Tracking walleyes and saugers on the Mississippi River.
A MAJOR TELEMETRY STUDY by the Minnesota Department of Natural Resources (DNR) revealed seasonal movements of walleyes and saugers on the Mississippi River, where strong populations exist.* Both species were most active during early spring as they moved to staging then spawning areas, traveling back downstream soon after. Yet, the two species demonstrated seasonal differences in habitat use.
SAUGER: Saugers staged for spawning along the navigation channel at the upper end of Pool 4 where it meets Lake Pepin. Many fish migrated there in mid- to late March and early April in both years fish were tracked. Water temperatures ranged from 40[degrees]F to 48[degrees]F during that period.
To spawn, saugers moved upstream to the upper 3 miles of Pool 4 where they deposited eggs at four primary locations, either in side channels or in the main channel. The peak of spawning occurred from early April to early May and it differed by at least 2 weeks from one year to the next. Water temperature at spawning ranged from 41[degrees]F to 51[degrees]F. In both years, staging and spawning locations for saugers were similar.
By early May, all saugers had moved back downstream into Lake Pepin, though several fish remained in the upper riverine stretches of Pool 4. Average depth of saugers in lower locations was 13 feet, though signals from fish in deeper water sometimes could not be picked up by the receivers.
During fall, tagged saugers remained scattered in Lake Pepin, typically on deep flats and at the base of deep shoreline structure breaks. Mean depth during fall was 23 feet. In winter, saugers moved even deeper, resulting in lost signals from many fish. But locations ranged from the tailwaters of Lock and Dam 3 to lower riverine stretches near Wabasha.
Most tagged saugers wintered in the lower two-thirds of Lake Pepin. During January, they gradually shifted upstream, resulting in large aggregations in deep water (24 feet) off major points. By February, locations were exclusively in the main shipping channel in the upper third of the lake.
WALLEYE: Walleyes primarily overwintered in the upper third of Lake Pepin, then staged for spawning in the upper, shallow reaches of the pool during the last two weeks of March. They favored dark-bottom backwaters where water temperatures were 3[degrees]F to 8[degrees]F warmer than water in the main river. Peak staging migrations occurred from the end of March into the first week of April, when water was 43[degrees]F to 50[degrees]E
Peak walleye spawning took place within a 16-day window in mid-April in both years. Walleyes and saugers spawned at the same time, but unlike saugers, walleyes spawned in a variety of habitats. Some used flooded, off-channel habitats with timber, bulrushes, and reed-canary grass, including a tributary, the Vermillion River. The fish also spawned over cobble substrate in side channels, and some fish used side channels and wing dams near Lock and Dam 3. Spawning along flooded channels also occurred. Biologists pinpointed 16 different spawning locations for walleyes and no grouping of tagged fish.
After the spawn, walleyes shifted downstream and established small nearshore home ranges in Lake Pepin, typically outside bays and pockets near deeper water. In summer, walleye depth averaged 10 feet, ranging from 4 to 22 feet. Several fish returned to spots where they'd been the previous fall before moving to spawn, demonstrating homing behavior.
During fall, walleyes were widely scattered, holding along shoreline breaks and points in the lake. Sixty percent of fall locations were along nearshore contour breaks, while 35 percent were on points. Fish rarely were in open water. Beginning in January, they began to shift upstream and gathered in the upper third of Lake Pepin through winter, with only one fish moving into the tailrace of Lock and Dam 3.
* Ickes, B. S., A. G. Stevens, and D. L. Pereira. 1999. Seasonal distribution, habitat use, and spawning locations of walleye Stizostedion vitreum and sauger S. canadense in Pool 4 of the upper Mississippi River, with special emphasis on winter distribution related to a thermally altered environment. Minnesota Dept. Nat. Res. Invest. Rept. 481.
A selection of pertinent science topics by STAFF FISHERY BIOLOGIST STEVE QUINN
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|Title Annotation:||Toothy Tidbits|
|Date:||Mar 1, 2009|
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