Improving Sunshine Bass Production

PEGGY GREB (K11239-1) ybrid striped bass production be- Ludwig studies the ecology of fish gan in the mid 1980s and is now culture ponds and develops new meth- a major aquaculture industry. De- ods of rearing fry and their food source H mand for the farm-raised hybrid indoors to increase production of sun- species resulted from diminished sup- shine bass fingerlings. plies of wild-caught striped bass. Al- Because fry demand live food instead though wild stocks have rebounded of feed, producers typically fill ponds enough that commercial fishing is once with well water and use fertilizers to de- again permitted in some locations, their velop zooplankton populations. Differ- numbers plummeted from 6,800 metric ent aquatic zooplankton communities tons in 1973 to 450 metric tons in the dominate in different stages—first late 1980s. protozoans, then rotifers, and finally Most hybrid striped bass that consum- crustaceans. Wild striped bass fry can eat ers purchase are a cross between female crustacean zooplankton called copepods white bass and male striped bass. Known and cladocerans, but sunshine bass fry commonly as sunshine bass, they have a are smaller (3-5 millimeters long) and high market value, which means they’re need the smaller rotifers, which are relatively expensive. Sunshine bass are available for only a limited time. Ludwig very popular with Asian immigrant pop- determined that sunshine bass must be ulations because the fish are similar to stocked just before rotifers dominate. He species found in their native countries. developed equations to predict when Hybrid striped bass could still find more rotifers will appear in outdoor fry-rearing Jerry Ludwig, fishery biologist, examines a room for growth in the market, consid- ponds. roughly 8-day-old, 7-mm larval sunshine ering wild striped bass were in record These predictive formulas are used to bass that has filled itself with rotifers, demand in the 1970s. indicate exact timing for fry stocking and microscopic animals that Ludwig cultures The palmetto bass is a cross between are based on studies of how environmen- to feed the tiny fish. female striped bass and male white bass. tal factors can influence the sequence of PEGGY GREB (K11248-1) All three are popular sports fish. zooplankton types and sizes present at a Sunshine bass fry are commonly given time. Sunshine bass farmers can raised in outdoor rearing ponds until estimate how long it takes to get a rotifer they’re 35-40 days old. Fingerlings, as bloom in fry culture ponds, which helps they’re then called, are generally avail- them stock at the optimal time. Ludwig able in the southeastern United States says there are many factors involved in from April through August. If more timing fry stocking just right, including fingerlings were available—especially water temperature and amount of rainfall, year-round—they could increase pro- which further cools the water and causes duction of market-size fish and stabilize a cloudiness that slows algae growth. seasonal price fluctuations. In fact, the “During experiments to field-test the industry has identified development of a formulas,” Ludwig reports, “fry surviv- year-round supply of fingerlings as one ability increased from an average of 10 of its highest priorities. percent to 35-55 percent. Fish farmers Sunshine bass reach market size at 1.5 using this technique in their ponds now to 2 pounds, usually after 15 to 18 average 30-40 percent fry survival over months. the entire spawning season.” “They have a nice white, flaky, firm- texture fillet,” says Gerald Ludwig, a Raising Rotifers, Fry in Tanks biologist with ARS’s Harry K. Dupree In temperate climates, indoor pro- Stuttgart National Aquaculture Research duction is required if producers are to Center, in Arkansas. “It’s the type of fil- have a year-round supply of fingerlings. The fish held by fish nutritionist Steve Rawles has an implanted microchip that let you can prepare any way. It has a mild Ludwig was able to produce sunshine allows him and technician Matt McEntire flavor that complements many dishes.” bass fry in indoor tanks for the first time to scan for growth rate.

