Assessing the impacts of disturbance on Australian Fur Seals
The ecology and social dynamics of the Port Phillip Bay (PPB) fur seals are largely unknown due to a lack of research into the non-breeding aggregation in this region. Much of the research on Australian fur seals to date has focused on the breeding colonies located throughout the Bass Strait, with most breeding occurring at Seal Rocks, Lady Julia Percy Island and The Skerries.
However, these non-breeding aggregations are not given the same protections as breeding colonies, leaving them open to disturbance, particularly in high traffic areas such as PPB. While breeding colonies cannot be approached within 300m (50-100m for permitted vessels depending on the season), seals on land can be approached to 30m, and seals on man-made structures, such as the haul-out sites within PPB, can be approached to 5m.
In partnership with Parks Victoria and Zoos Victoria, we used camera traps at known haul-out sites throughout Port Phillip Bay to assess levels of environmental and anthropogenic disturbance on fur seals. Elevated levels of disturbance have been shown to have both short- and long-term effects on pinnipeds (seals, sea lions and fur seals) including reduced fitness and changes in foraging strategies. As such, it is important to understand how these animals are responding to disturbance events.
We will also attempt to estimate site usage numbers and aggregation numbers, providing valuable information to Parks Victoria as to the adequacy of current structures or the necessity of future improvements. The impacts of environmental disturbances at these structures may also highlight management ideas for the Bay.
The study will also provide a minimally-invasive method of identifying entanglements and injuries that may otherwise go unreported, allowing for assessment by Zoos Victoria’s Marine Response Unit (MRU).
The project will endeavour to:
Assess the levels of environmental and anthropogenic disturbance impacting the fur seals across PPB;
Estimate aggregation size, age class, and site usage across PPB;
Identify entanglements and injuries MRU assessment.
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PUBLICATIONS
Speakman, C.N., Johnstone, C.P., Robb K. (2019) Increased alertness in Australian fur seals (Arctocephalus pusillus doriferus) at a high vessel traffic haul our site. Marine Mammal Science. https://doi.org/10.1111/mms.12654
Abstract:
Vessel impacts on marine mammals are of growing concern, and marine mammals in urbanized marine environments are at particular risk of exposure. Port Phillip Bay (Victoria, Australia) is one such environment, in which Australian fur seals (AUFS; Arctocephalus pusillus doriferus) haul-out to rest, yet little is known about the impacts of vessels on resting seals. We used remote camera traps to investigate the influence of vessel traffic on AUFS behavior at a nonbreeding haul-out site. Environmental, temporal, and vessel-related variables were all associated with changes in AUFS alertness at this site. All vessel types elicited increased alertness above base-line levels (25%), with recreational and commercial motorized vessels associated with a 5.7%–10.8% increase in alertness. Unidentified vessels, the government vessel, and kayaks were associated with significantly increased alertness of 21.7%, 46.4%, and 60.7%, respectively, though accounted for only 6.2% of vessel observations. Vessels breaching current approach regulations (<5 m) showed a 32% increase in alertness, significantly higher than nonbreach approaches. Partial and complete flushing of the platform was rare, occurring in 1.0% of images analyzed. These results suggest that vessels do elicit a response from AUFS at this haul-out site, and that further monitoring of vessel activity and compliance is required.