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Ashland NFWCO
 Midwest Region
 Dedicated To The Tribal Aquaculture Program September 1996 - Volume 17
  **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: Dome Technology Methodsof Controlling Growth Rate of Rainbow Trout Walleye Spawning in Michigan Examination of External Signs and Behavior Patterns Tribal Hatchery Updates Hatchery Tip  DomeTechnology an Economic Solution to Scaling Down Costs in Aquaculture **By: Lane Roberts, Dome Technology, Marketing Management Team, Idaho Falls, ID83401, 208-529-0833, Fax -0854** Throughout history, the dome has been the architectural form of choicewherever efficiency and strength are required of a structure. From the simple igloo thatshelters the Arctic hunter throughout the ravages of a blinding storm, to theawe-inspiring magnificence of the Sistine Chapel, the dome has been used in every culture,on every continent, as one of man's most versatile buildings. Today, the modern construction techniques and materials reinforce thedome's position as the most classically versatile of all structures. The insulatedconcrete dome is the ideal solution wherever strength combined with low construction andmaintenance costs are called for. Compared to other types of structures, the dome enclosesmore volume with the greatest floor area, and the least amount of surface area andperimeter. Superbly energy-efficient, firesafe, and with an inherent strength that enablesit to withstand whatever nature throws at it--hurricanes, earthquakes, even tornadoes. Itis no wonder that the modern concrete dome is experiencing a surge of popularitythroughout the world. Dealing with the unpredictability of weather is rarely a factor in domeconstruction. Since most of the construction process takes place under the shelteringumbrella of an inflated form, work goes on regardless of the weather. Dome construction israpid and cost-efficient compared to other construction techniques. Modern insulatedconcrete dome construction combines several materials to create a strong, efficient,weather-proof structure. Compared to other types of structures for the same application,the insulated concrete dome is 50-75% more energy-efficient. **CONSTRUCTION PROCESS** Insulated concrete dome construction consists of four main phases.Refinements to the design are dictated by application which will determine the workrequired after the construction of the basic dome. Phase One-Pour Ring Beam Footing. Continuous reinforcing bars areembedded in the ring beam foundation. These rebar dowels securely connect the dome to itsfooting. Phase Two-Attach and inflate Airform. The airform is attached to thering beam footing, and inflated with dual inflator fans, each powered by an independentpower source. An airlock entrance allows free access to the interior. The airform is athin, tough membrane that becomes the dome's outer covering when construction is complete. Phase Three-Apply Polyurethane Foam. Polyurethane foam is spray-appliedfrom the interior to stiffen the air from and provide a secure surface to whichreinforcement bar is affixed. The foam hardens and creates a superior insulating layer inthe final structure. Phase Four-Reinforced Concrete. After the polyurethane foam is appliedand allowed to harden, a framework of reinforcement bar is place and attached to theinterior surface of the foam. This will serve as a skeleton to which concrete is applied.Application of shotcrete to the reinforcement bar framework comprises the final step inconstruction of the dome. The rebar framework is embedded by the shotcrete, creating anextremely strong, fire resistant and energy efficient structure. Let's briefly explore the reason why this innovative method ofconstruction is so energy efficient by taking a page from the California Energy CommissionPassive Solar Handbook, paragraph 1.4, Optimal Use of Mass and Insulation. "A heavy wall must have two qualities in order to dampen diurnalchanges in the exterior environment and thus keep the internal temperature of a roomrelatively constant: heat capacity--the ability to store heat, and low heatconductivity--the ability to resist, or to insulate against heat flow. If oneintermittently exposes an adobe brick first to a blow torch and then to cold water (and ifeach exposure time is relatively short) the temperature of the brick never reaches eitherextreme, but oscillates somewhere in between. The heat capacity of the brick keeps itstemperature from rising rapidly with the small heat addition, or dropping rapidly with thesmall heat extraction. The brick's insulating quality prevents heat from entering orleaving very rapidly. "Adobe, however, doesn't happen to have the optimum combination ofeat capacity and insulation. This problem can be resolved by the way the material is usedwhich is an important as what material is used. The most effective way of maximizing thetwo qualities--the capacity and insulation--in a building wall is to use two separatematerials. Ideally, one