Whales generally feed for four to six months in the Arctic, according to Stewart. After this feeding period, they fast for the next 6-8 months, making these Arctic feeding grounds their primary source of nutrition.
The factors influencing food availability in the Arctic are complex, and scientists continue to investigate them. However, Stewart explains that the historical process was as follows: Algae grows on the underside of sea ice and descends to the ocean floor when the ice melts. This decomposition fertilizes the seafloor, nourishing the amphipods in the sediment, which in turn supports the whales as they consume the nutrient-rich soil.
Recent research indicates that sea ice is melting earlier each year, which allows for more sunlight to penetrate the water column sooner. This stimulates the growth of phytoplankton and other organisms, absorbing nutrients that were once available to the ocean floor. Scientists believe this reduction in nutrient availability is contributing to a decrease in prey for whales.
For gray whales, misfortunes experienced in summer often manifest the following spring, as their northern migration consumes more energy than they were able to regenerate through feeding in the previous year.
“During their migration north, they are at their leanest. This is the longest duration they’ve gone without food, making them highly vulnerable to starvation,” says Stewart.
Kalambokidis noted that some whales have been appearing in unusual locations this season, including one that tragically died in the Willapa River, possibly in search of food to sustain its journey.
“Malnourished whales tend to become desperate, which can weaken their awareness of their environment and impair their navigation,” Karambokidis observed.
NOAA’s latest data suggests that the gray whale population has plummeted from 27,430 a decade ago to approximately 12,950 last summer. However, Stewart cautions that these models may not accurately reflect the population decline.
Interestingly, not all Pacific gray whales rely solely on Arctic feeding grounds. A small group, known as a sounder, located north of Seattle, diverges from the typical migration route to hunt for ghost shrimp in the northern Puget Sound, heading north toward the Bering and Chukchi Seas. Another group, the Pacific Feeding Group, includes over 200 whales thriving in coastal waters off Northern California, Oregon, Washington, and southern Canada. These small populations display resilience against broader decline trends.
“This indicates that some gray whales may develop alternative foraging strategies to navigate environmental challenges in the long term,” states Elliot Hazen, a research ecologist at NOAA’s Southwest Fisheries Science Center.
Historically, gray whale populations in the eastern North Pacific faced severe declines due to commercial whaling during the 19th and early 20th centuries, possibly dropping to around 1,000 individuals. Nonetheless, with the implementation of whaling restrictions and protection under the Marine Mammal Protection Act, gray whales emerged as one of the fastest recovering whale species, ultimately being removed from the endangered species list in 1994.
Stewart expresses cautious optimism, noting that while he is not particularly worried about the whales approaching extinction, he is concerned about the diminishing progress in their recovery.
“We are entering uncharted territory in terms of recovery since the population is significantly lower than when the species was delisted from the Endangered Species Act,” he concluded.
Source: www.nbcnews.com
