REFERENCE RANGES AND AGE-RELATED AND DIVING EXERCISE EFFECTS ON HEMATOLOGY AND SERUM CHEMISTRY OF FEMALE STELLER SEA LIONS ( EUMETOPIAS JUBATUS).

Decreased health may have lowered the birth and survival rates of Steller sea lions ( Eumetopias jubatus) in the Gulf of Alaska and Aleutian Islands over the past 30 yr. Reference ranges for clinical hematology and serum chemistry parameters needed to assess the health of wild sea lion populations are limited. Here, blood parameters were serially measured in 12 captive female Steller sea lions ranging in age from 3 wk to 16 yr to establish baseline values and investigate age-related changes.

Physiological constraints and energetic costs of diving behaviour in marine mammals: a review of studies using trained Steller sea lions diving in the open ocean.

Marine mammals are characterized as having physiological specializations that maximize the use of oxygen stores to prolong time spent under water. However, it has been difficult to undertake the requisite controlled studies to determine the physiological limitations and trade-offs that marine mammals face while diving in the wild under varying environmental and nutritional conditions. For the past decade, Steller sea lions (Eumetopias jubatus) trained to swim and dive in the open ocean away from the physical confines of pools participated in studies that investigated the interactions between diving behaviour, energetic costs, physiological constraints, and prey availability.

Sensitivity to hypercapnia and elimination of CO2 following diving in Steller sea lions (Eumetopias jubatus).

The diving ability of marine mammals is a function of how they use and store oxygen and the physiological control of ventilation, which is in turn dependent on the accumulation of CO2. To assess the influence of CO2 on physiological control of dive behaviour, we tested how increasing levels of inspired CO2 (hypercarbia) and decreasing inspired O2 (hypoxia) affected the diving metabolic rate, submergence times, and dive recovery times (time to replenish O2 stores and eliminate CO2) of freely diving Steller sea lions. We also measured changes in breathing frequency of diving and non-diving individuals.

Steller sea lions (Eumetopias jubatus) have greater blood volumes, higher diving metabolic rates and a longer aerobic dive limit when nutritionally stressed.

Marine mammal foraging behaviour inherently depends on diving ability. Declining populations of Steller sea lions may be facing nutritional stress that could affect their diving ability through changes in body composition or metabolism. Our objective was to determine whether nutritional stress (restricted food intake resulting in a 10% decrease in body mass) altered the calculated aerobic dive limit (cADL) of four captive sea lions diving in the open ocean, and how this related to changes in observed dive behaviour.

High diving metabolism results in a short aerobic dive limit for Steller sea lions (Eumetopias jubatus).

The diving capacity of marine mammals is typically defined by the aerobic dive limit (ADL) which, in lieu of direct measurements, can be calculated (cADL) from total body oxygen stores (TBO) and diving metabolic rate (DMR). To estimate cADL, we measured blood oxygen stores, and combined this with diving oxygen consumption rates (VO2) recorded from 4 trained Steller sea lions diving in the open ocean to depths of 10 or 40 m. We also examined the effect of diving exercise on O2 stores by comparing blood O2 stores of our diving animals to non-diving individuals at an aquarium.