... The following material is based upon work supported by the Cooperative StateResearch Service and Extension Service, U.S. Department of Agriculture, under SpecialProject No. 87-EXCA-3-0836.

When a Tribal fish hatchery program is first conceived and construction begins, theinitial cost of the program can be substantial. This problem is compounded by the monthlyoperation and maintenance cost that are needed to keep the facility operating properly.Perhaps one solution to help offset these expenses is to build into your program a meansof maximizing your initial investment. One method of accomplishing this is to diversifyyour aquaculture facility to also include a baitfish production program. Part 2 of thisarticle will appear in the next issue of the MTAN.

Baitfish production provides an attractive alternative to traditional fish farming in manyparts of the United States. Baitfish are used by sportfish enthusiasts who prefer livebait over artificial lures or attractants. Baitfish are also used as feeder fish.
Although the baitfish industry has not always been profitable, previous successes andincreasing demand for baitfishes present an optimistic future for new producers. Speciespreference in selected regions of the United States indicates golden shiners are mostpopular in the Southeast, Southwest and West. Fathead minnows are the dominant species inthe Midwest and Northeast. White suckers and golden shiners are also important species.Feeder fish markets are developing in the mid-Atlantic and Southeastern states for use instriped bass and hybrid striped bass culture.

PRODUCTION METHODS

Quality, disease-free fish from a cultured line are the best broodfish. These fish can beobtained from established, reputable farms. Select ungraded yearling broodfish and havethem evaluated by a diagnostician. Avoid fish which display any kind of bacterial orparasitic infection of any kind.

Wild Spawn is an extensive method of production. Stock 20-40 pounds of broodfish per acre.Fish should weigh 3 to 12 pounds/1000 or be from 333 to 83 fish per pound. Golden shinersare vegetative spawners. Plant a band of rye grass around the pond to serve as spawningmaterial. Fish start spawning when water temperatures reach 70F and stop at watertemperatures above 85F. Eggs are deposited on the rye grass and hatch in 7 to 10 days.Fertilize each pond within a week after hatching. Apply 100 pounds of fertilizer (0-46-0,18-46-0 or equivalents) per surface acre. Start feeding minnow fry 4 days after hatching.Feed a high protein meal, 38% crude protein or higher. Overfeed initially to insure allfish have the opportunity to feed. When fish are one month old, change to a 32% crudeprotein meal or crumbled pellet. Begin feeding 2 pounds per acre and gradually increase to10-20 pounds per acre.

Using the wild spawn method, egg laying, hatching, and grow-out occur in the same pond.Harvest the adults shortly after spawning stops. This prevents spread of disease from theadults to the young. Production using this method ranges from 200-350 pounds per acre.
INTENSIVE CULTURE

Two methods are used: (1) egg transfer and (2) fry transfer. For either method, stockbroodfish at 300-500 pounds per acre. Place spawning mats, 21 x 30 inches, made ofSpawntex (material similar to heating and air conditioning filters) sandwiched between6" x 6" concrete reinforcement wire in the pond. Keep the pond free ofvegetation to prevent uncontrolled egg deposition.

Egg Transfer Broodfish start "running" (swimmingparallel) to the pond bank prior to spawning. Place spawning mats in shallow water about1" below the surface when fish begin running. Stake the pond side of the mat to holdit parallel to the bank. Place mats in an end-to-end arrangement. There is no recommendednumber of mats for brood ponds, but it is not uncommon to use 500 or more in a ten acrebrood pond.

Mats are ready to transfer to fry rearing ponds when they are uniformly covered witheggs. Egg covered mats appear as if dusted by a fine powder or snow. Mats are usuallycovered with eggs in 12-24 hours after placement. Never leave a mat in a brood pond morethan 24 hours regardless of egg coverage. As spawning slows down, decrease the number ofmats in the pond. Mats are picked up, stacked on a trailer or pickup truck bed, andcovered by a tarp or burlap-like material. Mats can stay out of water up to one hour ifthey are kept moist and out of direct sunlight. For rearing ponds, stock 50-75 egg-coveredmats per acre. Place the mats in shallow water 6-12 inches deep to allow eggs to hatch.Leave mats in the rearing pond for one week after hatching. This provides a protectivearea for fry. Use the same fertilization and feeding schedule as with the wild spawnmethod.

