Drought puts the heat on poorly constructed ponds
If you think it's dry, try being a fish during the drought, said a Texas AgriLife Extension Service expert.
"You know it's dry when your fish have ticks," joked Billy Higginbotham, Ph.D., AgriLife Extension wildlife and fisheries specialist.
Jokes aside, it's a serious matter as water levels drop for the owners of the more than a million private water impoundments in Texas, Higginbotham said. Channel catfish, bluegill and largemouth bass must survive both a shrinking habitat and dropping water-oxygen levels.
Dropping oxygen levels can be a problem during a hot Texas summer even when there's normal rainfall. But there's nothing like a drought to highlight a poorly constructed pond and magnify the potential for fish kills, he said.
"It's hot and dry even by Texas standards, but the ponds that show the problem first and foremost are those that have either very small watersheds or those ponds that were built on marginal soil," he said.
A small watershed means there is not a large enough area surrounding the pond for sufficient runoff to maintain water levels, even during years with average rainfall, Higginbotham explained. To hold that runoff, the soil the pond is situated in should contain enough clay.
"These are important construction concepts for landowners to remember whether they are watering livestock or if fish are an important recreation use of that pond," he said. "Fish remain a primary concern to many owners of small ponds, and there are more than a million private impoundments found statewide."
Obviously, Higgibotham said, when ponds are not much more than mud wallows, there's little that can be done about saving fish.
But even if a pond is well-constructed and its water level has only dropped a foot or two, it still behooves pond owners to pay attention to fish management and water oxygen levels, Higginbotham said.
"In any case, we want to avoid trying to carry more than a thousand pounds of fish per surface acre during the warm months," he said.
There are simple methods to determine the size of a pond, he said. If the pond is more or less rectangular, the simplest way to determine its size is to measure the length and width in feet, then multiply one measurement by the other to get surface area in square feet. Divide this number by 44,000 to get the approximate area in acres.
Calculating a round pond's size is a little more complicated. Divide the distance across the pond by two, square the result, then multiply that number by 3.14.
Once the approximate surface area is determined, the next step is to determine the pounds of fish in the pond, Higgibotham said.
"Usually, the pond owner knows how many catfish were originally stocked in the pond and has a pretty good idea how many have been removed since stocking," he said. "By catching a few fish and weighing them, an owner can estimate the total pounds of fish in the pond."
Pond owners who suspect low oxygen concentrations should monitor their ponds closely, even if their stocking levels are 1,000 pounds per acre or less, Higginbotham said.
"Visit the pond shortly after daybreak," he said. "If fish are crowded up at the surface at first light, that's a pretty good indication that you've got low-oxygen levels."
If this is the case, pond owners should either immediately harvest fish to reduce the stocking level or aerate that water, Higginbotham said.
"Aerate with a pump or boat motor just to get over the hump and through the immediate emergency in order to raise the oxygen levels, so you don't lose an entire pond of fish."