would choose a material with little heat capacity but highresistance to heat flow, and a material with high heat capacity having little resistanceto heat flow. By placing the insulating material next to the external environment,little heat is allowed into or out of the building and with the high heat capacitymaterial next to the inside environment, what heat does enter or leave (primarily throughwindows and interior heat generation) can't change the temperature of the heat capacitymaterial rapidly. Thus, little heat is let in or out, and the high capacity materialslowly stores heat. The building's thermal mass damps out temperaturefluctuations." Dome Technology has developed the technology to economically place theurethane insulation on the outside of the concrete while protecting the urethane from theharsh weather conditions and the degradation of the sun's ultraviolet rays. The end resultis a*Super Insulated* concrete facility. This method of technology has proveditself time and time again in reducing expensive energy costs to the owner 25%-50% andmore. Dr. Arnold Wilson, professor of civil engineering at Brigham YoungUniversity has engineered over 500 thin-shell concrete domes throughout the world and hasthis to say about the strength of the concrete dome. "Thin-shell, reinforced concrete domes are probably the mostdisaster resistant buildings that can be built without going underground or into amountain. "It is predicted that a wind of seventy miles per hour blowingagainst a thirty foot tall flat walled building in open flat terrain will exert a pressureof 21.97 pounds per square foot. If the wind speed is increased to 300 mph the pressure isincreased to 404 pounds per square foot. Wind speed of 300 mph is considered maximum for atornado. It is far greater than that of a hurricane. "Against that much pressure a dome 100 feet in diameter 35 feettall would still have a safety margin of nearly 1  times its minimum design strength. Inother words, the stress created by the 300 mph wind would increase the compressivepressure in the concrete shell to a 1098 psi. The shell is allowed 2394 psi using designstrengths of 4000 psi. "The fact is, the thin-shell, concrete dome is not flat;therefore, the maximum air pressure against the dome of 404 pounds per square foot couldnot be realized. The strength of the dome is much greater than 4000 psi. The margin ofsafety is probably more like 3 or 4. "The thin-shell dome at Port Arthur, Texas, has been hit by threehurricanes. A hurricane does not exert enough pressure on a dome to even be noticed. Asshown above, the dome can easily withstand the stresses of a tornado; however, debriscarried by a tornado could cut the surface membrane. If the debris contained a largetimber or metal object, it might be possible, if conditions were just right, puncture thedome. But the puncture would be very local and would certainly never cause a seriouscollapse of the dome. Possible damage to the doors or windows may occur if there was arapid decompression caused by the tornado. "For most domes, the likely disaster will be earthquakes. Theworst areas in the United States are listed as seismic zone 4. Earthquake forces do noteven approach the design strength the thin-shell, reinforced concrete dome which is builtfor every day usage. It would take an external force many times greater than an earthquaketo approach the design strength of the concrete itself. "Nuclear fallout is another disaster consideration. It isinteresting to note that the only structure left standing near ground zero at Hiroshimawas the concrete skeleton of a dome. Certainly, the thin-shell dome would be superior tomost buildings if a nuclear fallout condition occurred. Rain would tend to wash theradiation off the building much better than conventional buildings. Generally, domes are quite tall. Radiation strengths are inverselyproportional to the square of the distance from the source. The roof of the dome wouldhold the radiation further from the occupants than many other structures. Also, concreteitself absorbs radiation very well. The concrete dome would greatly reduce the effects offallout on the occupants. "It is interesting to note that German thin shell structures stoodup to allied Bombing in the second world war better than most other structures. When abomb would hit a thin shell, it would either bounce off the resilient exterior or wouldpuncture a hold through it. Since there are no single components that carry large loads,there is nothing that can be knocked down like a beam or column. Therefore, repair was asimple patch to cover the hole that was made when the bomb would go through. "The forces caused by a major earthquake are considerably lessthan normally provided for when a dome is designed for nominal vertical loads. "The forces caused by wind and earthquake on a concrete domegenerally do not control the design. Domes are very strong and durable and in a realisticsituation would probably still be standing when all conventional