Sharks Dying In San Francisco Bay Is Alarming Marine Biologists

An “unusual” number of marine animals are dying in San Francisco Bay, and wildlife experts are not sure why. The latest estimates show 2,000 leopard sharks, 500 bat rays, hundreds of striped bass, 100 halibut, and 50 smooth-hound sharks have died since February.

Research scientist Dr. Mark Okihiro with the California Department of Fish and Wildlife said the cause is likely a dangerous microorganism, one that may be infecting several species in San Francisco Bay.

“We’re pretty confident at this point,” Okihiro told NBC Bay Area. “It’s called Miamiensis avidus… it’s a small single-celled organism. It’s very similar to the common amoeba.”

The parasite was identified after Okihiro examined the bodies of several dead sharks. The organism enters the shark through the nose and makes its way to the brain. Just before dying, an infected shark will exhibit odd behavior like swimming in circles or beaching themselves.

Typically, most sharks affected by the parasite die in deep water, so only a few are ever found in the bay. As a result, Okihiro believes the death toll is likely much higher.

Dr. Andrew Nosal, a marine biologist and expert on leopard sharks, agrees. With so many unexplained deaths, Dr. Nosal is asking for additional resources to further study why these sharks are dying.

“We have to find out what’s killing these sharks. If we don’t find out, then there’s nothing we can do about it. If you remove leopard sharks from the population, it is going to have a chain reaction.”

Multiple marine species at risk in San Francisco Bay area.
Biologists concerned after numerous unexplained deaths of marine life in San Francisco Bay [Image by Chintla/Shutterstock]

Without action, Dr. Nosal fears the parasite will soon affect the entire ecosystem along the West Coast. There is no way to know for sure how much damage the parasite will cause or even how to stop it from spreading unless the Fish and Wildlife Department gets involved soon.

That is where Dr. Okihiro comes in. Yet, studying leopard sharks are not a part of his job. As of now, the department isn’t willing to reposition current funds to investigate the deaths since the species is not considered endangered.

Nonetheless, Okihiro has taken it upon himself to do the research. He brings the dead sharks to his Southern California home and examines them in his spare time, often right on the kitchen table.

“We’ll probably have to wash this [table] cloth before Thanksgiving,” he jokingly told NBC.

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As of now, the official position of the state’s wildlife department is to focus on higher-risk species and isn’t ready to dedicate any more money to studying their unusual deaths. According to Nosal, leopard sharks are one of the most plentiful sharks along California’s coast, but that makes them exceptionally susceptible to the rapid spread of deadly microorganisms.

While humans are not vulnerable to the parasite, countless other marine species are. How many other animals are dying and sinking to the bottom of the ocean without anyone ever knowing? As marine animals slowly disappear, major disruptions of habitat occur, hurting both land and sea animals. There is likely a lot more at stake here than just a few thousand leopard sharks dying in San Francisco Bay.

[Featured Image by David Litman/Shutterstock]