Iowa Fishkill Database Help

Due to the changes in technology and the emphasis on data quality, the locational information for some of the older fishkills (pre-1995 or legacy data era) is an estimate only, and should not be accepted to be the precise location of the kill.

Modern data also has limitations on the accuracy of the fish kill locations, especially those where no formal investigations took place, such as natural kills on private farm ponds. The data point also represents the approximate location of the start of the kill, not the entire extent of the kill.

The numbers of fish killed should not be taken to be an exact count of fish. The number is always an estimate, since it is extremely difficult to count dead fish in flowing water conditions or when the kill is not reported immediately.

When possible, the number of fish killed in a kill event is derived from procedures outlined in the American Fisheries Society Special Publication 30 and in the Iowa Administrative Code Chapter 113. The enumeration of fish during a fish kill investigation provides a basis for determining the value of the fish killed when restitution from the responsible party is sought.

Less accurate counts occur in the following cases:

• Fish kills that were reported several days after the event
• Unfavorable conditions for counting fish such as high water levels or flows, ice, etc
• Kills that are natural in origin

The reported number of fish killed in these cases is a rough estimate as determined by the field investigation staff, or by the account given by the person reporting the fish kill.

Records that do not have a number for fish killed, or display a zero, indicate that no official estimate was given at the time.

The exact cause of the kill is unknown. This may be due to several factors, including delayed reporting/investigation, weather events, environmental conditions, and so forth.

The exact cause of the kill is unknown, but field observations indicate that the kill was natural in origin. The onsite comments may provide more information as to possible/suspected causes.

The exact cause of the kill is unknown, but field observations indicate that the kill was human in origin. The onsite comments may provide more information as to possible/suspected causes.

A phenomenon typically found below dams at the large reservoirs (for example, Saylorville Lake and Red Rock Lake). Gas bubble disease occurs when levels of dissolved gasses (primarily nitrogen and oxygen) become supersaturated in a waterbody and in the blood of fish living in that waterbody. If a sudden change in river level prevents fish from reaching sufficient depth to keep the gasses their tissues and blood in solution, the gasses can come out of solution and form bubbles under the skin, in fins, and in the mouth. Hemorrhaging in the affected areas and exophthalmia (or “pop eye”) are conditions commonly associated with gas bubble disease. Fish mortality results from gas bubbles forming in the circulatory system of fish and blocking the movement of blood.

This category is classified as a Natural Origin kill, and includes fish diseases, viral, bacterial, and fungal infections, various parasites, and spawning stress.

This category is classifed as a Human Origin kill, and covers spills of any substance except animal wastes. It also includes run-off from storm events that wash pollutants into streams and cause a kill. If investigators were able to identify the specific pollutant, it is recorded in the Spill Type field. Spill types (with examples or clarification) include:

• Ammonia/Fertilizer
  • Anhydrous ammonia, land applied fertilizers (except animal wastes)
• Animal Waste
  • Further described in various subcategories
• Petroleum Products
  • Oil, gasoline, grease
• Pesticides/Herbicides
  • Atrazine, other commercially available agricultural and urban lawn care products
• Chlorinated Water
  • Typically from water main repair work or fire hydrant flushing
• Organic Waste
  • Milk, silage, corn syrup, processing by-products (blood, tissue, eggshells, etc)
• Soil/Storm Runoff
  • Soil from construction sites/bare fields and nondescript stormwater runoff
• Other
  • Rare occurrances not categorized above. See onsite comments for more info.
• Unknown/Unspecified
  • Typically only used for older fishkills where an exact description was not provided.

Human wastewater from lagoons, storage facilities, or private septic systems that experience malfunction or failure.

This category is classified as a Natural Origin kill. Kills of this type occur due to environmental conditions not directly caused by human activity. These kills include but are not limited to:

• Low Dissolved Oxygen
• Algal Blooms
• Temperature Extremes
• Summerkill
• Winterkill
• Water stagnation from lack of flow