structures hadfailed." **HUMIDITY'S EFFECT ON THE CONCRETE DOME** When the dome is used as a cover for sewer treatment ponds, swimmingpools or aquaculture centers, the concrete shell is subject to a great amount humidity.This humidity is hardly harmful to the concrete but actually helps the concrete cure.Concrete will cure for many years. When the moisture from the humidity is added to thecuring process, the concrete simply gets stronger and stronger year after year. **LOW MAINTENANCE** Roof repair and maintenance of heating and cooling plants-traditionallythe two highest maintenance costs for traditional structures are cut dramatically inconcrete dome structures. Snow and water inflict relatively little stress on the exteriorof the dome. Concrete dome structures need only a fraction of the HVAC equipment requiredin conventional structures to maintain comfort levels and maintenance costs areproportionately reduced. **SUMMARY** The insulated reinforced concrete dome is possibly the most energyefficient, economical, environmentally friendly, durable and low maintenance building onthe market. It is the ideal building to meet the needs and circumstances of those in thebusiness of commercial fish farming. Methods ofControlling Growth Rate of Rainbow Trout **By: George W. Klontz, Aquaculture Specialist, Nelson and Sons, Inc., 1908 EastE. Street, Moscow, Idaho 83843, 208-882-2617** Based upon the results of a recently completed two-year controlledgrowth study, the following feeding regimen could also be implemented to provide fish ofuniform size over extended periods. In this example, the production plan calls for amonthly harvest of 7,400 (450 g) trout. The process starts with 60,000 eyed eggs whichshould result in 6 months of market-size fish. In this scenario, the water temperature isa constant 150C, which makes production forecasting much easier. The first-feeding fry are raised in shallow troughs (3 m x 0.33 m x 0.1m deep) suspended over deep tanks (5 m x 1 m x 1 m deep). When the fry are approximately2,000 per kg they are to be transferred to deeper tanks. Daily feedings are to be such that the fish receive all they can eatseveral times during the day. When the fish are 500-1,000 per kg, one-sixth of thepopulation is to be transferred to another deep tank and fed full daily rations. Theremaining fish are put on a novel feeding regimen of 7 days of feeding at 50% of thefull-feeding level and 7 days of no feed. This feeding level provides little more than thedaily maintenance requirement. Thus, there will be little weight gain. However, there willbe some length increase as skeletal growth is more a function of temperature, genetic andhormonal activity rather than metabolizable energy. At monthly intervals, another group is to be removed from the reducedfeeding regimen lot and put onto a full-feeding regimen. Thus, the last group should be ofmarketable size 6 months after the first fully fed group was harvested. If the foregoing is considered to be a little too rigorous to implementon such small fish, then a feeding regimen of 7 days of full feeding followed by 7 days ofno feeding could be implemented. Other days of feeding followed by days of no feed couldbe used. The fish will have reduced weight and length gains, thus necessitating somethoughtful planning of harvest schedules. For example, this feeding regimen will requiremore rearing space than the 50% feeding regimen because the fish will be larger throughoutthe growing-on period. The main concern with the foregoing is to determine when to reinstate afull-feeding regimen so that the market date and size can be met. This is not toodifficult if the water temperature is constant and one understands that under suchsituations the daily length increase is linear. If the water temperature is not constant,then the calculated daily length increase must reflect that allowed by the watertemperature. To calculate the approximate date to reinstate full-feeding underconstant water temperature conditions, the length of the fish at market size minus thelength of the fish on reduced feeding divided by the daily length increase will indicatethe number of days of full feeding required. To calculate the approximate date toreinstitute full-feeding under varying water temperature conditions, the average monthlyor, better, weekly water temperature-dependent length increases should be available. Theprocess is then the same as for the constant water temperature conditions. **In summary, the step-by-step process to implement the suggestedfeeding regimen is:** Disinfect the eyed eggs with an appropriate iodophor upon receipt and    adjust the water temperature to that of the incubation system.  Incubate and hatch the eggs. It is advisable at hatching to remove the    egg shells from the system as soon as possible to prevent transmission of any bacterial or    viral pathogen in/on the egg shells. Upwelling incubators are ideal for accomplishing this    by merely increasing the water flow to flush the shells out. With tray or basket    incubation, the shells usually require manual removal.  