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Ashland NFWCO
 Midwest Region
 **** Dedicated To The Tribal Aquaculture Program December 1995 - Volume 14
  **Administrative        Coordinator:**        **Frank G. Stone        (715-682-6185) Ext.12        U.S. Fish and Wildlife Service****Email:        [email protected]**      **Edited        By:**        **Elizabeth W. Greiff        (715-349-2195)        St. Croix Tribal Nat. Res. Depart.****Email:****[email protected]**
  Topics Of Interest: Baitfish Production Part 2 Using Light to Harvest Fingerlings Fish Health Managementfor Intensive Fish Farming Fish Health Note Walleye Production -Using Pond Liners Hatchery Tip  **Baitfish Production****Part 2** **... The following material is based upon work supported by the CooperativeState Research Service and Extension Service, U.S. Department of Agriculture, underSpecial Project No. 87-EXCA-3-0836.** VIRAL DISEASES The only important viral disease of baitfish infects golden shiners.The golden shiner virus causes gradual mortalities over several months. **Theseverity, frequency and duration of disease outbreaks can be reduced by controlling fishstress.** A few dead or dying fish may appear each day. Hemorrhaging of theunderside, back, eye, and head of the fish are signs of this disease. The virus usuallyoccurs in the fall when fish reach 2 inches in length. Because of the low mortalityassociated with the disease and the lack of an effective control, the disease is usuallyallowed to run its course. Pond management including the isolation of infected stock andpond disinfection may help control the spread of the virus. **WATER QUALITY** Feeding and fertilizing enrich the waterto produce more fish. At the same time, wasted feed and fish wastes encouragephytoplankton blooms. Phytoplankton and bacteria may use the oxygen that could beavailable to support fish. Ammonia, nitrite and carbon dioxide also may accumulate and attimes cause stress or mortality in fish. The use of oxygen meters and chemical test kitscan remove a great deal of the risks associated with water quality deterioration. Carefuland routine monitoring of water quality allows the producer to respond to a potentialproblem with prevention before losses occur. This often involves using aeration orflushing with fresh water. Water quality is also important in the holding building. A commonproblem is iron. At 0.5 ppm, iron begins to coat the gills of fish causing impairedrespiration. Sand filters may be used with aeration to remove iron from incoming wellwater. Less common problems are the presence of hydrogen sulfide or ammonia in well water.Hydrogen sulfide leaves the water as a gas after aeration. **PREDATOR CONTROL** Sharing the profits of baitfishproduction with fish predators is not the desire of any producer. A predator problem leftunchecked can cause serious losses. Predators may include mammals, birds, reptiles,carnivorous fishes, insects and copepods. Using filtered or well water is the first stepin predator control. Filters reduce the introduction of predatory fishes. Mowing grass andweeds along the pond bank will discourage many shoreline predators. Well maintained leveeslopes which fill quickly to a depth of two feet or more discourage wading birds. **WEED CONTROL** Pond management for fish cultureencourages the growth of weeds by increasing the fertility of pond water and soils.Construction of ponds with water levels greater than 2 feet deep makes control easier.However, some weeds inevitably start to grow. Seining baitfish is severely impaired by thepresence of weeds. Rolling fragile minnows with weeds in a seine usually results in theloss of fish. Weed control can be accomplished mechanically, chemically or biologically.Mechanical control of weeds is limited to a few options. Periodic drying or pond drawdowncan be effective on partial infestations of shallow water weeds. Pulling or raking weedscan help control shoreline weeds if started early enough. The most widespread method ofweed control is use of approved algicides and herbicides. Several broad spectrum chemicalsare available for control of most water weeds. Before using any chemical, be sure thechemical is cleared for aquatic use, is effective against the weed species present, is nottoxic to the fish present and is as economical as other available methods. Biologicalcontrol of weeds is usually accomplished by weed eating fish. However, some insects havebeen used to control weeds such as water hyacinths and alligator weed. **Todetermine the species to be marketed and number of fish that can be sold, invest time intoresearching available market options.