Scientists alarmed after four gray whales found dead in San Francisco Bay | California

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Four dead gray whales have washed up on San Francisco Bay beaches in the past nine days, with experts saying on Friday that one was struck by a ship. They were trying to determine how the other three died.

“It’s alarming to respond to four dead gray whales in just over a week because it really puts the current challenges facing this species into perspective,” says Dr Padraig Duignan, director of pathology at the Mammal Center sailors.

The carcass of a 12.5-meter adult female gray whale landed at Crissy Field in San Francisco on March 31. A second adult female was found last Saturday at Moss Beach, San Mateo County. A third was found floating near Berkeley Marina on Wednesday and the next day one ran aground at Muir Beach in Marin County.

Whales migrate 16,090 km to overwinter off Mexican waters, where they mate and give birth near the coast of Baja California. They return north and stay off the coast of California in the spring and summer to feed on anchovies, sardines and krill before continuing their northward migration to the cool, food-rich arctic waters.

In 2019, at least 13 dead whales stranded in the Bay Area and scientists said they feared it was because the animals were starving and couldn’t complete their annual migration from Mexico to Alaska. . Biologists have observed gray whales in poor bodily condition on their annual migration since 2019, when an “unusual mortality event” was declared by the National Oceanic and Atmospheric Administration (NOAA).

Malnutrition, entanglement in fishing gear and trauma from ship strikes were the most common causes of death found by the centre’s research team in recent years.

Gray whales in Baja California, where they mate and give birth before heading north.
Gray whales in Baja California, where they mate and give birth before heading north. Photograph: Guillermo Arias / AFP / Getty Images

A necropsy of the whale found at Muir Beach revealed significant bruising and bleeding to the muscle around the whale’s jaw and neck vertebrae, consistent with blunt trauma from a collision with a ship. But experts noted that the whale was in good bodily condition due to the fat layer and internal fat levels, the center said.
Experts have not determined how the other three whales died or whether famine was the cause of their deaths.

Nearly one in four gray whales migrating along the west coast of the United States has died since the last recorded population assessment in 2015 and 2016, according to NOAA.

“These many whales that have died in a week are shocking, especially because these animals are the tip of the iceberg,” said Kristen Monsell, legal director of the Oceans program at the Center for Biological Diversity.

Experts estimate that stranded whales account for just 10% of the total death toll, with the rest sinking into the sea unnoticed by humans.

Monsell said California lawmakers should require fishing gear that does not use rope and federal regulators should set mandatory speed limits for vessels.

“Collisions with ships and tangles of fishing gear kill many whales that we never see,” she said.

His organization was suing the federal government for speed limits on shipping lanes off California, Monsell added.

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