[The Brazil Times nameplate] Overcast ~ 61°F  
High: 71°F ~ Low: 46°F
Sunday, May 1, 2016

How to prevent local fish loss

Thursday, August 19, 2010

It is sad to say, but there has been an increase in the number of local residents expressing concern for their ponds.

Many have fallen victim to a summer fish kill. Fish die as a result of many different causes, including old age, starvation, stress, suffocation, water pollution, disease, parasites, predation, toxic algae, severe weather and several other causes.

Often sudden, large fish kills in a pond are the result of fish suffocation caused by nighttime oxygen depletion in the summer.

Fish kills from oxygen depletion often occur in the early morning in very green water ponds. Some of the factors influencing the likelihood of a summer fish kill include: Vegetation Biomass, Water, Pond Size and Depth.

The amount of vegetation in August and September plays a big role in the chance of a summer kill. When ponds become choked with a large amount of vegetation, it is more likely to experience a summer kill. This is because the excess vegetation will not produce enough oxygen to fulfill the oxygen needed during the day and night when we experience hot, calm and cloudy weather patterns.

Weather can play a huge role when determining if a summer fish kill is likely. Unfortunately, the calm, hot summer we have been experiencing increases the likelihood of a summer kill. Conversely, a cool summer that has plenty of nice breezy days reduces the chance of a summer fish kill.

Pond size and depth is the final factor I want to discuss. Ponds that are small and very deep (more than 12-feet) are more susceptible to the effects of a summer kill than a large, shallow pond. This is because the smaller pond will have a higher proportion of the water that lacks oxygen when compared to the larger pond. Thus, this is why large, windswept ponds in open areas rarely stratify resulting in a summer fish kill.

Even though you may not have complete control on the factors that contribute to a summer fish kill, you can still take steps to prevent one in the future. For starters, if you are designing a new pond, make sure the shoreline slopes at a rate of 3:1 to limit summer aquatic plant growth. By doing this, you will help ensure a more balanced level of oxygen between day and night by reducing the amount of summer aquatic vegetation. For an existing pond, try to reduce the amount of plant growth early in the summer. Do this by adopting a strategy of using herbicide and algaecides before July 1. Later applications run the risk of indirectly causing a fish kill.

If you do have to do an application at a later date, then treat the pond a quarter at a time and allow two-to-three weeks between treatments. You can do this by using a granular formulation of selected herbicides.

One of the most effective ways to prevent a summer fish kill is by using an aeration system. By using an aerator, you will continuously add oxygen to the water and will help prevent summer stratification from occurring. It also helps keep nutrients suspended with promoting single-cell algae growth.

If you have an aeration system installed, it is best to run it throughout the night from May to September to help prevent a summer fish kill from occurring. Otherwise, an aeration system does not need to run 24 hours a day. A few other things that you can do to help prevent a summer fish kill from occurring include: Not overstocking your pond, not feeding ducks or sport fish, and preventing livestock from entering your pond.

Walking outside and realizing that you have fallen victim to a fish kill is a sickening feeling for the avid fisherman. However, you can help prevent that from occurring if you follow some of the suggestions provided, including treating your pond for vegetative growth before July 1, and using an aerator.

For help with any agriculture, horticulture, or natural resource topic, please contact your local Purdue Extension Office at 448-9041 in Clay County or 812-829-5020 in Owen County, or reach me directly at smith535@purdue.edu.

Purdue University is an equal opportunity/equal access/affirmative action institution.

Upcoming opportunities available to you through Purdue Extension include:

* Aug. 31 -- Indiana Integrated Resource Management Field Day, 2-6 p.m., Greencastle. Dinner is $10. RSVP by calling 1-765-494-9234,

* Sept. 6 -- Holiday. Extension office closed,

* Sept. 8 -- Venison Workshop, 6-9 p.m., Parke County Fairgrounds. Cost is $15. RSVP by calling 1-765-342-1010, and

* Sept. 11 -- Nature Day, Clay County Fairgrounds, 9 a.m.-noon. Free. Raptor presentation at 11 a.m.