Dedicated To The Tribal Aquaculture Program

 

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Topics Of Interest:

Baitfish Production Part 2

Using Light to Harvest Fingerlings

Fish Health Management for Intensive Fish Farming

Fish Health Note

Walleye Production -Using Pond Liners

Hatchery Tip

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Baitfish Production Part 2

... The following material is based upon work supported by the Cooperative State Research Service and Extension Service, U.S. Department of Agriculture, under Special 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. The severity, frequency and duration of disease outbreaks can be reduced by controlling fish stress.

A few dead or dying fish may appear each day. Hemorrhaging of the underside, back, eye, and head of the fish are signs of this disease. The virus usually occurs in the fall when fish reach 2 inches in length. Because of the low mortality associated with the disease and the lack of an effective control, the disease is usually allowed to run its course. Pond management including the isolation of infected stock and pond disinfection may help control the spread of the virus.

WATER QUALITY Feeding and fertilizing enrich the water to produce more fish. At the same time, wasted feed and fish wastes encourage phytoplankton blooms. Phytoplankton and bacteria may use the oxygen that could be available to support fish. Ammonia, nitrite and carbon dioxide also may accumulate and at times cause stress or mortality in fish. The use of oxygen meters and chemical test kits can remove a great deal of the risks associated with water quality deterioration. Careful and routine monitoring of water quality allows the producer to respond to a potential problem with prevention before losses occur. This often involves using aeration or flushing with fresh water.

Water quality is also important in the holding building. A common problem is iron. At 0.5 ppm, iron begins to coat the gills of fish causing impaired respiration. Sand filters may be used with aeration to remove iron from incoming well water. 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 baitfish production with fish predators is not the desire of any producer. A predator problem left unchecked can cause serious losses. Predators may include mammals, birds, reptiles, carnivorous fishes, insects and copepods. Using filtered or well water is the first step in predator control. Filters reduce the introduction of predatory fishes. Mowing grass and weeds along the pond bank will discourage many shoreline predators. Well maintained levee slopes which fill quickly to a depth of two feet or more discourage wading birds.

WEED CONTROL Pond management for fish culture encourages 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 the presence of weeds. Rolling fragile minnows with weeds in a seine usually results in the loss 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 drawdown can be effective on partial infestations of shallow water weeds. Pulling or raking weeds can help control shoreline weeds if started early enough. The most widespread method of weed control is use of approved algicides and herbicides. Several broad spectrum chemicals are available for control of most water weeds. Before using any chemical, be sure the chemical is cleared for aquatic use, is effective against the weed species present, is not toxic to the fish present and is as economical as other available methods. Biological control of weeds is usually accomplished by weed eating fish. However, some insects have been used to control weeds such as water hyacinths and alligator weed. To determine the species to be marketed and number of fish that can be sold, invest time into researching available market options.

MARKETING Selling baitfish to sports fishermen can be as simple as setting up a roadside bait house or as complicated as a system of wholesale distributors, jobbers and dealers. It is important to determine a production level that is matched to the market demand whether retail or wholesale. Sufficient time spent on marketing before production begins increases the chance of financial success. Remember that organized marketing in the baitfish industry is designed to discourage the entry of new producers. A new producer must find his own niche in the market or face stiff competition from existing growers.

OPTIONS

Live-hauling Live shipment of fish requires trucks equipped with water tanks and aeration, or contracting with live-haulers who have this equipment. Live-haulers can be hired to deliver fish to buyers or they can be buyers themselves. In most cases, the live-hauler is also the distributor or jobber. By contracting with several live-haulers, the producer can sell large quantities of fish. The live-hauling distributor sells to retail outlets and assumes risks associated with fish transportation and customer credit. Live-hauling trucks vary in design and holding capacities; however, most live-haulers transport between 3,000 and 6,000 pounds of live fish. Larger farm acreages are needed to supply live hauling distributors consistently. A farm size of about 100 water acres is considered large enough to supply regional or national distributors. On-farm sales can also be combined with fee fishing operations.

On-Farm Direct Sales Small fish farmers can sell baitfish directly to fishermen. The location of the farm in the proximity of a developed sport fishery is essential. A fish-holding facility is required to have fish readily available for customers. Ponds of 1 acre or less are used for growing a single species like fathead minnows or golden shiners. Fathead minnows can be raised with catfish. Small farmers often receive retail prices for their fish and sell ungraded lots of fish. Ungraded fathead minnows are usually sold on the farm as crappie bait.

