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Marine Ecology Progress Series

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MEPS 479:251-261 (2013)  -  DOI:

Stable isotope analysis of baleen reveals resource partitioning among sympatric rorquals and population structure in fin whales

Conor Ryan1,*, Brendan McHugh2, Clive N. Trueman3, Richard Sabin4, Robert Deaville5, Chris Harrod6,7, Simon D. Berrow1,8, Ian O?Connor1

1Galway-Mayo Institute of Technology, Dublin Road, Galway, Ireland
2Marine Institute, Rinville, Oranmore, County Galway, Ireland
3Ocean and Earth Science, University of Southampton, National Oceanography Centre, European Way, Southampton SO14 3ZH, UK
4Vertebrates Group, Department of Zoology, Natural History Museum, Cromwell Road, London SW7 5BD, UK
5UK Cetacean Strandings Investigation Programme, Institute of Zoology, Zoological Society of London, Regent’s Park, London NW1 4RY, UK
6School of Biological Sciences, Medical Biology Centre, 97 Lisburn Road, Queen’s University Belfast, Belfast BT9 7BL, UK
7Instituto de Investigaciones Oceanológicas, Universidad de Antofagasta, Avenida Angamos 601, Antofagasta, Chile
8Irish Whale and Dolphin Group, Merchant’s Quay, Kilrush, County Clare, Ireland

ABSTRACT: Stable isotope analysis is a useful tool for investigating diet, migrations and niche in ecological communities by tracing energy through food-webs. In this study, the stable isotopic composition of carbon and nitrogen in keratin was measured at growth increments of baleen plates from 3 sympatric species of rorquals (Balaenoptera acutrostrata, B. physalus and Megaptera novaeangliae), which died between 1985 and 2010 in Irish and contiguous waters. Bivariate ellipses were used to plot isotopic niches and standard ellipse area parameters were estimated via Bayesian inference using the SIBER routine in the SIAR package in R. Evidence of resource partitioning was thus found among fin, humpback and minke whales using isotopic niches. Highest δ15N values were found in minke whales followed by humpback, and fin whales. Comparison between Northeast Atlantic (Irish/UK and Biscayan) and Mediterranean fin whale isotopic niches support the current International Whaling Commission stock assessment of an isolated Mediterranean population. Significantly larger niche area and higher overall δ15N and δ13C values found in fin whales from Irish/UK waters compared to those sampled in adjacent regions (Bay of Biscay and Mediterranean) suggest inshore foraging that may be unique to fin whales in Ireland and the UK. Isotopic profiles support spatial overlap but different foraging strategies between fin whales sampled in Ireland/UK and the Bay of Biscay. Stable isotope analysis of baleen could provide an additional means for identifying ecological units, thus supporting more effective management for the conservation of baleen whales.

KEY WORDS: Diet · Isotopic niche · Foraging · Stock discrimination · Northeast Atlantic · Bayesian analysis

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Cite this article as: Ryan C, McHugh B, Trueman CN, Sabin R and others (2013) Stable isotope analysis of baleen reveals resource partitioning among sympatric rorquals and population structure in fin whales. Mar Ecol Prog Ser 479:251-261.

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