The Minnesota
VOLUNTEER
July-August 1988
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F UNNY
Top, left: Rain and melting snow carry animal wastes from feedlots
Into tributaries flowing to nearby lakes and rivers.
Bottom, left: Sediment from unvegetated building lot runs into water.
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Watersheds and Fishing mately affect water quality, which affects fish species and even the size of fish populations.
This response of fish to landowners' activities has been documented in the Horseshoe Chain of Lakes, a popular recreation area near St.
Cloud. Some surprising changes have occurred in fish populations in these lakes over the past 40 years. Most can be attributed to cultural eutrophication the premature aging of a lake system because of the activities of
, people..
Eutrophication is the natural aging process of a lake. All lakes have a trophic status. It's based on a lake's water quality and various physical characteristics.
Generally, oligotrophic lakes are geologically young. They have deep basins, clear water, low nutrient levels, and relatively abundant game fish.
Hypereutrophic lakes are at the other end of the lake classification scale.
They tend to be shallow basins with poor water clarity, high nutrient levels, and fish communities dominated by carp, bullhead, and suckers.
The Horseshoe Chain of Lakes is hypereutrophic. This doesn't mean the lakes in the chain are not good fishing lakes. They are. Gov. Rudy
Perpich can testify to that. He fished
C.B. Bylander is DNR regional information officer, Brainerd. He wrote "John
A.
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Latch: Winona's Shy Philanthropist" in the March-April 1988 Volunteer.
Tim
Goeman is DNR Fisheries research biologist, Brainerd.
several of the 12 lakes in the Horseshoe Chain last year for the Governor's Bass Opener and caught a dandy stringer of fish.
But the lakes' water quality has changed, and so has the fish community. In short, carp are more prevalent; sunfish are fewer and smaller; smallmouth bass and tullibee have disappeared. This has been documented through standard lake survey data collected by the Department of Natural Resources Section of Fisheries in 1949, 1972, 1980, and 1985.
Flow Into Lake. The first watershed activity to influence the Horseshoe
Chain was agriculture. The 950square-mile watershed underwent a
10 percent increase in tilled land from
1975 to 1985. Pastures were seeded to row crops; wetlands were drained and cultivated.
Though most folks don't relate growing crops to catching fish, farmland miles from shorelines alter lake water quality. How? Through rain leaching nutrients from fertilizers and soil into lakes.
Livestock play a role, too, especially those grazing on alternative sites because pastures have been converted to cropland. In some areas, cattle graze along streambanks and lakeshores, in woodlands and feedlots, and on other highly erodable soil.
Sediment and nutrients flow to lakes from these places when there is poor land management.
Lakeshore development is a second watershed activity that has influ-
4 THE MINNESOTA VOLUNTEER
Effects of removal of vegetation are shown in photographs above. Over-grazing of field
(left) and cutting down vegetation to provide view and access to lake (right) allow erosion to occur. Nearby waterways eventually receive washed-away soil.
enced the Horseshoe Chain. About
85 percent of the chain's lakeshore is lined with homes, resorts, and cabins. Lakeshore owners pollute lake water in two ways: by over-fertilizing lawns and by operating inadequate septic systems.
Have you ever seen a green lake?
This color is often a result of nutrients from fertilizer that runs offlawns and stimulates algae growth. Lakeshore owners should use fertilizers sparingly, and only those not containing phosphorous, a nutrient that encourages water plant and algae growth.
A faulty or outdated septic system also can leak nutrients into a lake, compounding the problem of nuisance vegetation weeds. Moreover, a leaking septic system can be a human health hazard.
A final watershed activity that has affected the Horseshoe Chain is the discharge of wastewater from towns and industries. During a dry year,
JULy-AUGUST
1988 wastewater has accounted for about
43 percent of phosphorus entering the
Horseshoe Chain.
The watershed as a whole contributes 77 to 600 pounds of phosphorus per square mile each year, depending on rainfall, land use, and slope of the land. Even in a dry year, this translates to 100 to 200 tons of phosphorus entering the Horseshoe Chain annually. High nutrient inputs have drastic effects on in-lake processes, which eventually affect those folks with fishing poles in their hands.
There are organisms algae that benefit immediately from the input of nutrients, often to the detriment of fish. Algae are natural in any lake system, but when high nutrient concentrations are available, algae blooms quickly develop. These tiny plants deplete oxygen fish depend on.
