BIOLOGY
AND HISTORY: The largemouth bass (Micropterus salmoides) is a member of the sunfish family (Centrarchidae). The largemouth bass is native to the Midwestern and southeastern United States and northeastern Mexico, but has been introduced throughout the United States and many other countries. The great demand for largemouth bass and their high selling price ($5/lb whole sale and $/lb retail sale) have raised interest in their commercial culture. There are two recognized subspecies of largemouth bass, the Florida and the Northern. Strain selection depends on market demand and suitability for your market. Florida strains are popular in warmer south areas because they usually grow to a larger maximum size. There are conflicting data on growth rates of Northern and Florida strains. This is particularly true for growth during the first year. In addition pure Florida strains subject to winterkill, especially in shallow culture ponds during prolonged sub-freezing weather. In the southern U.S. largemouth can spawn when 1 year old if they have reached at least 10 inches in length. Males begin to select nest sites when temperatures remain higher than 60o F. Individual females usually contain 2,000 to 7,000 eggs per pound of body weight, with an average of about 4,000 eggs per female. Males guard the nest and the eggs during incubation. Eggs normally hatch in about 10 days at 65o F or 5 days at 80o F. Fry will remain in the nest until their yolk sacs are absorbed (1 to 2 weeks) and disperse when they are about 0.5 to 1inch long. At about 1.5 to 2 inches in length largemouth begin adding larger food items, such as insect larvae and then smaller fish, to their diet. It is during this natural changeover period, when bass are “reprogramming,” that they can be trained to accept artificial diets under intensive culture conditions. As with most fish, the growth rate of largemouth bass is highly variable and depends on food supply and environmental conditions. Largemouth can grow to more than 2 pounds their first year under ideal conditions, but in nature about 0.5 pound is normal. Females are normally larger than males. BROODSTOCK: Largemouth bass are usually spawned in ponds and do not require hormone or photoperiod manipulations. Brood fish must be legally obtained according to the state laws. In most states, brood stock cannot be captured from the wild except with special permission. Purchasing brood stock from fish farms or fish brokers is acceptable. Brood fish are usually more than 2 years old and weigh at least 1.5 pounds. Very large fish are harder to handle and less dependable as spawners. Sexing of brood fish is most easily accomplished in the spring when ripe females should have distended abdomens and males freely emit milt when stripped. Bass larger than 13 to 15inches usually can be sexed by examining the scaleless area around the urogenital opening. This scaleless area is almost circular in males but more elongated in females. The surest way of sexing is to gently insert a capillary tube into the urogenital vent to remove eggs or milt. Brood fish are stocked into 0.5- to 1-acre spawning ponds at 50 brood pair per acre. Ponds must be free of existing fish. Spawning ponds are normally not fertilized so that spawning behavior, eggs and fry can be observed easily and so that the ponds can be harvested more easily. Largemouth bass are often spawned in raceways with good results. FEED TRAINING AND GROWOUT: To feed train largemouth bass (and several other species), the basic concept is to remove the fish from any natural source of food, crowd them at high densities, and present them with highly palatable prepared foods at frequent and regular intervals. Fish are often offered freeze-dried krill, ground fish flesh, or fish eggs. Freeze-dried krill is especially effective, commercially available, and easy to feed and store. These highly palatable products are then gradually mixed with a high quality salmonid diet. By day 7 the fish should be consuming straight feed. During the training period, tanks should be cleaned daily and water quality maintained by suitable water flow. Because of the crowded conditions and large amounts of feed used, external parasites can be a real problem, as can the bacterial disease columnaris (Cytophagus columnaris). Bass should grow to 6 to 8 inches (with some larger individuals) by the fall. This size is well suited for pond stocking and currently brings approximately 75˘ per fish wholesale and $1.50 per fish retail. Producing fish weighing more than 1 pound will require at least 1 additional year of growth. Fish can be thinned to grow-out densities either in the fall or spring; however, fish should not be handled when water temperature is below 55o F because of fungal infections. Some papers have recommended a grow-out density of 2,000 per acre. WATER QUALITY: Water quality tolerances in largemouth bass vary with age and other culture conditions. Feed conversion efficiencies are reduced when dissolved oxygen (D.O.) concentration is below 4 mg/L. Bass actively avoid waters with D.O. levels less than 3 mg/L, but can tolerate a D.O. of 1.4 mg/L at 25o C. Their ammonia tolerance is similar to or slightly less than that of channel catfish, with a 24-hour un-ionized ammonia LC50 value (a concentration that kills 50 percent of fish in 24 hours) of 1.69 mg/L. However, centrarchids appear to be very tolerant of high nitrite concentrations because of an ability to prevent absorption. The optimum temperature for growth is 30-32 o C. DISEASES: Largemouth are susceptible to many of the parasites and bacterial diseases