From a report in yesterday's StarTribune:
Those big December snowfalls have crews on some Minnesota lakes heading onto the ice earlier than usual this winter in an effort to prevent mass fish kills. They're on a rescue mission to install aerators and create open water before oxygen levels plummet to the point that fish essentially suffocate under the ice. Some lakes are already showing faster-than-usual oxygen depletion...
Winterkill is a natural process that happens when fish don't have enough dissolved oxygen in water, he said. Because of the ice cover, oxygen in winter comes mainly from aquatic plants, which receive enough sunlight through ice to grow. But in years with lots of snow, sunlight penetrates ice less and plants stop growing. Instead of producing oxygen in water, the plants consume it as they die and decompose...
Sometimes it kills all the fish in a lake, he said, and sometimes it only affects part of a lake or some species of fish. It is more of an issue in southern Minnesota, he said, where more lakes tend to be shallower. Trout require the most oxygen, followed by bluegill and largemouth bass, according to fisheries managers. Walleye, northern pike, carp and crappies can tolerate less oxygen, and bullheads and fathead minnows need the least amount of oxygen to survive...
The DNR grants about 300 permits for cities, lake associations, park districts and even some sportsmen's clubs to install and maintain aerators on lakes. The purpose is to keep open water during winter so fish will have a fresh source of oxygen...
ليست هناك تعليقات:
إرسال تعليق