Tracking tailwater saugeyes.
In recent years, the Ohio Department of Natural Resources has stocked more than 6 million age-0 saugeyes in some 30 reservoirs. During this period, it has become obvious that fingerling and adult fish frequently pass through dams, leaving the reservoir they were planted in and entering the tailrace below. From there, movement into other rivers is possible, including into the Ohio, where biologists have discovered increasing numbers of these hybrids. This raises concerns that saugeyes stocked in reservoirs are making their way there. Back-crossing of saugeyes with saugers or walleyes in larger waterways could lead to loss of genetic identity in parental stocks.
Testing the propensity of tailrace saugeyes to move downstream into other waterways, researchers at Ohio State University implanted radio transmitters in 205 saugeyes in the tailrace below Deer Creek Reservoir and followed fish for two years. * Fish were tracked from shore, by boat and helicopter, as well as from two base stations, one located in the tailrace and the other at the confluence of Deer Creek and the Scioto River about 28 miles downstream, which flows into the Ohio about 68 miles farther down.
Three-quarters of the tagged saugeyes remained in the tailrace. The others moved downstream at least once, though typically not too far. Four fish swam through Deer Creek and entered the Scioto and two of them subsequently returned to the tailwater. The primary impetus for leaving the tailwater was the release of water low in oxygen from the dam, which occurred during one July. Water quality was so poor that saugeyes remaining in the tailrace died. Those that survived typically returned to the tailrace once water quality improved.
Deer Creek's tailrace was a popular fishing spot; 49 percent of radio-tagged fish were harvested during the study. A creel survey estimated annual harvest there at more than 14,000 saugeyes. More fish left the tailrace during high flows, but numbers remained during those conditions, often moving closer to the bank to escape the brunt of the current. During low flows in spring and summer, the tailrace was as much as 7[degrees]F cooler than the creek, due to inflows from the cooler reservoir. During late summer, fall, and winter, the tailrace was up to 5[degrees]F warmer than the lake, thanks to these warm inflows.
Because the study followed only 200 saugeyes from a tailrace population estimated at around 17,000 fish over 10 inches, the authors were not able to rule out possible escapement into the Ohio River, although none was documented. Deer Creek Reservoir's tailrace offers the deepest water in the vicinity, so it seemed likely that saugeyes found habitat there more suitable than downstream. Larger, deeper rivers might pose less of a barrier to movement, though most systems in the Ohio drainage are similar to Deer Creek Reservoir.
* Spoelstra, J. A., R. A. Stein, J. A. Royle, and E. A. Marschall. 2008. Movement of reservoir-stocked riverine fish between tailwaters and rivers. Trans. Am. Fish. Soc. 137:1530-1542.
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|Title Annotation:||Toothy Tidbits|
|Date:||May 1, 2009|
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