http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Optimal foraging theory as a model to examine the relationship between relative prey accessibility and foraging energetics in Stellar sea lions (Eumetopias jubatus) in the Gulf of Alaska and Bering Sea
xi, 105 leaves : illustrations, maps ; 28 cm.
The western stock of the Steller sea lion (Eumetopias jubatus) (SSL) along the Aleutian Islands and in the Gulf of Alaska (GOA) has continuously declined over the past three decades, and is now listed as endangered. While the causes of this decline are not well understood, nutritional stress, resulting in excessive juvenile mortality, is the leading hypothesis. Optimal foraging theory predicts that predators should change their dive behavior (foraging strategy) as prey availability changes. Relative prey accessibility (RPA, the ability of an individual SSL to access prey during a dive cycle) is likely a crucial causal link between hypothesized reduced prey biomass resulting from commercial fishing activity and depressed foraging efficiency of SSL, but cannot be controlled in the wild, and is impossible to accurately quantify at the individual level. This study, for the first time, experimentally validates prey availability-foraging behavior relationships previously hypothesized by optimality and foraging theory, but never before experimentally tested for a diving mammal. I employed a combined approach of predictive model development and controlled experiments. Testable predictions were determined by developing a bioenergetics-based model of individual dive behavior for aerobic dives of otariids. To determine the relationship between RPA and dive behavior, I examined how dive duration, foraging time, surface interval, percent time foraging, submerged: surface time, dive efficiency, and foraging efficiency varied with changes in simulated RPA in optimal foraging experiments performed with three seven-year-old SSL (two females, one male) held captive at the Alaska Sea Life Center in Seward, AK. RPA had a significant positive effect on dive duration, foraging time, percent time foraging, and relative foraging efficiency. The dive model accurately predicted the observed effect of changing RPA on dive behavior and foraging efficiency. A population-based model was also developed in order to predict the effects of varying regimes of commercial fisheries activity on SSL population trends, based upon an estimate of annual SSL energetic requirements. The model accurately portrayed SSL abundance trends predicted by published projections, but failed to implicate competition with the commercial groundfish fishery in Alaska as a cause of the decline of SSL.
"Major Subject: Wildlife and Fisheries Sciences".
Issued also on microfiche from University Microfilm Inc.
Includes bibliographical references (leaves 96-103).