Dan Fournier, an Oakland resident, said he was walking around the lake Tuesday evening when he noticed something unusual: a bat ray.
"I never see anything aside from many teeny fish," said Fournier. "I had to google it. What is this? How did it get in there?" he said.
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Upon searching, he realized he was not the first to spot a bat ray in the lake. But he decided to post the video on Reddit where it generated a lot of discussion among Oaklanders.
Some were surprised to learn Lake Merritt is connected to the San Francisco Bay through a channel, though there is a grate that is designed to stop the flow of large debris.
Mariah Evin, a senior biologist at the California Academy of Sciences said she had not heard of many bat rays getting in to the lake.
"I'm still amazed he got through the gate," said Evin.
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Though, on second thought, she noted that bat rays have a cartilage skeleton, making them very flexible.
"That might have helped him get through the gate. Those wings can curl up," she noted.
She said he likely followed the high tide while looking for something to eat, saying they can easily survive brackish water.
"They are commonly found in waters that are about 14 parts per thousand. The ocean is about 34 parts per thousand," she said, referring to the salinity.
The fact that a bat ray can survive in the lake is also a good sign of the lake's health, she said.
"That is their native ecosystem. They were probably there way before we knew about it and hopefully that's a sign Lake Merritt is cleaning up," she said.