** **MARKETING** Selling baitfish to sports fishermen can beas simple as setting up a roadside bait house or as complicated as a system of wholesaledistributors, jobbers and dealers. It is important to determine a production level that ismatched to the market demand whether retail or wholesale. Sufficient time spent onmarketing before production begins increases the chance of financial success. Rememberthat organized marketing in the baitfish industry is designed to discourage the entry ofnew producers. A new producer must find his own niche in the market or face stiffcompetition from existing growers. **OPTIONS** **Live-hauling** Live shipment of fish requirestrucks equipped with water tanks and aeration, or contracting with live-haulers who havethis equipment. Live-haulers can be hired to deliver fish to buyers or they can be buyersthemselves. In most cases, the live-hauler is also the distributor or jobber. Bycontracting with several live-haulers, the producer can sell large quantities of fish. Thelive-hauling distributor sells to retail outlets and assumes risks associated with fishtransportation and customer credit. Live-hauling trucks vary in design and holdingcapacities; however, most live-haulers transport between 3,000 and 6,000 pounds of livefish. Larger farm acreages are needed to supply live hauling distributors consistently. Afarm size of about 100 water acres is considered large enough to supply regional ornational distributors. **On-farm sales can also be combined with fee fishingoperations.** **On-Farm Direct Sales** Small fish farmers cansell baitfish directly to fishermen. The location of the farm in the proximity of adeveloped sport fishery is essential. A fish-holding facility is required to have fishreadily available for customers. Ponds of 1 acre or less are used for growing a singlespecies like fathead minnows or golden shiners. Fathead minnows can be raised withcatfish. Small farmers often receive retail prices for their fish and sell ungraded lotsof fish. Ungraded fathead minnows are usually sold on the farm as crappie bait. **Local Retail Sales** Establishing retail outletsor selling to other local retailers may allow the small farmer to increase sales volume. **Locationsremote from metropolitan areas or those not already serviced by distributors may providebetter markets for small producers.** The species of fish produced should reflect demand for bait in thelocal area. One problem faced by retailing baitfish is competition from largerdistributors. If sales volume increases, competitors may take notice and competitivelyenter your newly developed market. Good customer service and high quality fish help anysmall producer retain established sales. The baitfish retailer may also want to providecustomers with worms, crickets and other fishing supplies. Snacks, drinks and some groceryitems may help attract customers to the bait outlet. **Marketing Strategies** Matching the harvest ofbaitfish from ponds with the market demand requires careful planning. Stocking rates,stocking times, and feeding schedules influence the size and number of fish available forsale. The producer must develop a strategy to deliver the desired sizes and species ofbaitfishes required by the market. The heavier a pond is stocked, the slower fish willgrow. Golden shiners stocked in excess of 200,000 fry per acre in June will not be largeenough to sell as 3 inch crappie bait in March of the following year. Whereas, stockingat 100,000-150,000 per acre will produce fish exceeding 3 inches the following spring.To produce larger golden shiners, stock at 50,000 fish per acre. Graded fish are separatedat the farm prior to sale. Three grades of fathead minnows and four for golden shiners arecommonly marketed. Goldfish 1-2 inches long are usually sold in the feeder fish market. Spring and summer are seasons of highest baitfish demand. Regional andseasonal differences can be overcome by marketing nationally. Weather conditions can causesudden peaks and declines in demand. Goldfish are sold to feeder fish markets throughoutthe year. However, this market is very restricted. Recent growth in the market has beenthe result of striped bass and hybrid bass production. Some baitfish have a very regionalmarket. The white sucker is used by fishermen in the Midwest and New England states. **Marketing for Different Production Systems**Production systems for baitfish vary in size and intensity of management. Marketing is themost important factor in the success and growth of baitfish farming operations. Producerswith small markets, limited time to develop new markets or part-time commitments shouldconsider less intensive, smaller, production systems. Large farms of hundreds or thousands of acres usually produce severalspecies of baitfishes. Golden shiners, fathead minnows and goldfish are grown in pondscontaining only one species of fish (monoculture). Broodfish are spawned, eggs arehatched, and young are grown to market size on the same farm. White sucker producers oftencollect small fish from the wild. Holding tanks equipped with aerators and graders areconstructed in a building. Baitfish are sold to wholesalers from these tanks. Few of thelarger farmers sell to retail customers. National markets are serviced by large farmingoperations. Smaller farms serve smaller market areas. Wholesale and retail sales are