The effects of seismic reflection surveys and vessel traffic on harbor seals in Johns Hopkins Inlet, Glacier Bay National Park: A preliminary assessment

Mathews, E

In August, 1994, seismic surveys and piston-core sampling were scheduled to occur in Johns Hopkins Inlet, a glacial fjord in Glacier Bay National Park used by 3,000-5,000 harbor seals as a pupping, rearing, and resting area from May to September. Because of concerns about the potential for disturbance of molting (shedding) and recently weaned seals, a preliminary study was initiated to monitor the effects of seisic sampling surveys on harbor seals, and to compare the effects of the research vessel's activities to those of seven private or commercial vessels which entered the Inlet. Seals which left an iceberg as a vessel approached were considered to have been disturbed'. Four variables were measured: 1) total number of seals disturbed, 2) disturbance rate, 3) percent of seals disturbed, and 4) average distance from seals when disturbance was observed. The values of these variables for the seismic survey vessel did not differ significantly from the mean values calculated for the seven non-research vessels. However, all but one of the eight vessels monitored violated the Marine Mammal Protection Act (1972) by causing seals to enter the water, and all vessels appeared to have violated NPS regulations for remaining more than 1/4 mile from seals on ice bergs. These results suggest that harbor seals experience additional energetic costs due to higher than expected disturbances during crucial phases in their life history (pup-rearing and molting), and that vessel operator compliance with Federal regulations for minimizing wildlife disturbance is lower than previously assumed.