San Francisco — The grey whale population on the North American Pacific coast fell this year to its lowest level since the late 1960s and early 1970s. But there are encouraging signs with more calves born and healthier looking animals, scientists report.
The grey whales are a majestic component of the West Coast ecosystem, visible from the coastline as they migrate thousands of kilometres between Alaskan waters and the lagoons of Baja California Sur in Mexico, where they birth and mate.
The decline has been linked to a reduced source of food in addition to human factors such as collisions with vessels and entanglements in fishing nets, experts said. The recovery may stem from whales adapting to the food shortage by finding it elsewhere.
The most recent estimate of their population is 14,526 from the 2022-23 southward winter migration, a number comparable to those of 1968-1970, among the lowest since records began in 1967, the National Oceanic and Atmospheric Administration said in a report published on Tuesday.
The census, derived from a visual survey taken off the central California coast, is a best estimate that falls between lower and upper confidence limits of 13,195 and 16,050.
All three of those numbers fell from a peak estimate of 28,790 in 2014-15, when confidence limits ranged from 23,6230 to 39,210. A severe drop began in 2019, when NOAA Fisheries declared an unusual mortality event (UME) as grey whale strandings surged.
Steven Swartz, who monitors grey whale migrations in Mexico for the Laguna San Ignacio Ecosystem Science Programme separately from the NOAA research, said he is optimistic over positive signs such as fewer mortalities spotted in the lagoons of Mexico, more calves than in recent years, and fewer emaciated whales.
“You always feel bad if you are a wildlife biologist and one of your focal species declines or suffers.... So to see the mortality rates come down, the birth rates come back up, even at this level at the beginning is ... a good feeling,” said Swartz.
In the San Francisco Bay, Kathi George and her colleagues from the Marine Mammal Center scout grey whales often and share data with NOAA. She said her team spotted a record high 19 grey whales in the bay this year, an unexpected rise.
“As a San Francisco Bay resident, that is a cause for celebration,” said George.
Reuters
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