Local Retail Sales Establishing retail outlets or selling to other local retailers may allow the small farmer to increase sales volume. Locations remote from metropolitan areas or those not already serviced by distributors may provide better markets for small producers.

The species of fish produced should reflect demand for bait in the local area. One problem faced by retailing baitfish is competition from larger distributors. If sales volume increases, competitors may take notice and competitively enter your newly developed market. Good customer service and high quality fish help any small producer retain established sales. The baitfish retailer may also want to provide customers with worms, crickets and other fishing supplies. Snacks, drinks and some grocery items may help attract customers to the bait outlet.

Marketing Strategies Matching the harvest of baitfish from ponds with the market demand requires careful planning. Stocking rates, stocking times, and feeding schedules influence the size and number of fish available for sale. The producer must develop a strategy to deliver the desired sizes and species of baitfishes required by the market. The heavier a pond is stocked, the slower fish will grow. Golden shiners stocked in excess of 200,000 fry per acre in June will not be large enough to sell as 3 inch crappie bait in March of the following year. Whereas, stocking at 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 separated at the farm prior to sale. Three grades of fathead minnows and four for golden shiners are commonly marketed. Goldfish 1-2 inches long are usually sold in the feeder fish market.

Spring and summer are seasons of highest baitfish demand. Regional and seasonal differences can be overcome by marketing nationally. Weather conditions can cause sudden peaks and declines in demand. Goldfish are sold to feeder fish markets throughout the year. However, this market is very restricted. Recent growth in the market has been the result of striped bass and hybrid bass production. Some baitfish have a very regional market. 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 the most important factor in the success and growth of baitfish farming operations. Producers with small markets, limited time to develop new markets or part-time commitments should consider less intensive, smaller, production systems.

Large farms of hundreds or thousands of acres usually produce several species of baitfishes. Golden shiners, fathead minnows and goldfish are grown in ponds containing only one species of fish (monoculture). Broodfish are spawned, eggs are hatched, and young are grown to market size on the same farm. White sucker producers often collect small fish from the wild. Holding tanks equipped with aerators and graders are constructed in a building. Baitfish are sold to wholesalers from these tanks. Few of the larger farmers sell to retail customers. National markets are serviced by large farming operations. Smaller farms serve smaller market areas. Wholesale and retail sales are mixed and fewer species are grown. Fish are usually grown in monoculture and the species is determined by local market demand. One adaptation of the small farm system is the polyculture 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 production facility. Major investment items include the purchase price of land, pond construction, holding tanks and equipment. Other expenses are for brood fish, mats or boards for spawning, fish feed, fertilizer, utilities, seines, other harvesting items. Most of the expense 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 often used 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 usually populated with undesirable wild fishes or predators.

Production Costs Two practices, spawning with mats and feeding, increase the cost of operation considerably. In contrast, wild spawning on grasses or fertilization alone costs less, but production would be 300 to 400 pounds per 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 requires additional equipment and labor.

Using Light to Harvest 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 an important tool in the commercial fishing industry. Similarly, sport anglers use lights to attract panfish when fishing in the evening. Over the past 15 years, we have developed and put into practice several methods of using light for both harvesting ponds and habituating pond-reared fingerlings to formulated feed.

Many species of fish including yellow perch and walleye exhibit a phototactic response, that is, they are attracted to or repelled by light. The direction and intensity of this response in percids is related to their size. Yellow perch fingerlings are strongly attracted to light from hatch until they reach about 1 inches, at which time they generally become photoneutral. Walleye are photopositive until approximately 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 fingerlings we quickly found that one way to maximize the number of fingerlings produced in ponds was to 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 formulated feeds. In perch this occurs when the fingerlings reach about inch. Because fingerlings this small are quite delicate, however, commonly practiced methods of pond harvest such as pond draw-down, fyke nets, or seines usually cause a high number of injuries and mortalities. To overcome this problem we use the strong phototactic response of these fingerlings to concentrate and lead them into capture nets. We have tested several systems, each consisting of a string of lights to attract the fingerlings and a net for capture.

