Fish are dying in large numbers from icy waters in Missouri, causing some residents to worry about poison, or industrial pollution.
Residents around the Show-me State are reporting dead fish in water bodies, including Table Rock, Truman Stockton, Pomme de Terre and Lake of the Ozarks.
These animals are perishing in both deep and shallow waterways across the land of six million people. Thicker-than normal ice on waterways around Missouri been covered by several inches of snow. This blocks sunlight that normally would have filtered into the marine system. Plants living underwater, unable to absorb sunlight, do not produce as much oxygen as normal. When the problem becomes severe, fish can suffocate.
"Without light, plants begin to die, and when they die, they not only are not releasing oxygen into the water, their decomposition actually consumes oxygen. If that goes on for long enough, like it has this year, fish can suffocate," Rebecca O'Hearn, of the Missouri Department of Conservation (MDC), said.
Many other fish, especially young ones, may also freeze to death in the cold water. However, the MDC is saying the deaths are no cause for alarm. There is no evidence fish were killed by pollution, disease, or contamination.
This winter is the ninth-coldest season on record, according to State Climatologist Pat Guinan. Temperatures were the lowest seen since 1978-1979. On 26 January and 2 February, loud popping noises were heard around the state. These were "frost quakes," produced as the ground rapidly freezes.
Shad, or river herrings, perished in great numbers at the Lake of the Ozarks. Fish build up a reserve of fat to help sustain them through the winter. But, extreme cold burns fat faster than swimming in warmer water. When fish deplete their reserves, they can die. This effect is more pronounced baby fish and smaller animals, including shad. There were a large number of the animals to begin the year, which may prove to be a disadvantage for the fish.
"When yearling shad are that abundant, they are generally smaller than average going into the winter, and with less fat reserves. Follow that up with a hard winter, and the result can be widespread die-offs of shad, especially the yearlings," Greg Stoner, state biologist, said.
Although the deaths are certainly sad, the effect on fish populations should be small. Shad have an average lifespan of eight years, giving them plenty of time to recover. The effect may be more pronounced in smaller bodies of water, where the effect is more common during winter. Some areas may require restocking fish populations in the spring.
