Article By Mike Kruse

Like blue ribbon trout streams, big bluegill impoundments are a refelection of good land use and respect for fish and their environment.

Imagine if you can, a 4 pound, 12 ounce bluegill. A day dream you say. Think again, because that is the current world record for bluegill, Lepomis macrochirus. It probably represents the maximum size for bluegill; at least no one has caught a larger one in the 31 years since T. B. Hudson caught the world record from Alabama's Ketona Lake. Any bluegill over one pound or ten inches is a trophy. I consider a large bluegill anything over eight inches. Any way you look at it, big bluegills are a unique resource, just as valuable and scarce as trophy bass or trout.

Bluegill Biology: Ready or Not

What does it take to produce big bluegill? I've been trying to answer this question for the last three years, while studying bluegill populations throughout Missouri. In the article that follows, I'll describe a few early findings that will probably be of interest to anyone, like me, who likes to cast flies at big bluegills. Unfortunately, blue- gills don't spring to life at eight inches, so to understand the big ones, we will have to talk about the small ones first.

While big bluegills are in short supply, small ones aren't. In Missouri, a female can spawn as many as nine times between May and September. When ready, female bluegills enter a spawning colony, which may contain 300 or more males. Each "bedding" male guards his nest from other fish. Males do all the work. They build the nest and care for the young. Males locate the spawning colonies in protected areas like the back of a cove, in shoreline notches, or pond dam corners. Colonies are frequently located under overhead cover, like the branches of an overhanging willow. The males build the nests at a variety of depths (1 to 16 feet) on all kinds of bottom (bedrock to loose organic silt) and a variety of water temperatures (63° to 86°F). In Missouri, the heaviest spawning takes place in late May and June. Once the nest is built the male bluegill defends the nest, eggs, and young vigilantly, aggressively at tacking anything that comes near.

The young bluegill feed almost exclusively on microscopic zooplankton... small animals about the size of a pinhead. As they grow larger, bluegills switch to insects. Sometimes, big bluegill eat small fish, but they really aren't designed to pursue fast moving prey. Their deep-bodied, long- finned, "pie-plate" shape helps them capture prey that demand quick turns, maneuverability, or careful searching of the vegetation or bottom, like the insects found in aquatic plants. As they feed on these insects, bluegills will often accidentally consume plants, but they're not able to use them as food.

Food availability determines how fast bluegills grow, and ultimately, how good the bluegill fishing will be. While growth rates of bluegill vary tremendously, it always takes several years to produce catchable size fish. How many years depends on how, much food is available for each fish. Usually, in populations with large fish, bluegills grow faster. Even in the best populations, however, it usually takes at least four years to grow to eight inches.
Usually poor populations, dominated by small, slow growing fish have too many young bluegills; not enough young bluegills die. Due to their prolific nature, bluegills nearly always produce more young than most lakes and ponds can support, If too many young survive, they compete among themselves for the limited food supply. Biologists describe such populations as "stunted". Nearly all bluegills in these populations die of natural causes (predation or old age) before they reach a desirable size of 8 or 9 inches.

The best way to reduce the number of small bluegills is by protecting largemouth bass. Bass eat small bluegills, thus reducing the competition among survivors. The relatively few remaining young can then grow to rod-bending size.

In contrast, angling generally removes only the largest bluegills with little effect on the small fish (less than 5 inches). This requires that we need to question the idea that you can "fish your way" to better bluegill populations. In fact, as I will show, recent evidence suggests that harvest may reduce the numbers of large fish.

Does Angling Impact Bluegill Populations?

It happens every spring. I'll pick up a copy of a fishing magazine or look at an outdoors column in a newspaper to find the author extolling the joy of fishing for bedding bluegill. After describing all the rod bending action the author will point out that bluegills are good to eat and because of their prolific nature, "anglers need not apologize for taking home a stringer full".

Over the last two years, as part of a research study, I've tried to determine the impact of angling and decide whether anglers should apologize for harvesting a limit of bluegills, or be encourage to take more. To date, over 2,500 catchable-size bluegills have been tagged in four impoundments in central Missouri. The tags are numbered and are worth $5 to $100 to any angler who returns one. Since tagged and untagged fish are equally likely to be caught, the percentage of tags that are returned gives an estimate of the percentage of the total population that are caught. This is an old method of determining angler harvest rates or "exploitation", but applying it to bluegills is new.

The first year's results should make you think twice about loading the boat with bluegills. In a public fishing lake, anglers returned 54% of the tags in a single fishing season! That is, over 50% of the adult bluegills were caught that year. In contrast at a private lake with limited fishing, only 2 percent of the tags were returned.

The second year's returns were quite different. Returns at the public fishing lake declined from 54 to 25 per cent. Why the change? Possibly, the depletion of large bluegills (over 8 inches) the first year discouraged anglers from fishing the second year. Also, despite heavy harvest of large fish, the numbers of five to six inch bluegills increased greatly. The tagged fish might have been diluted in this larger population of small bluegills.

