By Bob Mercer
Capitol Correspondent
PIERRE - State fishery biologists estimate the population of rainbow smelt remains very small in Lake Oahe, after massive releases of flood waters in the 2011 flood wiped out millions.
Their low numbers were significant this year and promise to be again in 2014. The finger-long smelt are highly important as food for bigger game fish, especially walleyes, in the giant Missouri River reservoir.
With the right conditions during the spring spawning season, smelt can quickly rebound. During the past summer warm-water bait fish, from shiners and drum to yellow perch and white bass, became a temporary and timely substitute. Biologists found some warm-water species were at all-time highs in population and their overall abundance was the sixth-highest in decades. Their high numbers are expected to help in 2014 and 2015.
Anglers on Oahe caught large numbers of walleyes, especially smaller ones, in May and June but then found difficulty catching any walleyes in July and August after the warm-water baitfish had hatched.
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Biologists and anglers found larger walleyes that were physically stressed from hunger. John Cooper of Pierre, a member of the state Game, Fish and Parks Commission, said he heard concerns that larger walleyes caught in May and June were thinner than normal.
Large fish need meat in their diet and can’t survive on invertebrates, GFP biologist Geno Adams said. Some places on the reservoir had pods of gizzard fish and walleyes there seemed to be in better shape. Some big fish didn’t have energy to feed, Adams said.
He said an “incredibly high” number of walleyes in Oahe were shorter than 15 inches this summer. There weren’t many in the range of 15 to 20 inches - although more than in 2012 - and walleyes longer than 20 inches were fewer in 2013 in comparison to 2012.
The 2014 outlook is mixed. The year-class of walleyes hatched in 2009 will be about 15 inches long and there are many, according to Adams. The 2011 year-class was a big hatch too and they were in the range of 10 to 12 inches during the biologists’ August survey.
Adams said the smelt population could rebound within a few years. The hope in the meantime is the warm-water bait fish will remain large enough in number to serve as a replacement.
