Lakecaster Online

Hydrilla
by Pete Gunn

Pete Gunn

Hydrilla marks a big difference in lakes having it is the best thing that has happened SAM RAYBURN. The lack of it sure changes fishing and the number of fish of fish caught. Hydrilla can grow more than a inch a day and spread from a few acres to thousands in a few years or less

Extending in a solid wall from above the water to 20 ft. or more. They have done 20 years of researching the bass and grass controversy, DR. Mike Maceina has to share with anglers concerns what happens to bass survival and growth rates in dense stands of hydrilla, milfoil or other aquatic vegetation. Great numbers of young bass fry survive in areas where plants are thickest . In late summer, when young bass are about 4 to 5 months old, densities can be as high as 1,000 fish per acre in submersed plants, compared to a low of 20 per acre in areas that don't contain plants. However bass populations follow the same rules as any other animal population ,higher densities mean more competition for food and space . For young fry bass that means they often don't reach 4 or 5 inches in length that many biologist believe they do to survive their first winter. One year on lake Guntersville, he found young bass in Eurasian milfoil was nearly 10 times higher in bare areas by the middle of fall, fish averaged only 3 inches in plants compared to 6 inches in bare areas. By next spring when fish were age 1, bass density was twice as high in areas that contained no plants then in areas with milfoil. Thus, the habitat provided by milfoil proved to be detrimental to bass reproduction. Whether a young bass reaches 4 inches long in its fist year or second, it should be eating fish at that size, adds Maceina. But in thick plants it often must rely on grass shrimp, crawfish and insect larvae for nourishment. In open water he adds, bass can effectively feed and grow rapidly by consuming numerous and easily available shad. But when vegetation exceeds 40 percent, shad populations typically decline, and sunfish and top minnows increase. Thus vegetation directly and indirectly affect feeding by altering feeding strategies and changing the types of pray that are available to bass. Slower growth, in turn means anglers are likely to catch smaller fish, as happened on Guntersville when milfoil coverage was high in the late 1980's. By contrast, catch rates were lower when vegetation declined, but the average fish caught was larger. In addition to hindering a bass ability to feed in thick plant mats also can rob water of oxygen at certain times, particularly during summer. This forces young bass out of protective plants and into open water where they are more subject to predators. Such a situation occurred on lake Seminole during the early 1990'. Maceina says. Three or four years later bass anglers experienced poor fishing which biologists suspected was due to the lack of bass for a few years he says. With the natural decline in hydrilla to about 18000 acres more young bass have been observed and the fishery is expect to recover. Too few plants can cause the same type of predator problem. In lake Conroe the stand stock of catchable size bass was two times less after grass carp completely eradicated the hydrilla, and this decline was attributable to the decline in age 1 recruitment. After complete hydrilla removal the average size bass increased in anglers catches, but the catch rate declined drastically. The overall weight per hour of fish also declined after hydrilla was eradicated. What plant management does to standing populations of adult largemouth bass is a little more of a mystery. From all the studies I have seen the impact of increasing or decreasing plant coverage on adult bass populations has been inconsistent. What extensive plant coverage can do the fisheries adds in drawing bass to the edge making these fish more vulnerable to angling. Thus thick coverage can be good for fishermen, if not for fish. Additionally , the fish caught along those edges often were produced three to seven years earlier, when environmental and plant conditions may have been a lot different .

Current research suggest that 15 to 40 percent coverage by submersed vegetation is best for bass in larger lakes systems he continues. Higher plant abundance has the potential to negatively affect bass fisheries, hurt other fisheries, cause other ecological imbalance, and certainly reduce other recreational opportunities besides fishing. With Sam Rayburn the lake has not caught up in the last three years when the lake was so low. It well take two or three more years to get all the hydrilla back that we had. Sam Rayburn is one of the best lake in the world ,with the loss 20% of the hydrilla a lot the big fish are out in deep wate. This spring we should see lots big bass caught and released. The hydrilla is making a slow come back but with the great fishery we have a lot of states would like to have in their state. If you have any questions about fishing or the lake ,guides ,fishing school or tackle call Pete's Tackle 872-3572 Pete Gunn

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