By Nick Simonson

While angling on Lake Sakakawea has been excellent the past several years, one trend that has fishery warning lights flashing is a noted decrease in the overall size of smelt found in the water.  A primary forage, rainbow smelt have gone boom and bust on the lake in the past due to fluctuating water levels, and in low number years, the change in both average body size and numbers of game fish in the impoundment were notable.  The issue at hand this spring, however, is where typically the smelt have been larger sized fish, surveyors are finding that the currently good populations of year-old rainbow smelt and two-year-old smelt are not as big when compared to the averages which agents of the North Dakota Game & Fish Department (NDG&F) were finding in decades past, according to Russell Kinzler, Missouri River Fisheries Supervisor for the agency.

“Over time our age-one smelt are smaller now than what they used to be. Age two smelt are smaller now than what they used to be.  Smelt are a relatively short-lived species, not many make it past the age of four.  So, we continually need to make sure that we have good water levels to maintain that spawn, but along with that, when we have the high water levels helping us with that spawn for a long period time, we start losing productivity.  It is nice every once in a while to get a little drawdown in order to get some vegetation to grow on the shore, and then re-flood that and then that boosts that productivity from the bottom up of the food chain.  Right now, we’re almost at that stage where we could use a little increase in productivity to get them back up in their sizes,” Kinzler explains. 

Rainbow smelt were initially stocked in Lake Sakakawea in 1971 to provide additional forage after the water formed and stabilized following the building of Garrison Dam in 1953.  The long, cylindrical fish which get to lengths of 8 inches or so typically spawn in cold, shallow waters shortly after ice-off each spring.  The young fish feed on microorganisms and other small prey, where adults eat decapods, worms, and a variety of small fish. Since their initial stocking in Sakakawea, they have become a key element in the diets of walleyes, pike and the chinook salmon stocked in the reservoir.  In the latter species, the impact of smaller smelt overall has been noticeable during the past few fishing seasons.

“Salmon [angling on Sakakawea] to some people was kind of a down point to last year.  Fishing was pretty good overall for numbers, but the average size has continued to decline.  That just feeds back into that our smelt are getting smaller and for a salmon swimming around there, when they used to catch a really nice smelt, now they’ve got to put in twice the energy to catch two smaller fish. So, they’re just using more energy in maintaining, and less in putting on growth. So, our average size has declined, and that just goes into where we need that increase in primary productivity to basically jumpstart everything from the bottom up,” Kinzler relates.

Kinzler suggests that a low-water year would likely help increase productivity, as exposing shorelines helps recharge nutrients in the lake, which in turn helps populations of baitfish flourish in the boosted shallows shortly thereafter, feeding on the many increased species of tiny life forms that create the base of the lake’s food pyramid.  Currently, a shortage of snowpack in the eastern Rocky Mountains which feed meltwater to the Missouri River and help maintain reservoir levels may balance out against increased water in the water body right now, creating an interesting dichotomy.

“Going into this spring, Sakakawea and Oahe are expected to be about eight to nine feet higher than they were last year at this time. If the drought continues out west, it’s not looking real good for our lake elevations, but then that goes into that fact it’s not necessarily always a bad thing to have a little drawdown to get that vegetation to grow up and then flood that in subsequent years and start that productivity up,” states Kinzler.

With three strong incoming year classes of walleyes, anglers will likely find smaller fish mixed in with the 15-to-24-inchers which have dominated the past three fishing seasons.  The question looming is how their forage base will look as they grow, with the significantly smaller set of smelt dominating the available baitfish options for the lake’s most popular game fish.

Simonson is the lead writer and editor of Dakota Edge Outdoors.

Featured Photo:  The overall size of rainbow smelt in Lake Sakakawea has decreased in recent seasons, requiring predators to chase and catch more of them to add weight. Thus, more energy is spent maintaining size, and not getting bigger. Creative Commons Photo.