Rotenone Application

Each species of fish reacts differently to rotenone.  Gizzard shad have very low tolerance for rotenone, sunfish have intermediate tolerance, and catfish, gar, and bowfin are very tolerant.  Relative concentrations needed are given in Table 1 below.

Table 1: Rotenone concentrations for selected pond situations.

Pond application	Acre-feet treated by 1 gal (5%)	Concentration (ppm)
		Active rotenone	5% rotenone
Normal pond, no very resistant species (bullheads, bowfin, gar)	6.0-3.0	0.025-0.50	0.50-1.0
Ponds with carp and/or bullheads	3.0-1.5	0.050-0.10	1.0-2.0
Ponds with bowfin, gar, etc.	1.5-1.0	0.10-0.15	2.0-3.0

A carefully applied rotenone dose will remove all or most fish from a pond. Consider that this is a pointless exercise if the situation is such that new undesirable fish will be able to quickly re-infest the pond.  For example, if your pond is located immediately below another pond containing the undesirable fish species, it’s likely that your pond will become contaminated again with the next big rain. If eliminating the source of these undesirable fish isn’t possible, forget about the rotenone and concentrate on controlling undesirable species by maintaining a healthy population of predators like largemouth bass.

To prepare the pond, reduce the water level as much as possible.  This will concentrate fish into a smaller volume of water, reducing the amount of rotenone needed.  Also, reduction of pond level will drive fish out of shallow water structure, making them more susceptible to the rotenone.

Liquid rotenone is the easiest to apply, and usually is sold as a 5% rotenone preparation.  This chemical must be diluted with water and evenly distributed throughout the water column.  It can be sprayed on the surface, or a drip line can be used to mixed rotenone with pond water in the prop wash of an outboard motor.  Apply the rotenone in a random 'S' pattern around the pond to ensure an even distribution.  Areas that do not receive adequate concentrations will become safe areas and allow some fish to survive.  If this happens, you will have to renovate the pond again.

After rotenone treatment, make sure that the chemical is gone before adding new fish. One practical method is to place several small fish in a porous minnow bucket and leave them in the pond for a day or two. If the fish die, rotenone may still be present. [Note: if the fish survive, do not release them in your pond!].  At warm water temperatures, rotenone may be gone in as few as four days.  However, it is a good idea to wait a month before restocking unless you are concerned about undesirable species re-colonizing the pond.