BORN AGAIN!! The Phenomenon of Lake Draw-down
by Jim Porter
Where is that fabled `Fountain of Youth', our wistful dream of the ages. Who says that it cannot really exist? Why can't the aging process be slowed, or a body and mind rejuvenated to the status of youth?
For the creature, Man, those answers may lie in the cold and misty realm of the Twilight Zone. But, for your favorite fishing lake, the fabled Fountain DOES exist and it DOES work. Time CAN be stopped and the subject returned to the days of its youth. This Fountain of Youth is real and it dwells in a package marked "Draw-down".
The pre-planned and controlled process of lowering the water level within an impoundment is termed a `draw-down'. In nearly all cases, the final stage of this action is returning the body of water to its normal elevation.
Originally, projects of this type were carried out to allow certain work to be accomplished, such as the repair of an associated dam or dike system. And, in the first few years following the completion of the job, a soon-to-be- predictable change gradually began to be recognized. During the third year following draw-down cycle completion, fishing success in the lake began to improve. By the fourth year, catch rates reached the point of being termed `miraculous'. While the `cause' was not immediately known, the `effect' was certainly being noticed by the angling public. Consequently, the governmental game and fish activities, anxious to take any credit which might be due them, began to investigate this strange phenomenon of apparent fishery rejuvenation.
The first thing noted was that the lake in the post- draw-down state was exhibiting the exact same traits it had during the first few years after its initial formation and filling. Biologists had noted the extremely high productivity of a new fishery during the third through seventh year. They attributed it to the tremendous abundance of the lower end of the food chain from the heretofore dry land and vegetation areas and its support of the emerging mid-and upper-echelons of the chain, which eventually sustained the game fish populations. What appeared to be happening was an `instant replay' of the highly-fertile early years of the lake's life cycle.
Early studies showed that the lowering of a lake's level for a significant period of time allowed three very beneficial things to occur. First, it bared the usually thick, non-contributory vegetation in the extreme shallows and caused it to die off. Second, the heavy muck accumulations from numerous generations of aquatic plants gone by were allowed to dry and gradually dissipate to some degree. And, thirdly, new plant and insect life began to take root in the now-exposed, dry shallows zones.
Given that Man did not interfere in the process, this latter event was the more influential factor, in that it provided a rejuvenation of the lower food chain elements. The first and second events provided improved access to the shallow spawning areas required by most game fish species, and insured a better oxygen content in the area.
A major finding by fishery biologists was that extremely dense vegetation in the shallow zones can actually preclude the production of oxygen through the normal photosynthesis process. Oxygen level measurements reflect that the surface layer of aquatic growth is often relatively lifeless, but its sheer density can effectively prevent the penetration of photosynthesis-dependent sunlight to the plants beneath. No oxygen content simply means no fish will use the area.
As scientists began to better understand what was taking place after a draw-down, they noted that Man could effectively influence the quality of the outcome. First, game and fish authorities could plan for draw-downs when the fertility of a given lake appeared, or could be expected, to be on a significant decline. And, they could hold the lower water levels as long as felt advantageous for optimum results. Second, they could assist Nature's workload by employing machinery to remove selected vegetation and bottom muck. And, thirdly, officials found that they could plant new vegetation which would actually contribute increased support of the emerging food chain and new fishery spawns.
Draw-downs have taken place all over the country. Two of the more recent draw-downs in Florida took place on the Panhandle's Lake Talquin and the Central Peninsula's West Lake Tohopekaliga (generally referred to as West Toho). In both cases, the effect on the fishery was extremely positive, to the point that certain slot sizes and minimum- length restrictions had to be placed in effect to protect the newly-emerging bass populations.
Talquin's program was initiated to allow work on the lower dam. Seizing upon the opportunity, the Florida Game and Fresh Water Fish Commission (FG&FWFC) made it a cooperative venture with the Department of Natural Resources (DNR), the appropriate Water Management District, and the Corp of Engineers.
A beneficial time-line was developed, as well as a unique staggered schedule for refilling to the normal pool levels. A large amount of grass and other selected vegetation was planted in key locations and for pre- determined depths. The staggered refilling schedule allowed the vegetation to mature to varying degrees before final inundation and provided a basis for study and analysis.
The eventual result was a massive increase in the `young-of-the-year' spawn of largemouth bass the first Spring after refilling. The second year spawn results was generally a repeat of the first, while the first year crop exhibited a very high survival rate and rapid growth. As the initial post-draw-down spawn approached its third birthday, the numbers of one and two-pound bass in Talquin began to amaze and delight the local anglers. Sadly, many took advantage of the situation to exhibit their angling prowess to their friends down at the gas station and failed to practice catch- and-release. The FG&FWFC found it necessary to impose slot- size restrictions which, if sustained indefinitely, will greatly assist in maintaining this fine fishery for years to come.
West Toho has experienced deliberate draw-down three times in the past two decades. The first two were in 1971 and 1979. The last one, in 1987, was required due to the rampant vegetation growth in the shallow zones and the loss of major spawning areas due to decaying muck from that vegetation. The explosive growth was caused by the continuous dumping of massive amounts of poorly-treated sewage from Shingle Creek on the northwest corner of the lake.
The 1971 draw-down project produced the following results:
The draw-down of 1979 produced similar results regarding the densities of new fry produced and surviving. The big news, however, was that the harvestable population increased by an amazing 400%. Now we know why West Toho continues to produce such great angling experiences year after year.
- By the second year, the spawn-produced bass fry density was up an astounding 450%!!
- In the third year, the population of harvestable bass (i.e., 12-inches, or larger) had increased 130%.
During the most recent draw-down, Nature was provided a major helping hand, thanks to a massive pre-planning effort, excellent cooperation among the governmental agencies involved, and an allocation of operating funds.
The West Toho draw-down was timed to coincide with a law that greatly reduced the sewage problem from Shingle Creek. And, an armada of earth-moving equipment and transport vehicles were staged to remove muck and undesirable vegetation to preplanned agriculture areas, where they would be used as fertilizers. This cleansing of selected shallows of the lake was very carefully planned to provided maximum support of forthcoming fish spawns.
Large plots of new vegetation were planted on the 60% of the lake bottom which was exposed. These provided the start- up of the lower food-chain elements and eventual cover and feeding areas for the newly-hatched fry of the spawn.
After refilling and the initial spawn, FG&FWFC biologists reported an explosion of bass fry in the shallow grasses, with apparent high survival rates. The second year after the refilling West Toho, we anglers noted extremely high numbers of 6-10 inch bass throughout the lake. Today, the West Toho fishery has an amazing population of 2-3 pound largemouths. Although the official figures have not been released, we would expect the results in spawn success and harvestable populations to rival the other draw-downs. We are still awaiting data on the latest Florida draw-down, that being big Lake Kissimmee. It appears the results will be impressive!!
So, you see, Virginia, there really is a Santa Claus and there really is a Fountain of Youth. They are just like anything else worth having-- we have to believe in them and work at it a bit.
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