COSTA, D*; WEISE, M; KUHN, K; SHAFFER, S; ARNOULD, J; STERLING, J; CROCKER, D; BURNS, J; UC Santa Cruz; UC Santa Cruz; UC Santa Cruz; UC Santa Cruz; Deakin University Australia; NMFS Seattle; Sonoma State University; Univ Alaska Anchorage: Physiological Capacity Correlates with Diving Behavior Among Sea Lions and Fur seals

Foraging strategies of air-breathing marine vertebrates develop as as a dynamic relationship between physiological performance, energetic requirements and characteristics of environment. Within this context, different phylogenetic groups vary in their physiological capabilities. One of the primary determinants of physiological capacity is the aerobic dive limit (ADL), which is influenced by the rate at which total body oxygen stores are consumed while diving. Differences in ADL correlate with variations in foraging behavior. For example, true seals (Family Phocidae) have greater oxygen stores than sea lions and fur seals (Family Otariidae) and as a group, true seals dive longer and often deeper than sea lions and fur seals. While the pattern between members of each family has been well documented, variation within a family has not been as carefully examined. Inspection of the diving behavior and ADL within the sea lions and fur seals shows that there is considerable variation in physiological capability. Further, these differences correlate with the diving behavior observed in the wild. We measured the total body oxygen stores (muscle myoglobin and blood hemoglobin concentration and blood volume) of 7 otariids, Australian sea lion, and fur seal, the northern fur seal, the Hooker�s sea lion, the Sub-Antarctic fur seal, the Antarctic fur seal and the California sea lion. Oxygen stores varied from a low of 38.1 ml O2/kg in Antarctic fur seals to a high of 58.6 ml O2/kg in a population of deep diving California sea lions. There was a highly significant relationship between mean dive duration measured for each species in the field and their mean total oxygen stores.