The Largemouth Bass, Micropterus salmoides, is one of the most widely stocked species in inland ponds and lakes in North America. The original natural range of the largemouth was from northern Mexico to the Great Lakes, along the Gulf and south Atlantic seaboard, and cutting inland through eastern west viginia and western Pennsylvania to the St. Lawrence River. It has been introduced throughout the U.S., southern Canada, most of Mexico and into Central America. By 1900, the species had become established in all of the lower 48 states. And as a result of numerous international introductions, it is also now established in more than 50 countries, on every continent except Australia and Antarctica.
For a number of years now, two subspecies of largemouth bass have been recognized. The Northern largemouth (M. salmoides salmoides) is found throughout the range described above and the Florida bass (M. salmoides floridanus) is found throughout most of the Florida peninsula and northward into Georgia. Although these two fish readily hybridize some biologists now consider them two distinct species that diverged some 4 to 5 million years ago.
While it is adaptable to various conditions, the largemouth bass is a warmwater species, preferring calm or slow moving waters. Largemouth can tolerate low dissolved oxygen, but growth is limited at levels below 4 ppm and extended periods at 1 ppm or less usually result in total mortality. Largemouth are skilled carnivores, primarily consuming fish but also eating virtually any living animal that can be swallowed (including insects, crayfish, birds, reptiles, amphibians, mammals and even zooplankton).
While the propagation of largemouth bass was historically focused on producing fingerlings and advanced juveniles for recreational fishing, the species is now being cultured as a food fish in a number of countries, including the U.S. Data from the UN’s FAO indicate that worldwide production increased 20-fold between 1999 and 2018, and virtually all of this increase took place in China.
Propagation of largemouth bass dates back to the mid- to late-1800s in the U.S., when adult fish were stocked in outdoor ponds and surviving fingerlings later harvested for stocking elsewhere. Many of the spawning and rearing methods developed for largemouth around the turn of the twentieth century are still being used.
Largemouth bass spawn only once a year under normal conditions, but they have been observed to spawn more than once in tropical settings. Spawning begins in early spring as water temperatures climb above 60o F, peaking around 66o F, and then declining as water warms to 75o F, at which point spawning ceases. In pond spawning, the male digs a shallow nest in the mud and protects the surrounding area. Once a female takes notice, the fish spawn over the nest and the male then fans and guards eggs for 3-4 days until hatching. The male continues to guard the fry for as long as they remain in the nest (5-10 more days) and for some time after they begin to swim on their own. Occasionally, females may assist in guarding the nest and fry. Parental care can often last another 1 to 2 weeks until fry stop schooling, at a length of around 1 inch.
For commercial production, largemouth bass brood fish should be hatchery raised and have been feed trained as fingerlings. Fish to be used for spawning purposes are usually 1.5 to 2.5 lb., and stocked into spawning ponds at ratios approximating 60 males/40 females per acre, or 50/50. Using feed trained broodstock has resulted in improved feed acceptance over the course of several generations, as a result of domestication selection.
Throughout the year, broodstock should have access to forage fish in addition to pelleted feed. In the early spring, while water temperatures are still below 60o F, spawning boxes or mats can be placed every 10 to 15 feet along the edge of the pond, at depths of 3 to 5 feet. Once spawning begins, eggs can be left in the pond or, preferably, mats can be transferred to designated fry production ponds with abundant zooplankton, with a target of 40,000 to 100,000 fry per acre.
Alternately, many government hatcheries and some large businesses transfer brood fish into raceways prior to spawning. Raceway spawning is more costly but results in more control over the timing of spawning, easier incubation and treatment of eggs, and higher survival rates.
Largemouth bass fry are roughly 4 mm long at hatching, slightly more than 1/8th inch. They grow quickly if provided with abundant live feed, and they become cannibalistic by the time they reach 1 inch. At 1.2 to 1.5 inches, feed training begins. Fry are graded and stocked into flow-through tanks at 40 to 50 fish per gallon (higher densities are possible with aeration, but water quality becomes an issue). Feed should be offered every 2 to 3 hours, at a rate of 15% by weight daily. Most hatcheries start with ground freeze-dried krill, ground fish, fish eggs, or a combination thereof, and gradually replace these components over time with a commercial diet such as would be used for newly hatched trout or salmon. Before transferring them into fingerling ponds, trained fish should remain on feed for at least 2 weeks after they are consuming 100% manufactured diets.
A typical production cycle for largemouth bass in the U.S. begins with spawning from April through June, followed by fry culture in ponds in May and June, feed training in June and July, and grow-out to advanced fingerlings prior to winter. Ideal temperatures for largemouth grow-out appear to be 80o F to 86o F. As winter approaches, growth slows at 50o F and stops entirely at 40o F.
Fish that are to be raised over a second growing season cannot be handled or moved at temperatures below 55o F because they will be susceptible to fungal infections. But if food size fish will be produced, the first year of fingerling and juvenile production is followed by grow-out to market size over the following spring, summer and fall at 3,500 to 4,500 fish per acre (although research and anecdotal information suggest that higher densities are possible and even more advantageous).
