Scientists from Stanford University, the Wildlife Conservation Society, the American Museum of Natural History, and other organizations are closing in on the answer to an important conservation question: how many humpback whales once existed in the North Atlantic?
Building on previous genetic analyses to estimate the pre-whaling population of North Atlantic humpback whales, the research team has found that humpbacks used to exist in numbers of more than 100,000 individuals. The new, more accurate estimate is lower than previously calculated but still two to three times higher than pre-whaling estimates based on catch data from whaling records.
Known for its distinctively long pectoral fins, acrobatics, and haunting songs, the humpback whale occurs in all the world's oceans. Current estimates for humpback whale numbers are widely debated, but some have called for the level of their international protection to be dropped.
The study appears in the recently published edition of Conservation Genetics. The authors include: Kristen Ruegg and Stephen Palumbi of Stanford University; Howard C. Rosenbaum of the Wildlife Conservation Society and the American Museum of Natural History; Eric C. Anderson of the National Marine Fisheries Service and University of California-Santa Cruz; Marcia Engel of the Instituto Baleia Jubarte/Humpback Whale Institute, Brazil; Anna Rothschild of AMNH's Sackler Institute for Comparative Genomics; and C. Scott Baker of Oregon State University.
"We're certain that humpback whales in the North Atlantic have significantly recovered from commercial whaling over the past several decades of protection, but without an accurate size estimate of the pre-whaling population, the threshold of recovery remains unknown," said Dr. Kristen Ruegg of Stanford University and the lead author of the study. "We now have a solid, genetically generated estimate upon which future work on this important issue can be based."
"Our current challenge is to explain the remaining discrepancy between the historical catch data and the population estimate generated by genetic analyses," said Dr. Howard Rosenbaum, study co-author and Director of the Wildlife Conservation Society's Ocean Giants Program. "The gap highlights the need for continued evaluations of whale populations, and presents new information informing the debate and challenges associated with recovery goals."
"We have spent a great deal of effort refining the techniques and approaches that give us this pre-whaling number," said Dr. Steve Palumbi of Stanford. "It's worth the trouble because genetic tools give one of the only glimpses into the past we have for whales."
Reaching some 50 feet in length, the humpback whale was hunted for centuries by commercial whaling fleets in all the world's oceans. Humpbacks had predictable migration routes and were reduced to several hundred whales in the North Atlantic. The global population was reduced by possibly 90 percent of its original size. The species received protection from the International Whaling Commission in North Atlantic waters in 1955 due to the severity of its decline.