Perhaps you already have a pond that contains non-native species such as goldfish, bullfrogs, and non-native plants - but you want to “go native” and convert your pond to native species. Even if you can’t get permits for native wildlife, there are ways you can make your pond more ecologically friendly.
Removing Invasive Species
The first step in converting a pond to native species is to eliminate the non-natives. The most drastic but effective measure is to consider drying the pond. May and June are our driest months and the best time to dry a pond. If any of the species in your pond are mobile, like bullfrogs, turtles and crayfish, you will need to set up a perimeter fence to contain them and make arrangements for their removal. Contact the Arizona Game and Fish Department, Invasive Species Coordinator at (623) 236-7600 or the University of Arizona, Department of Ecology and Evolutionary Biology (520) 621-3187 for help in placing these animals where they will not do any more harm. As the plants are drying, remove them and haul them off to the county landfill.
Removing Nonnative Turtles
Turtles like red-eared sliders and painted turtles are commonly found in urban parts of the Southwest and are frequently finding their way to our wetlands. Turtles can be easily attracted to traps with bait such as canned tuna. Turtle traps can be purchased online. If the pond is small, try lowering the water level and then you should be able to net the turtle with a dip net.
Crayfish removal requires a thorough drying of the pond and surrounding soil. Dry the pond in early May and keep dry until the rains come in July. All plants in the pond should be removed. Crayfish will burrow into the soil around the perimeter of the pond so any holes should be searched out and dug-up. Keep watch on the pond as the water is being removed. Gather any crayfish that try to leave the pond. Crayfish can be easily killed by freezing overnight.
Removing Clams and Snails
Aquatic snails can be beneficial to the native pond by consuming algae. Snails will hitchhike on the plants you acquire and are almost unavoidable. There are invasive species of snail like the New Zealand mud snail that are very difficult to tell apart from native snails and very little information on other common snail species. There are a number of introduced species of fresh water clams that are of major concern over their impacts on wildlife so it’s best to avoid all clams and avoid distributing your snails unless you are positive they are native. Drying the pond is the only practical way to remove either mollusk.
If the pond is not too large, bullfrogs can easily be removed, but their tadpoles present a challenge. The frogs will attract to a spotlight if the light is left on for several consecutive nights. Set up the light at the edge of the pond, aimed at the water, along an open shoreline where you can easily approach from behind the light. The blinding light will hinder the frogs ability to see you and you should be able to get close enough to net them. Some will get away and become wise to your technique so leave the light on for a few nights before you try again. Some pond owners in rural areas prefer to use a BB gun for bullfrog removal. BB’s are nontoxic and unlikely to puncture a pond liner but injuring or killing the frogs is not for the faint at heart. If a captured bullfrog needs to be destroyed, the most humane way is to bag it and throw it into your freezer overnight.
Search the edges of the pond and plants for egg masses (pictured in side column). When removing egg masses be aware that very small tadpoles might be emerging from some of the eggs. These helpless black “slugs” lie on the bottom of the pond under the eggs, unable to swim for the first few hours. These very small tadpoles can be easily gathered in a fine mesh aquarium net. The eggs will be quickly destroyed if allowed to dry in the sun. Any tadpoles that might emerge from the eggs as they dry will not be able to get to the water and will quickly succumb.
Free-swimming tadpoles in the pond are much more difficult to catch. Funnel shaped minnow traps can be purchased at sporting goods stores. These traps can be quite effective at catching tadpoles and fish without the use of any bait. Without drying the pond, it will be close to impossible to get all the tadpoles. Try lowering the water level to help in the removal effort. You can also try waiting a year or two for the tadpoles to transform into young frogs and then revisit the spot light strategy.
Fish are even more difficult than tadpoles to remove as they are much quicker and the tiny babies and eggs are almost undetectable to the human eye. However, in relatively small ponds, persistent efforts to net and trap out fish have proved successful. Employ the minnow traps mentioned in the tadpole section, retrofit the traps with window screen if the mesh is too large to contain the target fish species. Try baiting the traps with a few pieces of dry dog food. Along with the trapping, you will need to spend a lot of time stalking fish with a net around the edges of the pond. Lower the water level to isolate the fish from dense vegetation. Try using a headlamp or flashlight at night to see and net the fish. Just when you think you’ve gotten the last one, there will probably be very small babies hiding out so wait a couple weeks and do it again. Fish can be humanly dispatched by freezing or donated to a zoo or university.