Have watched Gibbons decline which corresponded with separate naturual and man-made events....
Water temps in winter months have dropped and fluctuate greatly causing major fish kills such as when the power plant was routinely shut down for several days of power plant maintenanc. When electricity demand is low (also winter)and coal costs are high plant is shut down for weeks. Bait fish tilapia numbers have dropped significantly.
Successive hurricanes have caused major shore line erosion which has fully filled in most all creek beds and eliminated what was once deep waters allowing thermoclines. When power plant is running, no longer are there areas of significant current paths which once were concentrating baitfish and offering lake structure/habitat. The now exposed shorelines deliver directly into the lake heavy agriculture and livestock runoff which keeps the water unclear and allowing little or no light penetration, except for seasonal pads which die and leave the reservoie barren of vegetation during the cold months. Often now it is an unheated cold, shallow unclear reservoir during the harshest cold front weeks of winter with bait die offs seen. Crappie, sunfish and baitfish once were common but no longer.
Power company for several drought years delayed buying water until Spring rainsfailed ..which resulted for successive years in several feet of newly purchased muddy water( from the Navasota River) to be pumped in at time of bass spawn. Beds with fry were overnite covered by several feet of purchased water and produced little/no bass or baitfish some years.
Water hyacinth spraying (with Round-up equiv) by the plant personnel eliminated much of the lakes vegetation cover. If you fished around the plants much, you could see the beneficial effects the water plants had on improving water clarity which now no longer exists.
Once at a football game a board member of the power plant told me if they could, they would find a way to eliminate all fish in the gibbons waters as it would help the plant save significant costs of trapped fish causing interruptions/shutdowns to the plant's water intake.