There is nothing more alluring to a fisherman than a bass on the bed or that distinctive smell of those honey combed shaped nests of bedding bluegill. During many evaluations I have crossed paths with that smell and each time I am reminded of my first experience when my dad introduce two young anglers to the world of bream busters, crickets and bluegill “beds”. I was instantly hooked that day and it was probably my first step towards a fisheries career. So what is so attractive about those “beds” and why do they become one of the hottest fishing spots in the spring? Looking below the surface you will find such a social gathering and spicy courtship that any Hollywood director’s mouth would water for the movie rights. As fisheries biologists, we are always stressing the importance of reproduction, but management aside, the “dance” that goes on under the surface is quite interesting.
Before getting “down and dirty” with the particulars of reproduction in ponds, we must first understand some of the biology behind the species involved. In the Southeast, three members of the Centrarchidae family, the largemouth bass, bluegill and redear sunfish are the most common species stocked as sportfish in small impoundments. The Centrarchidae family is the 2nd largest freshwater family found in North America. All members of this family are nest builders, where as the male typically guards the nest after mating.
Largemouth bass are classified in the genus Micropterus and are one of the most popular members of the Centrarchidae family. The genus Micropterus or “black basses” are highly predaceous and function as the top predators in small impoundments. Bluegill and redear or “shellcracker” belong to the genus Lepomis or as they are more commonly known, the “sunfishes”. The genus Lepomis is the largest in the Centrarchidae Family, comprising of 12 species. The name sunfish most likely derived from their deep and rounded profile, bright coloration and tendency to hover in open water often times called “sunning.” Both bluegill and redear reproduce several times throughout the growing season which is why they make excellent candidates as forage in small impoundments.
Since they are one of the most sought after and most popular freshwater species, it is only fair to discuss the spawning rituals of the largemouth bass first. I know we have all spent hours watching that “10-pounder” toy with every lure in our arsenal just to get no more than a slight glance or possible peck. Heck, almost every spring bass tournament around the country is usually won or lost with just one bite from that monster female circling the bed. Have you ever wondered why she hardly ever bites but that little dink in the bed beside her bites everything you got? Spawning may be the only time of the year when the female largemouth bass has something more important on her mid than feeding.
Reproduction of largemouth bass in ponds and lakes is probably the single most important factor that can influence the total balance of a fish population. For this reason so much thought and research has gone into managing and predicting reproductive success of largemouth bass. However, with all our efforts stressing the end result with bass reproduction, we have missed the most interesting part.
In most southern states, largemouth bass generally begin spawning in March when water temperatures range from 60 to 65º F. Sexual maturity in largemouth bass is reached when the fish reaches 10 inches in total length, which is usually within the first year after hatching.
The spawning process begins when the male largemouth bass clears a disk shaped depression making sure it is free of leaves, silt and other debris. Generally most nests are located along the shoreline near physical structures, such as stumps, logs or boulders or among aquatic vegetation. Each nest is the sole property of the individual male largemouth bass that constructed it and they will exhibit extremely aggressive behavior to protect their “pad”. This particular behavior is most likely one of the reasons these smaller males are easily caught during the early spring.
Once construction is complete, the male circles the nest with the hopes of attracting a female. If a female is interested she will circle the nest side by side with the male. Males circle outside the females and occasionally nip or nudge the female in the opercular, or ear, region or along the underside of the body near the vent or tail. When the actual spawning occurs, the male and female tilt on their sides and simultaneously release both eggs and sperm. Female largemouth bass can release several hundred eggs during each spawning act. The male fans the eggs with his pectoral fins to ensure fertilization and for dispersal into the nest. After spawning, the female leaves the nest to either mate with a different male or return later for another “dance”. Male largemouth bass can accept several different females in succession and each nest can contain from 5,000 to 40,000 eggs.
After spawning, the male maintains and guards the nest from predation. He will hover over the nest, fanning it to help protect the eggs from being smothered by silt from sedimentation. Many species, especially bluegill, will aggravate the male bass, darting in and out of the nest trying to consume the fertilized eggs. In ponds and lake that have extremely dense sunfish populations, especially intermediate sized (3-5 inches) bluegill, successful largemouth bass reproduction is reduced.
