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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

A fisheries biologist gently drags a net toward shore, creating a 'bag' to capture any fish. © Robert Queen
A fisheries biologist gently drags a net toward shore, creating a 'bag' to capture any fish.

© Robert Queen

February 2005

Shoreside sentinels

Shrinking populations of tiny two- to three-inch fish warn how shoreland development.

Lisa Gaumnitz


Updating 30-year-old surveys | Geneva Lake
Teasing out the causes
Some of the neat rare fish

Pugnose shiner. Banded killifish. Least darter.

Small fish with bodacious names and diminutive public profiles.

Though anglers readily recognize the panfish and game fish species that make fine eating, few people recognize the many minnow-sized species that form the broad biological base of aquatic communities and food chains.

"These fish are little known, ignored or invisible to most people, but they are essential to lakes, streams, game fish and the anglers who pursue them," says Dave Marshall, a DNR water resources management biologist.

Some fish species are fast disappearing from Wisconsin waters, even from lakes with the best water quality.

"We sampled small streams a few years ago and weren't too surprised to find declines in populations of small forage fish where there were water quality abuses from urban and agricultural land uses," Marshall says, "but we didn't expect to see that small fish populations are declining in lakes where the water quality is considered good. When you start seeing a decline in [fish species] diversity that isn't related to water quality, then you start looking at habitat. It could be a number of factors, but the primary change over time has been shoreline habitat."

Species that adapted and evolved over thousands if not millions of years, survived several ice ages, and moved into new habitats are now succumbing in the blink of an eye in geologic time as humans replace their natural shoreline habitats with piers, seawalls and sandy beaches.

"Maintaining a diversity of fish is a sign of lake health," says John Lyons, a longtime DNR fisheries researcher. Their decline signals bigger problems for the ecosystem, for game fish populations that rely on small fish for food, and for people who enjoy Wisconsin's most popular and lucrative outdoor sport-fishing.

There are deeper moral concerns that Wisconsin is losing its ichthyological treasures. These fish display an incredible palette of colors, genetic variation and niches, Lyons says.

"We have an ethical responsibility to maintain them," he says. "They're part of our heritage, and whether they play an obvious function or not, as stewards of the land we have an obligation to see they survive if it can be shown we're responsible for their demise."

Updating 30-year-old surveys

On a warm June day torn between the threat of rain and brilliant sunshine, Marshall, Lyons and crew arrive for a day that will focus on the fate of small native fishes.

Lyons is midstream in updating the book "Fishes of Wisconsin," the seminal fisheries reference by the late George Becker, a University of Wisconsin-Stevens Point biologist. From 1958 to 1978, Becker drew information from thousands of scattered research reports, examined specimens from more than 1,800 fish collections, and synthesized the results into a 1,052-page tome that detailed the biology, range and habitats of 157 native fish species he determined were present in Wisconsin.

Lyons is bringing together new information that he and other biologists have gathered in the last 20 years. A federal grant is helping him fill in gaps about the current status, distribution and abundance of fish in Wisconsin. His particular quarries today are the rare, small fish species that inhabit shallow water habitats.

Marshall's research grew from work to develop lake management plans for Rock Lake and Lake Ripley in Jefferson County. Surveys of the lakes' nearshore areas revealed that native and rare fish populations plummeted over the past 30 years despite stable water quality.

He and other team members want to see if other lakes with good water quality show the same trends. They'll explore possible links to shoreline development and piers in particular. Studies in Massachusetts and other states suggest that docks directly threaten aquatic plants that are key to fish survival and growth. Marshall's Rock and Ripley lake studies suggest that the growing number and larger sizes of piers in Wisconsin's inland waters are reducing aquatic plant and small fish populations.

On a shoestring budget, the two men recruited Laura Stremick-Thompson, DNR fish biologist for Jefferson County, Steve Galarneau, DNR water biologist, a crew of DNR staff and professionals from other cooperating institutions to survey native, nongame fish populations on 13 lakes in southeastern Wisconsin last summer. They selected lakes with good or fairly good water quality that also had marl lakebeds. Marl forms a sticky, gray, clay bottom that contains lots of calcium carbonate, which helps buffer water quality from pollution. All 13 lakes were previously sampled in the mid-1970s and had relatively high numbers of rare fish species.

No one has checked the fish diversity on these lakes since the 1970s surveys, Lyons says. "Are these species still here and in what numbers?"

