten marine mammal species: humpback whales, fin whales, minke whales, pilot whales, bottlenose dolphin, Atlantic white-sided dolphin, common dolphin, harbor porpoise, gray seals, and harbor seals. Ranges of daily individual consumption and diet compositions were compiled from literature values, and consumption was then expanded to annual, population-level consumption estimates based on abundance estimates and annual residence of each species in the NEUS LME. Bounds on the population-level annual consumption estimates of each marine mammal species were determined using Monte Carlo simulations, and total marine mammal consumption was then summed for each prey group.  Results indicate that for small pelagic groups that are targeted by fisheries, marine mammal consumption can be similar in magnitude to commercial fishery landings. This indicates that marine mammal consumption is likely to be important to both prey population dynamics and future efforts toward ecosystem-based fisheries management.