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19 - The method of multiple hypotheses and the decline of Steller sea lions in western Alaska

Published online by Cambridge University Press:  31 July 2009

C. J. Camphuysen
By
N. Wolf ,
J. Melbourne  and
M. Mangel
Edited by
I. L. Boyd  and
S. Wanless
C. J. Camphuysen
Affiliation:
Royal Netherlands Institute for Sea Research
N. Wolf
Affiliation:
MRAG Americas, 110 South Hoover Boulevard, Suite 212, Tampa, Florida 33609, USA
J. Melbourne
Affiliation:
Department of Astronomy and Astrophysics, University of California Santa Cruz, 1156 High Street, California 95064, USA
M. Mangel
Affiliation:
Center for Stock Assessment Research, University of California Santa Cruz, 1156 High Street, California 95064, USA
I. L. Boyd
Affiliation:
University of St Andrews, Scotland
S. Wanless
Affiliation:
NERC Centre for Ecology and Hydrology, UK
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Summary

In recent years, enormous effort has been expended to explain the cause of the precipitous decline of the western population of Steller sea lions (Eumatopias jubatus) since the late 1970s; however, despite these efforts and the proposal of a wide variety of hypotheses, the decline has proven to be very difficult to explain. The authors of a recent comprehensive review of the problem emphasized repeatedly that the system is in dire need of a modelling approach that takes advantage of the data available at small spatial scales (at the level of the rookery). We view this as an opportunity for ecological detection, a process in which multiple hypotheses simultaneously compete and their success is arbitrated by the relevant data. We describe ten hypotheses for which there are sufficient data to allow investigation, a method that allows one to link various sources of data to the hypotheses and the conclusions from this approach.

The decline of the western Alaska population of Steller sea lions has proven to be very difficult to explain, in part because most aspects of the population and the environmental variables proposed to explain its decline involve a combination of high spatial and temporal variability, and limited data. Consequently, most researchers pooled data across rookeries or across time, obscuring spatial and/or temporal patterns (Fig. 19.1). Some of these previous studies are described below.

Type
Chapter
Information
Top Predators in Marine Ecosystems
Their Role in Monitoring and Management
 , pp. 275 - 293
Publisher: Cambridge University Press
Print publication year: 2006

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