Small Freshwater Fish Darting Out of Sight in Florida

Two-year study on the southern tessellated darter will lay the groundwork for conservation of this species in north-central Florida.
southern tessellated darter

A team of researchers has been trekking through the dense vegetation of the Ocklawaha River basin in north-central Florida’s Marion and Putnam counties to search small streams for a fish in troubled waters. They’re looking for the southern tessellated darter – a small freshwater fish that has been historically found at six locations in the basin. In recent years, however, this fish has only been consistently collected at one location. In 2010, experts with the FWC, U.S. Geological Survey (USGS), and U.S. Fish and Wildlife Service recommended listing the southern tessellated darter as a state-listed threatened species because of its small known geographic range and low population numbers in Florida. This prompted the FWC to draft a conservation action plan to secure the Florida population to the point that these fish are present throughout their historic range. But to achieve this, we must first learn more about darter population numbers, find out where these fish are located and identify what habitats they prefer. In 2012, FWRI began a two-year collaborative study with the USGS and the University of Florida to collect this information and lay the groundwork for carrying out the plan.

To determine where these darters currently occur in Florida, researchers are using two techniques to search for them at randomly-selected locations throughout the Ocklawaha River basin. At sites where researchers can wade in the stream, one researcher uses a backpack electrofisher to apply a small electrical current to the water and stun the fish. Meanwhile, two other researchers stretch a seine net across the stream to collect all the fish that float downstream. At deeper sites, researchers conduct snorkeling surveys to visually count and attempt to catch southern tessellated darters with nets.

At each site, researchers count any southern tessellated darters collected or observed. Before releasing collected darters, researchers also obtain a tissue sample from each so they can analyze the genetic differences between fish in the same stream, those in different streams and those in the Florida and Georgia populations. Managers will use this genetic analysis to evaluate whether it would be feasible to introduce fish from larger populations into areas where the species is rare or no longer seen.

Researchers also record the habitat characteristics at each site, including canopy cover, stream width, bottom type, water depth and velocity, and any structure present. Revealing which types of habitat these darters use will help managers determine where to focus habitat restoration and protection efforts.

So far, researchers have only collected southern tessellated darters where these fish have been found in recent years. After researchers determine where darters are present and what habitats they prefer, they will revisit sites where they were able to collect these fish and conduct additional sampling to estimate population numbers in those areas. Researchers will share what they learn with managers and work collaboratively to develop strategies to sustain Florida’s southern tessellated darter population.



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