Apparently on the advice of a fisheries biologist, the City Council has voted to approve $60,000 for vegetation control to prevent fish kills for decaying vegetation as the lake refloods.
I did my Master of Science degree in warm water fisheries management at Texas A&M. While I have primarily been employed as a wildlife biologist (Doctor of Philosophy in wildlife management at Texas A&M), I have also done some fisheries management over the years. I also have many contacts in the fisheries management profession with whom I correspond.
In the Southeast, and elsewhere, it is a long standing and successful management practice to draw down reservoirs to improve the fishery. As the plants grow, they pull nutrients out of the sediment. When they die from flooding, those nutrients (especially nitrogen and phosphorous) are released into the water producing a plankton bloom. That provides an abundant food source for baby fish (fry).
The second major benefit of drawdown is that the new shallow water habitat provides excellent spawning habitat for most of the desirable species here (largemouth bass, white crappie, and the various species of bream) the next spring. Other benefits include firmer bottom sediments and fewer small fish as the predators feed in the crowded remaining water.
The essential question is, “Is biological oxygen deficit (BOD) a serious problem. While BOD can cause fish kills, it rarely happens after drawdowns. OK, why not on this drawdown?
First, the timing of this is optimal. IF they finish the dredging in the next few weeks, we will be into fall when the lake refills. Fish kills of the species with which we are working due to low oxygen are almost exclusively in the summer. Cooler water slows the decomposition of the dead vegetation and allows the water to stay oxygenated. In my expert opinion, the probability of a fish kill from BOD is EXTREMELY low.
OK, So what is the worst case scenario? We get a major fish kill and the herons, egrets, ospreys, and eagles have a field day feeding on dying fish. Georgia Department of Natural Resources will stock fish for free because it is a publically accessible fishery. AND we have $60,000 to purchase fish from commercial fish farmers. That will buy a great many fish.
Dr. Bert Bivings
Environmental consultant and certified wildlife biologist
Peachtree City, Ga.