mixedand fewer species are grown. Fish are usually grown in monoculture and the species isdetermined by local market demand. One adaptation of the small farm system is thepolyculture of fathead minnows and catfish. While using the minnows as forage for catfish,the producer sells some minnows as bait. The cost of development depends on the size and type of productionfacility. Major investment items include the purchase price of land, pond construction,holding tanks and equipment. Other expenses are for brood fish, mats or boards forspawning, fish feed, fertilizer, utilities, seines, other harvesting items. Most of theexpense involves lifting water from a well and distributing it through supply pipes.Several ponds are often constructed near a well to reduce plumbing costs. Canals are oftenused as an alternative to pipes. Water can be aerated in canals to precipitate out iron.However, canals take up acreage that could be used for fish culture. They are usuallypopulated with undesirable wild fishes or predators. **Production Costs** Two practices, spawning withmats and feeding, increase the cost of operation considerably. In contrast, wild spawningon grasses or fertilization alone costs less, but production would be 300 to 400 poundsper acre rather than 800 to 1,000 pounds per acre. As bait production intensifies,aeration is required to prevent oxygen depletion and fish kills. Aeration requiresadditional equipment and labor. **Using Light toHarvest Fingerlings from Ponds and Train Them to Accept Formulated Feed** **By: J.A. Held and J.A. Malison, University of Wisconsin-Madison Aquaculture,Program 302 So. Main Street, Lake Mills, WI 53551,**414-648-2902 The use of lights for concentrating and leading fish into nets is animportant tool in the commercial fishing industry. Similarly, sport anglers use lights toattract panfish when fishing in the evening. Over the past 15 years, we have developed andput into practice several methods of using light for both harvesting ponds and habituatingpond-reared fingerlings to formulated feed. Many species of fish including yellow perch and walleye exhibit aphototactic response, that is, they are attracted to or repelled by light. The directionand intensity of this response in percids is related to their size. Yellow perchfingerlings are strongly attracted to light from hatch until they reach about 1 inches,at which time they generally become photoneutral. Walleye are photopositive untilapproximately 2 inches, after which they gradually become photonegative. **HARVESTING FINGERLINGS FROM PONDS USING LIGHTS** In our early studies on the pond production of yellow perch fingerlingswe quickly found that one way to maximize the number of fingerlings produced in ponds wasto harvest the fish at the smallest possible size. For producing feed-trained fingerlings,pond harvest can be conducted as soon as fingerlings are large enough to accept formulatedfeeds. In perch this occurs when the fingerlings reach about  inch. Because fingerlingsthis small are quite delicate, however, commonly practiced methods of pond harvest such aspond draw-down, fyke nets, or seines usually cause a high number of injuries andmortalities. To overcome this problem we use the strong phototactic response of thesefingerlings to concentrate and lead them into capture nets. We have tested severalsystems, each consisting of a string of lights to attract the fingerlings and a net forcapture.  One system consists of a series of 4 independently wired 75w, 12v bulbsencased in waterproof jars and attached to floats so that each light is suspended justunder the surface of the water. The lamps are spaced approximately 15 ft apart andrheostats are used to control the brightness of each lamp. Fish are initially attracted byilluminating the entire light string, and are then lured into the vicinity of the net bysequentially extinguishing all but one light (beginning with the light furthest from thenet). Several types of nets have been tested for fingerling capture. Onemethod (not shown) uses a lift net which measures 6 ft x 12 ft x 6 in deep and is securedto a floating tubular frame. The frame and net are held on the bottom of the pond by polesor weights (see Manci et al. 1983). Once fingerlings are attracted by light to the areaabove the net, it is simply raised until the sides are a few inches above water level,thereby forming a floating corral. Fry can then be easily dip-netted from this corral. Asecond method also uses a sequentially extinguished light string, but in this system thefingerlings are lead into a floating box net similar to that shown in the above figure.The net (8 ft x 8 ft x 4 ft deep) is suspended from a floating collar so that all sidesexcept one remain above the water line. One side of the box is left open until the fishenter the net. Then, using draw strings, the open side of the box is raised. As with thefirst system, fingerlings can then be gently removed with a dip net. Using either of these systems, typically about 