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The spatio-temporal variability in marine resources influences the foraging behavior and success of top marine predators. However, little is known about the links between these animals and ocean productivity, specifically, how plankton density influences their foraging behavior. Southern elephant seals (Mirounga leonina) have two annual at-sea foraging trips: a 2 month post-breeding foraging trip (Nov–Jan) that coincides with elevated summer productivity; and an 8 month post-molting foraging trip (Feb–Oct) over winter, when productivity is low. Physical parameters are often used to describe seal habitat, whereas information about important biological parameters is lacking. We used electronic tags deployed on elephant seals during both trips to determine their movement and foraging behavior. The tags also recorded light, which measured the bio-optical properties of the water column, the bulk of which is presumably influenced by phytoplankton. We investigated the relationship between plankton density and seal foraging behavior; comparing trends between summer and winter trips. We found a positive relationship between plankton density and foraging behavior, which did not vary seasonally. We propose that profitable concentrations of seal prey are more likely to coincide with planktonic aggregations, but we also acknowledge that trophic dynamics may shift in response to seasonal trends in productivity. Seal prey (mid-trophic level) and plankton (lower-trophic level) are expected to overlap in space and time during summer trips when peak phytoplankton blooms occur. In contrast, aggregated patches of lower trophic levels are likely to be more dispersed during winter trips when plankton density is considerably lower and heterogeneous. These results show that southern elephant seals are able to exploit prey resources in different ways throughout the year as demonstrated by the variation observed between seal foraging behavior and trophic dynamics.

Item Type:	Refereed Article
Keywords:	trophic link, lower-trophic distribution, foraging behavior, Mirounga leonina, Ross Sea, Antarctica, elephant seal
Research Division:	Biological Sciences
Research Group:	Microbiology
Research Field:	Infectious agents
Objective Division:	Environmental Management
Objective Group:	Coastal and estuarine systems and management
Objective Field:	Assessment and management of coastal and estuarine ecosystems
UTAS Author:	O'Toole, MD (Dr Malcolm O'Toole)
UTAS Author:	Lea, MA (Professor Mary-Anne Lea)
UTAS Author:	Hindell, MA (Professor Mark Hindell)
ID Code:	100676
Year Published:	2015
Web of Science® Times Cited:	10
Deposited By:	IMAS Research and Education Centre
Deposited On:	2015-05-25
Last Modified:	2016-04-18
Downloads:	386 View Download Statistics