The mystery of the 2011 shark die off along the Bay Area coast may be solved.
The Associated Press reports this winter's heavy rains may be to blame for a rash of leopard shark deaths in the San Francisco Bay.
State biologists told AP the rain may be reducing the salinity of the bay's water, and that would have a deadly effect on the sharks' internal chemistry throwing it off balance.
More than 100 of the sharks have washed ashore in San Mateo, San Francisco and Marin counties over the past month.
Necropsies of some of the sharks showed they were suffering from internal bleeding and brain lesions.
The evidence for that theory is so far not conclusive. Biologists are hopeful that blood and tissue samples expected to be released this week will shed more light on a possible cause.
Researchers said their analysis is still in the early stages, but note that hundreds of leopard sharks and rays also died in 2006, the last year rainfall was this far above normal.