7059

• UCREFRP Catalog Number: 7059
• Author: Binns, N. A.
• Title: Effects of Rotenone Treatment on the Fauna of the Green River, Wyoming.
• USFW Year: 1967.
• USFW - Doc Type: Fisheries Research Bulletin Number 1,
• Copyright Material: NO

ABSTRACT
From July, 19'62 to October, 1964, samples were taken of the invertebrates
and fishes of the Green River in southwestern Wyoming to determine the effects
of rotenone treatment on the river fauna. The river was treated in September,
1962, with emulsified rotenone, and concentrations applied to the river ranged
from 2.5 ppm to nearly 10 ppm of a five percent rotenone product. The reac-
tion of the fauna to the toxicant was. investigated at the time of treatment,
and post-treatment population levels of the fauna were followed closely to
establish the time needed far recovery to pretreatment levels.
Fish as well as adult beetles, leeches, snails, stonefly nymphs, and other
invertebrates were observed dying during the treatment; their bodies were
often conspicuous in quiet eddies of the river. Many of the fishes fled down-
stream ahead of the rotenone during the treatment, but were eventually trapped
at the next rotenone introduction station. Reactions of intoxicated fish are
described.
The invertebrate populations in the Green River were drastically reduced
by the rotenone treatment, but began to reappear in the upper 30 miles of the
treated area within one month. The lower treated area was almost barren of
invertebrate organisms until the spring of 1963. By September, 1963, inverte-
brate numbers throughout t'he treated area were equal to or greater than those
found prior to treatment, but changes in the composition of the invertebrate
fauna were noticeable. Sufficient fish food organisms to sustain a fishable
trout population were present by the late summer of 1963. A succession of
invertebrate groups occurred during the post-treatment recovery period. Two
years after treatment, the patterns of dominant invertebrate groups in the river
were still dissimilar to pretreatment patterns. Tendipedidae were usually the
predominant organism.
Two rare mayfly genera, Pentagenia and Hexagenia, did not reappear
after treatment, but several other mayfly genera, including Leptophlebia,
Traverella,-Iron, Paraleptophlebia, and Isonychia, apparently immigrated into
the area.
Intensive sampling with dynamite and gill nets immediately after the treat-
ment produced no fish in the mainstream below the upper ten miles of the
treated area. A few untreated sloughs were probably the source from which
the river was later repopulated by flannelmouth suckers (Catostomus latipinnis
Baird and Girard), Pantosteus suckers, redside shiners [Richardsonius balteatus
(Richardson) ], speckled dace [Rhinichthys osculus (Girard) ] fathead minnows
(Pimephales promelas), and carp (Cyprinus carpio Linnaeus). These species,
except for carp, had regained their pretreatment distribution at the close of
study. Carp were found only in scattered areas. Whitefish [Prosopium william-
soni (Girard) ], and brown trout (Salmo trutta Linnaeus) required nearly two
years to regain their pretreatment distribution pattern. This apparently was
due to a slow downstream migration from untreated areas. .Forage fish were
abundant two years after treatment, but coarse fish population numbers were
still below pretreatment levels. Squawfish I,Ptychocheilus lucius Girard), hump-
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