14 Agricultural Research/June 2004 by feeding them freshwater rotifers, Finding Fish Feed Formulas which he also cultured indoors. More than 40 percent of the variable Ludwig also developed a method of cost of hybrid striped bass farming is at- harvesting zooplankton from outdoor tributed to feed. One strategy to reduce ponds with a rotating drum filter. His costs is to find other, less expensive in- predictive equations reveal when maxi- gredients to use in commercial diets. mum concentrations of rotifers will be ARS physiologist Steven Rawles is available for harvest. The collected roti- studying nutrition in adult hybrid bass. fers are then used for fry feed in indoor He’s interested in the digestibility and tanks. This is followed by feeding larger metabolism of nutrients and energy from zooplankton collected from the ponds. commercially available feed ingredients In another step toward the affordable, and blended components for extruded year-round production of sunshine bass, hybrid striped bass diets. Ludwig developed an automated indoor Rawles says fish evolved on high- feeding system for rotifers with Tim quality protein as predators of smaller Pfeiffer, an ARS agricultural engineer. It fish, insects, and other aquatic animals. ensures that fry will have live rotifers So, sunshine bass require protein-rich available throughout the year. Tanks are diets that are high in fats but low in car- filled with saltwater and a starter popu- bohydrates. High-protein ingredients, lation of rotifers. The temperature is kept such as fishmeal, are expensive because between 77ûF and 86ûF, and a paste supplies are limited and in demand for composed of concentrated micro algae other animal feeds. Ingredients in com- is diluted and constantly fed to the mercially formulated diets vary from rotifers through peristaltic pumps. company to company. When sunshine bass fry were fed ro- Many carbohydrate-rich ingredients tifers grown with this system, followed used in other animal feeds, such as wheat, by larger brine shrimp larvae, different PEGGY GREB (K11252-1) corn, or rice, are inexpensive, but fish amounts of feeding resulted in 22, 35, do not use them well. Most carbohy- and 58 percent survival rates only 28 drates appear to be wasted through ex- days after fry hatching. This is much bet- cretion or stored as fat. Producers would ter than the 7 percent survival rate re- like to increase the amount of carbohy- ported by industry. drates in sunshine bass diets and still see Once there are 1,500 rotifers per mil- good growth performance. Ultimately, liliter, a third of the culture can be har- they would prefer fish to use carbohy- vested daily. Culture reached desired drates for immediate energy needs and concentrations 70 percent of the time. spare dietary proteins for growth. “In our latest indoor rearing experi- “Grains such as rice, corn, oats, and ments, we were able to move 50 percent barley might be substituted for wheat and of the fry from rotifers to commercial wheat middlings,” Rawles says. “We’re feed after only 21 days,” Ludwig says. evaluating the production performance “That’s a good survival rate in much less of fish fed these alternative carbohy- time than the typical 30-40 days needed drates to see whether they perform as to move fry in ponds to commercial pel- well as fish fed diets that contain wheat lets.” He’ll conduct more studies to sub- or wheat middlings.” stantiate these results. His future goals Rawles collaborated with Delbert M. include determining the optimum stock- Gatlin, III, a professor at Texas A&M ing density for sunshine bass fry culture University’s Department of Wildlife and in tanks and the optimum feeding densi- Fisheries Sciences, to determine nutri- Hybrid striped bass, also known as ty of rotifers and brine shrimp. He also ent availability in 19 common feedstuffs sunshine bass. wants to find alternative diets for fry and for hybrid striped bass and red drum. train them to take feed sooner. They used commercial methods and

Agricultural Research/June 2004 15 PEGGY GREB (K11243-1)

equipment to manufacture extruded feed, To make an in which ingredients are combined under experimental diet for hybrid striped bass, high temperature, pressure, and shear technician Rebecca force and ejected as bite-sized pellets. Jacobs first prepares to Nutrient digestibility values were de- mix ingredients. termined and made available to feed mills and producers. This research could lead to lower-cost feeds. Rawles and colleagues are currently working with a major poultry processor and a fish-feed manufacturer to explore use of poultry-byproduct meal as the primary protein source in sunshine bass diets. So far, the fish are readily consum- ing several experimental diets consisting of poultry byproducts and supplemental amino acids, but it is too early to tell whether those fish are performing as well as some being fed diets containing mostly fishmeal. Rawles is also studying a diet contain- ing meal from poultry meat, bone, feath- er, and blood instead of supplemental amino acids. These byproducts are high in protein and less expensive than feed- grade amino acids. Initial work indicated PEGGY GREB (K11247-1) that the nutrients in these byproducts are Fishery biologists Ray highly digestible, but unfortunately the Carter, back left, and mix doesn’t appeal to the bass. Rawles Scott Snyder, front left, with technician is investigating ways to increase the Matthew McEntire, combination’s palatability by adding fish right, sample hybrid solubles, betaine, or other ingredients. striped bass Rawles says research is continuing on fingerlings to assess growth performance diets containing animal byproduct in ponds. They’ll blends. “If any of the byproduct meal/ evaluate the fish for amino acid-supplemented diets perform weight gain, fillet as well as the fishmeal diet, then we’re yield, and fat content. on our way to a less expensive diet for hybrid striped bass,” Rawles says.—By Jim Core, ARS. This research is part of Aquaculture, an ARS National Program (#106) de- scribed on the World Wide Web at www.nps.ars.usda.gov. Gerald Ludwig and Steven Rawles are with the Harry K. Dupree Stuttgart Na- tional Aquaculture Research Center, P.O. Box 1050, Stuttgart, AR 72160; phone (870) 673-4483, exts. 238, 249, fax (870) 673-7710, e-mail [email protected]. usda.gov, [email protected]. ★

16 Agricultural Research/June 2004