Heron – Control
Every year, many pond keepers lose fish from their ponds following the visit of a heron. The occasional visit of these magnificent birds can create a great deal of interest, but unfortunately they are efficient predators and can decimate the fish population in your pond.
The following suggestions by Dr. David Pool, TetraPond, Blacksburg, VA.
Because there are a wide variety of types inhabiting most of North America, the threat from heron predation can occur anywhere. It can also occur at any time of the year, although the problem is at its greatest in spring and early summer when the herons feed their young. Each day, an adult heron needs about 13 ounces of food, which is equivalent to three 6-inch koi or 10 2-inch goldfish. Herons take twice this amount when feeding their young. They are generally shy birds and visit garden ponds when everything is quiet, usually early in the morning or in the evening. Once the herons have found an easy source of food, such as colorful fish in a shallow pond, they will return on several consecutive days until most of the fish have been taken.
There are several ways of reducing heron attacks on your pond fish, which can be used with varying success. Here are measures you can take to prevent herons from attacking your fish. If you do lose some fish, don’t resort to harming or killing the herons, especially since they are a protected species.
Suspending a net 6-12 inches above the pond surface will prevent the heron from attacking your fish. Make sure the net is taut and cannot fall into the pond when the heron may try to land on the net and spear the fish through it. While this may not be the best looking solution this is by far the most effective deterrent for most herons.
Herons will not normally land directly in the pond, as they will scare the fish. Instead, they land in the garden and stalk toward the water. Suspend strong fishing line 12-18 inches above the ground surrounding the pond perimeter to stop the heron from reaching its destination. Make sure the fishing line is positioned 6-12 inches back from the pond to prevent the heron leaning over the barrier to catch the fish.
There are a number of commercial scarers available that work in different ways. Some work on a “tripwire” basis, producing a loud noise and, in some cases, a visual deterrent which scares the heron away. There are scarers available that work using sound inaudible to the human ear. Others detect the presence of the heron using infrared detection and scare them away by spraying a high-pressure jet of water.
Artificial plastic herons are very popular. Their success is based on the principle that herons are territorial and will not feed close to another heron. Unfortunately, this is not completely effective at anytime, especially in late winter and early spring when the herons are searching for a mate. In this case, it may actually attract herons to your pond.
When designing your pond it is possible to make life difficult for the heron. Dense growths of tall marginal plants or shrubs around the pond will limit the herons’ access to the water. Ensuring the pond side is steep and the water is 8-12 inches below the edge of the pond will also help because the heron will not be able to reach the fish.