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LAKE NACOGDOCHES - It’s just after sunset on a pleasant spring evening and all is quiet at the upper reaches of Lake Nacogdoches in eastern Texas.Things are about to change, though. Todd Driscoll and his crew just rolled up in their 20 foot electrofishing rig.The upcoming drill is representative of every springtime electrofishing survey — crank up the juice, rattle some cages and gather some useful trend data on bass populations.
Welcome to the world of a Texas Parks and Wildlife Department freshwater fisheries biologist. Driscoll is one of 14 district supervisors with the state agency’s inland fisheries division.Like other leaders, the scientist is tasked with managing Texas’ freshwater fisheries for the best fishing possible while protecting and enhancing our aquatic resources. Driscoll has nine public reservoirs totaling more than 300,000 surface acres under his watch — a small fraction of what is out there.Conducting periodic surveys play a vital role in helping biologists gather information used in making fisheries management decisions. The surveys range in scope from simply talking to anglers to using nets, traps and shocking devices for sampling sport fish populations.Here’s a synopsis of primary sampling methods and surveys TPWD biologists use to keep check on our freshwater fisheries and assess how well the angling public is satisfied with them: ElectrofishingElectrofishing is a highly effective fish collection technique biologists use during to gather critical data related to numbers and size structure of bass and various forage fish (small sunfish and shad) populations from one lake to the next.The fall/spring surveys are carried out in shallow water from specialized boats, usually at night to avoid disturbing fishermen.Electrofishing boats are equipped with a large, elevated front deck, water level spotlights and a spacious holding tank that is oxygenated to keep fish lively. A gasoline-powered generator is used to send electrical current through a pair of booms mounted to the bow.The current is displaced into the water through steel cables called anodes. Fish within a 6-8 foot radius of the anodes experience electrotaxis, otherwise known as "forced swimming" towards the anode. Think of it like steel drawn to a strong magnet.The electrical field intensifies as a fish swims closer. This stuns the fish, causing it to float to the surface. Bass fully recover from stunning within a couple of minutes.Driscoll always limits current strength to seven amps to avoid harming the fish. It’s called “responsible shocking.”The boat driver uses the outboard engine to inch the boat along shorelines at idle speed in water depths no deeper than 5-6 feet. Two men are posted on the front deck with long handle nets. It is their job to scoop up the stunned bass and place them in the holding tank for evaluation.Lakes are randomly divided into sample sites that vary in number according to the size of the reservoir. Each shocking sequence lasts five minutes. Biologists log pertinent data, toss the fish back in the lake and move to the next station.Fall electrofishing surveys are standard practice carried out once every four years on public reservoirs 500 acres and larger. Biologists assess total numbers, lengths and weights of bass. They also record lengths of forage species in the fall surveys.Spring surveys are optional and less time consuming than fall surveys. Supervising biologists dedicate these surveys to higher profile fisheries, usually every other year. Spring surveys are geared strictly to assessing bass numbers and lengths of individual fish, no forage.Driscoll says electrofishing data helps scientists establish a relative abundance estimate to gauge the approximate number of bass per acre in a reservoir and the stability of a given bass population over time.“Spring electrofishing surveys provide a second snap shot of the bass abundance and we compare the relative abundance (catch per hour) from year to year,” he said. “This helps us determine if the population is stable, increasing or decreasing.”Biologists usually don’t collect many fish upwards of four pounds with electrofishing because of the water depth factor, but it does happen on occasion. In March 2018, crews shocked up a fish estimated to weigh around 12 pounds at Lake Naconiche.
The biggest bass ever reported by TPWD shocking crews was a 13.9 pounder collected during a 2005 fall survey at Lake Alan Henry. TPWD inland fisheries chief Craig Bonds was the district supervisor in San Angelo at the time. Bonds was driving the shocking boat. He was accompanied by fisheries biologist Charlie Munger and fisheries technician David DeLeon.“I remember that night vividly,” Bonds said. “We rounded a mainlake point and went over a flooded juniper bush. When those electrodes hit that bush she rolled up out of there. We shut things down and just gawked at that fish. We were like three kids on a Christmas morning.”Angler Creel SurveysAngler creel surveys are vital in fresh and saltwater fisheries management because they allow scientists to converse with angling constituents. The surveys are great sources of information regarding target species, harvest rates, angling effort, angling expenditures and overall angler satisfaction.Driscoll considers the angler creel survey the most important type of survey fisheries biologists do.“These surveys allow us to interact with anglers and ask them questions, plus it gives our customers the chance to ask us questions,” he said. “Angler creels help us measure what is essentially our end product — angler catch and satisfaction.”TPWD fisheries biologist Randy Myers of San Antonio estimates scientists interact with around 5,000 freshwater anglers in creel surveys in Texas each year.Angler creel surveys are conducted in two ways: On-the-water surveys: Biologists rove the reservoir by boat and interview anglers on the water. Roving surveys are most efficient on large reservoirs with lots of ramps that spread out the fishing traffic.* Boat ramp surveys: A biologist is positioned at a popular boat ramp and interview anglers when they come off the water. Ramp surveys are most efficient on smaller lakes with only a handful of access points. These surveys are less costly than roving surveys. They also are more thorough, because they are based on completed fishing trips. Gill NetsGill net surveys are most commonly used for springtime evaluation of pelagic (open water) freshwater species like striped bass, hybrid stripers, catfish and white bass, and popular saltwater fish like spotted seatrout and red drum. Scientists relied on gill nets to collect alligator gar during an intensive stomach contents study on Lake Falcon in 2014. Freshwater gill net surveys are generally performed every four years but may be more frequent on high profile lakes. TPWD fisheries biologist Dan Bennett of Pottsboro conducts gill net surveys annually at Lake Texoma, arguably the best striped bass lake in the state.Gill nets are about 125 feet long and 8 feet deep. Nets are made with openings of varied sizes designed to entangle the fish, usually around the gills. Bennett says the nets are most effective at water depths of 8-35 feet.Trap NetsA trap net works best for sampling crappie and other cover-seeking fish, mainly during the fall months.The device consists of a lead net about four feet deep and 60 feet long. The lead net connects to a roomy 3-foot X 6-foot diameter trap with an opening that allows fish to swim inside.The best trap net sets are often on gradually sloping banks 3-15 feet deep.The idea is that crappie will follow the lead net from shallow to deeper water and get caught inside the trap thinking it is a planted brush pile. Trap nets are always most effective on lakes with turbid water that distorts the fish’s vision.“They aren’t real effective in clear water lakes with a lot of vegetation,” Driscoll said. “Crappie tend to avoid the gear in lakes that are clear enough that the trap is recognized as unnatural.”Driscoll says fisheries biologists in eastern Texas, where lakes are relatively clear, rely more on angler creel surveys for monitoring crappie populations than another survey method.Matt Williams is a freelance writer based in Nacogdoches. He can be reached by e-mail, [email protected]
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