Stable isotopes indicate population structuring in the Southwest Atlantic population of right whales (Eubalaena australis)

VIGHI MORGANA; BORREL ASUNCIÓN; CRESPO ENRIQUE ALBERTO; OLIVEIRA LARISSA ROSA DE; SIMÕES LOPES PAULO C.; FLORES PAULO A. C.; GARCÍA NÉSTOR ANÍBAL; AGUILAR ALEJANDRO

PLOS ONE

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2014 vol. 9

1932-6203

AbstractFrom the early 17th century to the 1970s southern right whales, Eubalaena australis, were subject to intense exploitationalong the Atlantic coast of South America. Catches along this coast recorded by whalers originally formed a continuum fromBrazil to Tierra del Fuego. Nevertheless, the recovery of the population has apparently occurred fragmentarily, and with twomain areas of concentration, one off southern Brazil (Santa Catarina) and another off central Argentina (Peninsula Valde´ s).This pattern suggests some level of heterogeneity amongst the population, which is apparently contradicted by recordsthat traced individuals moving throughout the whole geographical extension covered by the species in the SouthwestAtlantic. To test the hypothesis of the potential occurrence of discrete subpopulations exploiting specific habitats, weinvestigated N, C and O isotopic values in 125 bone samples obtained from whaling factories operating in the early 1970s insouthern Brazil (n = 72) and from contemporary and more recent strandings occurring in central Argentina (n = 53). Resultsindicated significant differences between the two sampling areas, being d13C and d18O values significantly higher in samplesfrom southern Brazil than in those from central Argentina. This variation was consistent with isotopic baselines from the twoareas, indicating the occurrence of some level of structure in the Southwest Atlantic right whale population and equally thatwhales more likely feed in areas commonly thought to exclusively serve as nursing grounds. Results aim at reconsidering ofthe units currently used in the management of the southern right whale in the Southwest Atlantic Ocean. In the context ofthe current die-off affecting the species in Peninsula Valde´ s, these results also highlight the necessity to better understandmovements of individuals and precisely identify their feeding areas.