Geneva Lake

Today, Lyons and Marshall hope to learn the answer for Geneva Lake. For decades this Walworth County lake has been ringed with large estates, manicured, highly landscaped lawns and terraced bluffs. Geneva Lake is hardly anyone's idea of pristine, but nature has maintained good water quality here over time because the lake is fed by groundwater, has no inlets, and drains a very small land area – roughly 2.5 acres of land for every acre of lake according to the Geneva Lake Environmental Agency. That compares favorably to nearby Lake Delavan, with a 19 to 1 ratio, so Geneva receives considerably less polluted runoff than many other lakes with larger watersheds.

To cover the 17 sampling stations on the 5,400-acre lake, the crews split into three groups. Lyons and Marshall get help from Frank Veraldis, of the U.S. Army Corps of Engineers in Chicago, and Philip Willink of the Field Museum of Chicago. The group's first two survey sites or "stations" are Riviera Beach in downtown Lake Geneva and along the shoreline at Big Foot Beach State Park.

Using the same type of fishing gear used a quarter-century earlier, Lyons and Willink measure out 100 meters parallel to the shore and unfurl a long seine net. They walk the net around the perimeter of the sampling site then drag the net toward shore and each other into a tight circle creating a bag to capture any fish. Marshall busily scribbles notes about the lake bottom material and about other habitat features. Both sites have sandy bottom materials, no rooted aquatic plants, no downed trees, and little of the habitat little fish like.

The two men bring the net together and all start picking through the weeds for fish. Nothing moves. "The third time's the charm," Lyons tells the crew. "Think positive."

He's right. The third station the crew reaches by boat yields fish to sort, count and record, as do the fourth, fifth and sixth sampling sites.

The sixth sampling site suggests the trends the study seeks. In the 1970s, this site yielded 15 species including rainbow darters, banded killifish and least darters – all sensitive, rare species dependent on aquatic plants. Today, the crew must make two hauls at the site because the shoreline is broken by a pier with 15 slips. The area now has no aquatic plants, no overhanging cover, no downed logs – and only eight species of fish, none of which are rare or sensitive to shoreline habitat changes.

Overall lakewide results are similarly bleak. Though the other two sampling crews found pockets with more diverse species, the total haul on Geneva Lake is 17 native species compared to 29 at the same sites in the 1970s.

Across all 13 study lakes, an average of 14.4 native species are found in 2004, compared to 19.2 in the 1970s; nongame species dropped from 11.8 to 8.2; rare fish dropped from 5.5 to 3.3 species. Lyons cautions that the differences on a particular lake could reflect some sampling errors and natural fluctuations. However, it is significant that the researchers looked at a broad group of lakes and found the same patterns of declining fish species and numbers.

"The results are indicative of larger problems," Lyons says. "It's a heads-up that things are heading in the wrong direction."

These small fish species are key food sources for some game fish species, particularly during the first summer of their life, he says. If the small fish are lost, populations of their predators will suffer, and all game fish species will be affected because they'll be competing for a smaller number of remaining forage species.

Teasing out the causes

As the 2004 field season wound down, Marshall, Lyons and others were starting to crunch numbers and conduct other analyses to help untangle why native fish are vanishing from Wisconsin waters. Their findings may well reflect continental and global trends.

Fish species are disappearing from the world's lakes and streams at an alarming rate; in North America, 30 to 35 percent of fish species are considered at risk. Habitat alterations are the leading cause of fish extinctions, followed by the introduction of nonnative species, overfishing and pollution, according to an oft-referenced 1999 report in the Journal of Conservation Biology.

Research in Wisconsin, Minnesota, Iowa and elsewhere over the last 15 years documents that native plants, fish, frogs, songbirds and other species are suffering as a result of overdevelopment and improperly done development along the water's edge.

Finding evidence that links a specific change on the shoreline to a population drop of a particular fish species has been more difficult because shoreline "development" encompasses so many different activities.

For instance, when seawalls are installed, these retaining walls often replace a mixture of cattails, bulrushes and other plants, rocks, logs and undercut banks that a variety of fish need for food, spawning and hiding places. Waves bouncing off these walls also reflect a lot of energy back into the water, scouring the lake bottoms. It's much more difficult for aquatic plants to take hold and root in more turbulent waters. Further, turtles, ducks, frogs and other wildlife find it difficult to move from water onto land with a wall blocking their way.

In other projects, bulldozers and other heavy equipment that "grade" or clear a site for construction and reshape bluffs or shorelands can allow dirt to spill into the water, smothering fish eggs and interfering with feeding by fish and other wildlife.

