Do patterns of Steller sea lion (Eumetopias jubatus) diet, population trend and cetacean occurrence reflect oceanographic domains from the Alaska Peninsula to the central Aleutian Islands?
Article first published online: 27 SEP 2005
Volume 14, Issue Supplement s1, pages 223–242, November 2005
How to Cite
SINCLAIR, E. H., MOORE, S. E., FRIDAY, N. A., ZEPPELIN, T. K. and WAITE, J. M. (2005), Do patterns of Steller sea lion (Eumetopias jubatus) diet, population trend and cetacean occurrence reflect oceanographic domains from the Alaska Peninsula to the central Aleutian Islands?. Fisheries Oceanography, 14: 223–242. doi: 10.1111/j.1365-2419.2005.00375.x
- Issue published online: 27 SEP 2005
- Article first published online: 27 SEP 2005
- Received 12 December 2003 Revised version accepted 20 July 2005
- generalized additive models;
- killer whales;
- Steller sea lion
Shipboard surveys were conducted along the Aleutian Islands in 2001 and 2002 to assess the influence of a suite of biophysical parameters on regional patterns in the distribution of cetaceans and Steller sea lions (SSL; Eumetopias jubatus). Distributions of four large whale species: fin (Balaenoptera physalus), humpback (Megaptera novaeangliae), minke (B. acutorostrata) and sperm (Physeter macrocephalus) aligned with proposed metapopulation breaks in diet and population trend of SSLs. Dall's porpoise (Phocoenoides dalli) and killer whales (Orcinus orca) were widely distributed throughout the study area, and killer whales were particularly prevalent along the north Aleutian Island coastlines between Unimak Pass and Samalga Pass. Biopsies determined that most killer whales (92%) were of the piscivorous (resident) ecotype as opposed to the mammal-eating (transient) ecotype observed in 2002 only. Generalized additive models (GAMs) were used to explore relationships between these multispecies patterns in distribution, oceanographic variables (salinity, temperature, fluorescence and depth) and proximity to six Aleutian passes. The GAMs indicated the best-fit models and most significant correlations as determined by the Akaike function and Cp-statistics were: depth and proximity to the nearest measured pass for SSLs and all cetaceans, respectively; frequencies of herring and salmon in SSL diet with population trend; fluorescence in the top 50 m with occurrence of humpback, minke, and killer whales; and surface temperature with occurrence of humpback, killer, and sperm whales. Results of the GAM analyses suggest foci for future investigation of relationships between physical variables and interspecific patterns of marine mammal distribution.