Fry Transfer Place 100-200 egg-covered mats per acre in ponds. Theobjective is to produce as many fry as possible, grow them to about " then transferthem to grow-out ponds. Fry are harvested using lift traps and fine mesh fry seines.Stocking densities for golden shiners depend on when fish are to be sold, size of fishdesired and length of growing season. Most ponds are stocked with 50,000 to 200,000 fryper acre. Fry numbers may be determined by a volumetric displacement method. Count thenumber of fry in 1 ounce. Multiply that number by the number of ounces of fry transferred.

FATHEAD MINNOWS

Select broodfish at least 2" long. Males grow faster than females, so selectionbased on large size leads to mostly male populations. Fathead minnows have fewer parasiteproblems than other baitfishes. However, potential broodfish should be examined by adiagnostician. Fathead minnows are fractional spawners, releasing only a few eggs at eachspawn. Culture of fathead minnows is restricted to wild spawn and fry transfer methods.
Wild Spawn Stock broodfish at 500 to 2,000 (2 to 10 pounds) peracre. Fish should be 2 inches long and weigh 5 pounds per 1000 (200 fish per pound). Sexratios should be five females per male. There is a size difference between adult male andfemale fathead minnows, and the sexes can be separated using a 15/64 or 16/64-inch bargrader. Most females swim through the grader while males are trapped. Take samples of eachsex to estimate numbers.

Fathead minnows spawn on the underside of objects in the pond. Use spawning boards, 12 x 4x 1 inches stapled to wire stretched parallel to the pond bank. Space boards about 1 footapart. Some producers use oak pallets tied to posts driven into the ground (placing fourto six pallets per acre). The broodfish spawn over several months. Ponds are fertilizedand fed at the same rate as with golden shiners.

Fry Transfer Stock broodfish, five females per each male, at20,000 to 25,000 fish per acre (100 to 125 pounds per acre). This method can produce up tothree million fry per acre. Stock fry at 100,000 to 300,000 per acre. Estimate numbersusing the same method as with golden shiners.

GOLDFISH

Broodstock selection depends on the market. Fish are produced for the aquarium, landscapepond, feeder or bait market. Pay attention to color and shape of the adult fish.Slim-bodied varieties are preferred for bait. Cull heavy, thick-bodied fish. Plumper fish,trilobed tail, and "bug-eyed" condition are desirable traits for the aquariummarket. Feeder goldfish are smaller (3-5 pounds/1000 fish), so use the same criteria usedfor selecting broodfish for bait.

The same spawning methods are used in goldfish production as with golden shiners. For wildspawn, stock 10-20 pounds of broodfish per acre. Fish should weigh 17-50 per pound (3-5inches in length). Avoid using broodfish over pound. These fish may have parasites suchas: Trichodina, Gyrodactylus and Dactylogyrus. Avoid using broodfish infected with"ulcer disease." This disease can kill 100% of the broodfish.

For the egg and fry transfer methods, stock broodfish at 800-1000 pounds per acre. Rearingponds are stocked at 50-150 mats per acre. Fry are stocked from 25,000-1,000,000 per acre.Rearing ponds are fertilized and fed at the same rates as golden shiners. Many producersfertilize ponds based on light penetration into the pond water. Ponds are fertilized whena shiny object is visible at water depths greater than 16 inches.

WHITE SUCKERS

This species is more common in northern states. Broodfish are harvested from the wild.Broodfish collection may require special permits or be subject to regulation.

Collection of Eggs Sucker spawning dates are regulated by watertemperature and may range from mid-April to late May. Suckers "run" when watertemperatures are between 45F and 59F. Fish are trapped or seined below dams or waterfalls.Brooders are sorted by sex and put in tanks for transportation to the hatchery. Beforereleasing the fry, let the plastic bag float along the pond's edge. This lets thetemperatures equalize and prevents temperature shock.

Sucker fry settle to the bottom of the hatching jar when the water is shut off. Numbers offry can be estimated at this time. Pour the fry into a graduated container and allow themto settle. Determine the volume of fry in ounces. There are about 2,720, 5-day-old fry perounce. A pond stocked at 40,000 fry would need 14.7 ounces of fry. Fry can be transportedfrom the hatchery to rearing ponds in oxygenated plastic bags.

Stocking Rearing Ponds Sucker ponds are stocked at 40,000 fry peracre. Some growers adjust stocking rates to influence fish size. Suckers require nospecial feed. They grow on plankton, insects and invertebrates in the pond.

Overwintering Suckers Suckers too small for sale the first yearcan be overwintered in ponds. It is essential to keep snow off ice-covered ponds. Snowcover prevents light penetration and limits oxygen production. Some producers use largeaerators to prevent formation of ice cover.

FEEDING AND NUTRITIONAL REQUIREMENTS

Most baitfish ponds need to be fertilized and supplemental feeding increases production.Fry need a nutritionally complete diet high in protein. Starter feeds should be fine. Fryfeed should be made into a slurry and fed on all sides of the pond. This ensures all fishhave the opportunity to feed. Feeding rates are determined by species and stocking rates.Golden shiners, goldfish and fathead minnows are fed 10-20 pounds per acre per day duringthe growing season.

HARVESTING, HANDLING, HOLDING AND TRANSPORTING

Baitfish species may be harvested by baiting and seining a pond corner, seining a wholepond or draining the pond. Traps are sometimes used for goldfish and fathead minnows.
Seining Seines and dip nets should be made from knotless, wovennylon. The most common mesh size is 3/16 inch. Smaller mesh seines collect debris and aremore difficult to handle. Large mesh seines catch fish behind the gills (gilling). Seinelength should be 50% longer than the width of the pond. Seine depth should be twice theaverage pond depth. For ponds 1-2 acres in size, stretch the seine across the end of thepond. One or two people are needed on each end of the seine. Walk slowly when pulling theseine so the lead line drags across the pond bottom. Angle the brail at 45 to 60 to pullthe lead line ahead of the float line. Beaching the seine is the most critical step inseining. The lead line must not be raised off of the bottom, but it should not dig intothe mud. Pull the float line in faster than the lead line. The float line "rollsover" to form a bag when the lead line is pulled into the shore forming a box typetrap. "Stake" the corners with concrete reinforcement bars or electric fenceposts. Fish are dipped out of the seine into 5 gallon buckets. A bucket holds 15-20 poundsof water and 25 pounds of fish. The buckets are carried to a transport truck and emptiedinto aerated tanks. Many fish mortalities are caused by improper harvesting,handling and transporting.

Lift Nets and Traps Lift nets and traps can be used for harvestingfathead minnows and goldfish. To use a lift net, lower the net in a shallow area. Place aball of moistened fish food in the center of the net. Wait 15-30 minutes, approach the netcautiously, and lift the net rapidly by means of a lever. Dip the fish out of the net andreset.

Several traps can be used simultaneously. For traps, wrap the fish food in burlap orcheesecloth. Lower the trap to the pond bottom. Wait 15-30 minutes, grab the float line,lift the trap, empty the fish into a bucket, and reset the trap.

Holding Holding vats are made from concrete blocks or pouredcement. Sizes vary depending on the operation. Vats 5 feet x 30 feet x 18 inches deep aremost common. Holding facilities need an adequate water supply. Aeration for vats isusually provided by electric agitators or blowers.

Transportation Long distance hauling trucks have liquid orcompressed oxygen tanks and insulated holding compartments. Hauling tanks may beconstructed from marine plywood, styrofoam insulated sheet metal or insulated fiberglass.Tanks need a drain at least six inches in diameter. Hauling tank aeration systems include12 volt agitators, blowers and oxygen systems. Two to four agitators are needed percompartment. One blower can serve four, 75-gallon compartments. Oxygen systems require aoxygen cylinder, regulator, one flow meter per compartment and an oxygen dispersion hose.The regulator is set at 20 pounds per square inch. Flow meters are set at 3-5 liters perminute. Both can be adjusted depending on the fish load and the number of compartments.
PROBLEMS OR CONSTRAINTS

Anticipation of problems and knowing how to solve them are essential to the successfuloperation of a fish farm. In the baitfish industry, some common problems includeparasites, diseases, water quality deterioration, predators, weed infestation and legal orregulatory constraints. The severity, frequency and duration of disease outbreakscan be reduced by controlling fish stress.

... The next issue of the MTAN will contain additional information regarding baitfishproduction. The focus of which will cover water quality, weed and predator control andmarketing techniques.

Best Management Practices For BaitfishProduction

... Reprinted from the May/June 1995 issue of Aquaculture Magazine.
The baitfish industry is currently facing several concerns includingincreased regulations and the fear of spreading zebra mussels. To address these concerns aBest Management Practice (BMP) program should be initiated. A well conceived BMP programwill identify critical areas in the baitfish production cycle. Proper care and practicesat each of the critical areas will improve quality of the final product. Critical areasand practices include site selection, water source, broodfish screening, animal husbandrypractices, maintaining good water quality, not sharing equipment between 'wild water' andpond water and education at the final sales point.

Regulatory agencies are concerned with chemicals that reside in non-food as well as foodfish. Therefore, producers should be concerned about pond site selection including landuse history.

Wetlands are another consideration. Before any pond construction begins, the site'swetland status must be determined.

The baitfish producer's BMP program should include careful selection of the water source.Groundwater is the ideal source for fish farming. The water must be free of chemicalcontaminants. Spring water is also a good source but must be available during the droughtseason. Streams can be used as a water source but must be free of zebra mussels andcontain pathogen free (wild) fish. Stream water must be also be screened to prohibit theentry of predatory fish into your pond facility.

Healthy broodfish produce larger eggs, which result in improved fry survivability. A goodscreening program should eliminate the presence of such diseases as "goldfish ulcerdisease," milk scale, various grub species and the anchor worm. Reject any fish thatare unusually thin or has abnormalities such as curved spine, misshaped head or lacks thebody conformation the fish culturist desire.

Good animal husbandry should be part of the producer's BMP program. Cultured fish need aquality diet. The fish must be reared under the least stressful conditions possible. Roughhandling during harvest and transport should be avoided as well as unneeded chemicaltreatments. Good quality water in ponds and tanks is essential for fish survival. Anotherimportant practice is to not share equipment between "wild water" and pondwater.

To eliminate stress, adequate aeration is needed in ponds, during transport and at thegrading facility. Proper tempering is also a must when changing fish from one body ofwater to another.

Wildfish can introduce unwanted disease organisms into ponds and the water can also be asource of zebra mussels. It is imperative to avoid using equipment utilized in harvest ofwildfish in commercial aquaculture ponds. This includes the use of nets and seines,dipnets, waders, buckets and boats.

Another concern involves genetics. Baitfish from cultured ponds may have a differentgenetic make-up than the baitfish in the native body of water. If these fish happen tocross, the native batifish can loose some of its genetic identity. Baitshop owners shouldurge fishermen to avoid releasing unused baitfish into the water. Fishermen should beurged to destroy the unused bait when finished fishing.

A final BMP practice involves educating people at the final sales point of the baitfish.People are becoming very concerned over the impact fishermen have on the aquaticenvironment caused by the release of baitfish into a receiving body of water. Many peopleare concerned that non-indigenous species may upset the balance of nature in these areas.

Although these suggestions will not solve all the baitfish industry's problems they makegood sense and are also easy and inexpensive to implement.


A BIBLIOGRAPHY ON THE CULTURE OF BAITFISH

Ball,R.C., and E.H. Bacon. 1954. Use of pituitary material in the propagation of minnows.Prog. Fish-Cult. 108-113.

Bauman, A. C. 1946. Bait minnow production in ponds. Mo. Cons. 7(6)3-5.

Bell, R. C. 1960. Propagation of bait minnows in California.

Calif. Dept. Fish Game Inland, Fish. Admin. Rept. No.56-1 1.

Benoit, D. A., and R. W. Carlson. 1977. Spawning success of fathead minnows on selectedartificial substrates. Prog. Fish Cult. 39(2):67-69.

Branch of Fish Hatcheries. 1965. Fish baits: Their collection, care, preparation andpropagation. U.S.F.W.S. Leaflet FL-28.

Clark, C. F. 1943. Creek chub minnow propagation. Ohio Cons. Bull.7(6):12-13.

Cook, F. A. 1954. Baitminnows - their propagation is a necessity. Miss. Game Fish18(2):3-5.

Cooper, G. P. 1935. Some results of forage fish investigations in Michigan. Trans. Amer.Fish. Soc. 65:132-142.

Davis, H. S. 1953. Culture and diseases of game fish. Univ of Calif. Press, Berkley,Calif. 332 p

Davis, J. T. 1986. Baitfish. In: R.R. Stickney Culture of Nonsalmonid Freshwater Fishes.CRC Press, Boca Raton, Florida.

Doble, J. 1948. Minnow propagation. Minn.Dept.Cons.Bull.No. 13.

Doble, J. 1972. Rearing suckers for bait in Minnesota. Minn. Dept. Nat. Res. Invest. Rep.No. 256.

Dobie, J. R., 0. L. Meehean, S. F. Snieszko, and G. N. Washburn. 1956. Raising baitfishes. U.S.F.W.S. Cir. 35.

Flickinger, S. A. 1969. Pond culture of bait fishes. Colo. State Univ. Coop. Ext. Ser.Bull. 478A. 39 pp.

Flickinger, S. A. 1973. Investigation of pond spawning methods for fathead minnows. Proc.Annu. Conf. S.E. Assoc. Game Fish Comm. 26:376-391.

Fomey,J.L. 1957. Bait fish production in New York ponds. N.Y. Fish Game J. 4:150-194.
Fomey, J. L. 1975. Raising baitfish and crayfish in New York ponds. Cornell Univ. Coop.Ext. Ser. Bull. No. 986, Ithaca.

Gast, M. M., and W. A. Brungs. 1973. A procedure for separating eggs of the fatheadminnow. Prog. Fish-Cult. 35:54.

Giudice, J. J., D. L. Gray, and J. M. Martin. 1981. Manual for bait fish culture in thesouth. Univ. of Arkansas Coop. Ext. Ser. EC-550, Little Rock.

Guest, W. C. 1977. Technique for collecting and incubating eggs of the fathead minnow.Prog. Fish-Cult. 39(4):188.

Hasler, A. D., H. P. Thomsen, and J. Neiss. 1946. Facts and comments on raising two commonbait minnows. Wis. Cons. Dept. Bull. No. 210.

Hedges, S. B., and R. C. Ball. 1953. Production and harvest of bait fishes in Michigan.Mich. Dept. Cons. Misc. Publ. No.16. 30pp.

Hickman, G. D., and R. V. Kilambi. 1974. Growth and production of golden shiner underdifferent stocking densities and feeding rates. Proc. Ark. Acad. Sci. 28:28-31.
Hubbs, C. L. 1934. Some experiences and suggestions on forage fish culture. Trans. Amer.Fish. Soc. 63:53-63.

Huner, J. V., and H. K. Dupree. 1984. Third Report to the Fish Farmers. U.S. Fish andWildlife Service.

Hutchens, L. H. 1946. Bait minnow and their propagation. L11. Cons. II:14-15.

Jensen, J. W. 1983. Home fish bait production. Auburn Univ. Coop. Ext. Ser. Cir. ANR 329,Auburn.

Johnson, S. K. 1978. Maintaining minnows - A guide for retailers. Texas A&M Univ.Coop. Ext. Ser. Bull. MP-1320, College Station.

Johnson, S. K., and J. T. Davis. 1978. Raising minnows. Texas A&M Univ. Coop. Ext.Ser. Bull. NIP-783, College Station.

Langlois, T. H. 1937. Bait culturists guide. Ohio Dept. Ag. Bull. No. 137.

Markus,H.C. 1939. Propagation of bait and forage fish. U.S.Bur. Fish. Cir. No.28.
Martin, M. 1954. Minnow culture in Kentucky. Div. Fish., Ky. Dept. Fish Wildl. Res. 28pp.
Mayer, F. L. 1976. 2,4-D reduces Saprolegnia on fathead minnow eggs. Prog.Fish-Cult. 38(l):19.

Mural, T., and J. W. Andrews. 1977. Effects of salinity on the eggs and fry of the goldenshiner and goldfish. Prog. Fish. Cult. 39:121.

Nagel, R. 1976. Techniques for collecting newly hatched fathead minnow fry. Prog. Fish.Cult. 38(3):137.

Prather, E. E. 1956. Experiments on the commercial production of golden shiners. Proc.Annu. Conf. S.E. Assoc. Game Fish Comm. 10:150-155.

Prather, E. E. 1957. Preliminary experiments on winter feeding small fathead minnows.Proc. Annu. Conf. S.E. Assoc. Game Fish Comm. 11:249-253.

Radcliffe, L. 193 1. Propagation of minnows. Tran. Amer. Fish. Soc.61:131-138.
Raney, E. C. 1941. Propagation of the silvery minnow in ponds. Trans. Amer. Fish. Soc.71:215-218.

Rosenberg, R. B., and R. V. Kilambi. 1975. Growth and production of golden shiner underdifferent stocking densities and protein levels. Proc. Annu. Conf. S.E. Assoc. Game FishComm. 28:385-392.

Saylor, M. L. 1973. Effect of harvesting methods on production of fingerling fatheadminnows. Prog. Fish-Cult. 35(2):110-114.

Wascko, H., and C. F. Clark. 1948. Pond propagation of bluntnose and blackhead minnows.Ohio Div. Cons. Nat. Res., Wildl. Cons. Bull. No. 4.16 pp.

Washburn, G. N. 1945. Propagation of the creek chub in ponds with artificial raceways.Trans. Amer. Fish. Soc. 75:336-350.

COMMON DISEASE PROBLEMS IN BAITFISHCULTURE

By: Terrence Ott, La Crosse Fish Health Center, La Crosse, WI

Commercial warmwater fish farming was begun in the late 1920's and early 1930's by afew persons who raised minnows to supply the growing demand for baitfish for sportfishing. Shortly after World War II, the demand for minnows increased as the result of theboom in farm pond and reservoir construction and the many water conservation projectsinspired by the dust-bowl years of the 1930's.

The baitfish industry blossomed during the 1960's producing over 20 species of fish forbait in North America with golden shiner Notemigonus crysoleucas, fatheadminnow Pimephales promelas and white sucker Catostomus commersonibecoming the three most popular species cultured in the Upper Midwest.

Parasites and diseases pose a serious threat to the intensive production of baitfish andloss of income can be substantial. Many producers have learned that some parasites anddiseases can spread rapidly and kill an entire fish population in a short time.
It is essential that a baitfish producer observe the fish daily and be able to recognizethe clinical signs of fish diseases when they first appear. Good health managementpractices is the key to successful production of healthy baitfish.

Bacterial diseases occur in baitfish as primary or secondary invaders. Columnaris diseaseis caused by the bacterium Flexibacter columnaris and is a primaryinvader of baitfish. The disease begins externally on the body surface producing lesions.As the disease progresses, these lesions spread over the rest of the body causing necrosisof the underlying muscle fibers. Virulent strains of F. columnaris mayattack gill tissue and cause a "gill rot" condition. Systemic infections due toless virulent strains may occur with no apparent external signs. However, cutaneousinfections seem to be more prevalent in most baitfish. Water temperature is amajor influence on the occurrence of columnaris.

Outbreaks seldom occur below 13C, but may be explosive above 18C. Summer is the seasonwith the highest incidence of columnaris outbreaks. Crowding, handling, and otherstressors are also predisposing factors to columnaris outbreaks.

A. hydrophila is a secondary invader closely associated with handlinginjuries and stress. This motile aeromonad is among the most common bacteria in freshwaterhabitats throughout the world. These bacteria can be opportunistic and develop increasedvirulence under ideal conditions. Stress caused by high water temperatures, low oxygenlevels, accumulations of waste products, and overcrowding are predisposing factors whichcan lead to disease outbreaks. Nutritionally deficient fishes are especially susceptibleto secondary infections, as are fishes with injuries or damaged skin or gills.
The organisms are usually transmitted orally except in those instances when fish have skinor gill abrasions and the organism may enter through these routes. External parasiteswhich abrade skin and gills have been implicated in the transmission of A.hydrophila. The bacteria multiply in the intestine or at the site of invasion andare spread throughout the body by the blood stream.

Saprolegnia is the major fungal disease encountered at baitfish farms.This fungus is thread-like in appearance, and possesses profusely branched non-septatehyphae that appear as white to gray tufts in the water. There are no primary causes of saprolegniaamong baitfishes; rather infection may be secondary to other infections or injuries.Bacterial disease, external parasites, and physical or environmental stressors maypredispose a fish to fungal infection. Saprolegniais more detrimental tofish eggs than to fish.

A microsporidean, Plistophora ovarie, parasitizes the developing ovariesof adult golden shiners. This parasite reduces fecundity and may produce sterility inolder females. P. ovarie is an intracellular parasite with a tremendousreproductive capacity. Microsporiasis is characterized as a chronic condition in whichmasses of developing spores form within the ovaries of the shiner. Disintegration of thetissue in which the spore is present releases spores. Ingestion of infected fishes byother fishes also releases spores from the infected fish. Those released to theenvironment must be ingested by the new host, either directly or as contaminants on food.Golden shiners with microsporiasis at an advanced stage of development may becomelethargic, emaciated, may become solitary or may have different body colors.

Golden shiner virus is another pathogen infecting golden shiners. This disease causeslow-grade chronic mortalities in ponds and has been reported to cause high mortality inshiners held in tanks. Visible signs of the disease include a red-back or red-headcondition caused by expanded blood vessels beneath the surface of the skin, and intestinalhemorrhage and hyperemia on the ventral surface of the fish.

Ichthyophthirius multifilis a protozoan parasite is a ciliated, motileprotozoan with a horseshoe-shaped nucleus. "Ich", as this parasite is commonlycalled, thrives at temperatures around 15C. The adult form becomes attached and forms avisible cyst that appears as white pustules on the fins and body. Slight to moderateinfections will not cause behavioral changes in the fish. Marked or extreme infections maybe accompanied by lethargy, listlessness, rubbing on the sides or bottom of the pond anddifficulty in obtaining oxygen if the gills are badly damaged.

Another common parasite of baitfish is the monogenetic trematode, Gyrodactyluselegans. This trematode can be identified by the developing embryo inside theadult along with the lack of eye spots. The posterior end has a haptor with a single pairof large hooks. Under optimum conditions these worms can be seen by the naked eye. G.elegans occurs in epizootic levels during late winter and early spring. Usuallylittle or no harm is done to the fish, but on occasion this fluke contributes to diseaseof the fish if it becomes too numerous at any one time.

Another consideration in a baitfish culture operation is the control of predators andcompetitive organisms. Predators must be controlled in and around baitfish productionponds. A few predators can often capture and eat enough baitfish to make the productionsystem unprofitable. Control of these predators often depends on the ingenuity of thefarmer. Since a special license or permit is often required before some nuisance animalcan be killed or removed, the baitfish farmer should consult with appropriate State andFederal conservation authorities before beginning a control program.

Keeping levees and dikes clean of debris and mowed helps control small borrowing mammalslike muskrats.

Snakes of various species can be quite abundant around baitfish ponds. Sometimes snakeswill lie on spawning mats or boards waiting to prey on brood fish.

Tadpoles and crayfish are a nuisance in harvesting, and are also a competitor withbaitfish. In addition, there is evidence that tadpoles and frogs carry certain fishparasites and diseases.

A successful baitfish culture is the result of an effective health protection program, andcan be as challenging and complex as the actual control of existing diseases. Keycomponents of disease prevention include the reliable detection of disease carriers,knowledge of how pathogens are transmitted, development of effective methods to limit theentry of pathogens or carriers into clean baitfish cultural facilities, and the capacityto provide environmental conditions conducive to good fish health.

Flow Rates Control FungalInfections Of Rainbow Trout Eggs

By: Jeff Rach, Jennifer Marks and Verdel Dawson, National Fisheries ResearchCenter, La Crosse, WI 54602

Hatchery personnel have used many chemicals to control disease outbreaks on fish eggs.The number of chemicals presently permitted for use with eggs has dwindled to three:hydrogen peroxide, salt, and formalin. Chemical treatments can be expensive to apply andtoxic to sensitive fish species.

Elevated flow rates to roll eggs in hatching-jar systems seems to reduce the incidence offungal infections. Green eggs can be highly sensitive, however, and vigorous rolling mayinduce death. We tested various flow rates for controlling fungal infections and improvingegg survival in a hatching jar system by using both uninfected rainbow trout egg's andeggs artificially infected with fungus (Saprolegnia parasitica).

EGG HATCHING JARS WERE USED To EVALUATE TREATMENTS

Green eggs were obtained from Trout Lodge (Sumner, Washington) and shipped to the NationalFisheries Research Center, La Crosse, Wisconsin. Eggs were received within 36 h ofspawning, acclimated to 12 1C, and 30 ml (about 300 eggs) of eggs were transferred intoeach miniature egg hatching jar (5 cm in diameter; 15 cm long).

The egg hatching system was composed of a headbox, miniature egg hatching jars, and glassaquaria.

Continuously flowing well water at 12 1C entered the headbox and flowed by gravityto the egg jars. The effluent from the egg jars then flowed into glass aquaria thatcollected hatched fry from the jars.