Pond production is common when raising largemouth for food fish markets, but cages and split ponds can also be used. In China, ponds, cages and In Pond Raceway Systems (IPRS) have all proven suitable for largemouth bass production. Largemouth bass are inherently cannibalistic and aggressive, so fish to be raised to food size are graded and restocked at 3-4 inches, at 1-2 oz., and again at about 1/3 lb. average weight.
High protein diets (44% to 48%) are required for good growth and development, and the primary protein source in largemouth bass diets was mostly fishmeal in the past (this is still the case in countries such as China). However, diet formulations are continually being refined and recent research even suggests that marine ingredients can be completely replaced in largemouth diets without negatively impacting growth, health or consumer acceptance. This species also needs sufficient dietary lipid levels to maximize winter survival, but high lipid levels can cause liver problems and high deposition of visceral fat.
Largemouth bass are hardy fish, but parasitic, viral and bacterial pathogens can cause significant losses. One particularly lethal disease is caused by the Largemouth Bass Virus. Producers should limit and control vectors for disease, such as infected fingerlings or stockers, wild broodstock, and visiting wildlife predators, especially birds.
The most recent USDA Census of Aquaculture, conducted in 2018, indicated a total of 195 farms producing largemouth bass in the U.S. Of these, 71 reported sales of food size fish, 66 sold stockers, 88 sold fingerlings or fry, and six sold broodfish. Total sales were reported as $27,458,000, of which $21,876,000 (79.7%) was attributed to sales of food size fish. Ohio led the nation with 20 largemouth bass operations, followed by California with 17, Texas with 16 and Illinois with 14. Altogether, 31 states reported at least one largemouth bass producer.
As is the case with a number of other aquaculture species in the U.S., largemouth bass producers can target live markets for food size fish, fingerling markets for stocking, or a combination of the two. Note that selling live product in either of these markets involves prolonged holding and handling. Largemouth bass are particularly sensitive to transport related stress and injury, so extra care must be taken to provide the highest quality product.
Producers have found live fish sales to be lucrative in cities like Chicago, New York, Oakland, Philadelphia, San Diego, San Francisco, San Jose and Toronto. Most cities with substantial Asian communities will have demand for live food size largemouth. Critical factors for offering product to these communities involve both customer service and regulatory compliance (see below). Additionally, once buyers have been located in these or other live fish markets, keep in mind that they will require regular, year-round supplies.
In contrast, there are several million private ponds throughout the U.S., with more being constructed every day. Largemouth bass are stocked in virtually all of these ponds, and demand is not expected to decline in the coming years. However, in this market maintaining required permits and licenses is also an important consideration, so potential producers should consult with regulatory agencies early in the planning process.
Regulatory issues can be complex when raising and marketing largemouth bass, especially when it is necessary to transport fish across state lines. Some state agencies take the position that if any sales of largemouth are allowed, unscrupulous operators will try to sell illegally caught wild fish as farm-raised product. Conversely, other states have determined that legal trade in farm-raised fish probably reduces the possibility of wild fish entering the marketplace.
When planning a largemouth bass farming facility it will be necessary to calculate the carrying capacity of the system in order to estimate capital costs, projected production, revenues and input requirements (especially fry/fingerlings and feed). At this point, an evaluation can begin in order to determine if the operation will be large enough to generate profits and if so, a market analysis can be undertaken. Markets must be available to accommodate production when it is ready for harvest because maintaining fish beyond a harvestable size requires excessive feed, labor and energy costs as well as unproductive use of facilities and capital.
Projected costs (variable, fixed, marketing and opportunity costs) must be compared to prevailing market prices for the sizes and quality of the fish that will be produced, be they fingerlings for stocking or live, food size fish. Keep in mind economies of scale – a smaller operation will have higher per-fish costs and will require a number of small-volume, local markets that are willing and able to pay higher prices for food size fish. When a small operation loses a customer, alternatives may be limited or nonexistent. Input suppliers (feed, fry/fingerlings and equipment) must be reliable and trustworthy, even when larger customers are potentially competing for those same inputs.
Suitable feed for largemouth bass is expensive. Dietary requirements for largemouth differ somewhat from what would be found in typical commercial rations for catfish, trout or tilapia, so feed may have to be specially made or sourced from more distant suppliers. When raising largemouth bass for food size sales, considerable attention must be paid to projected feed requirements – who will supply it, at what cost, and in what quantities will it be delivered? Bulk delivery only makes sense if the entire quantity will be used before its quality begins to deteriorate. However, if buying feed in bags instead of bulk deliveries, costs of production will automatically go up.
Fingerling availability is crucial to economic survival and success in any finfish aquaculture operation, and this is especially true for largemouth bass producers that focus on raising fingerlings purchased from other facilities for sale as food size fish. Seasonality of fingerling production and availability also impacts production schedules in largemouth bass farming, and marketing activities must be adapted to this constraint. Multiple ponds will allow varying stocking and feeding rates to make harvestable fish available year-round, or at least over a more extended period. This, however, will influence the minimum size and scale of the operation in order for it to be competitive and profitable.
Prepared by C. Greg Lutz, Louisiana State University Agricultural Center