Observations on the ventilation cycle of the harbour porpoise Phocoena phocoena (L.) in coastal waters of the Bay of Fundy

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Abstract
The ventilation cycle of the harbour porpoise was studied through analysis of 700 dive sequences recorded in the Fish Harbour region of southern New Brunswick. Two basic ventilation patterns were recognized; one (pattern A) was exhibited by travelling animals and was characterized by short submergence periods (24.4 ± 1.6 s (SE)), the second (pattern B) by animals apparently feeding, and was characterized by restricted ventilation periods, between which the submergence periods averaged 1.44 ± 0.07 min. Submergences during pattern B behaviour ranged from 35 s to 4 min 4 s. One animal observed over an extended period took considerably more breaths (6.6 ± 0.4) after dives of above-average duration than after dives of less than average duration (3.6 ± 0.2). We found that the number of breaths per minute in each behaviour pattern were very similar (2.4 and 2.3, respectively), supporting statements by other workers that the energetic demands of diving in marine mammals may not be greater than that required for surface activity. In behaviour patterns A and B, respectively, harbour porpoises in this area were at the surface for only 7.2 and 7.5% of any observation period. The maximum to mean dive-time ratio in P. phocoena was noted as being almost identical to that observed in Orcinus orca; this may be a generalized relationship in all odontocetes.