10,000-50,000 perchfingerlings can be captured in one set of the net. The box net, however, has the followingadvantages over the lift net: 1) the box net can be operated by a single person as opposedto the two people needed for the lift net; 2) the box net can be fished from shore,whereas the lift net is operated from a "C" shaped raft anchored in the middleof the pond; 3) most of the "captured" fish will remain in the box net even ifthe gate is left open, and therefore several sequences of lights can be run before the boxis closed and emptied; 4) fingerlings can be left in the box net overnight and collectedthe following morning. Both the lift net and the box net are very low stress methods ofharvesting fingerlings, and the fish are virtually unaware that they are corralled untilthey are dip-netted from the capture nets. Obviously, using light to harvest ponds is a nighttime operation. Ourobservations suggest that fish activity may be highest between 9:00 pm and midnight.Typically, we find that 50-80% of the fish can be harvested from  to 1 acre ponds inone or two nights of light-trapping. Factors that affect the success of light harvestinginclude water clarity and pond vegetation. In a manner similar to that described here,lights can also be used in combination with dip nets, seines or lift nets to collect smallsamples of fish from ponds. **One of the most important assets of these systems isthe low degree of stress to which the fish are subjected, which in our experience clearlyresults in improved post-harvest survival.** **USING LIGHTS TO IMPROVE FEED-TRAINING IN TANKS** Once fingerlings are harvested from ponds they can be trained to acceptformulated feeds, a process often conducted in tanks or raceways. Nagel (1985) found thatunderwater lights could be used to concentrate walleye fingerlings in the area of the tankdirectly underneath automatic feeders. We found the same to be true for perch. Using thistechnique, fingerlings are frequently exposed to food as it drops into the tank. In contrast, fingerlings in tanks illuminated by overhead lighting areusually dispersed throughout the tank, and observe food less often. We also noticed thatperch fingerlings in tanks with underwater lights are much less disturbed by routinehusbandry and maintenance activities such as feeding and tank cleaning. Additionally, wehave observed that shadows and movements in the vicinity of tanks illuminated withoverhead lights frequently alarm the fingerlings and trigger excited swimming behavior. **Overall,the use of internal tank lighting can improve feed-training success by as much as 25%.** **FEED-TRAINING FINGERLINGS IN PONDS USING LIGHTS** Our most recent application of light has been to feed-train yellowperch fingerlings while they remain in production ponds. Instead of harvesting andtraining fingerlings in tanks, we have found that lights can be used to attract andconcentrate young perch to feeding stations that are dispersed across fingerlingproduction ponds. For initial tests each station has been comprised of a submerged lightlocated adjacent to a vibrating feeder. Approximately 2 weeks afterstocking (when fingerlings reach  inch), pond lights are switched on at night toconcentrate fish under the feeders. The feeders are activated by timers to broadcast foodfor about twenty, one-second pulses per hour throughout the night. Response to the lightsis immediate. The highly photopositive fingerlings swarm around the light, occasionallychasing and striking at zooplankton that are also attracted to the illumination.Initially, fish are disturbed by the vibration of the feeder, and for the most part ignorethe feed as it drops through the water column. Within a week to ten days, however,increasing numbers of fingerlings are attracted to the feeders, and they actively pursuethe feed as it is broadcast onto the water. At this time we begin to extend the feedingperiods into the daylight hours. For the rest of the training period feeders are activefor 20 min out of every hour throughout the day and night. The fish remain in the pondsfor 46 weeks, or until pond conditions (e.g., elevated water temperature, depresseddissolved oxygen levels) require removal of the fingerlings. Our trials of this system to date have yielded very promising results.Pond harvests have averaged 150,000 feed-trained perch fingerlings/acre. The harvestedfingerlings ranged in size from 1-2 inches, and have had high condition factors,indicating that they were well fed. Subsequent tests in tanks have shown that virtually100% of the fingerlings harvested were successfully trained in the pond. Areas of further investigation that we are currently conducting includetesting these light harvesting and feed-training techniques with other cool water speciessuch as walleye and hybrid striped bass. Additionally, studies are currently underway todefine optimum fry stocking densities for in-pond training of yellow perch. **FishHealth Management for** **Intensive Fish Farming** **By: George