Preventing Spring Fish Kills
It’s hard to remember spring is right around the corner when the temperatures seem to keep dropping, but it won’t be long until those temperatures start to rise. Each spring our office received numerous calls about fish kills in personal ponds.
Oftentimes, the tendency is to blame the farmer neighbor. And while less than ideal manure applications can certainly result in a fish kill, more often than not, the kill is a result of natural processes. Even though those processes are natural, there are some steps you can take as a pond owner to help minimize the risk of a spring fish kill.
Ponds are a beautiful addition to winter landscapes, but winter weather can create high stress levels in fish, resulting in spring fish kills.
First, remember that spring is vulnerable time for your fish: they’ve (hopefully) been dormant most of winter and surviving off of their fat stores. It won’t be until water temperatures climb into the 70s, the fish will start feeding and replenishing their body stores. This makes them more vulnerable to other stress factors.
Weather patterns and temperature as we move into spring will determine how long those fish stay in dormancy. If we experience a really cool spring like last year, the water may not warm up enough to bring the fish out of dormancy as early as we might like, and they will continue to rely on that fat stores, which are already low at that point.
To help combat this stress, consider feeling your fish a pelleted food more heavily during the summer months to help them build a good fat reserve. Another suggestion is to stock your pond with 3-4,000 minnows per acre in early October to help build fat stores in your other fish as well. Ashland SWCD’s fall fish sale provides a great opportunity to stock your pond with minnows in the fall.
Oxygen stress is another concern, especially when ponds become covered with ice and snow over the winter. The most consistent fix that brings benefits to your pond year round is installing an aerator. Aerators add more oxygen to your water and help keep that oxygen moving.
In the winter, bring your aerator closer to the surface or place it in shallow water for the most benefit. In the winter, bubblers only need to run as ice starts to form; if there’s no ice, you can turn your bubbler off.
If you don’t have an aerator or bubbler, it’s time to get to know your shovel. Try to learn 25-50% of your pond surface of snow. Removing the snow allows sunlight to penetrate the ice and encourage plant growth, with increases oxygen levels in the water. Remember, safety first: make sure your ice is at least 4 inches deep
It’s common every spring for ponds to lose a small number of fish from these stress levels, but bluegill are a more common loss because they are susceptible to a bacterial gill disease. A simple fix to this disease can be adding copper sulfate to your pond.
Not only will copper sulfate help manage bacterial gill disease, but it will also help control algae in your pond as well. One pound of copper sulfate can be mixed with 3-4 gallons of water and broadcast into the pond. In most cases, one treatment will be enough.
And finally, be proactive in keeping plants and algae in check. Aquatic plants can add beneficial oxygen to your waters, but too many plants eventually leads to decay - which can quickly deplete oxygen levels. A good goal to shoot for is having 25 percent of your pond covered in plant materials.
One non-chemical method for controlling vegetation is to stock your pond with white amurs from the Ashland SWCD fish sale. Amurs are aggressive at cleaning up vegetation and can live for 10-15 years. But remember, all amours sold in Ohio are sterile and will eventually need re-stocked.
If you have a lot of built-up decaying materials in your pond, consider purchasing Nature’s Pond additive. This two-in-one product contains beneficial bacteria that will, over time, turn your pond’s black muck into clean water, helping to lower the fertility levels in the pond, Secondly, it contains a food-grade dye to help create a natural green color in your pond to help block sunlight and slow the growth of unwanted vegetation.
For more pond management tips, be sure to pick up a copy of the book Pond Management by Steve Fender. The book is available through Ashland SWCD’s spring fish sale.