Fish data helps Everglades restoration

By: Nathan Valentine / BBC Photo Editor
When grad student Meagan Dunphy-Daly and marine scientist Kirk Gastrich aren’t doing research in their lab, they are playing hooky in the marshes of the Everglades.

But this trip was no walk in the park. It was a boat ride.

Leaving the Biscayne Bay Campus around 5 a.m. on Feb. 24, the duo had one goal in mind: insert three transmitters into wild snook caught in the Everglades.

The team headed toward Shark River Slough (which feeds into the Everglades and goes into the Gulf of Mexico) where they met up with an electrofishing team.
Electrofishing is an alternate method for sampling fish. Instead of using fish traps or large nets, an electrical current controlled with a foot pedal is released into the water via two electrodes, stunning fish in the immediate vicinity. The immobilized fish are then scooped up with a dip net, identified and measured, according to grad student Philip Matich.

“Our sampling is standardized, with 5 minutes of pedal time, more than 120 meters of shoreline,” said Jennifer Rehage, electrofishing team leader.

The electrofishing team collects the fish, while the data collection team scrubs in for the dirty work.

“Our research is looking at the roles of large consumers in Shark River, and how environmental conditions affect their behavior and habitat use,” said Matich, who helps analyze the data in the Dr. Michael Heithaus Marine Community Ecology Lab in the Marine Science Building at the Biscayne Bay Campus.

The Comprehensive Everglades Restoration Project provides a framework for the restoration, protection and preservation of central and southern Florida, including the Everglades, as well as research funding to the University. The project aims to increase seasonal freshwater flow to the lower Everglades. This would cause the salinity level to decrease in the lower Everglades and coastal wetlands, according to the CERP official Web site.

“This may change the dynamics of the ecosystem [in Shark River],” Matich said. “Our research will be used to advise managers on the possible results of doing this and how restoration efforts should best be planned.”

According to Rehage, fish catches vary depending on the season, peaking during dry season between February and May.

“We get a mixture of species in our samples,” said Rehage.

But on this day Dunphy-Daly and Gastrich were only interested in snook and gar.

Rehage’s team presented five fish to the duo to begin data collection and tagging.

“The exciting work of field biologists begins right now,” Dunphy-Daly said. “It never ends.”
Gastrich agreed. “It never ends.”

The field work conducted by Dunphy-Daly and Gastrich included a quick surgery to insert an acoustic tracking transmitter into the fish, which by rule of thumb should be at least 45 centimeters based on the size of the transmitters surgically implanted, according to Matich.

The minimum size limit is based on previous lab experience with fish that were not affected by the surgery.

“There are no official regulations on size requirements in our research permit,” Matich said.

The transmitter’s dimensions are similar to a wine bottle cork. Its battery lasts for about three years.

For the surgery, a scalpel makes a ventral incision down the stomach, which is widened with blunt tip scissors. After the transmitter is inserted, the incision is sutured with one stitch.

The surgery start and end time is documented, as well as the apparent health of the fish after the surgery before it’s released.

“The average surgery time is about two to four minutes,” Dunphy-Daly said.

It takes about two to three weeks for the incision around the transmitter to heal completely in bull sharks, for which the same methodology as the snook is applied, according to Matich.

Of the three snook that underwent this procedure, all were released and able to swim within minutes of the surgery’s completion. It takes less than a day for the fish to resume normal behavior, according to Matich.

Tagged animals are tracked as they swim by any of the 41 monitors placed around the survey area, according to Dunphy-Daly.

“We track the fish in order to understand their behavior and habitat, and to determine their role in the ecosystem,” Matich said.

Data collected at the harvesting site included exact GPS coordinates of where the fish were caught, salinity of the water, dissolved oxygen content of the water and water temperature.

Along with habitat field samples, the data illustrates how the animals influence the system as predators and how marine nutrients are deposited in the estuary, according to Dunphy-Daly.

The electrofishing team and the data collection team finished by 2 p.m. Feb 24.

Including travel time, a typical day of field work in the Everglades begins at 4 a.m. and ends at 9:30 p.m., according to Gastrich.

If the teams receive more funding, they will continue their research tracking fish in the areas affected by CERP’s efforts, but accomplishing daily goals in a timely manner is still cause for celebration.

“That was successful, short and sweet,” said Dunphy-Daly. “We got the job done.”

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