W. Klontz, M.S., D.V.M., Retained Aquaculture Specialist, Nelsonand Sons, Inc., 1908 East E. Street, Moscow, Idaho 83843-9504, 208-882-2617** **INTRODUCTION** During the past three decades, the raising of fish for humanconsumption has been increasing dramatically, especially in the sociologically andindustrially developed countries of North America and Europe. The increased production hascome about largely as a result of consumer awareness that fish and shellfish arenutritionally beneficial to health. Unfortunately, the production increase in somecountries has been so great that the supply of propagated food fish has exceeded thedemand in the marketplace. Attendant to the increased production of food fish under intensiveculture conditions has been the increased loss of production potential through infectiousand noninfectious disease processes. In many cases the episodes have been so severe that45-55% of the numbers of fish at the beginning of the rearing process have died beforethey became ready for market. However, the loss of production potential has not beenreflected as dead fish only. Perhaps the greatest impact has been reduced vitality whichhas been recorded as reduced growth rate and increased feed conversion. The costs incurredfrom this have been, in the opinions of many, quite significant. The economics of food fish production have not been documented withprecision and perhaps there is no way to do so because of the diversity of the food fishraising community. However, data suggest quite convincingly that the greatest portion ofthe costs in producing a pound of fish under intensive culture systems is feed. Thus, itwould seem quite logical to assume that to pay considerable attention to that componentwould - or could - reduce loss of production potential. For example, weight gain in agroup of fish at a feed conversion of 1.9 kg feed per kg gain is 26.6% more expensive interms of feed costs than is the same group of fish at a feed conversion of 1.5 kg feed perkg gain. In this regard, it is beyond the comprehension of many that several fish farmersare apparently content with a 1.9:1 feed conversion when the commercially available dietsall can yield a 1.3:1 conversion with very little effort. Two of the prime factors in reduced feed conversion are subclinicalrespiratory (gill) diseases and asymptomatic infections of bacteria and viruses. Thepoultry and livestock (sheep, cattle, and swine) industries have learned that herd healthmanagement through application of the principles of preventive medicine is economicallysound. In other words, these industries start with healthy animals and strive to keep themin that state through monitoring growth rates, behavior, production (milk, eggs, etc.),and environmental conditions. This could be termed preventive medicine. **In thisregard, perhaps the most significant impediment to reducing the mortality rate and toincreasing the feed conversion is due to having more concern for disease rather thanhealth.** The foregoing is not a new concept or revelation to the majority ofpeople in the aquaculture community. All have attempted at one time or another, in somefashion, to implement these ideas. But the enormity of the task is often mind-boggling foran individual person. The adopting of the term "fish health" as opposed to"fish disease" in our professional jargon has helped a great deal. Then whereinlies the problem? The term "health" as it applies to an individual or apopulation of fish, either free-living or confined, should denote that the animal is ableto conduct all its physiological activities without impediments. Its oxygen demand is met,its nutritional energy demand is met, its reproductive capacity is realized, itsbehavioral needs are met, and so forth; i.e., it is "normal" (a term I despisebut use too frequently). It is my opinion that when any one of the physiological functionsof a fish are comprised for whatever reasons extrinsic or intrinsic - a state of diseaseensues. This disease state may be subclinical; i.e., not noticed by the observer, or itmay be clinical; i.e., quite apparent to the observer. **EXTRINSIC FACTORS AFFECTING FISH HEALTH** The extrinsic or environmental factors which are known to compromisethe health status of fish individually or collectively can be grouped into the followingcategories according to their location within the system: (1) water-associated; (2)pond-associated; (3) nutrition-associated; (4) management-associated. To some, thisclassification scheme may seem somewhat simplistic and/or conceptual. Nonetheless, theprocess of investigating the nature of a disease episode has been enhanced by identifyingand quantifying the associated factors. The quantitative evaluation of the prime factorshas permitted the raising of fish with a minimum of problems. **I think the problemof our collective inabilities to do much more than "put out the brush fires"stems from the absence of a good or adequate base of knowledge of health and its changeinto subclinical and then clinical disease.