But what about the private lake, you ask? Returns increased significantly from 2 percent to 10 percent. It seems a new, apparently very effective, bluegill angler began fishing this 37 acre lake during the second year of the study. In one season, he returned more than twice as many tags as all other anglers in both years combined.

Now lets step back and review a few facts about bluegill biology. Bluegills are very prolific - a single female may spawn as many as nine times a year in Missouri. Growth rates depend on the amount of food available per fish; if too many young survive, growth declines and "stunting' occurs. In typical Missouri populations, it takes about 6 or 7 years to grow an 8- inch bluegill and at least four years in the best populations.

Yes, angling can impact bluegill populations by reducing the number of large fish, but no, you cannot "fish your way" to a better bluegill population. It only takes a few spawners to produce a tremendous number of off spring and anglers cannot remove enough small bluegills to reduce the risk of "stunting". The tagging study has shown that anglers can harvest a high percentage of the largest fish. Also, many of the large bluegills can be harvested by a small number of skilled anglers, even a fairly large impoundment. Since it takes 4 to 7 years to grow an eight-inch bluegill in Missouri, a 50% harvest rate is not sustainable here. At this rate, a dramatic decline in the number of large bluegills result, with no effect on the small fish.

I'm not suggesting a ban on bluegill harvest. In most waters, surplus fish exist and anglers need not apologize for harvesting them. Besides, a platter of fried bluegill fillets fresh out of the pan is truly a sensational delight. However, we shouldn't let our appetites influence our perspective too much, because bluegill are capable of providing more than just meat fishing. Under optimum habitat conditions and light harvest, trophy bluegills - over a pound or 10 inches - are a possibility.

How to Find Big Bluegill

As a fisheries biologist, anglers often ask me where they can catch big bluegills. Since "big" is defined in the eyes of the beholder, I usually ask them to describe "big." They'll usually stretch out the palm of their hand and mark a spot somewhere on their wrist. I've measured many such "hand-sized" bluegills and found they've usually somewhere around eight inches in length. After I've established what the angler considers big, I can get to the business of helping them find the bluegill of their dreams.

Bluegills can grow large in good habitat that contains the proper density of bass and other fish and where fishing pressure is light. In Missouri, this combination is most often found in privately-owned impoundments, and anglers willing to do some scouting and obtain fishing permission usually have the best bluegill fishing.

What does the perfect bluegill habitat look like? I would concentrate your search on ponds and lakes with relatively clear, fertile, and weedy water. Sunlight penetrates the water of such ponds easily and stimulates the growth of algae and aquatic plants. These stimulate the production of zooplankton and aquatic insects that are important bluegill food. However, you should avoid impoundments where vegetation covers much more than a quarter of the surface area.

Fertile water is a basic ingredient that many waters lack. Like the bountiful harvest produced from rich soil, fertile water has the capacity to grow bluegill food and seems to be a common characteristic of the places where truly large bluegills are found. The easiest way to recognize rich water is by the greenish tint that an abundance of algae produces. Rich water is usually found in areas with high soil fertility or in impoundments that receive nutrients from human activities - farming operations, septic tank leaks or residential or golf course fertilizer run off. The problem with human inputs, that they may become too much of a good thing, initially charging the system with fertility, but eventually leading to over-enrichment and fish kills.

When searching for big bluegill, try to locate waters containing high densities of largemouth bass. Heavy predation by bass is a critical component in the production of big bluegills - preventing overpopulation and the stunted fish that result. Lakes with high densities of 8 to 12 inch bass are common in Missouri, and they often produce good fishing for bluegills up to 8 inches and occasionally larger. However, impoundments with trophy bluegill more often have many bass in the 12 to 16 inch range.

If you have a source of information on the bass population in a prospective impoundment, learn as much as you can about other fish that may be present. In Missouri, the biggest bluegill usually come from small impoundments with few fish other than largemouth bass and bluegill. Impoundments with large populations of gizzard shad, channel catfish, bullheads or carp rarely produce big bluegills. An abundance of crappie usually means poor bluegill populations, but big bluegills can coexist with low numbers of large crappie. Big redear sunfish are often found in the same impoundments with big bluegill.

Anglers searching for big bluegills should find ponds or lakes with the above characteristics and try the most lightly-fished ones first. Trophy bluegills are unlikely in heavily-fished bodies of water. In all my searching, I know of only a few Missouri impoundments that regularly produce bluegills over ten inches and they're all privately-owned with tightly controlled access. Sorry, I'm sworn to secrecy….

If any of this information helps you find some big bluegills, treat them with respect. Such populations don't necessarily last forever - overharvest of largemouth bass or bluegill, introduction of new fish species, excessive inputs of nutrients or siltation can all ruin a fishery. Like blue ribbon trout streams, big bluegill impoundments are a reflection of good land use and a respect for fish and their environment.

Mike Kruse is a Fisheries Reseach Biologost and fly fishier who works for the Missouri Department of Conservation in Cloumbia. He is a long standing Federation of Fly Fishers member and has written article on the past for the regional Federation of Fly Fishers publication.