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Ashland NFWCO
 Midwest Region
 ***Dedicated To Tribal Aquaculture Programs***
      Fish Jumping
          **December 1994 ~ Volume 10****Coordinator:
                  Frank G. Stone 
                  (715-682-6185) Ext. 12
                  U.S. Fish and
                  Wildlife Service
                Email: [email protected]** Topics
  of Interest: MTAN ArrowLake   Sturgeon Egg Take  Procedures
  MTAN ArrowLake   Sturgeon Management
  MTAN ArrowTwelve Uses Of Salt
  MTAN ArrowSalt Fungicidal On Trout Eggs
  MTAN ArrowPump Alarm System
  MTAN ArrowHatchery Fomites
  MTAN ArrowHatching Eggs Out Of Water  Lake   Sturgeon Egg Take  Procedures **By: Roger Klindt** NYSDEC, 317    Washington St., Watertown, NY 13601  315-785-2261 Lake sturgeon have been  collected with a variety of gear. Collections have been made using both  monofilament and multifilament gill nets of mesh sizes 7-12 inch stretch  measure. Gill nets are set parallel to the current in approximately 6-12 feet  of water. Nets should be checked at no more than one hour intervals after setting.  Captured sturgeon are then kept in holding tanks with recirculating water for  several hours before surgery. **Surgical Sexing:** After a brief recovery from capture (2-4 hours) fish are  ready for surgery. The surgery area should be set up before hand to expedite  the procedure and reduce stress to the fish. All instruments are placed in a  bath of diluted betadine solution. The scalpel should have a fresh blade.  Probes should be cleaned before surgery. Fish are taken one at a time and placed on a wet stretcher  where they are measured and weighed to the nearest tenth of a kilogram. The  assistant places a thumb into the mouth of the fish to act as a calming  distraction. Once the fish is relaxed and not moving the surgeon cleans an area  for the incision. Water and mucous are wiped from the area. Next a small amount  of betadine is swabbed on the incision site. The area to be cut is located on  the ventral surface approximately 5 scutes anterior of the vent. (see  illustration). An incision of approximately 1-1.5 cm is made just off the  ventral midline. The incision should be made carefully, only through the skin  with a single stroke if possible. Sex is determined by probing through the incision with  forceps. Probing is done towards the body wall so as not to injure other  tissues. Males will produce a white granular material (teste) or sperm, females  will produce eggs if mature and in spawning condition. Once sex and/or maturity  is determined the incision is closed. A simple interrupted pattern is used with  2/0 nylon on a swaged cutting needle. The needle should pass through the middle  of the skin layer. The finished suture should be snug but not tight, to allow  for swelling. Either one or two sutures will be needed, depending on the length  of the incision. After sex determination is made the fish is tagged with a  numbered floy tag and returned to the holding tank. Fish are then left alone  for 24 hours to acclimate to the holding facility. **Hormone Injection:** Hormone injection is scheduled for egg take convenience.  Fish receive their initial injection 24 hours after sex determination. Sturgeon  will be ready for stripping about 30-32 hours after their first injection. Preparation Dry carp pituitary hormone (CCP) should be pre-weighed  before hand and stored in air tight vials. Vials should contain the following  amounts; 10mg, 20mg and 50mg. This will allow the proper dosage to be mixed  quickly. Specific dosages for male and females are different. Using a 1 or 3cc  syringe with a 23 Ga.  needle, add just enough distilled water (0.3-0.5 ml) to the vial to make a  solution. Shake the mixture and allow it to settle. With the syringe, remove  the solution. The injection sight is located between the dorsal and  lateral scutes, at the midpoint of the body. The solution is injected into the  musculature, as the syringe is withdrawn place a finger over the hole and  massage the solution into the tissue. Dosage for males Male sturgeon receive their entire dose of hormone in one  injection. Dosage for males is lmg/kg (0.4mg/lb). Because of differences in  gonadal maturity, some males may be injected 12 hours after the first to insure  mature sperm are available. Dosage for females