EAST MANATEE -- The long stretch of cold weather in 2010 decimated snook populations in Southwest Florida, causing the Florida Fish and Wildlife Conservation Commission to close snook fisheries for three years.
But snook, one of Florida's premier sports fish, have rebounded strongly, as proven by research on the Manatee River in East Manatee, and on three other Florida West Coast rivers: the Little Manatee, Alafia and Hillsborough rivers.
"The snook population is growing on both coasts," said Alexis Trotter, a biological scientist for the Fish and Wildlife Research Institute in St. Petersburg.
Snook season on Florida's west coast opens Tuesday and closes April 30. A second snook season runs from Sept. 1 through Nov. 30.
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The findings of a rebounding and growing snook population are based on monthly surveys taken by scientists on local rivers.
Monday, Trotter and fellow researcher Jared Ritch demonstrated how they use electrofishing to sample the population of snook in waters east of the Fort Hamer bridge project.
Ritch turned on the electrofishing boat's generator, sending a charge to booms at the front of the boat, stunning nearby fish.
As fish turned upside down and floated to the surface, Trotter used a net to scoop up a large snook in a net and deposit it in fast-flowing water in the boat's well.
The procedure doesn't harm the fish, and it allows scientists to collect data before returning the snook to the river.
Each month, researchers randomly select a 300-meter transect, or path through the water, where they not only take a snook census, but measure and record each fish's length and weight. They may also collect blood samples.
Florida is very protective of its snook fisheries. Snook are typically not found in large numbers above Tampa Bay on the west coast, or north of Melbourne on the east coast, Trotter said.
With the warming climate, however, snook are beginning to move into more northerly waters of Florida.
Anglers who wish to fish for snook must buy a snook stamp, which helps fund research on the species. Anglers are allowed one snook per day, as long as it is not less than 28 inches in length and no longer than 33 inches.
Snook may be caught on hook and line only. Electrofishing is illegal.
"It is such an important fish and brings so much money to the state," Trotter said. "Many of the anglers come more for the fight and the catch than the actual fillet, from what I can see."
Trotter has conducted research on snook for 16 years, and finds them to be an interesting and unusual fish.
All snook are born as males -- they are protandric hermaphrodites -- and some change sex to become female.
Researchers want to learn more about snook and why some skip one or more spawning seasons. Snook spend time not only in the fresh water of the Manatee River, but in the Gulf of Mexico as well. They are found primarily in Florida in the U.S.
Researchers can use their electrofishing technique only in fresh water, where the salinity is 10 to 12 parts per thousand, compared to saltwater where it is 35 parts per thousand.
"Snook seem to be using these rivers year round. Previously we thought they came up these rivers for thermal refuge," Trotter said.
Scientists enjoy support in their research from anglers themselves.
"Fishermen overall have gotten pretty smart and involved in conservation," Trotter said.
Some anglers take part in the logbook program where they record the time and size of snook that they catch and release.
Scientists are also interested in taking a look at the carcasses of fish that have been filleted. Anglers are invited to bring their snook carcasses to Discount Tackle Outlet, 3113 First St., Bradenton, where the fish can be frozen and kept until scientists can pick it up to take samples.
For the record, scientists find the most snook in the Little Manatee River: 5.5 per 100 meters sampled. The Alafia is next with five snook per 100 meters, the Manatee River is third with 3.5 snook per 100 meters, and the Hillsborough River is fourth with 1.5 snook per 100 meters.
In the Manatee River, scientists have caught and released snook ranging in size from 3.5 inches to 38 inches, with the majority in the 8 to 20-inch range.
Jared Ritch, who enjoyed fishing as a teen, says the biggest surprise for him has been finding so many large snook so far up the river.
"It's been really cool to see it," Ritch said.
James A. Jones Jr., East Manatee reporter, can be contacted at 941-745-7053 or on Twitter@jajones1.