Review Of Criteria For Index Sites For Monitoring Seal Abundance And Trends: Application To Southern New England

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New England populations of harbour seal and grey seal have increased and expanded their range since passage of the U.S. Marine Mammal Protection Act, (1972). In autumn there is an influx of harbour seals from Maine and the Canadian Maritimes into southern New England,(SNE; Massachusetts to western Long Island, New York), that generally departs the region by mid-May. Grey seal numbers increase during the autumn as well and peak during the winter breeding season (January/February) and then decrease by late May. Intermittent autumn to spring monitoring surveys have been conducted in SNE since winter 1998/1999. However, the high cost of aerial surveys has made it difficult to maintain coast-wide seal monitoring surveys in SNE. Therefore, we have evaluated criteria used in other regions to monitor seals to determine their applicability and practicality to SNE. Criteria considered include: operational (i.e., survey design); ecological (i.e., life history, site fidelity); and extrinsic (i.e., human disturbance) denote sites that are subject to disturbance factors. Based on this review we developed a two-stage survey that should provide a suitable index of SNE seal populations. Stage I requires monthly (October - May) aerial surveys of major SNE sites, particularly grey seal pupping sites. In Stage II a comprehensive census of all haul-out sites would be conducted over a 3-5 day window (mid-March). Stage II corresponds to the period of peak harbour seal counts, and would provide a reference point for the Stage I surveys. We believe the spatial and temporal range of the survey will provide sufficient data to adequately monitor abundance trends in SNE region.