SRAC Publication No. 438 VI September 2000 PR Bighead Carp Nathan Stone1, Carole Engle1, David Heikes1 and Donald Freeman2 In worldwide aquaculture, big- tial for canned and surimi Biology head carp (Hypophthalmichthys (minced, formed fish) products is nobilis) ranks fourth in production being studied. The bighead is aptly named, as this fish has a large head with a (2.8 billion pounds in 1995). Big- Producing bighead with catfish head were introduced into the protruding lower jaw and eyes requires that the bighead be hand- that “look down” (Fig.1). They are southern United States from sorted from catfish each time a China (the largest producer) in the deep-bodied fish with tiny scales pond is seined, or seined separate- and gray to black blotches on the early 1970s. Because the word ly with a large mesh seine before “carp” has a negative connotation body, which gives them a speck- catfish are harvested. This is a sig- led appearance. While bighead to some consumers, alternative nificant disadvantage in multiple- names proposed for bighead can reach 60 pounds or more and batch catfish production. Other 4-year-old fish may weigh 20 to 25 include “noble fish,” “speckled disadvantages of polyculture are amur” and “lake fish.” pounds, the primary market is for that bighead consume pelleted 6- to 12-pound fish. Bighead can In the United States, bighead are feed intended for catfish, compete survive in a wide range of tem- polycultured with channel catfish for aerated water, and may be peratures, but in one study their in approximately 5,100 acres of vectors of fish parasites. preferred temperature was 78 oF earthen ponds, including an esti- mated 4,000 acres in Arkansas, 500 in Mississippi, and 600 in Alabama. Bighead are an impor- tant source of additional income that, at times of low catfish prices, has kept some fish farmers in business. The primary market is to live-haulers who sell to special- ty markets in large cities. The cur- rent U.S. market is limited and easily saturated. Wide fluctuations in price and unique marketing requirements for bighead have prompted farmers to seek alterna- tive markets. Bighead have a pleasant, mild tasting flesh, but are too bony for most U.S. consumers. The poten- 1University of Arkansas at Pine Bluff 2USDA Agricultural Research Service Figure 1. Bighead carp. and the thermal death point was that they grow more slowly than worm) is rarely seen in catfish 100 to 102 oF. normal (diploid) fish. production, but there have been The natural food of the bighead is several major catfish losses from zooplankton, along with larger Culture this parasite after bighead were introduced into catfish ponds. phytoplankton. Bighead are filter As with the other Chinese carps, feeders and use their fine, comb- There is no legal treatment for this techniques for reproducing big- parasite in food fish ponds. like gill rakers to strain tiny ani- head by induced spawning have mals and large algae from the been perfected by fish farmers Bighead are thought to improve water. If zooplankton are scarce, and researchers (for additional pond water by continually crop- bighead may feed on detritus information, see Rottmann and ping plankton to make the pond (organic matter and associated Shireman, 1992). Brood fish reach plankton community more stable bacteria that accumulate on the maturity at 3 to 4 years of age, and less prone to die-offs. There is pond bottom). Pond bottom with males maturing earlier than no convincing evidence of this. In organisms are not a normal food females. Fish can be induced to reducing concentrations of zoo- item; in one study, bighead were spawn with hormones (see SRAC plankters (that feed on phyto- not found to have a significant publications 421-427). Optimum plankton) and large phytoplank- impact on the benthic (pond bot- water temperature for induced ters, bighead no doubt influence tom) community. spawning is 72 to 78 oF. For fin- the composition and size structure Under favorable conditions, big- gerling production, newly of the plankton community. head grow rapidly. After reaching hatched fry are stocked into pre- However, this does not necessari- 1 to 11/2 pounds they can gain 1 pared nursery ponds (see SRAC ly lead to improved water quality pound or more per month. publications 469 and 700) at rates or reduced off-flavor. Growth is largely dependent on of 100,000 to 500,000 per acre. Harvesting and marketing the fertility of the water and the Bighead are typically raised to stocking density. Market size fish market size in polyculture with The preferred market size for big- (6 to 12 pounds) are usually 2 to 3 channel catfish, although they can head is 6 to 12 pounds. Larger or years old. be raised alone in