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Tips to avoid fish kills

  • 9/3/2019 2:33:00 PM
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Avoiding a fish kill starts with understanding why they happen most often during mid- to late summer. Several factors contribute, but remember fish and aquatic animals like crayfish, frogs and beneficial insects are most vulnerable during hot, dry weather. Usually stream and pond levels are lower, vegetation and algae levels are higher and water temperatures are warmer. These factors combine to reduce dissolved oxygen levels, stressing aquatic animals.

When fish and other aquatics are stressed, they are more susceptible to pollutants. So, while you should always be careful, first and foremost, please take extra caution when mixing and land applying chemicals and nutrients especially during the dog days of summer. DNR staff offer the following tips to help you avoid a fish kill:

  1. Read and follow chemical labels. Some chemicals are toxic in very small amounts (parts per million—four drops of ink in a 55-gallon barrel of water—or parts per billion—one pinch of salt in a 10-ton bag of potato chips or one pound in 120 million gallons of water).
  2. Avoid applying near water, including near pond and stream banks.
  3. Check the weather and avoid application before a rain storm.
  4. Look for and avoid application near small feeder streams and grassed waterways where runoff could enter a stream or pond.
  5. Make sure rinse water is properly disposed of and doesn’t reach a stream or lake.
  6. If chemicals are applied by aerial spraying, check locations of small streams and ponds before application, watch wind speeds and drift, and shut off application when crossing small bodies of water.
  7. Take care with nutrient application. Whether manure or fertil