A report in the July 22 issue of the journal Science says the recent loss of eight whales, six of them adult females and three carrying near-term fetuses, is unprecedented in 25 years of study of this species, Eubalaena glacialis. Four of the females were beginning to bear calves, and since the average lifetime calf production is as high as five calves, the deaths of these females represents a reproductive loss of as many as 21 animals.
After almost 1,000 years of whaling that brought the species close to extinction in the early 20th century, the North Atlantic right whale has been protected from commercial whaling since 1935 but has faced constant threats from human activities, mainly collisions with ships and entanglement in fishing gear. In contrast, southern right whales, Eubalaena australis, are thriving, with a population estimated at more than 10,000 animals and growing at more than seven percent each year.
According to the recent study, led by Scott Kraus of the New England Aquarium, 50 right whales have been reported dead since 1986, at least half of them from human activities. At least 19 were killed by vessel collisions and at least six by entanglement in fishing gear. In addition, there were 61 confirmed reports of whales carrying fish gear, with about half of those whales able to shed the gear or were disentangled by humans.
Study co-authors Hal Caswell and Michael Moore of the Woods Hole Oceanographic Institution (WHOI) emphasize the consequences for the population. "The bottom line is that human
Contact: Shelley Dawicki
Woods Hole Oceanographic Institution