Doug Leier posted on May 07, 2010 09:12 :: 1376 Views
For the first time in years, both of North Dakota’s Missouri River reservoirs are starting off the spring at normal pool elevation, which should mean good things for fishing in the future. In the case of Lake Sakakawea, that doesn’t necessarily mean better angling this year, though, as it takes a few years for fish populations to catch up with improved habitat conditions.
Most of us are more tuned in to the bird world, where eggs that hatch in spring or even early summer grow into adult-sized birds available for harvest in fall. We all need to remember that, depending on the species fish take several years to reach even a minimum size of interest to anglers.
Higher water levels on both lakes Sakakawea and Oahe has provided some immediate benefits to anglers, most notably improved access. Ramps that were not usable for years are now available up and down the Missouri River System.
Under the water, positive changes occur more slowly. Fisheries biologist Dave Fryda explains, “While some impacts like boat access are immediately apparent to anglers, others such as declines in reservoir productivity occur more slowly and are the most difficult to address.”
Plankton abundance in Sakakawea, for example, follows reservoir elevations, and current plankton abundance has improved with the rise in water levels. Plankton serves as food for larval fish (walleye and others) and for forage fish, and make up the foundation of the food chain,. While rising water allows for more plankton, it has also inundated thousands and thousands of acres of previously exposed lake bed that had grown up in vegetation.
“That will provide phenomenal spawning substrate as well as dramatically increase reservoir productivity,” Fryda said. “Terrestrial vegetation was inundated for the first time in many years in 2008, and those benefits should begin to positively improve reservoir productivity for coming years.”
Of utmost importance, current conditions at Sakakawea hold promise for much-needed strong year-class of rainbow smelt, the primary forage fish in the reservoir. “For smelt to have a chance to successfully spawn in a given year,” Fryda said, “they need a stable to rising water level in mid-April to mid-May, access to suitable spawning substrate, favorable weather and adequate plankton abundance for newly-hatched smelt to feed on”.
Because of that, Fryda added, even with rising water levels, smelt reproduction isn’t guaranteed.
With a low smelt population the last several years, Fryda said walleye body condition in 2007 and 2008 was the poorest since smelt were introduced in 1971. This strongly implies that alternate forage species were not adequate to support the existing walleye population at a low lake level.
That changed a bit in 2009 as productivity of most fish species improved with rising waters, providing enough alternative forage that walleye body conditions improved noticeably. In addition, Fryda said that improved habitat and forage conditions will allow Game and Fish to return to supplemental walleye stocking in 2010 that will complement what is anticipated to be good natural reproduction."
On Lake Oahe fisheries biologists saw a significant improvement during last year’s electrofishing survey, which noted 200 walleyes per hour, including young-of-the-year, compared to 50 walleyes per hour in 2008. The big jump is the result of record walleye reproduction in 2009. With continuing favorable habitat conditions, fish from the 2008 and 2009 year-classes should be abundant in years to come. Those fish should fill in nicely as a large year-class from 2001 exits the system.
Through the drought years the Game and Fish Department and local cooperators spent considerable effort just to to extend and maintain boat ramps to put users on the water. Now that pool levels are back, it should mean good things to come for both the fisheries and access.
Doug Leier is a biologist with the Game and Fish Department. He can be reached by email:dleier@nd.gov
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