December 2025 • Nebraskaland 49
through Gavins Point Dam. "That
surprised me," Radigan said.
However, using trawl nets set at
various depths weekly between May
and September below Gavins Point
Dam, Radigan also found that roughly
8 to 16 million larval fish of 18 species
were flushed through the dam each
year. Of those, 90% were freshwater
drum, and 14,000 to 75,000 were
walleye and sauger. Radigan said that
was 10 times higher than the number
of fish flushed through Fort Randall
Dam, which has a lower exchange
rate and releases water from greater
depths.
That confirmed what biologists
in both states already knew: Lewis
and Clark Lake is a wide spot in the
Missouri River, with the volume of
water being replaced, on average,
every seven days. With that water goes
some fish. During historically high
releases in 2011, turnover occurred
every 1.5 days. That figure was nearly
matched during the flood of 2019. With
high flows, the number of fish flushed
through the dam is much higher.
"We find that when we have high
water years, where releases through
Gavins are over 30,000 or 35,000
CFS, our gill net catch in Lewis and
Clark Lake drops, and there's a pretty
University of Nebraska-Lincoln
graduate student Will Radigan pilots
a boat as his assistants cast a trawl
net to sample larval fish in the
spillway below Gavins Point Dam.
