DETERMINANTS OF THE AEROBIC DIVE LIMIT OF WEDDELL SEALS - ANALYSIS OFDIVING METABOLIC RATES, POSTDIVE END-TIDAL PO2S, AND BLOOD AND MUSCLEOXYGEN STORES

The mean aerobic dive limit (ADL) for Weddell seals was calculated fro m data collected on diving metabolic rates (VO2) and blood and muscle O2 stores. Mean diving VO2 of adult seals during predominantly explora tory dive patterns was 4.5 mL O2 kg-1 min-1; mean VO2 of a subadult se al engaged in foraging dive bouts was 8.5 mL O2 kg-1 min-1. The adult value was 30% greater than that used in past ADL calculations. Mean pl asma volume was 7% body mass (BM); blood volume calculated with the hi ghest hematocrit (Hct) observed (66) was 21% BM. Hemoglobin concentrat ion at such an Hct was 26% by weight. End tidal PO2 (pre- and postdive ) justified the use of 95% and 20% arterial O2 saturations in the bloo d O2 store calculation. Total blood O2 stores were 50% greater than th ose used in past ADL calculations. Mean myoglobin concentration (5.4% by weight) and more recent anatomical estimates of muscle mass yielded a 35% increase in muscle O2 stores. The mean estimated ADL for a 450- kg seal calculated with these new data was 19.1 min, 2.3 min greater t han in past calculations and only 1 min less than the 20-min inflectio n point of the curve of dive duration versus postdive lactic acid appe arance. For the subadult engaged in foraging dives, the mean estimated ADL was about 9 min, again quite similar to past ADL calculations.