THE AEROBIC SUBMERSION LIMIT OF BAIKAL SEALS, PHOCA-SIBIRICA

An aerobic dive limit (ADL), the diving duration beyond which postdive lactate concentration increases above the resting level, has been est imated theoretically for many species. Such calculations have been bas ed on an oxygen store/diving metabolic rate (MR) equation. Until now, an ADL has been determined empirically from measurements of blood lact ate concentration only in the Weddell seal, Leptonychotes weddellii. W e measured post-submergence plasma lactate concentrations during spont aneous voluntary submersions of three captive adult Baikal seals (Phoc a sibirica). Two-phase regression analysis revealed a transition in th e lactate concentration - submersion duration relationship after the a nimal had been diving for 15 min. Data collected in prior studies on o xygen stores and submersion metabolic rates of Baikal seals yielded a calculated aerobic limit of 16 min. As in Weddell seals, the empirical ly determined aerobic limit was very similar to the theoretical limit. Furthermore, most diving durations recorded during recent studies of free-ranging Baikal seals are under this limit. These data support the concept of an ADL and its estimation by means of an oxygen store/divi ng MR calculation.