** **Water-associated factors**: Among water-relatedfactors identified as affecting the productivity of aquaculture systems, water temperatureand dissolved oxygen content have the most significant insidious effects on fish health.They are inherent in all water supplies and are subject to fluctuations to which the fishin the system must adapt. The physiological effects of the fluctuations are very broad,ranging from a change in metabolic rate to altering the susceptibility to pathogens. In this regard, the documentation of environmental changes and theoccurrences of infectious and noninfectious disease processes could be an invaluable aidin predicting the likelihood of a subsequent disease episode. Examples of this are legionbut not sufficient to be a widespread practice. **Pond-associated factors**: The primary effecthere is requiring a particular fish to live in a pond configuration which does not meetits behavioral requirements. **Our studies over the past 4-5 years on productionforecasting have shown the health of fish can be compromised when the fish are fed at arate permitting less than 80% of the "Allowable Growth Rate".** **Nutrition-associated factors**: One would thinkthat in this day and age of high quality commercial diets, nutritional problems would notoccur, but they do, all too frequently. We have found growth rate to be a very reliableindicator of the health of the population. Deviations of as little as 1% from the expectedgrowth rate can be measured quite accurately and evaluated with a high degree ofstatistical validity. Overfeeding a population is another health-compromising situation. Inthis case there are frequently abnormal amounts of abdominal fat and hepatic glycogendeposits. The effects are not often seen immediately, but can be implicated in the milieuof casual factors of an unhealthy state. **Management-associated factors**: The primaryhealth-threatening factors in this category emanate from exceeding one or more of the pondcarrying capacities; from inadequate housekeeping practices to inadequate record-keepingand undue physical stressors. **INTRINSIC FACTORS AFFECTING FISH HEALTH** The intrinsic or somatic factors originate within the fish itself. Theyare largely governed by the genetic make-up which by and large dictates the physiologicaland psychological responses of the fish to the extrinsic factors. Perhaps the major intrinsic factor which fish health managers have somecontrol over is the generation of endogenous ammonia (NH4+). We allknow that free ammonia (NH3) in the system is deleterious to the health of fishwhen specified limits are exceeded. The main impact, as we now understand it, is on thegill lamellae in the form of epithelial hypertrophy and hyperplasia which reduce theoxygen uptake by the fish, thus impacting the physiological well-being of the fish. Thecontrol of this process is to reduce: The dietary protein.  Decrease the retention time of ammonia in the pond by increasing the    water flow.  Reduce the population of fish in the pond.  Reduce the water temperature.  Decrease the pH of the system.  Any one of the foregoing will serve to preserve the health of fish,    within limits. A second intrinsic factor over which we can exercise some control isthe healthy or chronic asymptomatic carrier of infectious agents. It is apparent from ourstudies with Renibacteriumsalmoninarum and Aeromonas salmonicidacarriers that the presence of these bacteria within the fish negatively impact theirgrowth potential and represent a measurable threat to the uninfected portion of thepopulation. **SUMMARY AND CONCLUSIONS** Up to this point, this presentation has been rather gloomy, in myopinion. But, we must face reality - we could do better with preserving the health of ourfish if we only would. To that end, I would offer the following as food for thought, and,hopefully, subsequent action by both the fish farming community and the fish healthmanagement profession, collectively. Practice preventive medicine through detection and elimination of thecarrier states of bacterial and viral pathogens, through mass immunization of fish againstpathogens, through implementation and maintenance of health-preserving managementpractices, and through implementation and enforcement of live fish transportationregulations. Apply the principles of epidemiology to investigations of disease    occurrences.  Maintain open lines of communication among all facets of the aquaculture    community.  Encourage the provision of continuing education opportunities.  