Stable isotope assessment of temporal and geographic differences in feeding ecology of northern fur seals (Callorhinus ursinus)

• Main Author: Kurle, Carolyn Mary
• Format: Thesis
• Language: English
• Published: Texas A&M University 1998
• Subjects: wildlife and fisheries sciences; Major wildlife and fisheries sciences; Bering Sea; George Islands; Callorhinus ursinus; Northern fur seal
• Online Access: https://hdl.handle.net/1969.1/ETD-TAMU-1998-THESIS-K87

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [e-mail], referencing the URI of the item. Includes bibliographical references (leaves 53-63). Issued also on microfiche from Lange Micrographics. The feeding ecology of northern fur seals (Callorhinus ursinus) and their primary prey was examined by analyzing their skin tissues for stable-carbon and nitrogen isotope content. The Pribilof Island northern fur seal population was designated as depleted in 1988 because their numbers were, and continue to be, below their optimum sustainable population. The primary cause for this decline is thought to be a decrease in their prey base in the eastern Bering Sea. Determination of fur seal feeding ecology is important so that disturbances in prey availability can be further studied. This study was able to augment current northern fur seal dietary knowledge using stable-carbon and nitrogen isotope analysis. Parturient and lactating female and juvenile male skin tissue and prey items were analyzed. Female and male tissues were collected in July, August and November, and July and August, 1997, respectively, from both St. Paul and St. George Islands. July/August samples represented spring migratory diet, while November samples illustrated breeding season diet. Females were found to be more enriched isotopically in ¹⁵N and ¹³C over juvenile males during their migration. November females on St. Paul island were enriched in ¹⁵N over July/August females, while St. George females were not significantly enriched. July/August females on St. George Island were more enriched in ¹³C over November females, while St. Paul females were not significantly enriched. There were no differences in ¹⁵N or ¹³C enrichment for migratory animals of the some sex traveling to either island, and there was no difference in ¹⁵N between islands for November females. There was a significant ...