When the fish are ready for feed they should be fed several times during    the day. Ideally, feeding should be done by belt feeders to provide a constant feeding.    Uneaten feed, fecal solids, and dead fish must be removed several times during the day. It    is especially important to remove dead fish expeditiously to prevent transmission of any    bacterial or viral pathogen to the fish dining on their fallen brethren.  When the mean weight per fish is 2-3 g (or larger if fingerlings are    purchased), transfer an appropriate amount by weight to another container and put them on    a full feeding regimen until they are the desired size for the market.  The remainder of the lot is to be fed 50% of the daily requirement for 7    days followed by 7 days of no feeding. Or the fish may be fed at the 100% daily level for    7 days followed by 7 days of no feeding. On the day of resumed feeding following the 7-day    feed deprivation, care should be taken to feed in a fashion that all fish receive their    share. This will reduce the potential for unwanted size variations in the population.    Population inventories of length and weight should be done at the end of the 7 days of    feed deprivation so that the daily feeding regimen for the ensuing 7 days can be    calculated properly.  At monthly intervals, appropriate portions of the controlled growth    population are removed and put on full feeding. During the growing-on period, strict    attention should be paid to not exceeding the population density or dissolved oxygen    limits of the system.  The end result should be the production of uniform-sized fish over a    period from a single lot of eggs or fingerlings. If the process is implemented and    maintained with care, size grading should be necessary only at harvest times. **During the production cycle, the following performanceindicators should be monitored at 14-day intervals (preferred) or 28-day intervals:** Size variation within the population: This is obtained by weighing and    measuring at least 40 fish during the inventory process. From these data the following can    be calculated: a. Average, mid-range, and variance of fish lengths/weights. b. Daily length increase and specific growth rate. c. Biomass and weight gain of the population. Condition factor: This is the length to weight relationship. It is    calculated by dividing the average weight (g) per fish by the cube of the average length    (mm3). As time passes in the reduced feeding groups, the condition factor will    decrease. After the fish are put on 100% feeding regimens, the condition factor will    increase to the appropriate level of approximately 0.0000126.  Feed conversion: Most commercial trout and salmon feed formulations are    capable of providing feed conversions of 1.2:l. Feed conversions less than this; i.e.,    >1.2:1, should indicate that something is amiss. The most common causes are    over-estimating the pond population and/or the allowable growth rate.  Mortality: The daily mortality should not exceed 0.02% in well-managed    populations of trout. Mortalities greater than this should be thoroughly evaluated for    causal factors. **As the fish approach market size, the following performanceindicators should be monitored:** Dress-out as percent recovery after removal of the gills and viscera.    For most strains of rainbow trout, there should be a recovery of 83-86%. Boned, skin-on    fillets should have a yield of 51-54% .  Gross appearance of the fish is judged by the body coloration, body    conformation, and fin condition .  Flesh quality (taste, color, and texture) of table-fish .  Calculate production costs versus sales income to estimate net profit. In closing, there is a caveat. Should one decide to implement thisprocedure, it is recommended that (1) small lots (<20,000 2-3 g fish) be usedinitially; (2) the pellet size fed throughout the growing-on period remain at one levelless than the manufacturer's recommendation (thus, there will be more pellets to goaround); (3) the fish be fed attentively to assure that all fish in the population receivetheir fair share to preclude unwanted size variation. The procedure presented has beenevaluated extensively under laboratory conditions for two years. It has yet to be formallyevaluated under commercial production conditions, although there are reports that limitedattempts are being conducted without mishaps. The bottom-line is - are you, the reader, satisfied with the way yourfish perform? If not, then something should be done. I have offered an idea. Others haveoffered ideas. Gather them in, evaluate each in terms of the situation, and, as they sayhere in The Colonies, "Go for it!" The Effectsof Density On Fish Growth Performance - Abstract Only - By: Lawrence C. Belusz, Alexandria Technical College, Alexandria, Minnesota, Above a specific temperature, which varies by species, a fishes'metabolic processes