fertilized ponds. smaller fish bring much lower Bighead are native to large rivers In either case, farmers stock 300 to prices. and will not spawn in still waters 400 small fingerlings per acre or Bighead are gentle and relatively or small streams. Although fish 100 to 150 larger fish (stockers, easy to capture with a seine. They 1 1 do mature in ponds and can be typically /4 to /2 pound) per must be separated from catfish by induced to spawn with hormone acre. The higher stocking rate for hand at harvest, unless a very injections, they do not spawn nat- small fingerlings is based on large mesh net is used. Where urally in still water. In large anticipated low survival rates. pond seining is done by crews rivers, spawning typically occurs Stocking rate is also adjusted from a catfish processor, stocking when spring rains flood the river according to the required market of bighead is discouraged because and water temperature reaches 77 size at harvest. If stocking density the sorting process slows the cat- o to 86 F. Eggs are slightly heavier is too low, bighead may grow fish harvest. Some producers have than water and settle out in still beyond the desirable market size learned the art of “swimming off” water. In rivers, eggs are suspend- before the producer is able to mar- bighead. This involves using an ed by turbulence and carried ket them. Although bighead do aerator to create a current through downsteam. not grow well on pelleted feeds the net containing the bighead Bighead have become established alone, they will consume catfish and catfish. A 10- to 15-foot sec- in the Mississippi River system feed, especially when stocked at tion of the float line of the live car and reportedly spawn in the higher densities. Data from exper- (sock) is then submerged slightly Mississippi, Missouri and Illinois imental ponds indicate that when (6 to 8 inches) so that the bighead Rivers. Larval bighead have been stocked at recommended rates, will swim against the current and collected from the lower Missouri bighead do not significantly affect out of the live car, thus separating River in late June and early July. catfish production or food conver- themselves from the catfish. New There is some concern that big- sion ratios. advances in grading technology head compete with native species Bighead will grow during the designed to select only market- such as the paddlefish and big- winter months in the southern size fish from multiple-batch cat- mouth buffalo, which have simi- U.S., but much more slowly than fish ponds may speed sorting of lar food habits and distribution. in the summer. Yields depend on bighead as well. Many states prohibit the introduc- fish size, pond fertility and culture Fish are transported in 10,000- to tion of bighead or require a spe- period, and typically range from 20,000-pound loads. Shrinkage cial permit for a bio-secure facili- 500 to 800 pounds per acre. (loss in individual fish weight) ty. Triploid bighead (apparently Before stocking bighead into cat- during shipping can be as much sterile) have been produced and fish ponds, it is critical to check as 8 to 15 percent in the summer could be raised for market, fish health and treat for parasites and 2 to 5 percent in winter. although a limited study showed if necessary. Lernaea (anchor Regardless of season, the changes in water chemistry and tempera- Economics ture during transit and holding stress fish and can cause losses. Annual costs and returns for big- head raised in polyculture with Successful marketing of any prod- channel catfish or alone in fertil- uct requires a basic understanding ized ponds were estimated from of the perceptions and desires of studies conducted at the the end user. The primary con- University of Arkansas at Pine sumers of bighead in North Bluff. A 15-acre pond with or America are persons of various without catfish was used as a Asian cultures in major metropoli- basis for estimating costs and tan areas such as Chicago, Boston, returns. In polyculture with cat- Toronto and New York. Live, high fish, bighead carp provided addi- quality fish are critical for this tional revenues of $95 to $391 per market. The typical consumer will acre at market prices of $0.25 to buy only enough fish for the cur- $0.70 per pound, respectively. An rent day’s meal and will pay top average farm-gate price of $0.40 dollar only for live fish. Fish that per pound would yield an addi- die in retail markets are sold tional $194 per acre. For bighead cheaply, at about 20 percent of the raised alone, the break-even prices live price. above variable and total costs Most live bighead are sold from were estimated at $0.28 and $0.52 small street markets clustered per pound, respectively.