Fort Myers, Florida (News-Press) -- With a spectacular splash, a shark-like tail slapped the surface of the shallow water of Iona Cove in the Caloosahatchee River as the fish struggled in the 600-foot gill net.
Three Florida Fish and Wildlife Conservation Commission fish biologists were hunting smalltooth sawfish, which are shark-like rays, and this looked promising.
Iona Cove is one of five known sawfish hot spots in the area; the others are the Peace River, Glover Bight off Cape Coral, the Cape Coral Bridge and the U.S. 41 bridges.
"One thing we're trying to figure out is why these are hot spots," team leader Gregg Poulakis said. "Shallow water near areas that drop off to deeper water seems common."
Smalltooth sawfish, which Poulakis describes as looking "like a shark with a hedge-trimmer for a nose," were listed as endangered under the Endangered Species Act in 2003; the species' current population is 5 percent of its historic size.
Poulakis has been studying sawfish in the Caloosahatchee since 2005 and in upper Charlotte Harbor for the past three years; in all, he and his teams have caught 283 sawfish.
Unfortunately, when biologists Rachel Scharer and Matt Schubart waded in waist-deep water to check on the struggling fish in Iona Cove, they discovered that it wasn't No. 284.
Instead, it was a 3.5-foot female bull shark, which Scharer and Schubart carefully removed from the net and took to the boat, where the scientists measured it and removed a small piece of the animal's dorsal fin — comparing stable isotopes (different forms of the same element) in tissue of bull sharks to stable isotopes from sawfish tissue can help determine what sawfish eat.
"We've found sawfish eat fish at all stages of their lives," Poulakis said. "That's not to say they don't eat crabs now and then, but it's mostly fish."
Once common throughout Florida and often encountered from Texas to North Carolina, with sightings as far north as New York, smalltooth sawfish are now mainly restricted to Southwest Florida from Charlotte Harbor to the the Keys.
From February through September, Poulakis and his team hunt sawfish eight days a month in the Caloosahatchee and upper Charlotte Harbor.
Among other things, these fishing trips have revealed that, while smalltooth sawfish can live in salinities of 0 parts per thousand (fresh water) to 35 ppt (full sea water), they prefer salinities of 18 to 30 ppt.
In the Caloosahatchee, Poulakis has documented that juvenile sawfish typically travel less than one-half mile a day but can move 12 to 15 miles a week when large releases of freshwater from Lake Okeechobee lower salinity in the river.
"Sawfish we've tagged by the U.S. 41 bridges move to the mouth of the river," Poulakis said. "They hang around a while then move back upstream. We're trying to figure out what cues the movement, when the fresh water is gone, to go back up the river."
Poulakis has also found that sawfish have genetic ties to the area.
"The same females are coming back to give birth every other year," he said. "There's no indication of inbreeding, which is obviously good. The population is low, but not that low."
One of Poulakis' sawfish was recaptured in the Ten Thousands in southern Collier County and another was found dead on Key West; pop-off satellite tags attached to two female sawfish in Florida Bay by Florida State University researchers showed up off Charlotte Harbor.
"Those four data points point to connectivity between the Charlotte Area and Florida Bay and the Keys," Poulakis said. "That's where their current range is, so there's movement in both directions."
Cruising at idle speed downstream from where the bull shark was caught, the boat spooked a 5- to 6-foot sawfish (this animal was about a year old: Poulakis has determined that sawfish double in size during their first year, growing from 2.5 feet at birth to 5 feet).
Poulakis drove to where he thought the animal might be, and Scharer and Schubart set the net.
Again, only bycatch, this time a 30-inch redfish.
"We were this close," Poulakis said holding his thumb and index finger an inch apart.
Attempting to change the team's luck, Scharer put her hands over her head with palms together to imitate a sawfish and did The Sawfish Dance.
It didn't help: The day produced only bycatch — two more bull sharks (a 3-foot male and a 3-foot female), 16 spadefish and an Atlantic stingray.
Fin clips were taken from the sharks, and all fish were measured and released.
"We keep track of the sizes of what we get," Poulakis said. "Those data can be used combined with other data if somebody is interested in those species. A lot of people are doing species-specific distribution-and-abundance studies."
Back at the Cape Coral Yacht Club boat ramp, Schubart said the day had been productive.
"There are definitely sawfish in this area," he said. "We saw a sawfish. Unfortunately we didn't get a net around it."
Scharer applied biological logic to the day's lack of sawfish.
"This is an endangered species: You're not going to catch one every time," she said. "This was one of those days we didn't catch any. That's all part of the data, too. And it didn't rain; it was a beautiful day."
Smalltooth sawfish facts
• Scientific name: Pristis pectinata ("pristis" is Greek for "saw"; "pectinata" is Latin for "comb" or "comb-like")
• Status: Endangered
• Reasons for population decline: The primary cause was fishing pressure. Recreational fishermen caught sawfish while fishing for other species and cut off the saws as souvenirs; commercial fishermen didn't target the species, but many sawfish were killed when they became entangled in gill nets. Another cause is loss of habitat due to development.
• Reproduction: Female sawfish bear up to 20 live pups.
• Size: 2.5 feet at birth; can grow to more than 20 feet.
• Diet, feeding behavior: Eats schooling fish such as mullet and herrings; slashes into schools of fish with saw then eats injured fish. Studies show it can pick out and kill a single fish with its saw. Also stirs up the bottom with saw to find crustaceans.
• Range: In the U.S., Southwest Florida. Also lives from Brazil through the Caribbean. The last confirmed record of a sawfish north of Florida was 1963 in North Carolina.
• Habitat: Shallow coastal waters — sheltered bays, river mouths, mangrove edges and seagrass beds; sometimes found in deeper coastal water.
• Historical perspective: The earliest record of smalltooth sawfish in Florida is an 1834 museum specimen from Key West.
• Commercial trade: Sawfish fins are used in Asia for sharkfin soup; saws are traded in some countries as ceremonial weapons and for use in traditional medicines; in Peru, teeth from the saw are strapped to roosters' legs for cockfighting.
