January 2023 - 29

where it flows into Nebraska, " Neebling said.
" Not every inch of it. We were limited where
we could get access in some areas. "
The North Platte River begins at an
elevation of 7,740 feet, and drops to 4,025
feet when it leaves Wyoming. Seven major
dams exist along the main river channel,
which creates five reservoir complexes. Over
the years dams have altered water flow and
temperature. There also are smaller dams
along the river for irrigation diversions, most
of which are downstream from Casper, along
with a dam that provides cooling water for
the coal-fired Dave Johnston Power Plant
near Glenrock.
TECHNIQUES
Electrofishing is a common technique
when sampling any body of water for fish,
and this was used in certain areas of the
North Platte.
A relatively new technique for rivers in
Wyoming was used in this work, too.
Trawling is commonly used to sample
small-bodied fish in rivers in the Midwest,
and Neebling said he used this technique
during his master's degree work in Iowa.
There are several different kinds of trawls,
but the ones used on the North Platte were
pulled behind a boat and were dual-layered
where the inside featured a large-mesh net
designed to catch larger fish and debris and
allow small fish to move through where they
were caught in a smaller mesh net.
" It was very effective for those fish species
found in the main channel of the river, "
Neebling said. " It can be used on side
channels and backwaters, but it picks up
a lot of debris. More traditional gears work
better in those areas. "
FISH FINDINGS
A total of 22,337 fish of 33 species were
collected from 213 backpack electrofishing
attempts. There were 328 trawl hauls that
produced 5,827 fish from 24 species.
Electrofishing from rafts also was conducted,
but not in shallow water. There was sampling
in some reservoirs, such as Alcova, Pathfinder
and Seminoe. Fyke nets were used in those
waters. Fyke nets combine netting bags
mounted on supports and anchored to the
bottom with a trap fixed at the end.
There were six species of small-bodied
fish sampled that are Species of Greatest
Conservation Need in Wyoming. That
Wyoming Game and Fish Department workers look for small fish in a trawl during sampling along the North Platte
River. Trawling is a common technique to sample small fish in large rivers. (Photo by Travis Neebling/WGFD)
designation means those species' conservation
status warrants increased management
attention, funding and consideration in
conservation, land use and development
planning in the state. Those species include:
bigmouth shiner, brassy minnow, common
shiner, Iowa darter, northern plains killifish
and orangethroat darter.
Siddons said some species were doing
better than originally thought. Orangethroat
darter was a fish not previously found in the
North Platte in Wyoming and was found to
be fairly widespread. Iowa darters and brassy
minnows were found in good numbers in
the lower part of the river. Bigmouth shiners
seem to be doing better lower in the river
than anticipated, but they were absent from
the upper stretches.
" The most important findings were the
Species of Greatest Conservation Need, but
also to collect data on nonnative species all
the way up to the more common species, "
Siddons said. " We got a good snapshot of all
the species that were collected. It's the only
holistic baseline data we have for the North
Platte in Wyoming. "
Neebling said none of the species
thought to be extirpated for a number of
decades were found. He also said some
native species like Johnny darter that had
isolated distributions 50-60 years ago are
now widespread in the river.
Wyoming Wildlife | 29
" The most important findings
were the Species of Greatest
Conservation Need, but also
to collect data on nonnative
species all the way up to
the more common species. "
- Stephen Siddons

January 2023

Table of Contents for the Digital Edition of January 2023