One system consists of a series of 4 independently wired 75w, 12v bulbs encased in waterproof jars and attached to floats so that each light is suspended just under the surface of the water. The lamps are spaced approximately 15 ft apart and rheostats are used to control the brightness of each lamp. Fish are initially attracted by illuminating the entire light string, and are then lured into the vicinity of the net by sequentially extinguishing all but one light (beginning with the light furthest from the net).

Several types of nets have been tested for fingerling capture. One method (not shown) uses a lift net which measures 6 ft x 12 ft x 6 in deep and is secured to a floating tubular frame. The frame and net are held on the bottom of the pond by poles or weights (see Manci et al. 1983). Once fingerlings are attracted by light to the area above 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. A second method also uses a sequentially extinguished light string, but in this system the fingerlings 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 sides except one remain above the water line. One side of the box is left open until the fish enter the net. Then, using draw strings, the open side of the box is raised. As with the first system, fingerlings can then be gently removed with a dip net.

Using either of these systems, typically about 10,000-50,000 perch fingerlings can be captured in one set of the net. The box net, however, has the following advantages over the lift net: 1) the box net can be operated by a single person as opposed to 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 middle of the pond; 3) most of the "captured" fish will remain in the box net even if the gate is left open, and therefore several sequences of lights can be run before the box is closed and emptied; 4) fingerlings can be left in the box net overnight and collected the following morning. Both the lift net and the box net are very low stress methods of harvesting fingerlings, and the fish are virtually unaware that they are corralled until they are dip-netted from the capture nets.

Obviously, using light to harvest ponds is a nighttime operation. Our observations 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 in one or two nights of light-trapping. Factors that affect the success of light harvesting include 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 small samples of fish from ponds. One of the most important assets of these systems is the low degree of stress to which the fish are subjected, which in our experience clearly results in improved post-harvest survival.

USING LIGHTS TO IMPROVE FEED-TRAINING IN TANKS

Once fingerlings are harvested from ponds they can be trained to accept formulated feeds, a process often conducted in tanks or raceways. Nagel (1985) found that underwater lights could be used to concentrate walleye fingerlings in the area of the tank directly underneath automatic feeders. We found the same to be true for perch. Using this technique, fingerlings are frequently exposed to food as it drops into the tank.

In contrast, fingerlings in tanks illuminated by overhead lighting are usually dispersed throughout the tank, and observe food less often. We also noticed that perch fingerlings in tanks with underwater lights are much less disturbed by routine husbandry and maintenance activities such as feeding and tank cleaning. Additionally, we have observed that shadows and movements in the vicinity of tanks illuminated with overhead 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 yellow perch fingerlings while they remain in production ponds. Instead of harvesting and training fingerlings in tanks, we have found that lights can be used to attract and concentrate young perch to feeding stations that are dispersed across fingerling production ponds. For initial tests each station has been comprised of a submerged light located adjacent to a vibrating feeder.

Approximately 2 weeks after stocking (when fingerlings reach inch), pond lights are switched on at night to concentrate fish under the feeders. The feeders are activated by timers to broadcast food for about twenty, one-second pulses per hour throughout the night. Response to the lights is immediate. The highly photopositive fingerlings swarm around the light, occasionally chasing 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 ignore the 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 pursue the feed as it is broadcast onto the water. At this time we begin to extend the feeding periods into the daylight hours. For the rest of the training period feeders are active for 20 min out of every hour throughout the day and night. The fish remain in the ponds for 46 weeks, or until pond conditions (e.g., elevated water temperature, depressed dissolved 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 harvested fingerlings 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 virtually 100% of the fingerlings harvested were successfully trained in the pond.

Areas of further investigation that we are currently conducting include testing these light harvesting and feed-training techniques with other cool water species such as walleye and hybrid striped bass. Additionally, studies are currently underway to define optimum fry stocking densities for in-pond training of yellow perch.

Fish Health Management for Intensive Fish Farming

By: George W. Klontz, M.S., D.V.M., Retained Aquaculture Specialist, Nelson and Sons, Inc., 1908 East E. Street, Moscow, Idaho 83843-9504, 208-882-2617

INTRODUCTION

During the past three decades, the raising of fish for human consumption has been increasing dramatically, especially in the sociologically and industrially developed countries of North America and Europe. The increased production has come about largely as a result of consumer awareness that fish and shellfish are nutritionally beneficial to health. Unfortunately, the production increase in some countries has been so great that the supply of propagated food fish has exceeded the demand in the marketplace.

