Research Article

Gray whale (Eschrichtius robustus) in the Mediterranean Sea: anomalous event or early sign of climate-driven distribution change?

Aviad P. Scheinin^a1 c1, Dan Kerem^a1, Colin D. MacLeod^a2, Manel Gazo^a3a4, Carla A. Chicote^a3 and Manuel Castellote^a5

^a1 Israel Marine Mammal Research and Assistance Center (IMMRAC), The Leon Recanati Institute for Maritime Studies and Department for Maritime Civilizations, The University of Haifa, Mount Carmel, Haifa 31905, Israel

^a2 IBES, University of Aberdeen, Aberdeen, UK

^a3 SUBMON—Conservation, study and awareness of the marine environment, Rabassa, 49-51. 08024 Barcelona, Spain

^a4 Department of Animal Biology, University of Barcelona, Diagonal 645, 08028 Barcelona, Spain

^a5 National Marine Mammal Laboratory, Alaska Fisheries Science Center, NOAA, Sand Point Way NE, Seattle, WA 98115 USA

Abstract

On 8 May 2010, a gray whale was sighted off the Israeli Mediterranean shore and twenty-two days later, the same individual was sighted in Spanish Mediterranean waters. Since gray whales were last recorded in the North Atlantic in the 1700s, these sightings prompted much speculation about this whale's population origin. Here, we consider three hypotheses for the origin of this individual: (1) it represents a vagrant individual from the larger extant population of gray whales found in the eastern North Pacific; (2) it represents a vagrant individual from the smaller extant population found in the western North Pacific; or (3) it represents an individual from the previously thought extinct North Atlantic population. We believe that the first is the most likely, based on current population sizes, on known summer distributions, on the extent of cetacean monitoring in the North Atlantic and on the results of a performed route analysis. While it is difficult to draw conclusions from such singular events, the occurrence of this individual in the Mediterranean coincides with a shrinking of Arctic Sea ice due to climate change and suggests that climate change may allow gray whales to re-colonize the North Atlantic as ice and temperature barriers to mixing between northern North Atlantic and North Pacific biomes are reduced. Such mixing, if it were to become widespread, would have implications for many aspects of the marine conservation and ecology of these two regions.

(Received July 29 2010)

(Accepted December 05 2010)

(Online publication April 19 2011)

Keywords

• global warming;
• climate change;
• migration;
• vagrancy;
• sea ice;
• ecosystem sentinels

Correspondence:

^c1 Correspondence should be addressed to: A.P. Scheinin, Israel Marine Mammal Research and Assistance Center (IMMRAC), The Leon Recanati Institute for Maritime Studies and Department for Maritime Civilizations, The University of Haifa, Mount Carmel, Haifa 31905, Israel email: scheinin@research.haifa.ac.il