Pond Fish

NOT ALL FISH ARE EQUAL

Your pond is a living ecosystem. An ecosystem in balance is desirable. When it’s out of balance, problems occur. The balance between prey and predator is an important consideration.

Sometimes, pond owners with the best intentions can cause themselves serious problems. “We’d just dug a pond and we wanted to see if fish would survive, so we put in couple dozen goldfish” – by the time we hear this common complaint, the fish have been in the pond for several seasons, two dozen fish have become thousands, and the pond is a mess.

Goldfish are carp and carp are very prolific. If there are no predator species in the pond with them, carp will multiply unhindered. When they feed, carp love to dig up the bottom of the pond, making the water murky. When a pond is over-populated, winter kill results, resulting in a putrid mess of fish corpses in the spring.

Other species to avoid are bullheads and catfish. They share the carp’s indestructibility, and they’re equally prolific. Bullheads and catfish also have a pectoral fin defense mechanism, making them even harder to control with prey fish.

Large mouth and small mouth bass are becoming popular species in shallow, warm ponds because they can tolerate warm water and low-oxygen conditions. Although bass are relatively expensive to purchase initially (two to three times the price of trout), they reproduce well. However, to thrive, bass need an adequate number of prey species in the pond with them, as well as a second predator species to keep the bass offspring in check. Without the right balance of prey and predator to regulate the food supply, bass will also over-populate, resulting in a few large bass and thousands of stunted ones. An over population of bass often results in winter kill.

There are different trout species available to suit different ponds. Trout, as a predator, can be used to control many undesirable species such as leeches, mosquitos and black flies. Trout also respond favourably to commercial floating trout food, eliminating the need for prey species. Only in exceptional ponds will trout reproduce. This is a good scenario as trout grow larger in size as opposed to more in numbers. Remember the pond system can only support so many fish or so many pounds of fish.

Maintaining the balance of your pond’s ecosystem does not have to be difficult, but it does require educated management. Bass, goldfish et al can over populate the pond’s stocking capability resulting in serious problems. Before forging ahead, you are well advised to contact your local fish farm or aquaculturalist for information on species best suited to your particular pond environment.

And a final word of caution: It is illegal to remove fish from the wild and introduce them into your pond. One reason to honour the prohibition is that wild fish may introduce disease, parasite, leeches or other such undesirables into your pond.