52 Nebraskaland • June 2023
found the reservoir was more turbid on
the west and south ends and clearer to
the north and by the dam.
From these fi ndings, researchers
produced maps showing which
locations had the lowest chance of
predation, the most zooplankton, and
the optimal water clarity. They then
combined these maps to fi nd locations
where stocked fi sh had the best
chances of survival.
Game and Parks biologists began
using this information in 2022 and also
tweaked their stocking protocol. Along
with 26 million fry and 1.3 million 1¼-
inch fi ngerlings, they stocked 280,000
1½-inch fi ngerlings. The latter were
stocked at a lower rate in the hatchery
ponds and kept there a week longer,
allowing them to grow larger. This
extra growing time got them closer
to the size when they could feed on
larval alewife instead of zooplankton,
in hopes of increasing their chances of
survival.
Biologists used a chemical to mark
fry and the larger fi ngerlings they
stocked in 2022. In the fall, they
collected 200 of these age-0 fi sh and
examined the otoliths to determine
which stocking they came from. That
examination of marked fi sh found the
survival of fi ngerlings to be greater
than fry. They are still working to
determine the origin of unmarked fi sh
by examining the microchemistry in
the otoliths to see if they came from a
hatchery or natural reproduction.
With lower reservoir levels,
biologists aim to stock 20 million
walleye fry, 800,000 1¼-inch fi sh and
200,000 1¾-inch fi sh in 2023. Those
fi sh will again be marked, sampled
in the fall and analyzed to determine
contribution to the fi shery. Results of
these assessments will guide future
stocking practices at the lake.
Researchers also are continuing
to explore other pieces of the
management puzzle. Knowing
zooplankton availability could be
aff ecting survival of stocked walleyes,
researchers have been looking into the
likely cause of declines: alewife. This
forage fi sh was introduced to the lake
in 1986 to supplement the gizzard shad
population that tended to be boom or
bust. Since their introduction, however,
zooplankton levels, especially the
larger species important in a young
University of Nebraska at Kearney researchers produced identifi ed locations on Lake McConaughy where young walleye had
the lowest chance of predation, the most zooplankton to eat and the optimal water clarity. Combining factors produced this
map, which shows where stocked walleye have the best chances of survival. SEAN FARRIER, UNK
University of Nebraska at Kearney
researchers sampled alewife in Lake
McConaughy using gill nets.
LOGAN ZEBRO, UNK