cannot keep up with increased demands for energy, and growth ratebegins to decrease. The result of these demands is that for each fish species there is anoptimum temperature for growth. Not as well understood is that each species of a specificsize has an optimum density, or degree of crowding per unit of space, which also producesan optimum growth rate. For fish culturists attempting to maintain fish density or loadingrates (carry capacity) as high as possible, it is important to realize that management andproduction tradeoffs are made in return for maximizing the pounds of fish raised per cubicfoot of space or gallon of water. These tradeoffs can be observed as: reduced rate ofgrowth which results in a longer time to market, decreased feed conversion efficiencywhich results in more feed to grow an equal weight of fish, less uniformity in growthwhich results in fewer fish reaching market weight and increased time spent insize-grading, lower survival of fish which results in more cost per fish, more incidenceof disease which results in added operational costs for treatments, and increases in waterquality emergencies which result in added operational cost and more stress for fish whichin turn leads to reduced growth. An understanding of the optimum spatial requirements offish and the performance factors which are affected, will enable the fish culturist toproduce a given crop of fish at optimum levels of management input which will be reflectedin an optimum cost of production. Walleye Spawning in Michigan **By: James A. Copeland and Martha M. Wolgamood, Michigan Dept of NaturalResources, Wolf Lake Hatchery, 34270 CR 652, Mattawan, MI 49071** Michigan Dept of Natural Resources has been utilizing walleye from theMuskegon River as a source of walleye eggs for many years. Fish migrate upstream and arecaptured by DC electrofishing below a barrier dam. Spawning techniques have evolved to thepoint where we can normally rely on >80% development to the eyed egg stage (eye-up in1986 was only about 27%). Between 80 and 100 million eggs are taken annually. Broodfish are selected and captured by district field crews when theMuskegon River water reaches 36F. Fish are then sorted by sex visually and taken to aspring-fed pond which is 50F. Most females are "green" upon arrival, and are allplaced in 54 cu ft holding nets. Average weight of the females is about 7 lbs. Fish are collected daily from the river and transported to the holdingnets until 500-600 fish have been captured. Females in each net are examined daily tocheck for ripeness, and ripe females are spawned daily until egg take goals are met.Experience has shown that all fish will be ripe within 2-3 days after capture. Ripe fish are anesthetized with MS 222 prior to spawning. Spawning isdone on a small dock at the pond. No protection from wind, sun, rain or snow is providedfor the eggs during stripping. Anesthetized fish are rinsed in fresh water and wiped witha towel before spawning. One female is stripped into a stainless steel 5 qt pan. Thenumber of eggs per female ranges from 160,000 to 200,000. If a female produces >200,000 eggs, they are usually split between two pans for fertilization. Prior to 1990, two males would be stripped into a pan of eggs and asmall amount of water (about one cup) was added. The eggs were stirred for 5-10 secondsand then allowed to set approximately 2 minutes before being poured into a 5-gal pail withFuller's earth and water. If eggs were allowed to set for more than 2 min, they wouldbegin to stick together. The fuller's earth mixture we used was: one cup to about 3.5 galwater. Beginning in 1990, a new fertilization technique was used. Two maleswould be rapidly stripped into a 1.6 qt plastic jar ( full of lake water). This mixtureis vigorously shaken and poured into a pan of eggs. The eggs are stirred with a featherand allowed to set for 30 seconds, if eggs begin to stick before 30 sec, they must bepoured into the Fuller's earth mixture immediately or they will form clumps. It isbelieved that fertilization is almost instantaneous. The Fuller's earth mixture is stirredwith a feather as the eggs are poured into it. This procedure is repeated until 8 or 10females have been stripped and fertilized, and the eggs put into a 5-gal pail. After the last pan of eggs has been added to the Fuller's earthmixture, the pail of eggs is allowed to set for a maximum of 5 min. At this time, the eggsare poured into a floating 30 cu ft holding net (with 1/16 in mesh) to allow the eggs towater harden. Eggs from up to 100 females are put into each water hardening net. The netalso serves to wash excess Fuller's earth out of the eggs. The eggs are packaged forshipment I hr after the final lot of eggs have water hardened. Fish that have beenstripped are held in 54 cu ft nets in the spring-fed pond for 24 hours and are thenreturned to the Muskegon River. Water-hardened eggs are dipped from the net using one of the spawningpans. Eggs are put into 12 in x 10 in x 9.5 in styrofoam boxes. A