Stranded Gray Whale. Photo by Barbie Halaska, The Marine Mammal Center.

Gray Whales Dying off Pacific Coast

Featured photo: a gray whale found dead off Point Reyes National Seashore in northern California. Photo by Barbie Halaska,The Marine Mammal Center.

Since January 2019, there has been an increase in gray whale strandings along the west coast of North America from Mexico through Alaska.

Migration path to San Ignacia Lagoon

Gray whales' migration path to San Ignacia Lagoon.

Each fall, gray whales migrate about 5,000 miles from their feeding grounds in Alaska to their birthing grounds in Mexico. Baja, Mexico has the only three lagoons in the world where gray whales give birth: Guerrero Negro, Ojo de Liebre and Laguna San Ignacio. These shallow lagoons are protected from the swell and currents of the Pacific Ocean. Orcas, which prey upon gray whales, will not enter the lagoons’ shallow waters.

The whales only feed while in Arctic waters. Their feeding grounds are in the Bering and Chukchi Seas, where they feast on small crustaceans called amphipods. The whales have store enough fuel to survive their entire 10,000-mile round trip migration route.

Why are Gray Whales stranding?

If the whales don’t build up enough fat while in Alaska, they won’t have enough energy to complete their journey. That seems to be the case with the majority of the stranded whales that have been examined. Most of the dead animals are emaciated with very little body fat. It’s likely that the whales that are found dead are just a fraction of the whales that have died on their migratory journeys, since most whales actually sink to the ocean floor when they die.

Why are these whales starving?

So far, researchers have two main theories as to why the animals are starving. One is that the North Pacific Gray Whale population has essentially reached the carrying capacity of its environment, or the level that food resources can sustain. It’s possible there are too many whales and too few amphipods for the entire population to get its share during last summer’s feeding.

Gray Whale in Mexico. Photo Tom Bergh.

Gray whale in Mexico. Photo Tom Bergh.

Warming trends in the Arctic could also be at play.

Reduced sea ice may be impacting the amphipod population, reducing the food resources available for the whales. Researchers suspect the amphipods the whales prefer, which live in the sediment on the bottom of the sea, are fertilized by algae associated with the sea ice. With the ice melting away, the amphipods may be in short supply. Whales may be relying on other food sources like krill, which may not contain the amount of fatty lipids they need to build up their blubbery energy reserves.

Gray Whale strandings along the west coast of North America through Jan 10, 2020.

Gray Whale strandings along the west coast of North America through Jan 10, 2020.

Report a Stranded or Floating Whale

The most important action someone can take is to immediately report a dead, injured, or stranded marine mammal. Make the report by calling in California, Oregon or Washington the West Coast Marine Mammal Stranding Network: 1-866-767-6114, in Alaska the Alaska Marine Mammal Stranding Network: 1-877-925-7773, and in Canada, the British Columbia Marine Mammal Response Network 1-800-465-4336.

You can also contact the U.S. Coast Guard on VHF Channel 16. Do not approach or touch injured or dead marine mammals.

All marine mammals are federally protected by the Marine Mammal Protection Act. Only local and state officials and people authorized by NOAA Fisheries may legally handle live and dead marine mammals.

Posted in Environment.