Fishkill mystery: Something is killing endangered sawfish in the Florida Keys

There’s something deadly in the waters of the Florida Keys, and no one knows what it is.

It’s not harmful to humans, but something is killing the critically endangered sawfish. In the last six weeks, 20 sawfish have floated up dead.

"Unknown, rare occurrence, we really haven’t seen anything like this before," said Dr. Michael Parsons, of Florida Gulf Coast University.

Parsons is part of a team of researchers who have combined their areas of expertise to try to unravel the mystery.

"All of us obviously want to know why it’s happening and if there’s anything that can be done about it,” said another remember of the team, Dr. Dean Grubbs of Florida State University.

He’s an expert on the smalltooth sawfish, one of the five species of sawfish and the one which is found in Florida and the Bahamas.

"We were just celebrating less than a year ago the fact that we are starting to see signs of recovery of the population in the US," Grubbs said.

Then, the iconic fish, part of the ray family, started dying in the Lower Keys.

"I think it’s an emergency that we figure out what’s causing it and if it’s anything that can be reversed and anything that can be avoided in the future, if this becomes something that happens annually, that would be a huge concern, obviously," Grubbs said.

Grubbs pointed out that there are only about 450 adult females in Florida waters right now.

“Sawfish are pretty mobile, they can move pretty fast, why did they stay in that area, whatever this is must hit them pretty rapidly,” Grubbs said.

Sawfish are not the only victims. Divers and fishermen in the Keys are seeing species such as snapper, snook, and grouper behaving erratically, swimming in circles, which becomes a death spiral to the bottom.

What’s causing it? Parsons is an expert on dinoflagellate algae, single-cell organisms, one of which causes red tide. Parsons thinks the culprit could be a different species of algae.

"I would say the sawfish mortality are a big problem, I would say the erratic fish behavior and the other fish mortalities are unusual but we’re not seeing the numbers of dead fish that we saw with red tide so it’s not the scale of a red tide fish kill but the fact that sawfish are dying is very concerning,” Parsons said.

Parsons said it will take weeks or months to determine if the algae is the cause of the fishkill, and he says it is possible that last summer’s record high water temperatures may have played a role in allowing the algae to proliferate much more than normal in the Lower Keys waters.

There is, however, no smoking gun yet.