Just the same, the experts say further testing is being done to get to the bottom of what happened. The die-off occurred mainly in St. Joseph Bay near Cape San Blas and in nearby Gulf of Mexico waters from March 10 through April 23.
Red tide also was blamed for killing up to 130 dolphins in the same area in late 1999 and early 2000. Biologists want to know why such repeat events take place in the upper Gulf and not farther south.
Red tide, however, has killed southwestern Florida manatees. Of eight unusual mortality events declared by federal officials since 1992, three were for manatee die-offs from red tide in southwest Florida.