In the silty coastal waters of upper Cook Inlet southwest of Anchorage, a pod of beluga whales is feeding. Beluga whales use sound to find their prey, and to communicate with each other. They hunt in murky coastal waters and swim up silty glacier rivers, and can hunt entirely by echolocation. They are found in Arctic and sub-arctic Alaska waters, including Cook Inlet.
These belugas are year-round residents of Cook Inlet. Cook Inlet belugas were once common in both the upper and lower inlet with a historical population estimate of 1,300. The population dropped to just half that number in the mid-1990s due to unmanaged subsistence harvests. Since the 1990s it's declined further and population in 2017 is estimated to be 340 belugas, which mostly stay in the upper inlet.
In 1999, Congress imposed a moratorium on the subsistence harvest of Cook Inlet belugas, and the population was designated as depleted under the Marine Mammal Protection Act. In 2008 they were listed as endangered under the Endangered Species Act. In 2011, an area of 3,013 square miles of critical habitat was established. In spite of these efforts, Cook Inlet belugas have not recovered and the reasons why are unknown.
Fish and Game is studying these endangered Cook Inlet beluga whales. Understanding the foraging ecology, diet and habitat use of the Cook Inlet beluga may help determine if changes in prey availability were a factor in the population decline, and if it is impeding recovery.
Because they use sound to find prey, communicate, and navigate, loud human-generated noise may interfere with their ability to find and capture prey. Biologists are using hydrophones to detect and identify noise sources, and learn if noise may displace belugas from feeding areas. This acoustic monitoring has already provided insights into the seasonal distribution of belugas in Cook Inlet.