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Fish Kills and Sick Fish

  • Fish kills due to low oxygen levels sometimes occur naturally in the summer and fall, when water temperatures are warm and overcast skies or rain occurs for a few days. Fish will be at the surface gasping for air and the larger fish die first. The kill is immediate and involves all species in a short time. Emergency aeration with paddle wheels or aerators is the only remedy.
  • Fish kills due to disease typically occur over a longer period of time. Fish behavior may be abnormal and a few fish will die each day over an extended period. One or more species may be affected. Fish diseases can be caused by parasites, bacteria, and viruses. The external signs of some diseases are similar, so internal examinations are necessary to determine the specific disease and correct treatment method.
  • To determine the cause of fish kills due to diseases, it is necessary to send a properly collected sample of fish to the Aquatic Diagnostic Lab at the College of Veterinary Medicine, Mississippi State University (listed below). It is best to ship your fish by US Postal Service Priority Mail or Federal Express Next Day Service. Please call the Aquatic Diagnostic Lab and tell them you have sick fish and need to ship them to their office. They need to know when your fish will be shipped to them. You can also bring the fish to them. Lab personnel will conduct various tests on the fish to try to determine the specific disease and suggest treatment methods. This is a free service.
  • It is important to follow the collection and packaging instructions on the enclosed sheet. It is best to collect sick fish that are still alive because there is a better chance the cause of the disease can be determined. Fish that have been dead for several hours at a warm temperature begin to decompose. This makes accurate disease diagnosis very difficult.
  • Fish kills due to chemicals usually involve all species and the kill is immediate. If you suspect that chemicals caused the fish kill, you should immediately contact the Mississippi Department of Agriculture and Commerce, Bureau  of Plant Industry at Mississippi State University at (662) 325-3390.
  • The Mississippi Department of Environmental Quality, which can be contacted at (601) 961-5701 or (601) 961-5599, does not usually investigate fish kills on private waters unless a pollution source is suspected. The Mississippi Department of Wildlife, Fisheries, and Parks does not have the laboratory equipment, materials, and technical specialists necessary to diagnose disease problems. 

Ship Fish To:

Aquatic Diagnostic Lab College of Veterinary Medicine
P. O. Drawer 9825
Aquatic Diagnostic Lab
Spring Road
Mississippi State, MS 39762
(662) 325-3432  


Lora Petrie-Hanson - Certified Fish Pathologist (AFS-FHS)

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