common to most cultured fishes, especially columnaris during feed training. Diseases specific to the largemouth bass are not common, although there are recent reports of a largemouth bass virus. Little is known about how infectious the virus is, what damage it produces, whether certain sizes of fish are more or less susceptible, or if there is a seasonality to infections. The best advice for avoiding disease problems is to minimize handling during summer and winter. MARKETING AND ECONOMICS: Asian consumers appear to prefer live largemouth bass to most other freshwater fish. They desire fish of 1.5 to 2.0 pounds, which may require a third year of growth. The main markets for food sizes are ethnic markets in big cities like New York, Chicago etc. the marketing is really a tough job in the production of largemouth bass, as the target market needs live fishes. So it needs elaborate transporting facilities for the extensive and successful marketing of this species. At present there are only few farmers doing the intensive production of food size fish. Based on a stocker price of $0.50 per feed-trained fingerling, a yield of 4,250 pounds per acre, and a selling price of $3.00 per pound (live sales), approximately $12,750 per acre gross revenues is generated. This produces a return of $6,623 per acre above variable costs and $5,950 after operator labor. A break-even estimate under these assumptions would be $1.60 per pound. REFERENCES:
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DISTRIBUTION: The largemouth bass is predominantly found in the southern United States; however, it has been introduced to Hawaiian mainland in addition to many continents across the globe. In short, the present distribution cannot be precisely determined due to exotic introductions of this species into lakes, ponds, and river systems. The largemouth bass can survive in most temperate regions in warm, sluggish waters of lakes and streams. Clear water with minimal visibility of 8 to 12 inches is necessary for the survival of this species. HABITS: This voracious carnivore will feed upon a variety of live fish, amphibians, avians, invertebrates, small swimming mammals, and most anything that that is both animate and doesn’t exceed the fishes gape limitation. This fish is traditionally portrayed as an "eating machine" generally lurking in deep or well shaded areas during the afternoon and cruising the shore line during the dusk and dawn periods. These fish do feed at night; however, their dependence on vision feeding may explain their tendency to be crepuscular feeders. Very often the largemouth bass is considered to be a lie-and-wait predator, which is often the case during the daylight hours; however, their uniform body morphology and fin placement allow them to cruise equally well. Schooling is observed in smaller largemouth bass (up to 2 inches), but fish will often cluster in feeding aggregates until they reach a foot in length. Larger fish are generally solitary in nature. SPAWNING: Largemouth bass reach sexual maturity at a length of 8-10 inches (about 1 year old depending on environmental conditions). In natural settings, males will begin selecting nesting sites when the water temperature reaches 60F in the spring. Shallow near-shore circular nests are constructed in the hard pond floor substrate in waters averaging in 1-4 feet in depth. Nesting sites have been observed in clear water ponds as deep as 20 feet however. Approximate diameter of the nest is twice the length of the male excavator. Males will generally guard a 6 foot circumference around the nest until an interested, ripe female joins him. The pair then slowly circles the nest side by side tilted laterally such that their vents are aligned and close. The actual act of spawning commences with the shuttering of both fish as eggs and sperm are released simultaneously. Multiple spawnings are very common within this species throughout the season (up to 3 spawns per season). Females generally average about 4,000 eggs per pound. Males will guard the eggs from predators (sunfish and salamanders) until hatching. In warm waters eggs generally hatch in 2-4 days and become swim-up fry approximately 7 days post hatch at which time they feed exogenously on phytoplankton. GROWTH: Growth rates of the largemouth bass, as with all poikilothermic organisms, are directly related to environmental temperature. Optimal growth temperatures are between 65 and 75F and with adequate forage some strains have reached 2 pounds in the first year of life. Generally they gain 0.25 pounds during this period however. Females have a higher growth rate than males and although most northern strains do not exceed 10 pounds, Florida stains crossed with first generation northern strains have been grown to more than 20 pounds. Approximately five pounds of forage fish are required to add one pound of flesh. USES: Largemouth bass are eaten by many anglers; however, their demand as a recreational sport fish greatly surpasses its gustatory desire. CULTURE: These fish are most often cultured for stocking both public and private fishing waters. Two culture methods are primarily implemented for this fish including the "spawning-rearing" method and the "fry-transfer" method. The former entails adult fish producing fry that remain in the spawning pond until they reach 1 inch in length. The second method is used to produce larger fingerlings in a separate rearing pond. Current largemouth bass culture and research is performed in North American states of Texas and Oklahoma. REFERENCES:
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