In summer, algae prosper in warm water. Photosynthesis increases during the day, and oxygen is produced
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Watersheds and Fishing as a by-product. During hours of darkness, the plants "breathe" at an equally high rate. Oxygen deficiency in the lake may soon occur, resulting in dead fish.
High algal densities also stop sunlight from penetrating the water, there by hindering or halting the growth of rooted plants. Under the worst conditions, blue-green algae may release poisons that can cause death in many animals, including some mammals.
In winter, algae die in the icy water.
This process consumes dissolved oxygen and may result in a fish kill.
Degraded Water. Just how serious is the problem of nutrient inputs into the Horseshoe Chain?
Biologists have established levels for total phosphorous and
(the green pigment in algae) that indicate hypereutrophic conditions.
Total phosphorus has been measured at a level nearly 20 times greater than would be needed to assign a lake to this trophic category.
All of which goes to show the
Horseshoe Chain is clearly hypereutrophic water is unclear and nutrient levels are high. Experts agree that fish kills can be expected when
values get as high as they do in the Horseshoe Chain, even for a short period. Furthermore, sediments run off from the surrounding watershed, degrading the water.
The end result is altered habitat that has altered the fish community.
One response of fish in the Horseshoe Chain to cultural eutrophication is that carp are more widespread. In
1949, carp were collected in only one of four lakes sampled. In 1972, carp were taken in five of nine lakes surveyed. All but one of nine lakes sampled in 1980 contained carp. By 1985, carp were present in all lakes sampled.
Three other fish species tullibee, smallmouth bass, and rock bass
also were drastically influenced by cultural eutrophication.
Tullibee are cool-water fish that prefer deep-water habitat and require substantial dissolved oxygen. Surveyors' collected tullibee in 1949,
1972, and 1980, but none in 1985.
Samples of water showed that dissolved oxygen did not exist deeper than 10 feet in summer. The tullibee's habitat had been virtually eliminated. The absence of this species was not surprising.
Smallmouth bass and rock bass require gravel or rocky ledges for spawning. Sediment and decayed vegetation covered much of this bottom rock, thereby reducing habitat.
Smallmouth bass and rock bass were
Left: Cattle use culvert to cross under road from one pasture to another, trample streambank, deposit wastes In water. Above:
Draining fluids from junk cars pollute streams and groundwater.
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Watersheds and Fishing collected during surveys in 1949,
1972, and 1980, but not in 1985.
More changes in the fish community became apparent by examining the catch of black bullhead, bluegill, and black crappie during four periods of sampling in the Horsehoe Chain.
Black bullhead numbers were the lowest of the three species in 1949, but by 1972 had increased IS-fold and had become the dominant species.
FolloWing intensive commercial fishing, black bullheads declined dramatically by 1980.
tion, or other attempts to improve eutrophic conditions within the
Horseshoe Chain can be considered treatments of symptoms rather than solutions to the problem ifwatershed considerations are ignored.
The Horseshoe Chain is not unique.
Many lakes in Minnesota are victims of similar conditions. Responsibility for improving water quality and maintaining fisheries only partially falls upon government agencies such as the DNR and the Pollution Control Agency.
Bluegills were dominant in 1949.
By 1972, however, they became least
Anyone who owns or uses land within a watershed carries the priabundant and remained in that position relative to black crappie. Black crappie are more tolerant of turbid mary responsiblity for the condition of any lake or stream in that conditions and have a competitive edge in water that has a transparency of only 18 inches in summer. While crappie numbers have increased, bluegills have decreased.
watershed. This responsibility falls to everyone, the residential lakeshore owner, the farmer, the logger.
A well-managed watershed is the key to improving water quality, preserving fisheries habitat, and generally enhancing Minnesota's natural
Treating Symptoms. Managing fish resources. A lake or stream merely species, remoying nuisance vegetareflects its watershed.
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ALMOST 2 million Minnesotans nearly one-half of all state residents fish
Minnesota's lakes, rivers, and streams. During the next 20 years, fishing is expected to increase by at least 15 percent. The number of hours spent fishing will increase more than for any other outdoor recreation activity. DNR News Service
WHEN
Swedish wildlife artist Bruno Liljefors (1860-1939) was a boy, a farmer gave him two grouse chicks killed during a crop harvest. Liljefors later wrote:
"[These] wonderful combinations [of colors] ... seemed to come from the gray predawn of history, and told of the forest, the marshland, the moss on the rocks, the night sky between branches. You could see forever into this world; there was no bottom or end, only new things."
Imprint, James Ford Bell Museum of Natural History
THE MINNESOTA VOLUNTEER