Riprap – large rocks piled along shorelines – cover fallen and overhanging trees and aquatic plants that provide food, spawning and hiding places for fish, and nesting areas for loons and other birds.

Piers with boats docked at them shade out the rooted aquatic plants that serve as the spawning grounds, pantries, nurseries and hiding places for a variety of fish, including small nongame fish, at some or all stages of their lives.

Research wrapping up on Lake Ripley and Rock Lake in Jefferson County shows that fish will seek shelter under piers if no other refuge is available, but they prefer and need a variety of aquatic plants to meet their spawning, feeding and shelter needs. To measure the impact of piers on fish, investigators used snorkeling gear and light meters to measure the light intensity underwater, comparing the space under piers to open water areas. They also compared plant, fish and aquatic bug populations under piers, in open waters and in designated "sensitive areas" that are known important sites for fish spawning. "It's important to protect those sensitive areas because that's where we found the broadest diversity of fish," says Patricia Cicero, one of the Jefferson County researchers. Preliminary findings document that shading under piers is significant, reduces plant growth and shifts the plant communities to shade-tolerant species.

Another concern with piers, Marshall says, is that they are not just narrow floating rectangles along the shore. They are several feet wide, they often have extending decks and the boats moored alongside also create shade. The average piers on Lake Ripley were 546.4 square feet and 370.2 square feet on Rock Lake.

Marshall and Lyons acknowledge that other factors beyond shoreline development and piers may play a role in the fishes' demise. For example, exotic invasive species such as zebra mussels remove algae that's an important component of the food web and can disrupt the ecosystem. But zebra mussels aren't present or a dominant feature in many of the study lakes where fish diversity is declining, they note.

The researchers' counts of piers from 2004 show that study lakes with greater densities of piers per mile of shoreline showed the steepest declines in rare fish species and in the number of different fish species, Marshall notes.

"Something as common as lakefront piers, once they become abundant, are no longer a benign thing," he says. "Piers are not the sole problem, but piers are part of the problem."

Marshall and Lyons hope their results will be a wake up call for Wisconsin citizens and government. Ten fish species are already listed as endangered in Wisconsin, another 11 are considered threatened, and some of them, like the pugnose shiner, are in trouble everywhere in their range.

"Wisconsin's population of pugnose shiners is as good as anywhere else," Lyons says. "If we don't protect it, who will?"

Marshall hopes the research and survey work will attract the interest and attention of citizen advisory groups as state rules on shoreland development are revised. He hopes that sensitivity to developing in a manner that maintains natural shorelines can keep pugnose shiners, banded killifish and least darters from a watery grave.

"I was lucky from the ages of eight to 13 to have a rich life exploring the underwater habitat and watching the diversity of minnows and different fish," Marshall reflects. "Future generations are being robbed of a really interesting feature of lakes – their biodiversity."

Lisa Gaumnitz is public affairs manager for DNR's water programs.

Some of the neat rare fish
Pugnose shiner: This herbivore grazes on plants like filamentous green algae. It is timid and secretive. When a school is threatened, these shiners immediately drop to the bottom and conceal themselves in the densest vegetation, so they are also tough to collect with conventional sampling gear.

Brook silverside: This fish spawns one time in its first year and dies shortly thereafter. It is the only species of silversides found in Wisconsin.

A brook silverside. © David Marshall
A brook silverside, one of the small fry bringing
big benefits to Wisconsin's lakes and rivers.

© David Marshall
Bowfin: One species (Amia calva) is known in Wisconsin and North America. The bowfin is a primitive fish, a lone survivor of a large family found only as fossils in the rocks of Europe and the United States. The male provides parental care, building the nest and protecting the eggs and newly hatched fry. The newly hatched fry form a "fry ball," a large mass of small fry swimming close together. If one becomes separated from the male parent, it will swim in close circles until the parent returns. Male bowfin are well known for their fierce protection of the young and will throw themselves out of the water towards a perceived threat that may be on the shoreline. Bowfins have a gas bladder they can use as a primitive lung, and can survive prolonged periods of low oxygen by becoming air-breathers.

Starhead topminnow: This minnow escapes predation from largemouth bass by jumping onto the bank and remaining there for several minutes before jumping back into the water. Studies suggest starheads can orient themselves with respect to the sun in order to return to their original habitat, even if they have to jump over land.

Least darter: One of only two darter species where the female is larger than the male. Males establish well-developed territories in heavy vegetation. The male develops "breeding tubercles" on all underside pelvis fins and some anal fin spines that are thought to help maintain spawning position on the female.

Average length? 1.2 inches!