Female sturgeon receive two separate doses of hormone. Their  first injection is 10% of the total dosage. The second injection consists of  the remaining 90% of hormone and takes place 12 hours later. The dosage for  females is 5mg/kg (2mg/lb). **Egg Take:** Egg take operations commence about 30-32 hours after the  first hormone injection. The procedure begins with taking sperm, then eggs,  fertilization and packaging for transport. **Sperm:** Sperm is extracted from each male sturgeon that shows signs of  being ripe. Fish are removed one at a time from the holding tank, identified,  and placed in a stretcher. With an assistant restraining the fish with the  "thumb in mouth" technique another individual removes the sperm. A  50-60cc syringe with a 3" piece of tygon tubing (trimmed to a point) on  the end is used. The tube is inserted into the vent and is moved back and forth  as the syringe plunger is withdrawn. With 40-50cc of sperm in the syringe, it  is removed from the fish, capped, labeled and stored on ice. The syringe should  not come in direct contact with the ice. **Egg Removal:** Egg removal requires preparation and TEAMWORK, as time is a  limiting factor. Having people assigned specific tasks can be very helpful when  dealing with several fish at once. Before taking eggs be certain that all  fertilization equipment is set up. This equipment should include (but not  limited to) the following: Two water baths to keep materials at river temperature. At least 3 thermometers. Fullers Earth "mud": in 5 gallon bucket add water  and enough earth so the mud will settle out 2 inch on the bottom when left  alone. Beaker for diluting sperm. 4 stainless steel bowls 2-4 extra buckets Clear plastic bags and duct tape for transport.  Stripping is done in stages as eggs mature. Each female will  be stripped normally 2 times, the 3rd will be done by opening the incision  (which was previously made to sex the fish) to remove the bulk of the eggs.  Females are placed in the stretcher as before. Eggs are stripped into a dry  stainless steel bowl. When the first batch of eggs has been stripped, sperm is  diluted into a beaker with river water. A ratio of 1:200 sperm to water is  used. Sperm should come from at least 2 males, preferably 3 or 4. Eggs mature  in batches within a fish. It is important to inspect the holding tank for  presence of discharged eggs. If sticky eggs are present the female must be  stripped immediately, presence of nonsticky eggs means the females are  approaching maturity. **The following is done at river temperature by keeping pans  on water baths:** After sperm is diluted it must be placed immediately on the  eggs. The solution is swirled over the eggs for exactly 1-1.5 minutes. It is  then decanted off and replaced with a mud solution. Fullers earth solution is  added and mixed with the eggs. A swirling action is alternated with hand  mixing. This solution is changed 2 times after the initial treatment. Mudding  lasts for exactly 40 minutes. When mudding is complete the eggs are rinsed with  clear river water until clean. Eggs are then put into clear plastic bags half  filled with river water. Oxygen is injected into the bag and sealed. Eggs are  then placed in coolers filled with river water at the appropriate temperature.   Conservation and Management of Lake  Sturgeon In The Great   Lakes **By: MTAN** The MTAN was able to participate in a lake sturgeon workshop  which was held in Niagara Falls  on October 26/27. The two day meeting focused on five primary topics: 1)  Habitat, 2) Genetics, 3) Population Assessments, 4) Culture and  Reproduction/Life History, and 5) Management and Recovery Planning. If you  would like to develop additional contacts with other biologists who are working  on sturgeon recovery projects, the following list of workshop presenters may be  of some help. **Habitat:** Betsy Kozuchowski - USFWS, Lower Great Lakes Fishery  Resources Office, Amherst, NY. Habitat management using the guild  approach, (716-691-5456). Andrew Rossiter - Univ. of Guelph, Dept. of Zoology, Guelph,  Ontario, Food and foraging in juvenile lake sturgeon, (519-824-4120). Stephan Peake - Univ.  of Guelph, Dept. of Zoology, Guelph, Ontario,  Swimming performance of lake sturgeon, (519-824-4120). David Johnson - USFWS, Marquette Biological Station,  Marquette, MI. Tolerance of sea lamprey