New Model Suggests Northern Right Whale Population on Path to Extinction
Efforts to Reduce Mortality of the Endangered Species Could Alter Trend
The North Atlantic northern right whale, considered to be the most endangered large whale species, is headed for extinction unless human intervention improves survival, according to a new study by researchers at Woods Hole Oceanographic Institution (WHOI) and the University of Massachusetts, Boston (UMASS Boston). Their report, the first to obtain rigorous statistical estimates of survival probability of this population, was published today in the "Proceedings of the National Academy of Sciences."
The right whale population has recovered only slightly since the end of commercial whaling, and currently numbers about 300. The researchers used a photographic identification database maintained by the New England Aquarium. The photographs enable individual animals, distinguished by unique markings, scars and callosity patterns, to be identified and tracked. Scientists have recorded sightings annually since 1980 in calving areas in Florida and in waters off New England and into the Bay of Fundy in Nova Scotia. Over that time, the new results show, survival has declined dramatically, and population growth rate has gone from positive to negative.
Under current conditions, the population is headed for extinction in less than 200 years."Everyone has known for a long time that there aren't many northern right whales left," Senior Scientist Hal Caswell of WHOI's Biology Department said of the study. "The right whale is at risk from entanglement in fishing gear, from collisions with ships, and from pollution. The population seems to be recovering more slowly than other whale species, such as humpbacks. Why this is happening has not been documented. Until this study, no one suspected that the survival probability for northern right whales was going down, or that the population was actually declining."
Caswell and study colleagues used the New England Aquarium database to estimate survival and discovered the survival probability was declining over time. They then combined these data with an estimate of birth rate, which is also declining. Together, the numbers shows a decline in the rate of growth of the entire population. "Our study was possible only because of the long-term New England Aquarium database, which will also be essential to monitoring the population in the future," said Solange Brault of the University of Massachusetts Boston, one of the authors of the study.
The report notes that the most effective way to improve the prospects for population persistence is to reduce mortality. The research team's goal is to provide reliable models that can be used to choose targets for management intervention.
"The future is not as bleak as it may appear for the right whales, since a number of efforts are already underway to reduce their mortality rate," Caswell adds. "There is no question that reducing human-caused mortality is essential to the survival of the population. NOAA is at work to teach ship operators how to recognize and avoid right whales, and fishing grounds have been closed during certain periods in some areas frequented by the whales, such as Cape Cod Bay and Great South Channel."
New federal regulations, effective April 1, emphasize the development of whale-friendly fishing gear. They require gillnetters and lobster boats to avoid certain types of gear, and place bans on fishing in some areas in order to protect the whales. The National Marine Fisheries Service finalized rules to protect the endangered population in February. Officials hope that over time, as more people learn about how whales are entangled and how to prevent it, the population will start to rebound.
Caswell and study colleagues Masami Fujiwara of WHOI's Biology Department and Brault of UMASS Boston plan to continue their analysis of the population, looking in more detail at survival of males versus females, juveniles versus adults, and females of reproductive age. They also plan to look at the possible factors causing the declining trend in survival.
Funding for the study was provided by the National Marine Fisheries Service, the Office of Naval Research, the Woods Hole Oceanographic Institution's Rinehart Coastal Research Center, and the Massachusetts Environmental Trust.
The researchers' paper is available in PDF format to registered users of the PNAS section of EurekAlert! or by fax from the Proceedings of the National Academy of Sciences news office; tel. 202-334-2138. Visuals and graphics are available from the Woods Hole Oceanographic Institution News Office at 508-289-3340.