Dead salmon in Lake Merritt could point to healthier waters, researchers say

It’s a sunny Tuesday morning on the shores of Lake Merritt, and a small group of researchers and curious onlookers is crowded around a dead fish.

The silvery, 13-inch-long Chinook salmon, pulled that morning from a small, enclosed arm of Lake Merritt that leads to Glen Echo Creek, is placed on a concrete slab, and a  man with a sharp instrument gets to work. First he slices through the belly, and then separates the head from the body.  

“We are going to remove the ear bones, which have a lot of information,” says Katherine Noonan, founder of Oakland’s Rotary Nature Center Friends, an environmental education group, as the passers-by crane their necks to observe. “They have rings in them like the rings of a tree.” By analyzing them, she explains, it might be possible to decipher how this Chinook salmon found its way from the ocean to downtown Oakland. 

Noonan and other researchers have been watching the lake closely since news broke earlier this month that dead Chinook salmon were spotted in the 155-acre lake, the first sighting since 2021. Their theory is that the demise of these fish was not caused by pollution, but is rather part of their normal life cycle. Their presence may, in fact, be a sign that the lake’s water quality is improving.

With a license from the California Department of Fish and Wildlife, Noonan and the Rotary Nature Center Friends have been studying salmon in Lake Merritt since the beginning of the year. That day, they pulled three other salmon carcasses from the water. 

Lake Merritt, a mixture of fresh and salty water, is habitable to the Chinook salmon, but years of pollution and regular red algae blooms have made the species and other animals scarce.

Reports of salmon remains on the shores of the lake have been a regular occurrence for weeks now, and the carcasses have been drawing spectators. “For two weeks now, people have just been walking and looking down the lake,” said Alex Perez, who has been working in a house on the lake shore. 

Salmon begin their life in freshwater inland creeks, then swim through Lake Merritt toward salty water, passing through San Francisco Bay and into the Pacific Ocean. 

“They spend two to three years in the ocean, and in late fall, they swim back into the bay and move to the creeks they hatched from, to release eggs,” Noonan said. “Unfortunately for them, they can’t find fresh water when they enter Lake Merritt. So they die.”

Most of the salmon retrieved from the lake died with eggs in them. Noonan said they cannot spawn because the eggs would perish in the brackish lake.

Chinook salmon can live for up to nine years, with the average being two to four years. Unlike Atlantic salmon, which can release eggs repeatedly and still survive, they die after spawning. 

For researchers at the Lake Merritt Institute, an organization that works to keep the lake clean, Chinook salmon sightings are a sign that their work is paying off. Lake Merritt has long been an abused treasure for Oaklanders. Clean-up crews routinely pull out discarded mopeds, automobile tires, animal carcasses, construction debris and other kinds of refuse.

James Robinson, the Institute’s director, said the salmon are a “good sign of improving water quality,” even though they have been unable to spawn. He added that the grueling journey upstream into Lake Merritt may explain why the salmon carcasses look so ragged.

 “When you see their bodies worn and torn, that could be because of their contact with stones, cements and obstacles they are trying to get through,” he said. 

The lake’s water quality, measured at three monitoring stations operated by the institute, has been good recently, he added. 

Although Lake Merritt is home to other aquatic life, like bat rays and striped bass, many Oaklanders who live and work nearby say it’s a rarity to see any living creatures in its waters. Donald Blair, who comes to the lake three times a week to people-watch, read or walk, said he has never seen fish in it.

“I would be very surprised to hear there was salmon in this lake,” he said. “I have never seen any swimming or jumping.”  

Noonan said that Rotary Nature Center Friends will continue to monitor the lake in hopes that some of the Chinook salmon find a way to survive. In the meantime, they have preserved the salmon heads by freezing them for the purpose of science.

“We are going to keep the ear bones, hopefully they don’t get bad, until we get a chance to share them with a researcher who can study them,” she said.

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