Chuck Church
Indianapolis, Indiana USA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Chuck,
Rotenone, made from root of the Cube plant, kills fish by binding
with the gills and blocking uptake of oxygen, thereby suffocating the
fish. It is true that some species are less effected by small
doses. Rotenone toxicity is also a function of water temerature, size
of the fish, oxygen content of the water and amount of suspended organic
material in the water column. In bigger ponds and lakes that stratify
rotenone is usually mixed into a slurry with sand and/or piped directly
in deeper water to help get it through the different density layers and
get to all of the fish. Between 50-75 degrees F is about optimal for fish
control. Most fish will die in about a 0.025 ppm mixture, but for complete
control 1-2 ppm is usually applied to make sure you get a good dose to the
whole pond/lake. If you have a stratifed pond with a wimpy dosage,
sometimes fish can escape the high concentrations and revive. In this
situation bullheads and their kin have been known to burrow into the mud
and stay there until the chemical breaks down (usually within a day or two
in bright sunlight). Sometimes the eggs of cyprinids (carps and
minnows) can survive low doses that are strong enough to kill
mature fish. Rotenone will kill any fish (and invertebrate life) in
your pond if that is your objective. Obviously if you have inlets and
outlets with fish in them they will be back into your pond some day. I can
imagine a case where a pond or lake has a high flushing rate and the
chemical gets diluted too quickly. Rotenone will effect fish almost
immediately. Hope that answers your question.
Pete
<>< <>< <>< <>< <>< <>< <>< <>< <>< <><
<>< Pete VanDusen, MS Candidate in Fish Ecology <><
<>< Dept. of Biological Sciences <><
<>< Michigan Technological University <><
<>< Houghton, MI 49931 <><
<>< URL: <http://www.bio.mtu.edu/~pjvandus> <><
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