Aquatic Habitat Plan
Rehabilitation Challenges for Natural Lakes, Rivers and Streams
Shallow water, summer and winter fish kills and rough fish infestations are common problems in
Nebraska's natural lakes, including clear Sandhills lakes and muddy oxbow lakes along rivers.
About 1,300 Sandhills lakes provide about 80,000 surface acres of water. Many are too alkaline
to support fish, but those with suitable water chemistry can provide excellent fishing for bluegill,
crappie, yellow perch, northern pike and largemouth bass.
Sandhills lakes are clear, fertile and usually shallow, often less than six feet deep, allowing the
entire basin to produce aquatic plants and food organisms. Those characteristics also make
Sandhills lakes vulnerable to fish kills. Dense submerged vegetation usually produces abundant
oxygen, but several calm days with cloud cover in late summer or several days of snow cover
over winter ice can block sunlight penetration, interrupting photosynthesis. Without plants
producing oxygen and without wind mixing oxygen, fish die.
Oxbow lakes, channel segments left behind when a river changes course, share fish-kill, shallow-water and rough-fish infestation
woes with Sandhills lakes. They are also subject to siltation and re-infestation with rough fish when nearby rivers flood.
Natural Lake Rehabilitation Techniques
This technique reduces the likelihood of fish kills by increasing lake depth and volume. An area in the middle of
the lake with less aquatic vegetation also allows anglers to fish the lake more effectively in summer.
Aeration devices supplement natural oxygen levels at times of critical oxygen depletion.
3. Fish removal:
Removing the existing fish community with rotenone and restocking with desirable fish species is necessary in many
Sandhills lakes. In most cases, carp are the culprit, dominating a fish community once it gains a foothold. More pounds
of sport fish can be produced if carp are eliminated.
4. Fish barriers:
The return of undesirable fish species can be prevented by building dikes to protect oxbow lakes from river floods and by
installing self-cleaning fish barriers on streams that feed Sandhills lakes.
River and Stream Problems
Bank erosion, dewatering resulting from
irrigation, nonpoint-source pollution, warming caused by the loss of overhanging trees and shrub canopies and the loss
of habitat diversity because of channelization all can limit a stream's ability to produce fish. In addition, degraded
stream banks are the source of as much as 70 percent of the silt deposited in reservoirs.