Abstract

(…) A review of the status of harbor porpoise, Phocoena phocoena, in the U.S. waters of the western North Atlantic identified substantial information gaps in our knowledge about this species, and raised serious questions about the health of the North American population (Prescott and Fiorelli 1980). Significantly, no population estimate exists for P. phocoena in the western North Atlantic. Gaskin’s (1977) estimate of 4,000 in the Bay of Fundy region is admittedly preliminary, and includes only a portion of the known range. Prescott and Fiorelli (1980) used winter stranding records from a single year to postulate a minimum mid-Atlantic regional population of 726 to 1,525 (between Long Island Sound and Cape Hatteras), but acknowledged that no information on stock or population discreteness exists for U.S. coastal waters.
Harbor porpoise are one of the smallest oceanic cetaceans, reaching a maximum size of about 2 m (Gaskin et al. 1974). They are also behaviorally innocuous, seldom leaping from the water, are usually found in small groups of 2-4, and generally avoid motor vessels (Amundin and Amundin 1974). These factors frustrate attempts to study the species, and it was necessary to establish and test survey methodology prior to undertaking a full-scale survey. An experiment was designed to estimate the fraction of visible harbor porpoises observed from aircraft, shipboard, and land-based survey platforms.
Between 4 and 12 August 1980, 30 to 34 persons from College of the Atlantic, the University of Guelph, and the New England Aquarium took part in this experiment in Head Harbor Passage, a narrow channel running NE-SW, bounded by Campobello Island (N.B.) on the east and a series of small islands and ledges on the west (Fig. 1). Head Harbor Passage was chosen for three reasons: 1) Harbor porpoise regularly inhabit the passage; 2) the passage is only 800 to 1,000 m wide, with many identifiable landmarks, which permits accurate orientation and navigation; and 3) the northwestern coast of Campobello Island provides easy access to land observation stations of nearly uniform height. (…)