NOAA Fisheries is delaying a new aerial survey to track abundance and trends of Cook Inlet beluga whales until June 2025. Cook Inlet beluga whales are endangered under the U.S. Endangered Species Act and one of NOAA Fisheries’ Species in the Spotlight.
Since 2010, NOAA Fisheries scientists have been conducting a biennial aerial survey in early-to-mid June to estimate the abundance and trends of this endangered whale population. Beluga whales gather in the upper inlet in June to feed on returning fish runs. The last published abundance estimate was 331 in 2022. Scientists also noted that the population trend has been stable or slightly increasing since 2016.
The biennial aerial survey involved flying a coastal trackline of all nearshore waters in Cook Inlet and a series of offshore transects across the inlet. When they encountered a beluga group, the plane made multiple passes alongside the group so observers could count the whales present and collect videos. Scientists used these observation data to estimate group sizes.
“Our surveys were designed to take advantage of the clumped distribution of these whales in early June, when they are often found in a small number (two to eight) of large groups,” said Paul Wade, marine biologist, Alaska Fisheries Science Center. “However, in recent years, whales have not been as aggregated in places we used to regularly see them, such as the Susitna Delta.”
New Aerial Survey Approach May Better Capture Changing Behavior of Beluga Whales in Cook Inlet
To identify the best and most cost-effective approach for estimating abundance and trends, in 2021 and 2022 scientists added line-transect aerial surveys within:
- Susitna Delta
- Chickaloon Bay
- Trading Bay
They also conducted the conventional aerial survey for comparative purposes.
Scientists found that the sightings data from the line-transect survey approach produced a reliable abundance estimate similar to the conventional method. The method also does not require months of video analysis, instead producing an estimate shortly after the completion of field work.
In 2024, they had hoped to replace the conventional aerial survey method with a line-transect aerial survey conducted in combination with a Cook Inlet beluga photo-identification project. This project obtains overhead photos taken from an uncrewed aerial system (UAS). However, the plane chartered for survey operations had mechanical issues and the team was unable to secure an alternative. The team plans to conduct the survey next year.
Uncrewed Aerial Systems to Provide Valuable Data to Support Abundance Estimate in 2024
We expect to be able to obtain an abundance estimate from the photo-identification project, which uses UAS technology, in 2024.
“We have been using UAS since 2017, and it has been a success,” said Wade. “The count information we collect using this technology has allowed us to produce a comparable abundance estimate to other approaches.”
Wade is quick to point out, though, that it is important to move forward with the crewed aerial survey in 2025. It can provide distribution information as it covers the entire inlet’s coastline and offshore waters, areas where UAS/photo identification studies do not currently occur. Currently UAS use has been limited to areas in the upper inlet such as the Susitna Delta, Knik Arm, Chickaloon Bay, and Trading Bay. Further, UAS is limited in that it has to operate within line of sight of the person operating the drone. It is also limited by weather and tides. Tides restrict access to these areas for boats used to deploy the drones.
