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There is increasing overlap between feeding habitats of marine mammals and seabirds and the human interests of fishing, aquaculture, and recreation. A better understanding of foraging ecology and interactions between apex predators will facilitate advice on management/conservation strategies. Feeding interactions between dusky dolphins (Lagenorhynchus obscurus) and Australasian gannets (Sula serrator) in the Inner Admiralty Bay, New Zealand provide an opportunity to study multiple-species use of habitat, and interaction dynamics. This study examines habitat use, feeding tactics, and feeding interactions of dusky dolphins and Australasian gannets in the Inner Admiralty Bay. Information from boat-based research indicates that while dusky dolphins feed on schooling fish (mainly pilchard, Neopilchardus sp.) during the Winter in Admiralty Bay, gannets represent the most commonly-present bird species. As in Argentina, groups of dusky dolphins in Admiralty Bay surround schools of fish, apparently herding them into tighter aggregation to increase foraging efficiency. Australasian gannets are often observed circling above and diving into these fish aggregations. It is possible that the dolphins and birds work together, forming a commensal relationship, and using one another to more efficiently find and/or capture prey. Alternatively, the relationship may be a kleptoparasitic one, in which the gannets and other bird species make use of the prey resources made more available by the hunting activity of the dolphins, but with little or no advantage to the dolphins. We compare estimated costs and benefits of feeding alone versus in multispecies aggregations for dusky dolphins and Australasian gannets. Data used in this analysis include prey capture rates, dive and success rates, length of feeding bouts, and the numbers of dolphins and gannets present when the two species feed together versus alone.

Item Type:	Conference Extract
Keywords:	Dusky dolphins, Australasian Gannets, feeding, New Zealand
Research Division:	Biological Sciences
Research Group:	Ecology
Research Field:	Marine and estuarine ecology (incl. marine ichthyology)
Objective Division:	Environmental Management
Objective Group:	Marine systems and management
Objective Field:	Marine biodiversity
UTAS Author:	Watson, L (Dr Leslie Watson)
ID Code:	129353
Year Published:	2005
Deposited By:	Strategic Research Funding
Deposited On:	2018-11-26
Last Modified:	2018-11-26
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