Beginning in March, and for the second year in a row, hundreds of sharks have washed up dead or dying along the shores of the San Francisco Bay. Primarily the species that have been most affected are Leopard Sharks and Bat Rays. Mass elasmobranch die-offs have periodically been recorded in the San Francisco Bay since 1967, but scientists now think they are narrowing the possibility to one species of fungus that fatally infects the brains of these species.

While these sharks spend the majority of their time in deeper waters with more natural flushing, they migrate to shallower water in the spring and summer to spawn, which tends to be more prone to toxins. Under certain times of year and the right conditions these fungal pathogens grow out of control, creating a perfect storm for the breeding sharks. The fungi is yet unidentified.

This is what Mark Okihiro, the California Department of Fish and Wildlife senior fish pathologist and lead of the stranding investigation, had to say about the findings:

“I look at it as a 50-year-old shark murder mystery, and we are hopefully closing in on the killer.”

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