Historical summer distribution of the endangered North Atlantic right whale (Eubalaena glacialis): a hypothesis based on environmental preferences of a congeneric species

AIM: To obtain a plausible hypothesis for the historical distribution of North Atlantic right whales (NARWs) (Eubalaena glacialis) in their summer feeding grounds. Previously widespread in the North Atlantic, after centuries of hunting, these whales survive as a small population off eastern North America. Because their exploitation began before formal records started, information about their historical distribution is fragmentary. LOCATION: North Atlantic and North Pacific oceans. METHODS: We linked historical records of North Pacific right whales (E. japonica; from 19th‐century American whaling logbooks) with oceanographic data to generate a species distribution model. Assuming that the two species have similar environmental preferences, the model was projected into the North Atlantic to predict environmental suitability for NARWs. The reliability of these predictions was assessed by comparing the model results with historical and recent records in the North Atlantic. RESULTS: The model predicts suitable environmental conditions over a wide, mostly offshore band across the North Atlantic. Predictions are well supported by historical and recent records, but discrepancies in some areas indicate lower discriminative ability in coastal, shallow‐depth areas, suggesting that this model mainly describes the summer offshore distribution of right whales. MAIN CONCLUSIONS: Our results suggest that the summer range of the NARW consisted of a relatively narrow band (width c. 10° in latitude), extending from the eastern coast of North America to northern Norway, over the Grand Banks of Newfoundland, south of Greenland and Iceland, north of the British Isles and in the Norwegian Sea. These results highlight possibilities for additional research both on the history of exploitation and on the current summer distribution of this species. In particular, better survey coverage of historical whaling grounds could help inform conservation efforts for this endangered species. More generally, this study illustrates the challenges and opportunities in using historical data to understand the original distribution of highly depleted species.