Fish Biology
Bluegill
Bluegills are generally dark olive-green along the back and lighter along the side. They have five to nine dark vertical bars on each side, blue cheeks, and a dark spot at the rear of the dorsal fin. Bluegills do not have a margin on the opercular, "ear"-lobe.
Bluegill feed primarily on insects, both aquatic and terrestrial. However, they will often eat snails, small crayfish, zooplankton (microscopic animals), and other fish and fish eggs. Because of their varied diet, bluegills can be caught on many different kinds of baits, including insect larvae (bee moths, spikes, mousies), crickets, grasshoppers, and worms. Bluegills avidly hit on artificial flies that resemble aquatic insects.
The amount of food each bluegill eats determines how fast it grows. If food is abundant and bluegill numbers are low, they grow rapidly. If food is scarce and numbers are excessive, they grow poorly, or even not at all. Slow growing bluegill populations are the most serious problem in Indiana fish ponds. The simplest pond management techniques focus on maintaining good bluegill growth.
Bluegills grow more rapidly in southern Indiana ponds than northern Indiana ponds. This is a result of regional differences in the length of the growing season (climate). They usually reach six inches by age four and their typical life span is six years.
| AVERAGE GROWTH RATE OF BLUEGILL IN INDIANA | |||||||
|---|---|---|---|---|---|---|---|
| Age in years | 1 | 2 | 3 | 4 | 5 | 6 | |
| Southern Indiana | |||||||
| Length in inches | 1.70 | 4.20 | 5.50 | 6.30 | 7.10 | 8.00 | |
| Weight in pounds | 0.05 | 0.12 | 0.18 | 0.25 | 0.36 | ||
| Northern Indiana | |||||||
| Length in inches | 1.20 | 2.70 | 4.50 | 5.90 | 6.90 | 7.40 | |
| Weight in pounds | 0.01 | 0.06 | 0.15 | 0.23 | 0.29 | ||
Some bluegills begin spawning in their first year. However, most don't spawn until they are two years old. The older they get, the more eggs they produce. A four year old female produces about 20,000 eggs. Bluegills lay their eggs in shallow depressions, called "beds," fanned in sandy areas. Bluegills will spawn over most types of bottom and often throughout the summer. Eggs hatch in three to four days.
The tremendous reproductive ability of bluegills can cause problems for the fish pond owner. Bluegills often produce more young than the pond can support. When this happens, bluegill growth is very poor and few fish reach sizes desired by the pond owner. Corrective management is then warranted.
Bluegills not only provide good fishing and eating, they are a major food item for largemouth bass. In a well-managed pond, bass abundance should remain high enough to control bluegill overabundance.
Largemouth Bass
Largemouth bass are the major predators in Indiana fish ponds. Largemouth bass are dark olive-green on the back with green sides shading to a white belly. A dark horizontal band extends on each side from the eye to the tail. The most distinguishing characteristic is its large mouth with the upper jaw extending past the rear margin of the eye.
Largemouth bass usually eat smaller fish, primarily bluegills. But often, when crayfish, tadpoles and other minnows are abundant, bass may switch to these food items. On occasion, bass are cannibalistic. Because they are predators, bass bite well on artificial lures that resemble small fish and crayfish.
Like bluegill, food availability determines how well they grow. If forage items are plentiful and accessible, bass grow rapidly. However, many Indiana ponds contain too much cover (aquatic plants usually) that prohibits bass from catching ample food. When this happens, bass growth may decline and prey species become too abundant. Corrective fish management is then needed to increase the efficiency of bass predation.
Bass grow about three inches each year for the first four years in northern Indiana ponds and about four inches each year in southern Indiana ponds. They usually live to be six years old with some reaching 10 years and measuring over 20 inches long.
Some largemouth bass spawn at age two, but most begin spawning at age three. Three and four year old bass usually produce the most viable eggs, averaging about 10,000 eggs per female. After age six, the number of eggs declines.
| AVERAGE GROWTH RATE OF LARGEMOUTH BASS IN INDIANA | |||||||
|---|---|---|---|---|---|---|---|
| Age in years | 1 | 2 | 3 | 4 | 5 | 6 | |
| Southern Indiana | |||||||
| Length in inches | 4.4 | 8.3 | 11.4 | 14.0 | 16.0 | 18.0 | |
| Weight in pounds | 0.04 | 0.26 | 0.67 | 1.26 | 1.90 | 2.27 | |
| Northern Indiana | |||||||
| Length in inches | 3.1 | 6.4 | 9.4 | 12.0 | 14.0 | 16.0 | |
| Weight in pounds | 0.01 | 0.12 | 0.37 | 1.18 | 1.26 | 1.90 | |
Bass spawn once a year when the water temperature reaches 62 degrees F. Bass also build nests, but slightly deeper than bluegill beds. They prefer to spawn in more protected areas than bluegills, usually around aquatic plants. After the eggs hatch, the male keeps young bass schooled for about a week to 10 days.
Bass reproduction in Indiana ponds is influenced by environmental conditions much more than bluegill reproduction. Increases in turbidity (muddiness) and rapid changes in water temperature reduce spawning success. Since bass produce fewer eggs and are more susceptible to environmental changes, bass reproduction fluctuates dramatically from year to year. Weak year-classes can trigger population explosions among other fish, especially bluegills. As bluegill numbers expand, they eat bass eggs and fry, further limiting bass recruitment. The pond manager is once again required to initiate corrective management to restore balance in the fish population. While bass are popular to catch, a pond owner must work to keep ample numbers of bass in the pond to control bluegill. In many cases, a bass in the pond is worth two on a stringer.
Channel Catfish
"Mr. Whiskers," traditionally found in slow-moving rivers, is equally at home in Indiana fish ponds. Channel catfish are characterized by the lack of scales, their deeply forked tail, and 24-29 rays in their anal fin. They can easily be distinguished from bullheads (see section on Problem Fish) since bullheads have blunt tails.
Channel catfish grow well in Indiana fish ponds, usually 3-4 inches per year. They may reach over 20 pounds and are excellent tasting. Unfortunately, reproduction and survival of young channel catfish are severely limited in many Hoosier ponds. Young catfish make easy prey for other fish. You should not expect channel catfish to maintain good fishing without restocking.
Channel catfish are "omnivores." That is, they eat about anything they find. They usually feed on insects, crayfish, and fish, including dead fish. They feed primarily near the bottom and can be caught using worms or "stink baits" (chicken liver). Although channel catfish eat small bluegills, don't expect them to control bluegill overpopulation.
The channel catfish begins its life in a nest constructed by the male in a secluded, dark, quiet retreat. This may be under a bank or mass of vegetation, or in old tires, tiles or large cans sunk in the water. Spawning occurs in June and July in Indiana when water temperature exceeds 75 degrees F. The female catfish produces up to 4,000 eggs per pound of weight.
During their early development, the fry stay packed in a tight ball. This strong schooling instinct is their downfall. Often, the entire school can be consumed by a single bass as the harried fry regroup after each attack. If you want to keep a large channel catfish population, periodic restocking will probably be necessary.
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