box is initially filledabout half full with water. Eggs are gently poured into the box until the water overflows.At this point, water is poured off the eggs and this process continues until the eggs inthe box are about I inch from the top. The eggs are just covered with water for shipment.Each box contains about 16 qts of eggs. The trip to the hatchery is approximately 100miles and takes about two hours. Upon arrival at the hatchery, the eggs are measured into plastichatching jars. Five quarts of eggs are added to a jar, and the volume of eggs in this jaris used to fill the remaining jars. The eggs are siphoned into the jars. The jars are thenput on the hatching battery to incubate the eggs. Each jar is supplied with 1.06 qt/min of50F spring water. Eggs will not be rolled at this low flow. Eggs are treated daily with 1:600 formalin for 15 min. On day ten,treatments are discontinued, and water flow is increased until the eggs roll gently. Thisallows dead eggs to migrate to the top of the egg mass and allows them to be siphoned. Itmay take 3-4 days before most dead eggs will roll to the top. During this period, eggsshould be monitored for saprolegnia infestation. If one does occur, formalin treatmentshould again be given. In 1986, the average eye-up was 27%. In 1990, 1991, and 1992, themean had risen to 63%, 78%, and 83%, respectively. Eggs will be very near hatch on day 15 of incubation. At this time eggsare transferred to a heated water 62F battery. After about 3 days at this temperature,eggs will hatch. Hatching fry are directed into rectangular 9.7 ft x 13 ft long troughs.This allows the egg shells to settle. If tannic acid is used to eliminate eggadhesiveness, egg shells will not break down at hatch and settle in the troughs. Theoverflow from this trough leads into a 8-foot (100 cu ft) circular tank. The egg shellsettling trough is covered with a black cover and a light bulb is placed at the outlet.Fry are attracted to the light and are quickly pulled into the overflow. The carryingcapacity of the circular holding tank is about three million fry. Fry are held in thesecircular tanks for 2-3 days and are then shipped to rearing ponds or stocked. The same styrofoam containers that were used to transport eggs are usedto ship fry. Approximately 2 gal of water and 50,000 fry are put into a plastic bag in thestyrofoam container. Fry are measured using volumetric displacement in a 500 ml graduatedcylinder. The number of fry/ml is determined using a 3-4 ml sample of fry in a 10 mlgraduated cylinder and averaging 3-5 samples from each tank. Oxygen is then added and thebag is sealed. **Examinationof External Signs and Behavior Patterns of Fin Fishes for Disease Problems** **By: Terry Ott, U.S. Fish and Wildlife Service, La Crosse Fish Health Center,La Crosse, Wisconsin** The Chinese philosopher, Confucius once said, "the happiesthatchery worker is the one who feeds all fish by hand". For someone living so longago Confucius was wise to know the value in hand feeding. He knew how important it was towatch fish feed and how they behaved during the feeding period. He also understood thevalue of having a front row viewing seat into the clinical signs fish may express ifsomething is not just right with them. According to Webster's Dictionary, disease can be defined briefly asany deviation of the body from its normal or healthy state causing discomfort, sickness,inconvenience, or death. When microorganisms that cause diseases in fish become numerousthey may cause changes in behavior or produce other obvious signs. Some of which givevaluable clues as to the nature of the disease. Individual diseases do not always produce a single clinical sign orcharacteristic that is diagnostic in itself. Nevertheless, by observing the signsexhibited by fish one usually can narrow down the cause of the trouble to a particulartype of causative problem. It should be emphasized, that many external signs and behavior patternsare common to a multitude of fish diseases including nutritional and environmentalanomalies. The appearance of every sick fish tells a story, which fits into the proverbialjigsaw pattern of disease diagnosis. Good observation uncovers many useful clues. Following is a list of common external clinical signs, or changes inbehavior a hatchery worker can look for in fish suffering from a disease. Each sign orbehavior observed can occur as a direct result of fish experiencing one or more of thefollowing disease categories; viral, parasitic, bacterial, environmental, or nutritionaldisease. **Sluggish behavior -**fish may become very inactive andoften cease feeding. Lie listlessly on the bottom of the tank or float just below thesurface of the water. This behavior is the first observed in fish experiencing a disease.All five disease categories should be suspect with this behavior. **Flashing,scraping, darting, whirling -**fish may have protozoan parasites or neurologicaldamage. **Faded pigment -**fish become very pale in color, suspect anutritional or