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Cook Inlet beluga whale count drops NMFS annual whale count for 2011 results in second lowest number on record; agency says result consistent with 10-year decline Alan Bailey Petroleum News
The NOAA National Marine Fisheries Service’s 2011 survey of the Cook Inlet beluga whales resulted in an estimated population of 284 whales, NOAA announced on Jan. 9. That count was almost 20 percent lower than the 2010 population estimate of 340 and was the second lowest population estimate since the whale surveys began in 1993. NOAA says that the 2011 count is within the range of an inferred 1.1 percent annual decline in the whale population over the past 10 years.
“The real value of this survey is the long-term nature, which helps to determine trends that are valuable for monitoring this population,” said Rod Hobbs, lead scientist for the survey. “Year-to-year changes in the population estimates are less important than this long-term trend.”
The Fisheries Service conducts its whale survey every June by overflying most of the upper Cook Inlet, Turnagain Arm and Knik Arm, counting observed whales and supplementing visual observations with video imagery for more precise counting. The objective is to count the entire whale population, but the practical limitations of trying to observe all of the whales result in a count that is an estimate of the true population. The scientists, for example, try to estimate and account for whales that are diving at the time of an observation.
Uncertainty The uncertainty inherent in the population estimates results in some level of random scatter in the population data from one year to the next. However, the scientists use the data to infer multiyear population trends, with those trends averaging out the year-to-year data fluctuations.
For several years the Fisheries Service has argued that, although a precipitous drop in population in the 1990s ended following restrictions on subsistence whale hunting introduced in 1999, there has been a continuing slow population decline since 2001. Essentially, a straight line plotted through the population estimates for each year shows a downward slope. And in 2008, following an assessment of predicted future population trends, the agency listed the whales as endangered under the Endangered Species Act.
Some people have argued that the population estimate trend since 2005 indicates a whale population showing signs of recovery. In other words, the population has been flattening or even recovering, rather than continuing downwards. In 2010 Hobbs countered that argument when he told Petroleum News that arbitrarily picking the year with lowest population estimate as a starting point for assessing the population trend would automatically result in an upward slope in the trend.
NOAA says that it is not possible for the beluga population to recover at a rate of more than 20 percent per year. On the other hand, a population decline of 20 percent per year would likely result in more observations of dead whales than have been reported.
Doug DeMaster, director of NOAA’s Alaska Fisheries Science Center, said that only three dead belugas had been reported in 2011 and that the NOAA scientists do not believe that the low population count for 2011 represents a marked decrease in the whale population.
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