Largemouth Bass, Bluegill and Other Sunfishes

Notes from Fundamentals of Aquaculture, James W. Avault, Jr., Ph.D., pgs. 84-85

Carnivorous largemouth bass is farmed commercially in Taiwan on a limited scale, this species is mainly sought for sport in areas it occurs naturally, or has been introduced. Largemouth bass has wide distribution range, from Southern Canada, the Great Lakes, south into Mexico, and on the Atlantic Coast from Virginia to Florida. The Florida strain is sought after because it grows faster and reaches a large size, making it a trophy fish. Because of its popularity, State and national hatcheries have propagated the largemouth bass for decades. Fingerlings have been stocked into public waters and distributed to citizens for private ponds.

The bluegill (Lepomis macrochirus) has been produced in state and national hatcheries in combination with largemouth bass. In new sportfishing ponds that are fertilized, bluegill fingerlings are stocked in the fall at 3707/hectare (1500/acre). The following spring, largemouth bass are stocked at rate of 247 fingerlings per hectare (100 acres).

With most species, when a culture species is grown for food it is not desirable to reproduce in grow-out ponds. But in largemouth bass-bluegill ponds, the pond may never be drained as long as the fishing remains productive. The pond owner would naturally want both species to spawn naturally. Bluegill are prolific and usually spawn the first summer after stocking, and may spawn up to three or four times, depending on water temperature (above 27 degreesºC (80ºF).

Bass spawn once annually, in the spring when water temperature reaches 21ºC or 70ºF. The largemouth bass depend on the bluegill for a source of food, to realize maximum growth potential. Thinned down, bluegill have ample food supply and also reach a desirable size for sportfishing. Both species expand, filling the pond to its maximum carrying capacity and fish population ultimately reaches a "balance".

This balance is determined by three causes
1. Both species must reproduce each year.
2. Good fishing must exist. Though it may vary, generally the pond should allow harvesting up to 56 kg/ha (50 lb/ac) of largemouth bass and 225 kg/ha (200 lb/ac) of bluegill.
3. The population of forage (F) species (bluegill) must be in a proper ratio by weight in contrast with the carnivore (C) (largemouth bass), determining that a pond ratio F/C ratio may range from 1.4 to 10.

A number of other sunfishes are popular for sportfishing. The red-ear (Lepomis microlophus) has been stocked into largemouth bass ponds, to add variety to fishing. It grows slightly larger than bluegills, but is not prolific enough to be stocked alone with largemouth bass. Both white crappie and black crappie (Pomoxis annularis and P. nigromaculatus) are both sport-fish that grow well in large reservoirs, more than 20 ha (50 acres), with largemouth bass, bluegill and red-ear. Crappie compete with these species for food and space, and all species may become stunted in smaller farm ponds.

Entrepreneurs who are considering propagating largemouth bass and sunfish for commercial purposes must take into account the existing competition with state and national hatcheries. Some states prohibit farming of sportfish for commercial food purposes. However, there are limited possibilities for private investors, probably the best being operations of fee-fishing managed lakes, which appeal to urban citizens. Fishing rights can be leased by the day or annually, or charging by weight of fish which are caught.

No comments: