Red tide likely killed whale shark that washed up on Sanibel

A whale shark that washed up on a Sanibel beach over the weekend likely died due to red tide poisoning.

Biologists at the Florida Wildlife Research Institute in St. Petersburg examined various tissue samples and found that all contained Karenia brevis, or red tide.

"This does not indicate why it died, but because researchers had measured similar and higher levels than that in live fish caught in bloom areas, and given the high concentrations of Karenia brevis in that area and the large fish kills in that area, it’s fair to say it may be red tide," said Michelle Kerr, FWRI spokeswoman. "But we don’t know for sure. We may never know."

A strong red tide has lingered along the Southwest Florida coast since October, at times stretching from Tampa Bay to the Florida Keys.