Fish camps need fish

Shoreline development affects fish populations

Waterfront property is a valuable commodity, and a house by the water is a dream come true for many anglers.

The shorelines of almost all lakes and rivers where waterfront property is available for private ownership are being rapidly developed. People invest in waterfront property to escape city life and enjoy natural settings.

Unfortunately, most of these nature seekers immediately alter the ecosystem they invested in by clearing the shoreline and removing aquatic weeds. Unknowlingly, they might be contributing to the demise of the fishing and the aquatic ecosystem that attracted them to the water.

Studies have demonstrated changes in aquatic habitat and fish populations coinciding with development. Fisheries biologists in Minnesota found a 66-percent reduction in emergent and floating-leaf vegetation along segments of the shoreline with residential development. Averaged for 44 lakes, loss of nearshore vegetation ranged from 20 to 28 percent lakewide.

Declines in northern pike, bluegill and pumpkinseed were associated with the loss of vegetation.

Another Minnesota study demonstrated that crappie and largemouth bass avoided developed shorelines during the spawning season. Fewer crappie nests were found along shorelines lacking emergent vegetation in the water, and understory brush and trees on shore near the water’s edge. Fewer nests in areas lacking emergent vegetation reflect crappies’ preference for spawning in emergent vegetation. Avoiding shorelines lacking brush and trees that might serve as an anti-disturbance curtain suggests that human activity might deter crappie spawning.

The same study also found bass nests were less frequent along developed shorelines. The few nests that occurred were deeper than those along undeveloped shorelines.

In Wisconsin, researchers removed a little more than 75 percent of the naturally occurring wood — large brush and laydown logs — from the shoreline in one basin of a small, private lake. Natural wood was left in place in the other basin of the lake, and the two basins were separated by a net to prevent fish movement. Largemouth bass and yellow perch were the predominant fishes in the lake.

Within one year after wood removal, the bass had consumed almost all the perch — their primary forage — and subsisted mostly on terrestrial vertebrates and invertebrates. Bass growth rate declined significantly.

In the basin where wood was left intact, the perch and bass populations persisted, and bass growth rate remained high.

Clearly, large wood benefits both predators (the bass) and the prey (the yellow perch). The decision by the researchers to remove about 75 percent of the wood, rather than some other amount, was not just happenstance. The 75-percent removal of wood simulated the average amount of large wood that remains along the shorelines of developed lakes in Wisconsin.

Yellow perch was the predominant forage fish in the Wisconsin lake. I would expect similar effects on bluegill in more-southern waters.

In another study in Wisconsin lakes, snorkel surveys revealed that bass nests were typically located near or under logs and other large, woody material. Many bass anglers think bass nest near docks on some lakes. That may be, but no nests in this study were closer to docks than to large wood, suggesting that docks are not preferred nesting sites. It may be that docks become a suitable nesting site when no other woody cover is available.

Similar to the Minnesota study, bass nested deeper in lakes with greater shoreline development and less large woody material.

No similar studies have been conducted in southern waters, but I have little doubt that the results apply to any lake, anywhere. Bass, bluegill and other fish prefer wood and aquatic vegetation on both sides of the Mason-Dixon Line, and crappie prefer to nest in emergent vegetation.

Equally important is what happens on the land immediately adjacent to the water. Clearing all the trees and understory removes the wood that, in time, will fall into the water and create new fish habitat.

As we continue to develop the shorelines of our lakes and streams, we need to ensure that we do not remove important habitat for the fish that have thrived in the water long before the first cabin and dock were built.