Effects of climate change on the distribution and energy requirements of marine mammals

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Static bioenergetic models calculate the energy requirements of an individual or population as a function of age. Currently, the best bioenergetic model for marine mammals is a static model constructed for Steller sea lions (Winship et al. 2002; Winship and Trites 2003). This model will be refined and expanded to predict food requirements of key species of marine mammals in Canada and Alaska (walruses, harbour seals, fur seals, Steller sea lions, killer whales and beluga whales) using published records from wild and captive animals. Data required include diet, biological value of prey (digestibility and proximate composition), foraging costs (energy and time to find food), energy requirements (total and activity-specific), and body size at age estimates. These models will be used to estimate how food requirements for these species will change in response to changes in the prey base and physical environment (e.g., foraging cost, thermoregulation). The models will be further used to develop dynamic bioenergetic models that incorporate the physiological responses (potential range) to changes in animals' energy budgets. The dynamic models will incorporate functional responses that permit individual parameters to change in accordance with other changes in the system. Dynamic bioenergetic models are the most useful means of predicting the effects of changes in an animal's biotic (fish distribution) and abiotic (temperature, ice cover) environment on its behavior and physiology, and ultimately on parameters that impact population levels (survival, reproduction rates). They will be combined with habitat models that incorporate accessibility assumptions based on published age and sex specific constraints, as well as suitability assumptions that use a variety of physical variables (e.g., bathymetry, temperature, salinity, ice cover, haulout sites) to differentiate between regions of equal accessibility. Estimates of the food consumption and energy requirements of marine mammals, and the bioenergetic consequences of global warming on their range distributions have theoretical implications and practical applications for fisheries management.