MARY LOUISE KELLY, HOST:
An unprecedented ocean heat wave swept across south Florida and down to Key West last summer. As water temperatures soared, coral bleached. Seagrasses wilted. Well, now another unusual event is unfolding in the lower Keys. Endangered sawfish are dying, and dozens of other species have also turned up sick or dead. Jenny Staletovich with member station WLRN in Miami reports that scientists are trying to unravel the mystery.
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JENNY STALETOVICH, BYLINE: Joyce Milelli leads kayak tours in the Keys, where she grew up. Standing on a dock overlooking the Atlantic Ocean, she remembers seeing a large fin in shallow water in late January.
JOYCE MILELLI: I went around for a closer look, and I said, this is not a shark. And it was my first time seeing a sawfish. And it just went - like, a siren went off in my head like, sawfish.
STALETOVICH: But the thrill of seeing her first sawfish didn't last long. The normally deepwater fish was tangled in some mangroves.
MILELLI: And I knew right away something was not right.
STALETOVICH: Five days later, it was dead. The 12-foot-long smalltooth sawfish would become the first in what has become an extraordinary die-off of a very rare endangered species around the lower Keys. Since then, 28 more have been found dead. And more than 100 sawfish have been spotted in distress, waving their long chainsaw-looking snouts above the water, swimming into seawalls and circling erratically in shallow waters.
DEAN GRUBBS: That's not what they should be doing.
STALETOVICH: Dean Grubbs is a fish ecologist at Florida State University.
GRUBBS: They'll sit at the mouth of a tidal creek and wait for fish to come by them, and they slash at them. They should not be swimming in circles. They should not be coming that close to the shore.
STALETOVICH: This week the National Oceanic and Atmospheric Administration will begin rescuing sawfish for the first time. Biologist Adam Brame oversees NOAA's sawfish recovery team.
ADAM BRAME: To some degree, it's no different than an oil spill response, where there was a natural disaster. There's oil, and turtles are affected. You know, this is an emergency, and the agency is taking emergency action.
STALETOVICH: Smalltooth sawfish are the only sawfish found in the U.S. They were added to the endangered species list 20 years ago. But Brame says scientists still know very little about how the deepwater fish behave or just how vulnerable they may be to diseases. The captured fish will be moved to aquariums in a truck outfitted with a 30,000-gallon tank.
BRAME: It'll take some serious manpower when we're talking about 10- to 14-foot fish that has a large weapon, if you will, on its front end.
STALETOVICH: The die-off is also coincided with another mystery. Since November, more than two dozen other species have turned up sick across the lower Keys.
GREGG FURSTENWERTH: If we walk over there, we might see some fish spinning if possible.
SHAYLEE CRAWFORD: Maybe, yeah.
STALETOVICH: Gregg Furstenwerth and his wife, Shaylee Crawford, have spent the fall and winter documenting sharks, snook and other species spinning and thrashing near their house on Little Torch Key.
CRAWFORD: There's one right there. You see it?
STALETOVICH: Oh, yeah. Wow.
FURSTENWERTH: You see it spinning over there?
STALETOVICH: Uh-huh (ph).
CRAWFORD: And then it just...
FURSTENWERTH: There's another one right there.
STALETOVICH: Scientists suspect a neurotoxin is making the fish sick, possibly the same thing killing sawfish. But they still have so many questions. The summer heatwave peaked in July. So why did fish start getting sick months later in November? And why are just sawfish dying and not other big fish?
MICHAEL PARSONS: There's a lot of moving pieces, right?
STALETOVICH: Gregg Parsons is a marine toxicologist at Florida Gulf Coast University. He's part of a team trying to identify the cause.
PARSONS: So the wind patterns are different than they typically are. It's rainier this winter than it typically is. There's more fresh water coming in.
STALETOVICH: One theory is that the heatwave created hotter water at the bottom and cooler water near the surface. That may have allowed tiny bottom algae to spread upward, and those algae can become toxic. Martin Grosell is a fish ecologist at the University of Miami.
MARTIN GROSELL: Everything we know that can harm fish in our environment here and have caused fish kills in the past does not seem to explain this.
STALETOVICH: That includes low oxygen, chemical spills or algae blooms like red tide.
GROSELL: I hope that this is a transient thing. You know, unfortunately, we don't know. And that, I think, really is the most terrifying part about all of this.
STALETOVICH: Until they figure it out, scientists hope rescuing some of the sawfish will keep one of the planet's rarest species from vanishing for good. For NPR News, I'm Jenny Staletovich in Miami.
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