Studies of Harbor Seals Using Glacial Ice in Disenchantment Bay, Alaska, 2016-2017
This summary will provide an update on NOAA-AFSC’s latest research on seal-vessel interactions jointly conducted with the National Park Service. This research builds on studies since 2002 on ice-associated harbor seals in Disenchantment Bay which have focused on proximate effects such as when, where, and at what distances vessels were causing a disturbance. By employing GPS satellite tracking (for both seals and ships), we aim to address broader population-level effects, and in particular to better understand how vessels entering glacial ice habitats may approach and alter the haul-out behavior of nursing pups, thus potentially increasing their energetic costs of thermoregulation in the water. There is concern that chronic disturbances could reduce body mass of pups at weaning and survival, and ultimately impact population stability.
During two field deployments in June 2016 and 2017, scientists from NOAA’s Marine Mammal Laboratory and NPS’s Glacier Bay Field Office captured, sampled, and attached satellite-linked transmitters on 73 pup and 2 mother harbor seals hauled out on glacial ice. Vessel routes and speed upon entering the study area were tracked in both years using an AIS tracking station installed on Haenke Island. Coupling vessel AIS data with behavioral and spatial data from the seals’ satellite tags will allow researchers to model seal and vessel movements to estimate the distance and time of closest approaches to seals by vessels, which will then be related to timelines of pup haul-out behavior (in/out of the water). Over the next year, analyses will focus on comparing the behavior of pups with and without ships present, and outside and within the path of vessels, to detect any differences in time spent submerged. Previous energetic models have shown that extra time in the ice-chilled water could compromise the capacity of pups to gain body mass (i.e., blubber) necessary to support them in the first months of independence. Findings will be submitted to peer-reviewed journals and presented directly to stakeholders via meetings.