Effects of Climate Change on the Seasonal Diets, Energy Requirements, Abundances and Distributions of Marine Mammals in the North Pacific Ocean

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There is growing concern about the effects that climate change will have on marine mammals and other marine species. It has been assumed that polar species of marine mammals will be negatively affected by reduced ice coverage, and that the distribution of some temperate mammals may shift towards the poles in response to northward shifts in the distribution of their prey. However, these assumptions have never been tested. One means of quantifying the effects of climate change on marine mammals is to use bioenergetic models and historical data on diets, numbers and distributions of marine mammals to determine the bioenergetic limitations that constrain them. For the next 5 years, I propose to work with graduate students to formulate bioenergetic models and build databases of abundances and diets for 47 species of marine mammals in the North Pacific. I will also establish a complementary database on prey quantity, quality, composition, and distribution using data provided by PICES member countries (Japan, Korea, China, Russia, Canada and the United States). Prey consumption will be calculated for 1º cells (~100x100 km) based on energetic requirements of the individual species (determined by the energetic models), diets, energy densities of prey, and population sizes. Predictions of spatial and temporal effects of climate change on consumption and distribution of marine mammals will be based on projected changes in the quantities and qualities of prey (derived from independent models of climate effects on fish) and from the trophic linkages and dependences I believe can be established between marine mammals and their preferred prey species using the database of diets and population abundances, along with additional information about body sizes, swimming performance and physiologies. I also propose to evaluate the physiological linkages between dietary shifts over time, energy density of prey species, marine mammal physiologies, and population trends of marine mammals to test the applicability of the junk-food hypothesis as the major driver of marine mammal population dynamics in the North Pacific. The graduate students supported by this study will develop skills in programming, data analysis, and fisheries and marine mammal research; and will take part in workshops and symposiums organized at PICES annual meetings to support this initiative. Results from this research will provide 1) dietary data needed to parameterize ecosystem models, 2) estimates of food consumption, 3) predictions of marine mammal responses to climate change, and 4) new insights into the interdependencies and trophic linkages between marine mammals and their prey.