Many factors, such as the change in water level, extreme changes in weather conditions, and angling, can influence the reproductive success of largemouth bass. Under ideal conditions, most largemouth bass hatch within 3 to 4 days after fertilization. Male largemouth bass will protect their nest until the fry disperse and can survive on their own. Fry will remain in the nest until their yolk sac is absorbed which is usually 1 to 2 weeks after hatching. Once the sac is absorbed, the fry leave the nest and form a dense school which is guarded by the male for up to two weeks. The males are very aggressive during this two week interval and will chase every bluegill and other predator from getting close to the fry. This aggressive behavior often times results in the males being caught by anglers and in a good managed pond leads them to a frying pan!
The largemouth bass may very well be the most popular species in the Centrarchidae family, but in my opinion, the bluegill species is the most important, at least in small impoundments. This belief is based on the fact that bluegill not only spawn and provide the major source of food for bass in ponds, but that as I am reminded of my first experience over a bluegill bed, they make an excellent fish to catch.
Most bluegill are mature by age 1, however they have been observed spawning after just four months. During an electrofishing evaluation, I was surprised by the release of viable eggs from female coppernose bluegill that were only 3 inches long. The bluegill spawn is stimulated by increasing water temperatures and lengthening hours of daylight. In most Southern states we can expect to see bluegill crowding their nests, often times termed beds, to spawn in early April and continue the rituals roughly every month through October.
Bluegill nests are usually constructed during daylight hours by adult males. An established group of nests is considered a colony, where each nest is occupied by a male until spawning occurs. Nests are generally constructed in quiet waters near the shoreline or the back of a cove. Experienced males will often time colonize older nests to use during spawning instead of constructing a new nest each season. This is great for anglers, because if you find a bluegill “bed,” chances are that area will produce good bluegill fishing for many seasons. Colonies can hold from just a few nests to several hundred in an area. Each nest is guarded intensely by the resident male. Territorial males flare their ear tabs and perform sweeping movements to show dominance and aggression in the nest.
The onset of spawning occurs when female bluegill arrive in schools and mill above the nests. A female bluegill ready to spawn, drops out of the water column and into the nest below displaying dark coloration, dark eyes, and dark vertical bars. Is that not how we all were “hooked” at one time or another? Once both are in the nest, the male begins to swim in tight circles with the female following. Every few seconds the female tilts to one side, presses against the male, quivers, and releases eggs that are immediately fertilized by a simultaneous release of milt by the male. This action by the female is often described as a “dip” and a female bluegill can dip hundreds of times in a single spawning session. Bluegill are polygamous and many males house the eggs of several different females during a spawning season.
After the courtship and spawning sessions are over, the female leaves and just as with largemouth bass, the resident male is left with the responsibility of guarding the nest. Bluegill eggs usually hatch within 5 days of fertilization and after hatching, the male bluegill will protect the fry until they leave the nest. Unlike with largemouth bass, the male bluegill only “stands guard” for about 3 to 6 days and does not provided protection once the fry leave the nest.
The redear sunfish or shellcracker have similar spawning rituals as bluegill. Spawning begins in the early spring and will continue to the middle of summer. The male redear sunfish constructs a saucer-shaped depression and often times males form colonies similar to that of bluegill. Peaks in spawning activities in redear sunfish correspond with new or full moons.
During spawning, the male redear sunfish gets a dark mottling coloration along its sides which is used to attract females. Redear also produce popping sounds around the sides and head of a female during the courtship, which is believed to help stimulate the female sexually and help her overcome the tendency to flee the nest. This sound production is also believed to help synchronize spawning throughout the colony. Males defend the nests until the eggs hatch which generally takes 2 to 3 days after fertilization.
Because of their spawning similarities, many sunfish hybridize with each other and it is not uncommon to see a cross between a redear and bluegill in small impoundments. Some of the largest sunfish I have ever caught appeared to be a natural cross between a redear and green sunfish. Many hatcheries have taken advantage of this natural hybridization and experimented with crossing bluegill with green sunfish to create what is claimed to produce a trophy-sized hybrid offspring. In my experience, the growth rates of these hybrids are not as impressive as that of coppernose bluegill on a good supplemental feeding program. Also, the reproductive success of these species is extremely low and therefore they do not perform well as forage species in small impoundments.
So, the answer to the question about why these fish beds are such hot spots for fishing is simple, the aggressive male in the bed is just trying to protect his offspring. I wish I had known some of this 15 years ago when I would spend hours trying to catch that female that I know now was just not into feeding at the time. I should have just listened to my dad who would always say, “Leave that bass alone and come catch some of these bluegill.”
References:
Simon, T. P. and Wallus, R. 2008. Reproductive Biology and Early Life History of Fishes in the Ohio River Drainage: Elassomatidae and Centrarchidae, Volume 6. CRC Press.