Attendant to the increased production of food fish under intensive culture conditions has been the increased loss of production potential through infectious and noninfectious disease processes. In many cases the episodes have been so severe that 45-55% of the numbers of fish at the beginning of the rearing process have died before they became ready for market. However, the loss of production potential has not been reflected as dead fish only. Perhaps the greatest impact has been reduced vitality which has been recorded as reduced growth rate and increased feed conversion. The costs incurred from this have been, in the opinions of many, quite significant.

The economics of food fish production have not been documented with precision and perhaps there is no way to do so because of the diversity of the food fish raising community. However, data suggest quite convincingly that the greatest portion of the costs in producing a pound of fish under intensive culture systems is feed. Thus, it would seem quite logical to assume that to pay considerable attention to that component would - or could - reduce loss of production potential. For example, weight gain in a group of fish at a feed conversion of 1.9 kg feed per kg gain is 26.6% more expensive in terms of feed costs than is the same group of fish at a feed conversion of 1.5 kg feed per kg gain. In this regard, it is beyond the comprehension of many that several fish farmers are apparently content with a 1.9:1 feed conversion when the commercially available diets all can yield a 1.3:1 conversion with very little effort.

Two of the prime factors in reduced feed conversion are subclinical respiratory (gill) diseases and asymptomatic infections of bacteria and viruses. The poultry and livestock (sheep, cattle, and swine) industries have learned that herd health management through application of the principles of preventive medicine is economically sound. In other words, these industries start with healthy animals and strive to keep them in that state through monitoring growth rates, behavior, production (milk, eggs, etc.), and environmental conditions. This could be termed preventive medicine. In this regard, perhaps the most significant impediment to reducing the mortality rate and to increasing the feed conversion is due to having more concern for disease rather than health.

The foregoing is not a new concept or revelation to the majority of people in the aquaculture community. All have attempted at one time or another, in some fashion, to implement these ideas. But the enormity of the task is often mind-boggling for an individual person. The adopting of the term "fish health" as opposed to "fish disease" in our professional jargon has helped a great deal. Then wherein lies the problem? The term "health" as it applies to an individual or a population of fish, either free-living or confined, should denote that the animal is able to conduct all its physiological activities without impediments. Its oxygen demand is met, its nutritional energy demand is met, its reproductive capacity is realized, its behavioral needs are met, and so forth; i.e., it is "normal" (a term I despise but use too frequently). It is my opinion that when any one of the physiological functions of a fish are comprised for whatever reasons extrinsic or intrinsic - a state of disease ensues. This disease state may be subclinical; i.e., not noticed by the observer, or it may be clinical; i.e., quite apparent to the observer.

EXTRINSIC FACTORS AFFECTING FISH HEALTH

The extrinsic or environmental factors which are known to compromise the health status of fish individually or collectively can be grouped into the following categories according to their location within the system: (1) water-associated; (2) pond-associated; (3) nutrition-associated; (4) management-associated. To some, this classification scheme may seem somewhat simplistic and/or conceptual. Nonetheless, the process of investigating the nature of a disease episode has been enhanced by identifying and quantifying the associated factors. The quantitative evaluation of the prime factors has permitted the raising of fish with a minimum of problems. I think the problem of 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 change into subclinical and then clinical disease.

Water-associated factors: Among water-related factors identified as affecting the productivity of aquaculture systems, water temperature and 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 fish in 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 the occurrences of infectious and noninfectious disease processes could be an invaluable aid in predicting the likelihood of a subsequent disease episode. Examples of this are legion but not sufficient to be a widespread practice.

Pond-associated factors: The primary effect here is requiring a particular fish to live in a pond configuration which does not meet its behavioral requirements. Our studies over the past 4-5 years on production forecasting have shown the health of fish can be compromised when the fish are fed at a rate permitting less than 80% of the "Allowable Growth Rate".

Nutrition-associated factors: One would think that in this day and age of high quality commercial diets, nutritional problems would not occur, but they do, all too frequently. We have found growth rate to be a very reliable indicator of the health of the population. Deviations of as little as 1% from the expected growth rate can be measured quite accurately and evaluated with a high degree of statistical validity.