Two separate trials were conducted. Uninfected eggs (trial 1) were compared with eggsartificially infected (inoculated) with fungus (trial 2) in tests that exposed eggs tovariable flow rates of 300, 600, 1,200, and 1,800 ml/min. Each flow rate was tested intriplicate. Comparisons (P < 0.05) of percent hatch at different flowrates weremade by analysis of variance.

ROLLING OF EGGS INHIBITED FUNGUS

The four flow rates were selected to achieve a range of egg movement. Eggs cultured in the300-ml/minute flow showed no movement, whereas eggs in the 600-ml/minute flow displayedslight movement but did not roll. Eggs in the 1,200-ml,/minute flow were raised in thewater column and exhibited a slight to moderate rolling action. Eggs in the1,800-ml/minute flow were elevated higher in the water column and rolled vigorously.

In trial 1, the egg hatching success in the three lower flows (300, 600, and 1,200ml/minute) were not significantly different and average hatches were 85.4, 83.1, and82.2%. Because the incidence of naturally occurring fungus is generally low in eggscultured in the Center's well water supply, fungal infections did not develop at any ofthe flow rates. However, only 20.2% of the eggs hatched at the 1,800-ml/minute flow,presumably because of the excess agitation.

The procedure used to infect eggs with fungus (trial 2) resulted in the infection of eggsat the 300 and 600-ml,/minute flows and the hatch rates in these flows were less than 10%.At the 1,800-ml/minute flow rate, the hatch rate was only 25%. Although most of the eggsat this flow were dead within the first week of testing, there was no observed fungalinfection. The 1,200-ml,/minute flow was the optimum flow with a mean hatch rate of 78%,which was significantly (P < 0.05) higher than the hatch rates at theother flows. This flow was high enough to control the fungus without causing death ofeggs.

MANAGEMENT IMPLICATIONS

... The rolling of fish eggs is useful in controlling fungus on eggs. Itseffectiveness for hatchery use is dependent on the ability of culturists to observe eggmovement and adjust flows to generate the appropriate movement of the eggs.
Physical manipulation of eggs does not eliminate the need for chemical treatments. Raisingsalmonids in stacks of Heath incubators requires chemical treatments for fungal control.Hatcheries that use surface water for culturing eggs usually have a higher incidence offungal infestations. Eggs being shipped between hatcheries are vulnerable to stress andrapidly spreading fungal infections. A combination of chemical treatment and physicalmanipulation would probably be needed in most hatcheries.

Hatchery Tip

By: MTAN

The MTAN and the Bureau of Indian Affairs (Minneapolis Area Office) have beensuccessful in scheduling a one day workshop regarding "Rearing Fish At HighDensities In Water Reuse Systems". This workshop will be held during theSeptember 19-21 meeting of the Native American Fish and Wildlife Society. The fee for thiscourse will be paid by the Minneapolis Area Office. The workshop will be given by GeneHanson who began investigating in aquaculture in 1984. Intrigued by its potential, hecontinued he's research which lead him in the development of Aurora-Aqua Inc.. Since thenhe has developed several commercial water reuse systems. Currently Mr. Hanson is Presidentof Aurora-Aqua, Vice President and newsletter editor of the Minnesota AquacultureAssociation and an active member of the Minnesota Aquaculture Commission.

Keep that water cool! The MTAN recently heard of a South Dakota hatchery that lost 400,000walleye fingerlings while in transport to the release site. The heat and stress of themove were assumed to cause the death of the fish. South Dakota officials said the incidentmay cause the hatchery division to review fingerling transportation procedures. Thedepartment's fish transport vehicles are equipped with aerators and oxygen for the fish,but that may not be enough. They're now considering air and water temperatures morecarefully and may decide to wait for cool weather or transport the fish during coolertimes of the day. They may also consider adding ice to the water to reduce the heat stresson the fish.

Greg Fischer (Red Cliff Tribal hatchery biologist) recently received several fiberglassrearing tanks from the Hyperdyne Corporation, which is located in Bemidji, MN.According to Greg he is very pleased with the new tanks. He said they were strong andstill priced very competitively. If you're in the market for rearing tanks, you may wantto contact Greg or Paul Shough of Hyperdyne (218-751-9310) for more information.

The MTAN reviewed a video from Aurora-Aqua that very nicely describes the applicationof water reuse systems. If you would like to view this tape please call Frank Stone at theAshland FRO (715-682-6185).

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