UAPB Research on Arkansas Native Brown Trout Helps Inform Arkansas Game and Fish Commission Management Decisions
Will Hehemann | School of Agriculture, Fisheries and Humanities
Heber Springs, Arkansas, is home to the only self-sustaining trout population in the state of Arkansas, said Derek Owens, graduate student in aquaculture/fisheries at the University of Arkansas at Pine Bluff (UAPB). For nearly four years, he has been researching a 30-mile stretch of the Little Red River called “Greers Ferry Tailwater.” He says this part of the river is unique because stocking is not necessary to sustain the population of brown trout that live there.
“The Greers Ferry Tailwater is the stretch of the Little Red River below the Greers Ferry Dam that contains cold water due to hypolimnetic release from the dam,” he said. “This creates conditions cold enough for the trout to survive all year round. In fact, brown trout have not been stocked in the Greers Ferry Tailwater since the early 1970s.”
Owens said the UAPB Department of Aquaculture and Fisheries conducts research on trout fishing to help inform management decisions for the Arkansas Game and Fish Commission.
“Trout fishing is extremely valuable to Arkansas’ economy,” he said. “According to the US Census Bureau, trout fishing expenditures in Arkansas total over $180 million annually. Fifty-seven percent of trout anglers are nonresidents and 43 percent are residents of Arkansas.
In his research, Owens analyzed the habitat conditions of trout spawning grounds in the Greers Ferry Tailwater under the supervision of his advisor, Dr. Steve Lochmann, Professor of Aquaculture and Fisheries at UAPB. Specifically, they wanted to determine the microhabitat characteristics of locations that contained brown trout spawning nests.
“These spawning nests are called ‘redds,'” Owens said. “For a female brown trout to create a nest, she must first find a suitable location. It will then turn on its side and begin to rapidly strike the substrate particles on the bottom of the river with its caudal or “tail” fin. This rapid kicking motion, coupled with the speed of the water, dislodges sediment and individual rocks from the bottom of the river and begins to form a pit in the bottom of the river.
Owens said after a female trout creates the pit, she will lay eggs which a male will then fertilize. Then the female covers the fertilized eggs with other rocks from the bottom of the river.
“The female brown trout can lay up to 3,000 eggs in a nest. A fish can create multiple pits and lay eggs in each of them,” he said. “Redds come in different sizes – some are just two to three feet long and two feet wide, while others can be several feet long and wide.”
What conditions are suitable for trout spawning?
To understand which locations were best for brown trout spawning, Owens and his fellow researchers measured depth, water velocity, dissolved oxygen, temperature and substrate particles at about 145 spawning grounds over the course of of the 2019-2020 spawning season.
“We found that depth, water velocity and substrate size were the three most important microhabitat characteristics for brown trout spawning ground,” he said. “These three particular characteristics have also been determined to be the most important factors in brown trout spawning grounds in several other systems around the world.”
According to the study, the ideal location for a female brown trout to create a nest consists of water depths of about one to one and a half feet, water velocity of about one foot per second, and substrate particles between half an inch to two and a half inch.
“These are the ideal conditions you’d expect to find a spawning ground in the Greers Ferry Tailwater, as well as other systems around the world where wild brown trout spawn,” Owens said. “Many of these other systems are in Europe and contain native populations of brown trout – their microhabitat characteristics really don’t differ from Greers Ferry Tailwater.”
Owens said his team also wanted to determine if brown trout spawn on one or two main banks or if they spawn in a wide variety of locations with appropriate depth, water velocity and substrate. For this part of the study, they surveyed the river in two-week increments beginning in October 2020 and ending in February 2021.
“Every other week we worked from the Greers Ferry Dam to the Monaghan Womack Highway 305 access,” he said. “It took us about three days to cover the 30 miles downstream. Each redd encountered was georeferenced with a Trimble TDC 150 GPS unit.”
Owens said the GPS unit was crucial to the study because it was accurate to around 4 inches.
“We had multiple redds that were within a foot of each other and sometimes overlapped,” he said. “This Trimble unit allowed us to easily distinguish nests that are very close to each other. By recording a GPS position and searching for spawning grounds over two-week periods, we were able to examine a complete spatial and temporal distribution – or time and place – of the 2020-2021 spawning season. »
Spawning areas appeared in small quantities during the first week of October 2020. Most brown trout spawning occurred from mid-November to late December, with the peak being in the first half of December . February 6 was the last date the research team found spawning grounds.
“We found a total of 2,417 spawning grounds on 27 different beds across the Greers Ferry Tailwater,” Owens said. “Our study concluded that brown trout spawned not just in one or two locations, but wherever microhabitat conditions were appropriate.”
Owens said the Arkansas Game and Fish Commission (AGFC), which funded the project, has been very supportive of his work.
“Many people have helped me throughout this project,” he said. “Joseph Kaiser, UAPB alumnus and current AGFC trout biologist, was a great help with this project. Also, current UAPB graduate student Jamie Kindschuh has helped me many times over the past few years. UAPB’s School of Agriculture, Fisheries and Humanities gave me a great opportunity to work on a unique project.
In a recent AGFC press release, Christy Graham, the agency’s trout program coordinator, said that the work done by the UAPB for the AGFC on spawning habitat in the Little Red River will be essential to move the next management plan forward.
“These findings have implications for just about every aspect of future fisheries management,” Graham said. “I anticipate that we will use much of this data to formulate actions for the next management plan review, which is due to begin soon.”
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