Overfeeding a population is another health-compromising situation. In this case there are frequently abnormal amounts of abdominal fat and hepatic glycogen deposits. The effects are not often seen immediately, but can be implicated in the milieu of casual factors of an unhealthy state.

Management-associated factors: The primary health-threatening factors in this category emanate from exceeding one or more of the pond carrying capacities; from inadequate housekeeping practices to inadequate record-keeping and undue physical stressors.

INTRINSIC FACTORS AFFECTING FISH HEALTH

The intrinsic or somatic factors originate within the fish itself. They are largely governed by the genetic make-up which by and large dictates the physiological and psychological responses of the fish to the extrinsic factors.

Perhaps the major intrinsic factor which fish health managers have some control over is the generation of endogenous ammonia (NH₄⁺). We all know that free ammonia (NH₃) in the system is deleterious to the health of fish when specified limits are exceeded. The main impact, as we now understand it, is on the gill lamellae in the form of epithelial hypertrophy and hyperplasia which reduce the oxygen uptake by the fish, thus impacting the physiological well-being of the fish. The control 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 is the healthy or chronic asymptomatic carrier of infectious agents. It is apparent from our studies with Renibacteriumsalmoninarum and Aeromonas salmonicida carriers that the presence of these bacteria within the fish negatively impact their growth potential and represent a measurable threat to the uninfected portion of the population.

SUMMARY AND CONCLUSIONS

Up to this point, this presentation has been rather gloomy, in my opinion. But, we must face reality - we could do better with preserving the health of our fish 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 health management profession, collectively.

Practice preventive medicine through detection and elimination of the carrier states of bacterial and viral pathogens, through mass immunization of fish against pathogens, through implementation and maintenance of health-preserving management practices, and through implementation and enforcement of live fish transportation regulations.

• 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 capable of 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 best by a program of good management. A fish disease cannot occur unless a pathogen is introduced into the fish cultural system. Therefore it is very important to culture fish in a quality environment, with good nutrition and a minimum of stress.

Fish health professionals have recognized at least six general methods of disease control in fishes. Some are used extensively in pond culture and for limited disease control in wild fish populations. Some methods are used effectively, while others are 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 fish pathogens at your hatchery is the destruction or reduction of a link in the transmission cycle or as I like to call it, "containment". Containment plays a very important part in good management practices at your facility by not allowing the transfer of diseased fish or contaminated fishing gear (boats, gill nets, boots, etc.) into areas where fish are being cultured or the disease does not already exist.

The reasons for containment control are to prevent costly losses in hatchery production, to prevent transmission of diseases among hatchery ponds when boats and gill nets are brought onto hatchery grounds, and to prevent the spread of disease to wild stocks of fish when hatchery products are stocked out.

If a hatchery has been inspected or decontaminated and is pathogen-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 deadly fish pathogen can be prevented only by rigid cleanliness. All shipped-in equipment should be decontaminated thoroughly before it is placed in contact with clean hatchery equipment and the water supply to your fish.

Walleye Fingerling Production in Plastic Lined Ponds

by: Larry J. Wawronowicz, Tribal Natural Resource Director, Lac du Flambeau Band of Lake Superior Chippewa Indians

In the fall of 1993, The Lac du Flambeau Tribal Natural Resource Department 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 purpose of this article is to discuss the reasons why we decided to line the ponds, describe the production techniques we used to produce 1-2 inch walleye fingerlings in plastic lined ponds, and to discuss plastic lined ponds' production results.

The Lac du Flambeau Indian Reservation was blessed with a lot of surface 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 and seepage became a major problem. Depending on the pond, 10 to 12 inches of water would be lost over a 24 hour period. The seepage problem increased pumping costs and the amount of fertilizer needed to maintain desirable zooplankton populations. The water level fluctuations also enhanced filamentous algae growth, because pond depth could not be maintained at 4.5 feet. Ultimately, fish production decreased. Since clay is a rare resource on the reservation and trucking costs are very expensive, plastic liners became a more desirable alternative. Subsequently, 6 plastic lined ponds have been in production for two seasons using the following fertilization and production techniques.

