Summer fish kills are not uncommon in Missouri but the conservation department says they have skyrocketed this year.
The department says a combination of bad things is behind that big increase. There’s the heat and more than three months without a statewide rain. Department spokesman Jim Low says some Ozark springs have dried up. Some of the larger ones such as the ones that feed the trout hatcheries are down to half-flow. Many ponds, small lakes, and streams are at lower levels. Some have become isolated puddles. Adding to the misery for streams is that the drought has caused a lot of trees to shed leaves that normally would have shielded streams from the sun. That causes the streams to warm up, sometimes so much that fish are coming to the top to gulp oxygen.
As the water gets shallower, nutrients are concentrated and lead to growth of algae which can turn into consumers of the shrinking amount of oxygen in the water. Low says that’s when things “get dire” for fish and when we start seeing fish kills. He says some fish suffer more than others, including trout, which need cool, highly oxygenated water. Bass and bluegill and other sport fish are susceptible to poor water quality, too. Unfortunately, he says, carp thrive.
But there is a little tradeoff. Low says the hot, low-oxygen water that’s bad for most fish also is bad for invasive species, too..