Cross-seasonal foraging site fidelity of subantarctic fur seals: implications for marine conservation areas

摘要

Marine top predators show fidelity to foraging areas with predictable high-quality food patches. Areas of predictable prey yield are of conservation importance, and telemetry data aid in identifying such areas. This study examined colony-specific and intra-individual foraging site fidelity of lactating subantarctic fur seals Arctocephalus tropicalis from Marion Island, Southern Ocean (46 degrees 54' S, 37 degrees 45' E), during summer and winter, comparing commitment to foraging areas across seasons. Thirty females were tracked in 2009-2013, resulting in 109 foraging trips for analyses. Inter-annually, preferred foraging areas in summer were consistently similar to 200 km due east of Marion Island towards the Gallieni Rise. Summer individuals' core utilization areas overlapped by an estimated 32.84% (CI: 24.53-41.94%). Seals responded to a decrease in regional productivity in winter by foraging in more distant, alternative areas. In winter, individuals changed their travelling direction to northeast of Marion Island and foraged further afield, around the Del Cano Rise and along the Southwest Indian Ridge. Despite preferring some foraging areas in winter, there was a low amount of overlap 6.03% (CI 4.02-9.16%) of individual core utilization areas. The foraging grounds identified in this study have not been included in prior conservation assessments and are important for conserving this globally significant, and currently declining, population of subantarctic fur seals and perhaps other top predators breeding at Marion Island as well. Differences between foraging areas preferred in winter and summer highlight the importance of sampling during different seasons when using telemetry data for the identification of potential pelagic conservation areas.