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Rotenone is the most commonly used compound for treating lakes and impoundment's like Farmington Bay Waterfowl Management Area. It has been used in numerous lakes and reservoirs with great success to remove unwanted fish species and restore traditional fisheries. Strawberry Reservoir was treated in 1990 with rotenone and the treatment was 100 percent successful for removing Utah Chub's.
Rotenone is a natural substance derived from several tropical and subtropical plants. Natives in Central and South America have used the juices of these plants for centuries to help them collect fish for food. In developed countries, scientists have learned that dried roots of rotenone producing plants can be ground into a powder that is useful as a garden insecticide. For many years, it was also a widely used agricultural insecticide applied to crops and livestock to control insect pests. Rotenone is also used as a garden insecticide to control chewing insects, has been used as a dust on cattle, and is used as a dog and sheep dip, in addition to its use as a fish control agent.
Rotenone inhibits a biochemical process at the cellular level making it impossible for fish to use oxygen in the release of energy needed for body processes. Rotenone has some toxicity to all oxygen-breathing animals; it is selective to fish at the concentrations used by fishery biologists. In general, most common aquatic invertebrates are less sensitive than fish to rotenone but some of the zooplankton are equally sensitive. Snails and clams are quite tolerant. With respect to fish, trout and salmon are the most sensitive, sunfish are less sensitive and catfish are the most resistant. Fish, insects, birds and mammals have natural enzymes that will detoxify sub-lethal amounts of rotenone. Fish are highly susceptible because rotenone is readily absorbed through their gills, and they cannot escape exposure to it.
Rotenone is an unstable compound that breaks down rapidly when exposed to light, heat, oxygen and alkaline water. The breakdown process is very rapid. Ultimately, rotenone breaks down into carbon dioxide and water; two common substances.
Fishery resource managers have tried many ways to manipulate fish populations. Use of a fish toxicant enables managers to establish a definite population at a specific time. Generally, the problem species are gizzard shad, carp, and bullheads. These are fish that have very high reproduction rates and that are very tolerant of declining water quality.
The specific problem with Carp at Farmington Bay Waterfowl Management Area is that they root the bottom of the impoundment's, as they seek food. The rooting action stirs silt and keeps the water turbid, so that sunlight cannot penetrate for photosynthesis that is required for submergent plant growth to take place. The plant growth is necessary to provide food for migratory waterfowl.
Rotenone in dead, dying or surviving fish degrades at about the same rate as that in the water. Surviving fish quickly eliminate rotenone residues from their bodies. Mammals and birds that ingest rotenone by drinking treated water or by eating dead fish would simply digest it without any toxic effect. Most warm-blooded animals also have effective natural enzymes that would destroy small amounts entering the blood stream.
Rotenone is non-persistent so there is no accumulation in the water, soil, plants, or surviving animals. Because it breaks down so rapidly, its environmental significance does not extend beyond one year. Rotenone is highly toxic to insects and fish but represents little risk to people or other mammals. This characteristic makes it a useful pesticide.
Regards,
Bill Fenimore
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