Many different fertilization programs were tried before it was determined that organic fertilization was the best alternative. Alfalfa meal and Torulas yeast, a yeast used in the paper industry, is applied at an average rate of 1,175 lb/acre and 118 lb/acre, respectively. The amount of fertilizer used largely depends on pond fertility, weather conditions, number and size of the fish, and the quality and quantity of the zooplankton population. Generally, the fertilization program begins by applying 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 fry are stocked. Initially, the ponds are fertilized and filled to approximately the pond volume. This allows the water to warm faster which speeds up the establishment of a zooplankton population. Surface water from Pokegama Lake is used to fill the ponds; this is 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 to observe the zooplankton in the unfiltered hatchery water.

When the zooplankton are observed, water from Pokegama Lake is again pumped to the ponds to capitalize on the lake-produced plankton. An additional of the pond is filled when we first see the plankton in the hatchery water and the final is added when the walleye eggs start to hatch. Alfalfa meal is broadcasted evenly around the pond by using a scoop made from a one gallon milk container. Because Torulas yeast is a very fine powdery substance, it is applied by mixing it in 50 gallons of water and distributed evenly around the pond. It is important the fertilizer is evenly distributed. If there are clumps (of fertilizer), it has been our experience they become starting sites for unwanted algae.

Throughout the 40-day walleye fingerling production season, the zooplankton populations, oxygen, pH, temperature, weather and fingerlings (1-2 inches) are monitored. Standard fish culture sampling techniques are used to assure all parameters are conducive to good production. All fish are harvested and transported to reservation lakes. In 1994 and 1995, 303,085 (101,028 fish/acre) and 306,201 (102,067 fish/acre) walleye fingerlings were produced, respectively. Based on two production years using plastic lined ponds, a 2-inch fish was raised in 40 days; an approximate growth rate of 0.05 in/day. The walleye ranged between 417-450 fish per pound with 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) has introduced a new wildlife/fish feeder, the Little John. This scatter type feeder is constructed of heavy duty polyethylene that resembles a log. The device can hold up to 100 pounds of food and is controlled by a digital timer which can be set to feed up to eight times a day. The unit sells for $120.00 and comes with a three year warranty. If you would like 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-diagnosing electronics, one-button or automatic calibration, digital output communications, programmable set points and solid state relays and component housings constructed from space-age composite materials. Some of the monitoring systems made by Royce include: Dissolved oxygen analyzers and sensors, pond monitoring and aeration control, total suspended solids, pH-alkalinity-carbon dioxide, computer data collection and signal conversion module. If you would like additional information you can reach a Royce representative 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. The engineering staff can also manufacture specialized tank systems. Reiff can also make tanks to mount on your truck or trailer and can build a trailer to go with transport tanks. If you would like additional information you can reach a Reiff representative at 1-800-835-1081.

If you're planning a big project requiring plastic pipes, valves, pipe fittings, cement sealers and flexible hose, you may want to call Industrial Thermoplastic Solutions (P.O. Box 5029, Evansville, IN, 47716). They also offer engineering and technical data assistance. If you would like additional information you can reach a ITS representative at 1-800-262-4331).

Another "must have" book is the "Aquaculture Engineering Design and Specialized Equipment catalog from Keeton Industries (300 Lincoln Court, Suite H, Ft. Collins, CO 80524. You may know this company from their previous name Keeton Fisheries. These folks have put together an all you could want catalog for aquaculture related products. From A-Z some of these items include: Aeration, biofilters, chemical additives, diffusers, feeders, heaters, liners, pipe fittings, pumps, tanks, and zeolite. If you would like additional information you can reach a Keeton representative at 970-493-4831.

KEEP THOSE FRY TANKS CLEAN

The MTAN recently visited a trout hatchery in Idaho and observed a very interesting tool for keeping fry tanks clean of fecal material. The hatchery manager had connected a section of inch PVC pipe to the inlet pipe and had it positioned along the center of the tank bottom (see diagram).

Several small holes ( inch) were drilled in the two sides of the pipe on a 45 angle to the tank bottom. Water flow from the pipe prevented fecal material from settling to the bottom of the tank by keeping it in suspension until it could be moved to the end of the tank for easier cleaning.

The MTAN would like to wish you a Merry Christmas and a very Happy New Year. We sincerely hope your chosen direction is clear and your path to happiness is but a foot step away.

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Last updated: August 28, 2009

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