Encourage increased applied research in fish health management. **A Fish Health Note** **By: Terrence Ott, La Crosse Fish Health Center, La Crosse, WI 54650,608-783-8444** Did you know that many of the bacteria and parasites which are capableof causing serious diseases of fish are normal inhabitants of the aquatic environment?Control of these water born fish pathogens in hatchery environments can be achieved bestby a program of good management. A fish disease cannot occur unless a pathogen isintroduced into the fish cultural system. Therefore it is very important to culture fishin a quality environment, with good nutrition and a minimum of stress. Fish health professionals have recognized at least six general methodsof disease control in fishes. Some are used extensively in pond culture and for limiteddisease control in wild fish populations. Some methods are used effectively, while othersare less effective but offer alternative procedures when others fail or cannot be used.Six of the most used methods are: Test and slaughter.  Quarantine and restriction of movement.  Drug therapy and sanitation.  Immunization and disease resistance.  Destruction or reduction of a link in the transmission cycle.  Limitation or control of the release of toxic substances. **... The most important preventive method in controlling fishpathogens at your hatchery is the destruction or reduction of a link in the transmissioncycle or as I like to call it, "containment". Containment plays a very importantpart in good management practices at your facility by not allowing the transfer ofdiseased fish or contaminated fishing gear (boats, gill nets, boots, etc.) into areaswhere fish are being cultured or the disease does not already exist.** The reasons for containment control are to prevent costly losses inhatchery production, to prevent transmission of diseases among hatchery ponds whenboats and gill nets are brought onto hatchery grounds, and to prevent the spread ofdisease to wild stocks of fish when hatchery products are stocked out. If a hatchery has been inspected or decontaminated and ispathogen-free, recontamination must be prevented. The movement of any live feral fish,gill nets, and boats into hatchery grounds should be forbidden. The spread of a deadlyfish pathogen can be prevented only by rigid cleanliness. All shipped-in equipment shouldbe decontaminated thoroughly before it is placed in contact with clean hatchery equipmentand the water supply to your fish. **Walleye Fingerling Production inPlastic Lined Ponds** **by: Larry J. Wawronowicz, Tribal Natural Resource Director, Lac du FlambeauBand of Lake Superior Chippewa Indians** In the fall of 1993, The Lac du Flambeau Tribal Natural ResourceDepartment installed plastic liners in six- acre earthen fish culture ponds (MTAN,Volume 6, December 1993). These ponds have been in production for two seasons. The purposeof this article is to discuss the reasons why we decided to line the ponds, describe theproduction techniques we used to produce 1-2 inch walleye fingerlings in plastic linedponds, and to discuss plastic lined ponds' production results. The Lac du Flambeau Indian Reservation was blessed with a lot ofsurface water, ground water and sandy soils but with very little and poor clay soils.Originally, the six ponds were lined with clay but over time the clay liners failed andseepage became a major problem. Depending on the pond, 10 to 12 inches of water would belost over a 24 hour period. The seepage problem increased pumping costs and the amount offertilizer needed to maintain desirable zooplankton populations. The water levelfluctuations also enhanced filamentous algae growth, because pond depth could not bemaintained at 4.5 feet. Ultimately, fish production decreased. Since clay is a rareresource on the reservation and trucking costs are very expensive, plastic liners became amore desirable alternative. Subsequently, 6 plastic lined ponds have been in productionfor two seasons using the following fertilization and production techniques. Many different fertilization programs were tried before it wasdetermined that organic fertilization was the best alternative. Alfalfa meal and Torulasyeast, a yeast used in the paper industry, is applied at an average rate of 1,175 lb/acreand 118 lb/acre, respectively. The amount of fertilizer used largely depends on pondfertility, weather conditions, number and size of the fish, and the quality and quantityof the zooplankton population. **Generally, the fertilization program begins byapplying approximately  the total amount of fertilizer required when the pond is filled.Subsequent applications are weekly and approximately of the total is applied each time.** The ponds are partially filled approximately 4 weeks before walleye fryare stocked. Initially, the ponds are fertilized and filled to approximately the pondvolume. This allows the water to warm faster which speeds up the establishment of azooplankton population. Surface water from Pokegama Lake is used to fill the ponds; thisis the same water used to hatch the walleye eggs. This is beneficial in two ways. First,the walleye are reared in the same water they were hatched and second, we are able toobserve the zooplankton in the unfiltered hatchery water. When the zooplankton are observed, water from Pokegama Lake is againpumped to the ponds to capitalize on the lake-produced plankton. An additional of the pondis****filled when we first see the plankton in the hatchery water and thefinal is added when the walleye eggs start to hatch. Alfalfa meal is broadcasted evenlyaround the pond by using a scoop made from a one gallon milk container. Because Torulasyeast is a very fine powdery substance, it is applied by mixing it in 50 gallons of waterand distributed evenly around the pond. **It is important the fertilizer is evenlydistributed. If there are clumps (of fertilizer), it has been our experience they becomestarting sites for unwanted algae.