8257

• UCREFRP Catalog Number: 8257
• Author: Hesse, L. W., G. E. Mestl and J. W. Robinson
• Title: Status of Selected Fishes in the Missouri River in Nebraska With Recommendations for Their Recovery
• USFW Year: n.d.
• USFW - Doc Type: 327-339
• Copyright Material: YES

328 BIOLOGICAL REPoRT 19

River was shortened by at least 204 Ian and more
than 178 million ha of river channel, erosion zone,
floodplain grass and timber, and tributary valley
lands were either inundated or converted to crop
land (Hesse 1987; Hesse and Schmulbach 1991).
At least 160 species of wildlife were resident or
migrant visitors to this ecosystem, and 156 native
fish species lived in the mainstem and tributaries
(Hesse et al. 1988; Hesse et al. 1989). Nebraska's
imperiled Missouri River wildlife include the inte-
rior least tern. (Sterna antillaro.m), piping plover
(Charadrius melodu.s), peregrine falcon (Falco
peregrinus), and bald eagle (Hatiaeetus leuco-
oophalus), all protected by the Endangered Species
Act (ESA). The pallid sturgeon (Srophirhynchus
albus) was most recently (1990) listed as endan-
gered (Federal Register 55 (173):36641). Other spe-
cies have been federally listed as Category 2 (taxa
for which present information indicates the possi-
ble need to list, but more information is required
before listing can proceed), including: blue sucker
(Cycleptus elongatus), sturgeon chub (Macrhybop-
sis gelida), sicklefin chub (Macrhybopsis meeki),
and lake sturgeon (Acipenser fluvesoens). Paddle-
fish (Polyodon spathula) is a Category 2 species and
was recently proposed for listing in the Convention
on International Trade in Endangered Species of
Wild Fauna and Flora (CITES; Federal Register
56 (142):33894).
This paper discusses (1) differences in density
of selected fish species over time and between
reaches of the Missouri River, based on changing
harvest by sport and commercial fishermen and on
catch per unit effort (CPUE) from biological sur--
veys, and (2) remedial actions that will preserve
and restore original features and functions of the
Missouri River as an ecosystem.

Sources of Data and Methods

The Nebraska Game and Parks Commission has
supported research on Missouri River fisheries
since the late 1950's. Historical databases exist
from seining, explosives, creel surveys, commercial
fishing reports, electrofishing, gill netting, and
plankton drift netting.
Many other methods were used to collect in
unique situations. These methods are discussed in
Mestl and Hesse (1991). Seine samples are reported
as the number of fish per seine haul. One standard
seine haul constituted a perpendicular extension of
a 15.24- x 1.83-m bag seine, followed by an extended

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drag to shore while maintaining one end of the net
stationary. However, standardizing a seine haul
was very difficult because of varying depth and the
condition of the substrate. Mesh size was always
6.13 mm. All seined fish were preserved and iden-
tified in the laboratory. Cyprinids and catfish were
collected from tributary streams with an explosive
(primacord). A unit of effort consisted of a 15.2-m
length of explosive, containing 162.5 grains of
PErN/m. Bankline and sandbar habitats were
sampled. A block net was used to capture fish killed
by the blast. Angler surveys have been conducted
periodically in the tailwater of Gavins Point Dam
and at selected locations downriver since 1956. The
most recent survey was a recreational use survey
conducted during 1992.
Commercial fishers were first required to pur-
chase a license and report their catch beginning in
1944 (Nebraska) and 1945 (Missouri). Although
reports were required, they were completed annu-
ally, and by fishers themselves, with little oppor-
tunity for verification. However, we believe these
reports are useful to show trends in abundance of
selected species based on harvest trends.
Boat-mounted electrofishing (AC and DC) has
been used since the early 1960's to collect a wide
range of species. We have observed different catch
rates associated with the widely varying water
quality conditions throughout the river. For this
reason only catch per unit effort (CPUE) that dif-
fered widely is reported. Small differences cannot
be justifiably assigned to changing conditions of
habitat and water management. Collections were
based on time spent sampling, and CPUE was the
number of fish per unit of time spent electrofishing.
Experimental gillnet collections were usually
limited to the unchannelized Missouri River be-
tween Fort Randall Dam and Lewis and Clark Lake
(Gavins Point Dam; Figure). This is the only reach
in Nebraska with extensive off-channel and sand-
bar pool habitat remaining. The nets were either 91
m or 61 m long, and 2.44 m deep, with six equal
length panels of netting ranging from 12.7-mm to
76.2-mm mesh sizes. Nets were anchored late in the
aftem.oon and retrieved early the next day. Data
were recorded by net length, and CPUE was the
number of fish caught per net-night.
Larval fish were filtered from the main channel
at cutting and filling banks and at mid-channel
with paired, 1-m-diameter plankton nets (560 mi-
crons). Flow meters in the net mouths were used to
~anWYvmumemwaterffitere~anddmati~per
tow was minimal to prevent net clogging. The

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