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Cook Inlet Beluga numbers continue down
NOAA Fisheries releases report on biennial survey done in 2018; median estimate is 279 whales; next survey will be this summer Kristen Nelson Petroleum News
NOAA Fisheries has released its latest estimate of the Beluga whale population in Cook Inlet with numbers down from the last count and continuing a 10-year decline.
A Jan. 28 release said scientists have estimated the population size to be between 250 and 317, with a median estimate of 279.
“The population is estimated to be smaller and declining more quickly than previously thought,” the agency said.
Cook Inlet belugas were listed by NOAA as endangered under the Endangered Species Act in 2008 and the agency finalized a recovery plan in December 2016.
Year-to-year estimates can vary, the agency said, based on factors such as births and deaths, changes in behavior or distribution and statistical variability in the data.
But over the most recent 10-year period, 2008-18, the estimated trend in abundance is a drop of about 2.3% per year, a decline faster than the previous estimate of 0.5% per year.
The last population estimate, released in 2016, used the best methodology at the time, the agency said, and estimated some 328 animals. “Today, using the new, more reliable methodology, scientists estimate that abundance in 2016 was more likely around 293 animals,” the agency said. The new methodology for data collected in 2018 shows that the Cook Inlet beluga population appears to be continuing to decline and is now estimated to be around 279 animals.
“These new abundance and trend numbers are concerning,” said Jim Balsiger, Alaska regional administrator for NOAA Fisheries. “They indicate that we still have a long way to go to recover this iconic and highly endangered population.”
Surveys since 1993 The National Marine Fisheries Service began aerial surveys to estimate beluga numbers in Cook Inlet in 1993 and surveyed annually until 2012; biennial surveys began in 2014.
NOAA Fisheries provided background in its report on the 2018 surveys, dated December 2019 and released in January. The next survey is scheduled for June of this year.
The agency said belugas inhabit the waters surrounding Alaska from Yakutat Bay to the Alaska-Yukon Territory boundary, with five recognized stocks: Cook Inlet, Bristol Bay, Eastern Bering Sea, Eastern Chukchi Sea and Beaufort Sea.
Cook Inlet belugas are the most isolated stock, separated from the other stocks by the Alaska Peninsula. Cook Inlet belugas gather in river mouths and bays during the summer.
“The small population size … and geographic and genetic isolation of the whales in Cook Inlet … in combination with their strong site fidelity, has made this stock vulnerable to anthropogenic impacts,” NMFS said.
Until 1999 the whales were subject to an unregulated Native subsistence hunt, but after the stock was designated depleted under the U.S. Marine Mammal Protection Act in 2000, the hunt became regulated based on a 5-year harvest level based on the average abundance during the previous 5 years and population growth rate during the previous 10 years. “A harvest is not allowed if the previous 5-year average abundance is less than 350 beluga whales which has been the case since the first review period (2003-2007), and the harvest has been zero since 2005,” NMFS said.
In 2008 the Cook Inlet beluga population was designated a distinct population segment and listed as endangered under the U.S. Endangered Species Act.
June 2018 survey NMFS said the 2018 aerial survey provided thorough coverage of the coast of Cook Inlet north of Augustine Island, with most of upper Cook Inlet surveyed seven times, “especially areas where belugas have consistently been found in the past - such as the Susitna Delta, Knik Arm, and Chickaloon Bay.”
The agency said the large number of flights per year over many years have helped it “detect patterns of whale distribution and identify changes that have occurred.”
Historically large numbers of belugas have been found in both upper and lower Cook Inlet in June and July, but between 1993 and 1995, fewer than 3% of the annual sightings were in lower Cook Inlet, south of East Foreland and West Foreland. From 1996-2011, hardly any were seen in the lower inlet during the surveys.
Sightings south of North Foreland and Point Possession, which had averaged 1.5% of sightings from 1993-95, were zero until June 2012. In June 2012 and June 2018 a group of belugas was repeatedly found in Trading Bay.
Other than those sightings, belugas were only consistently found in waters north of North Foreland and Moose Point. There was also a steep decline in June sightings in Knik Arm and Turnagain Arm after 2007.
In addition to aerial surveys, NMFS said limited satellite tagging provides more detail over longer periods, with satellite results from tagged whales from 1999 to 2003 showing the distribution seen in aerial surveys in June is typical of most of summer through late fall, with whales remaining in waters north of East and West Foreland.
In winter some tagged whales dispersed into deeper waters and a few were as far south as Chinitna Bay, but never left Cook Inlet.
-KRISTEN NELSON
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