Update on Leopard Shark Strandings in San Francisco Bay

Earlier this week the Pelagic Shark Research Foundation released an update on the mass strandings on leopard sharks in the San Francisco Bay I wrote about back in April.

The update stated that as we have entered the 13th straight week of mass die offs. Strandings are still being reported in Richardson Bay, Oakland, and the Alameda areas.

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Pfaffendorn (Photographer). (2008, May 9). View of Richardson Bay above Sausalito, CA [Digital Image]. Retrieved from http://www.panoramio.com/photo/10063058

Senior fish pathologist and forensics scientists for CDFW, Dr. Mark Okihiro, reported that the lab is working full time and is at full capacity with shark specimens. The lab is continuing to collect additional specimens despite being at full capacity. Histology slides, which were sent for analysis in April, have shown that three of the San Francisco leopard sharks had the same necrotic protozoal (Miamiensis avidus) infections of their brains and condocranium.

 

“The aggressive and destructive Protozoa are entering the sharks skull via olfactory lamellae and naris, before penetrating and destroying vital parts of the brain. Other equally terminal infections gain access via the shark or rays endolymphatic ducts and ear canals. This year’s events have generated much concern as well as an avalanche of data and clarified perspective on the progress and course of the 2017 epizootic mass die off.”

Flannery, A. [Amanda Flannery]. (2017, June 13). San Francisco Bay, Stranding Report Update for late May and June 1, 2017. Retrieved June 13, 2017 from https://www.youtube.com/watch?v=nTF-R8hWftE

“Infections in stranded sharks are mixed, and involve protozoa, probably fungi, and possibly residual toxins associated with dead planktons. These are associated with stagnant and dead waters and storm water run off; the convergence of high spring time tides together with annual migrating and pupping sharks and rays were coinciding with periodic and seasonal tide gate closers and entrapments that exposed large numbers of sharks, rays and fish to toxic conditions that were further compounded by the decaying biomass of dead rotting sharks and fish, admixed with the storm water discharge following heavy rain run off and tide gate openings and closures.”

While these mass die offs are disturbing, these die offs have provided shark researchers various other opportunities. Dr. Okihiro has been able to provide specimen samples to other researchers in California working on a variety of things from the Ampullae of Lorenzini, which is the sensory organ in the nose of the shark which acts as a sixth sense when hunting, to the otoconia of the inner ear, which provides the shark information about where it is located in the water column.

Residents and beach goers are encouraged to contact the Pelagic Shark Research Foundation if you spot a distressed or dead shark.

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Pelagic Shark Research Foundation (2017, May 21). San Francisco Bay Stranding Event [Digital Image]. Retrieved from https://www.facebook.com/167200017410/photos/a.391167542410.177515.167200017410/10154530888217411/?type=3&theater

As always, I welcome your comments and open discussion.

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Featured Image Source

Flannery, A. (Photographer). (2017, June 12). Leopard Shark in Kelp Bed [Digital Image].

Literature Cited

Pelagic Shark Research Foundation (2017).  San Francisco Bay, Stranding Report Update for late May and June 1, 2017. Retrieved from https://www.facebook.com/Pelagic-Shark-Research-Foundation-167200017410/?ref=page_internal

 

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