environmental problem. **Darkened pigment -**fish become verydark in color look for viral, bacterial, or nutritional problems. **Exophthalmia(popeye) -** fish are showing one (unilateral) or two (bilateral) protruding eyes.Suspect first an environmental problem. Then look for bacterial, viral, or nutritionalproblems. **Hemorrhaging in the eye -**fish have blood spots in the eyes.Environmental, bacterial, or if the species is young lake trout suspect viral (EEVD). **Hemorrhagingin the mouth -**blood spots become apparent on the roof of the mouth and along thejaws. Suspect a bacterial agent especially if the fish are young rainbow trout. Themicroorganism could be Yersinia ruckeri the cause of Enteric Redmouth disease. **Erosionof the jaws/mouth -**necrosis of jaw muscle in salmonids, suspect bacterialinfection. **Hemorrhaging in opercula region -**redness on the gill coversand throat of fish. If fish have just been hauled suspect hauling stress (environmental);otherwise suspect a systemic bacterial infection. **Gill damage -**presenceof swollen gill lamellae, clubbing and gill rot. Check for bacterial infection,environmental (gas supersaturation), ecto-protozoan parasites, or nutritional problems. **Finrot -**fish have badly damaged fins or frayed fins, exposing the fin rays.Nutritional, bacterial, or environmental anomalies are to be suspected. **Saddle-likelesions -** necrotic tissue on dorsal surface. Generally located behind the dorsalfin. Look for nutritional, environmental, or bacterial problems. **Distended abdomen-**the abdomen is often filled with ascitic fluid (serous fluid). The fish mayhave a bacterial or viral infection. **Hemorrhaging on the surface -**thefish has redness around the base of the fins, on the ventral surface and along the sides.A systemic bacterial infection or nutritional problem would be the categories to seek helpon. **Furuncles (boils) -**blood filled blisters on the skin. This conditionis a result of the disease Furunculosis caused by the microorganism Aeromonas salmonicida.**Protruded anus -**swollen/redden vent with some discharge. Viral,bacterial, or an intestinal parasite may be the cause. **Eye cataracts -**eyesbecome cloudy, leads to blindness. Suspect a nutritional, environmental, or eye fluke(parasite). All these external signs and behavior patterns which were discussedabove require no specialized equipment or fish health biologist to point out to you. Allthat is required is some extra time spent when you are feeding your fish to look for anybehavioral changes or signs which may indicate a disease problem developing in your fish.If you are working at a hatchery that is using demand feeders spend a few minutes at eachpond during the day to watch the fish feed, and don't be alarmed, if you notice one or twofish within a pond expressing some abnormalities. Look for many fish expressing the samebehavior or clinical signs then talk to your manager immediately. If a serious disease problem is suspected a fish health biologistshould be contacted for assistance in isolating and identifying the causative agent orproblem. Clinical signs can be helpful, but also misleading. In almost all instances anaccurate evaluation can be made only at a diagnostic laboratory. Control of diseases in hatchery fish can be achieved best by a programof good management. Correct the problem before it starts! This involves maintaining thefish in a good environment, with good nutrition and a minimum of stress. **Tribal Hatchery Updates** Both the Lac Vieux Desert (LVD) and the Sokaogon Chippewa (Mole Lake)Bands are starting construction of a walleye fry rearing/distribution program. The LVDproject has already set the foundation for the hatchery rearing facility, while the MoleLake Band is still in the designing phase for its rearing building. For those MTAN readerswho have gone through this designing and construction process, you will recall howfrustrating the process can be. If you can find a few relaxed moments during your busy dayto call and offer your sympathy and advise, I'm sure it would be well received. **Hatchery Tip** **New Publication:** Zebra Mussels and Aquaculture *Zebra Mussels: A Crisis in Aquaculture* is a new four-pagepamphlet discussing potential problems zebra mussels can cause for aquaculturists. Writtenby North Carolina State University Extension Fisheries Specialist Jim Rice, the pamphletprovides suggestions for protecting aquaculture water supplies and discusses ways toprevent the contamination of water used for hauling fish and fingerlings. Other topicsinclude the use of disinfectants, control measures for infested facilities and theimplementation of inspection and monitoring programs to detect the presence of zebramussels. The publication is available from North Carolina Sea Grant, P.O. Box 8605, NorthCarolina State University, Raleigh, NC 27695-8605, phone 919-515-2454, Email:[email protected]. 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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