Food consumption by sea lions: Existing data and techniques

Knowing the quantity of prey that sea lions consume is a prerequisite for assessing the role of sea lions in aquatic ecosystems and the potential for competition to occur with fisheries. We reviewed the different approaches that have been used to estimate the food requirements for the six species of sea lions. We reviewed data on the quantity of food consumed by sea lions in captivity, and examined how consumption varied by species, body size, and season. We also reviewed and quantified available information on the energetics of sea lions and assessed the potential application of these data to parameterize an existing bioenergetic model that was developed to estimate the food requirements of Steller sea lions. Our study provided ranges of estimates of food consumption for sea lions that can be used in various modeling strategies to assess the impact of sea lions on prey populations, including commercially exploited fish species. The approaches reviewed in our study shared common difficulties arising from the quantity and quality of data, and the integration of data across scales and species. Our modeling exercise, in particular, identified the major uncertainties involved in estimating the food requirements of each sea lion species using an energetics approach. Our results provide direction for future research aimed at improving the accuracy and comparability of estimates of food consumption for sea lions.