By THOMAS P. WEAVER, HORIZON Editor
DALE HOLLOW-Concerns about the health of the smallmouth bass population here on Dale Hollow Lake have been on the minds of anglers, marina operators, and the Tennessee Wildlife Resources Agency (TWRA) since all three witnessed last summer’s fish kill targeting the sought-after species the lake is well known for producing.
Speculation over what may have caused the event has dominated discussion among the groups, but some of it can now be put to rest.
After a year’s worth of collecting and analyzing data from sampling, creel surveys, electrofishing, and other methods, the TWRA has released an extensive online report detailing their findings.
Though the findings are somewhat inconclusive, the in-depth work has ruled out much of what those concerned about the lake’s prized gamefish had most feared and has identified possible environmental and other factors that may have contributed to the die-off.
“When (we) received the news and also observed this fish kill at Dale Hollow in (the summer of) 2012, the investigation by the TWRA began immediately,” TWRA Region 3 reservoir fisheries biologist/manager Mike Jolley said in his report. “(We) observed approximately 250 floating smallmouth bass located from mid-reservoir down to the dam over the course of the die-off. A sample (of the fish) that were found dead was sent to a lab to screen for diseases or parasites.
“All specimens tested negative for viruses, bacteria, or parasites according to the tests conducted by the U.S. Fish and Wildlife Service,” Jolley explained. “This report was good news since there are many diseases (that) could have long term consequences.”
Jolley went on to say the test results “initiated more thought and credibility to the cause of the die-off being some type of environmental factor likely caused by the record drought” or a byproduct of “higher than average temperatures which in some cases were record setting” last summer.
“Environmental factors contributing to the die-off could include, but are not limited to, non-favorable oxygen levels at desired depth ranges which can change daily, harmful algal blooms (HAG’s), change in flow regimes affecting water layers and changes in reservoir retention time or other water quality issues,” Jolley wrote in the report. “Another potential cause or contributing factor to the kill was the possibility of post release mortality from angling pressure associated with summer months and corresponding high water temperatures.
“With the die-off taking place over multiple weeks, the possibility of an isolated one-time event was easy to rule out. Although, with smallmouth bass typically being in off shore schools that time of year, possible contributions by angling mortality could not be ruled out.”
Jolley stressed in his work the fact that “no estimations have been put forth by TWRA regarding the total amount or percent of dead bass that occurred with the die-off” and also explained the agency has not estimated the “percentage of remaining smallmouth bass that make up the existing population” here.
“It is not possible or credible to make such predictions and assessments regarding this event or like events,” Jolley explained. “Obviously, some questions still remain in regards to this fish kill.
“(We) are fully aware of the circumstances at Dale Hollow in relation to the fish populations and in particular this most recent fish kill in the summer of 2012,” he continued. “However, TWRA is limited as to what it can do to prevent these types of fish kills, especially when there is no one definite cause identified.
“Even though TWRA is unable to prevent fish kills such as this, the concerns and actions taken were no less. Through much effort by TWRA, we have been able to rule out some possibilities like diseases which carry major impacts that were of major concern initially, (and) like the anglers who fish Dale Hollow, TWRA very much wants this reservoir to operate at its full potential as witnessed by the success of fishermen (in the past).”
Jolley’s report said “TWRA is optimistic that the sustainability of Dale Hollow fisheries will continue,” but it also said “future unexpected changes in various conditions may alter this path.”
The biologist explained “Dale Hollow has overcome adversities in the past,” saying “fish kills in reservoirs are not uncommon” and reminding that the reservoir had endured such events including “notable fish kills” in 1975 (carp and white bass), 1989 (lake trout), and 1998 (smallmouth and walleye).
“We want Dale Hollow to continue to be a place of angling destination and live up to its reputation as being the crown jewel for smallmouth bass fishing in Tennessee as well as the nation,” Jolley said. “We will continue to diligently monitor fish populations in Dale Hollow and make recommendations accordingly, based on recent data collections, surveys and long term trends.”
The full report included a vast amount of data including positive electrofishing survey numbers from this spring, creel surveys pointing to an increase in fishing pressure, recommendations regarding summertime fishing tournaments, and details about the fact the kill had a greater effect on the lake’s population of older/larger fish.
See a future HORIZON for details regarding those findings, or visit http://tn.gov/twra/region3/dhollowfishkill.pdf Jolley’s complete report.