Evaluating quantitative fatty acid signature analysis (QFASA) using harbour seals Phoca vitulina richardsi in captive feeding studies

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 360:245-263 (2008) - DOI: https://doi.org/10.3354/meps07378 Evaluating quantitative fatty acid signature analysis (QFASA) using harbour seals Phoca vitulina richardsi in captive feeding studies Chad A. Nordstrom1,*, Lindsay J. Wilson1, Sara J. Iverson2, Dominic J. Tollit1 1Marine Mammal Research Unit, Fisheries Centre, Aquatic Ecosystems Research Laboratory, 2202 Main Mall, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada 2Department of Biology, Dalhousie University, Halifax, Nova Scotia B3H 4J1, Canada *Email: Chad.Nordstrom@vanaqua.org ABSTRACT: Quantitative fatty acid (FA) signature analysis (QFASA) has recently been developed to estimate the species composition of predator diets by statistically comparing FA signatures of predator adipose tissue with that of their potential prey. Captive feeding trials were used to further test the technique with newly weaned harbour seals Phoca vitulina richardsi (N = 21). Two groups of seals were fed monotypic diets of either Pacific herring Clupea pallasii or surf smelt Hypomesus pretiosus for 42 d while a third group was fed smelt for 21 d followed by herring for 21 d. Blubber biopsies were taken dorsally at Days 0, 21 and 42. Specific calibration coefficients (CC) used by QFASA were developed from 4 juvenile harbour seals and in some cases differed by 2-fold with previously reported phocid CC values. The QFASA diet estimates were evaluated using 2 CC sets, 15 FA subsets and a library of 3 to 11 potential prey species. Diet switches were best tracked using the harbour seal CC and the new FA subset. Overall prey misclassifications were apparent (mean = 12%, range = 4 to 25%) when modeled with 8 additional prey not fed, a trend consistent with overlapping prey FA signatures. Blubber FA turnover rates were not strictly linear and in the order of 1.5 to 3 mo in newly weaned seals. Following parameter optimization of the model, QFASA estimates reflected major diet trends in the feeding study, but were sensitive to the CC and FA subsets used as well as to prey species with similar FA signatures. Our results have important implications in the application of QFASA to the study of pinniped diets with more complex feeding histories and wider prey fields. KEY WORDS: Fatty acid · Diet · Blubber · Harbour seal · Phoca vitulina · QFASA Full text in pdf format PreviousNextCite this article as: Nordstrom CA, Wilson LJ, Iverson SJ, Tollit DJ (2008) Evaluating quantitative fatty acid signature analysis (QFASA) using harbour seals Phoca vitulina richardsi in captive feeding studies. Mar Ecol Prog Ser 360:245-263. https://doi.org/10.3354/meps07378 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 360. Online publication date: May 22, 2008 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2008 Inter-Research.