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Image of sunfish.

Sunnies—Everyone's Fish

Is the ever-popular sunfish too popular for its own good?

by Darby Nelson

I ease my canoe off the sandy shore and glide quietly onto Mary Lake in Itasca State Park on a beautiful sunny morning in early June. A breath of air nudges my craft through a thin stand of rushes in shallow water. Bluegills and pumpkinseeds dart among the plants as the canoe's shadow passes over them.

I love sunfish. So do anglers of all ages and abilities. Legions of kids first encounter the world of the lake with a squeal of delight as they stand on the end of a dock and pull up a fish the size of their hand. Thrashing wildly on the end of a line is a sunfish that had thrown caution to the waves and snagged a piece of worm enticingly suspended below a red-and-white bobber.

Anglers know sunfish as brightly colored fish that readily bite on nearly anything small enough to engulf—from worms and insects to artificial lures and flies. These fish fight hard and are easy to catch from a boat, a dock, or shore without sophisticated equipment. On the plate sunfish present another attraction—they're sweet and delicious with flaky, white flesh and tasty skin when fried to a crisp.

Such appeal puts considerable pressure on sunfish populations. Lakes with good habitat often have abundant sunfish, but large sunnies can be hard to find. Fisheries biologists have been studying the problem of stunted sunfish for decades. The most current research has shown that certain harvest limits can boost the average size of sunfish in a lake and produce a more robust sunfish population—over time.

Habitat Matters.

Sunfish are in the family Centrarchidae, which includes other game species such as largemouth and smallmouth bass and white and black crappie. Sunfish belong to the genus Lepomis. Minnesota has six species, including green, longear, orangespotted, and warmouth. Bluegills and pumpkinseeds, the state's most common sunfish, are also the largest and most popular.

Sunfish live amid the stems and stalks of myriad aquatic plants in the shallows near shore where food is plentiful and hideaways handy. Their compressed circular shape, with fins positioned around their center of mass, affords these fish exceptional maneuverability. This maneuverability enables sunfish to quickly and adeptly change direction to catch food or escape a predator.

The key to sunfish success is their intimate association with this world of plants. Sunfish find their Eden among an abundance of snails, water fleas, copepods, aquatic worms, and larvae of caddisflies, dragonflies, and mayflies. A shore without plants is a shore without sunfish.

Prolific Spawners.

Sunfish are as prolific as they are popular. A female bluegill's ovary can bulge with over 50,000 eggs.

Sunfish stake out plots of lake bottom as spawning beds. Males create shallow soup-bowl-like nests by hovering and fanning their fins, sweeping the sand clear of silt and debris. Spawning begins in May or June, but it can be delayed by cool weather. Bluegills can spawn during much of the summer.

Female sunfish prefer to lay eggs on a nest on firm sand or gravel. The female releases eggs over the nest and then leaves the male to protect the brood. The 1-millimeter-diameter eggs attach to stones, sticks, and other firm objects in the nest bottom.

After fertilizing the eggs, males fan the water around the nest, keeping water currents moving to maintain an oxygen supply to the eggs. The currents also help protect eggs against water mold, an aquatic fungus. Mold first infects dead eggs, byproducts of failed fertilization. If not brushed away, the mold quickly spreads to viable eggs nearby.

Males must fend off other male sunfish and lurking minnows that race into the nest for a meal of eggs. Young hatch after about three days. The male often must round up offspring that stray, returning them to the nest.

Size Appeal.

Found in every corner of the state except the trout waters of the northeast, "Sunfish are very important in Minnesota fisheries," says DNR fisheries biologist Keith Reeves. "They provide action for a wide range of anglers."

Minnesota anglers log an estimated 57 million hours fishing every year. Of those, the pursuit of sunfish accounts for about 18 million hours. Creel surveys suggest anglers catch eight times more sunfish than walleyes and 12 times more sunnies than largemouth bass.

Acknowledging that catch data have a wide error range, Reeves says, "Recent survey data reveal that more sunfish are caught per year than all other game species combined—23 to 30 million fish."

Sunfish reproduce quickly enough to maintain populations even under heavy angler pressure. But angler behavior, particularly catching and keeping larger fish, can change sunfish population dynamics. Sunnies are slow-growing and can be relatively long-lived. In other words, it takes lots of time to grow big sunfish.

"In many northern lakes, sunfish grow an inch per year, so a keeper-sized sunfish may be older than the kid that caught it," says Reeves. "In the Aitkin area, we routinely see bluegills that are 10 years or older. Keeper-sized sunfish can be harvested quickly. And in populations of slow-growing fish, those fish are only slowly replaced, resulting in few quality fish."

Better Fisheries.

Otter Tail County in west-central Minnesota has more than a thousand lakes and ponds that offer excellent opportunities to catch sunfish. DNR fisheries biologist Arlin Schalekamp has noticed an across-the-board decline in sunfish size there over the past 50 years.

"Some lakes have held up better than others," he says. "Larger lakes and those with diverse aquatic habitat appear to have maintained size quality or have smaller declines than smaller lakes with less aquatic habitat. We know that angler harvest of the large sunfish has changed the size structure of sunfish populations."

As Schalekamp explains, "Given the opportunity, anglers tend to harvest the largest sunfish in a population and, over time, as the larger fish are removed, size structure changes and the average size goes down."

As early as the 1940s, state fisheries managers were looking at ways to address the problem of stunted sunfish in lakes. They tried reducing the number of small sunfish through seining, more liberal bag limits, and even a toxin that affected only small sunfish.

"For many years we thought the solution was to thin out the small fish," says DNR fisheries biologist Peter Jacobson. "There has been a paradigm shift. You don't encourage high fishing pressure, you reduce it."

Between 1995 and 2001, Jacobson studied 12 small, clear lakes with poor sunfish size structure. Eight lakes had a special 10-sunfish bag limit and four lakes had the statewide daily bag limit of 30. By comparing these lakes, Jacobson's research revealed that continually removing large, sexually mature sunfish from a population caused the remaining fish to begin reproducing when younger and smaller. In the lakes with the least fishing pressure, sunfish populations had larger sexually mature fish and typically produced the largest bluegills.

Today, about 50 Minnesota lakes have special regulations that limit harvest in order to provide anglers with opportunities to catch sunfish larger than 7 inches. Roughly half of these lakes limit daily harvest to five sunfish.

Schalekamp says sunfish sizes are holding steady, rather than diminishing, in lakes with special regulations. However, he expects anglers might not see a boost in sunfish size for perhaps several decades.

Sunfish Morning.

My canoe drifts over a cluster of crowded nests, perhaps 60 in all. Sunfish scatter as the canoe's shadow passes over them. My intrusion increases their stress. For a moment, their unprotected eggs and sac fry are vulnerable to molds and minnows. They quickly return to their nests as the shadow departs.

As the morning ends, I have come full circle. I paddle slowly to shore and leave this delightful world of the sunfish. Hopefully, with a little help from more restrictive regulations on some lakes, quality sunfishing in Minnesota will continue to offer the perfect introduction to young anglers for generations to come.

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