** Throughout the 40-day walleye fingerling production season, thezooplankton populations, oxygen, pH, temperature, weather and fingerlings (1-2 inches)are monitored. Standard fish culture sampling techniques are used to assure all parametersare conducive to good production. All fish are harvested and transported to reservationlakes. In 1994 and 1995, **303,085**(101,028 fish/acre) and **306,201**(102,067 fish/acre) walleye fingerlings were produced, respectively. Based on twoproduction years using plastic lined ponds, a 2-inch fish was raised in 40 days; anapproximate growth rate of 0.05 in/day. The walleye ranged between 417-450 fish per poundwith annual pond survival rates ranging from 45-75%. **Hatchery Tip** **By: MTAN** **AQUACULTURE PRODUCTS INFORMATION UPDATE** Sweeney Enterprises (321 Waring Welfare Rd, Boerne, TX, 78006-7927) hasintroduced a new wildlife/fish feeder, the Little John. This scatter type feeder isconstructed of heavy duty polyethylene that resembles a log. The device can hold up to 100pounds of food and is controlled by a digital timer which can be set to feed up to eighttimes a day. The unit sells for $120.00 and comes with a three year warranty. If you wouldlike additional information you can reach a Sweeney representative at 1-800-443-4244. Royce Instrument Corp. (1332 Washington Ave, San Jacinto, CA, 92583)has a broad selection of monitoring and control instrumentation for Aquaculture programs.These items include state of the art technology like microprocessor-based self-diagnosingelectronics, one-button or automatic calibration, digital output communications,programmable set points and solid state relays and component housings constructed fromspace-age composite materials. Some of the monitoring systems made by Royce include:Dissolved oxygen analyzers and sensors, pond monitoring and aeration control, totalsuspended solids, pH-alkalinity-carbon dioxide, computer data collection and signalconversion module. If you would like additional information you can reach a Roycerepresentative at 909-652-2612. Reiff Manufacturing (Rt 4-183, City-County Airport, Walla Walla, WA,99362) has a wide selection of fiberglass fish hatchery rearing and distribution tanks.Over 200 molds ranging from a few square inches to over 40 feet long are available. Theengineering staff can also manufacture specialized tank systems. Reiff can also make tanksto mount on your truck or trailer and can build a trailer to go with transport tanks. Ifyou would like additional information you can reach a Reiff representative at1-800-835-1081. If you're planning a big project requiring plastic pipes, valves, pipefittings, cement sealers and flexible hose, you may want to call Industrial ThermoplasticSolutions (P.O. Box 5029, Evansville, IN, 47716). They also offer engineering andtechnical data assistance. If you would like additional information you can reach a ITSrepresentative at 1-800-262-4331). Another "must have" book is the "Aquaculture EngineeringDesign and Specialized Equipment catalog from Keeton Industries (300 Lincoln Court, SuiteH, Ft. Collins, CO 80524. You may know this company from their previous name KeetonFisheries. These folks have put together an all you could want catalog for aquaculturerelated products. From A-Z some of these items include: Aeration, biofilters, chemicaladditives, diffusers, feeders, heaters, liners, pipe fittings, pumps, tanks, and zeolite.If you would like additional information you can reach a Keeton representative at970-493-4831. **KEEP THOSE FRY TANKS CLEAN** The MTAN recently visited a trout hatchery in Idaho and observed a veryinteresting tool for keeping fry tanks clean of fecal material. The hatchery manager hadconnected a section of  inch PVC pipe to the inlet pipe and had it positioned along thecenter of the tank bottom (see diagram). Several small holes ( inch) were drilled in the two sides of the pipeon a 45 angle to the tank bottom. Water flow from the pipe prevented fecal material fromsettling to the bottom of the tank by keeping it in suspension until it could be moved tothe end of the tank for easier cleaning. **The MTAN would like to wish you a Merry Christmas and a veryHappy New Year. We sincerely hope your chosen direction is clear and your path tohappiness is but a foot step away.** Product and company names mentioned in this publication are for informational      purposes only. It does not imply endorsement by the MTAN or the U.S. Government.
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