It was a grim weekend on the shoreline of Como Lake in St. Paul, where crews spent days hauling out roughly 1,000 dead fish after a sudden warm spell left parts of the shallow lake starved for oxygen. Workers finished clearing the carcasses early Monday morning, and the sight of floating fish near the Lakeside Pavilion caught the attention of people passing by.
The Capitol Region Watershed District estimated the kill hit about 1,000 bluegill and crappies. According to the district, a rapid warming event sharply reduced dissolved oxygen in spots around the lake, dropping saturation from about 10 milligrams per liter to nearly zero and putting smaller fish under severe stress. The Star Tribune also reported that about 150 fish died last week in Lake Nokomis in Minneapolis.
Why the lake lost oxygen
Como Lake’s shallow depth and long history of nutrient loading make it especially vulnerable when sunlight and temperatures spike. The Minnesota Pollution Control Agency notes that the lake is officially listed as impaired, and the Capitol Region Watershed District explains in its Como Lake management plan that decaying curly-leaf pondweed and internal phosphorus pulses can fuel algal growth and hypoxia.
Cleanup and neighborhood impact
A contractor was brought in to remove the dead fish over the weekend, with crews wrapping up work Monday morning, according to the Star Tribune. Capitol Region Watershed District officials told the paper that pollutants were not to blame and urged residents to do their part by clearing leaves and pet waste and keeping storm drains free of debris to cut down on runoff into the lake.
What to watch this summer
The Capitol Region Watershed District management plan calls for continued monitoring and adaptive actions to respond to changing environmental conditions, including hotter summers that can raise the risk of future oxygen crashes. Como Lake supports bluegill, crappie and largemouth bass, according to the Minnesota Department of Natural Resources, and officials advised people to avoid contact with or consumption of fish found dead along the shore.