larva and lake sturgeon to TFM,  (906-226-6571). **Genetics:** Paul Fuerst - Ohio St. Univ., Dept. of Zoology and Molecular  Genetics, Columbus, OH. Molecular genetic and biochemical  studies of lake sturgeon, (614-292-6403). Rejean Fortin - Univ.  of Quebec at Montreal, Quebec, Canada, Morphology and population  biology of lake sturgeon, (514-987-6113). Harold Kincaid - NBS, Nat. Fisheries Research and  Development Laboratory, Welsboro,   PA. Breeding plan for small  populations of lake sturgeon, (717-724-3322). **Population Assessments:** Gary Whelan - Michigan DNR, Lansing, MI. Estimates of  historic lake sturgeon stocks, (517-373-1280). Ted Cavender - Ohio St. Univ., Museum  of Biological Diversity, Columbus, OH.  Decline and present status of lake sturgeon in Lake Erie,  (614-292-7873). Steve LaPan - NYSDEC, Watertown,   NY. Lake sturgeon field studies  on the St. Lawrence River,(315-785-2261). **Culture and Reproduction/Life History:** Andrzej Ciereszko - Ohio St. Univ., School  of Natural Resources, Columbus, OH.  Biology of lake sturgeon semen, (614-292-7964). Martin DiLauro - NBS, Nat. Fisheries Research and  Development Laboratory, Welsboro,   PA. Cryopreservation of lake  sturgeon sperm, (717-724-3322). Konrad Dabrowski - Ohio St. Univ., School  of Natural Resources, Columbus, OH.  Captive broodstock and diploid androgenesis, (614-292-4555). Bill Krise - NBS, Nat. Fisheries Research and Development  Laboratory, Welsboro, PA. Feeding dry diets to lake sturgeon larva  as a starter diet, (717-724-3322). **Management and Recovery Planning:** Chet MacKenzie - Vermont  Dept. of Fish and Wildlife, Pittsford,   VT. A feasibility study of  restoring lake sturgeon to Lake Champlain,  (802-483-2172). Elizabeth Hay-Chmielewski - Michigan DNR, Ann   Arbor, MI. Lake sturgeon management plan for the state of Michigan,  (313-663-3554). Steve LaPan - NYSDEC, Re-establishment of lake sturgeon in  tributaries of the St. Lawrence River,  (315-785-2261).   Twelve Uses Of Salt On The Trout Farm **Written By Charles W. Johnson****Submitted By Mike Donofrio (Keweenaw Bay  Indian Community)****Published in the September 1994 Issue of the Aquaculture  Magazine** Salt (sodium chloride) is one of the safest and oldest used  chemicals on fish farms. Granulated salt with no additives can be purchased in  50 or 80 pound bags at local farm supply stores. Some beneficial uses of salt  include: Parasite Control - one pound of salt for every two gallons  per minute water flow in raceways or earthen systems (with good water turnover)  has proven to be effective in controlling most parasites. Monthly treatments  are usually adequate when water temperatures are between 50-65 F. If summer  afternoon water temperatures rise to 65 F or above, weekly treatments may be  needed for effective parasite control. Costia is more difficult to control with  salt. If it becomes a problem, formalin treatments may be needed. Columnaris Control - Salt flush treatments have proven  effective in preventing columnaris. The frequency of treatments will vary  according to conditions on each farm and the water temperature. Monthly  treatments may be adequate when the water temperature is in the upper 50s.  Treatments at least once a week or more may be needed when the water  temperature is above 65 F. If lesions are seen on the gills of trout or other  symptoms increase, salt alone may not control columnaris. Promptly begin  feeding feed containing terramycin (3.5 grains active oxytetracycline per 100  pounds of fish) for 10 days. Saprolegnia Fungus Control - Routine salt treatments on  production fish usually help reduce fungal development. When fish are being  moved, a 1-1.5% salt solution (8.3-12.5 pounds/100 gallons of water) either in  the hauling tank or for thirty minutes prior to moving provides an effective  treatment. Another recommended treatment is exposing fish to a 3% (4  ounces/gallon of water) salt solution for about four minutes or until fish show  signs of distress. Weaker fish do better in the less concentrated salt  solutions. Some fish culturists have noticed that when fish are weak and in  water with high hardness, saprolegnia is more difficult to control. Fish culturists who do not like using formalin may consider  the use of salt on trout eggs. A treatment of 2-3% salt solution for 15 minutes  every other day has been found effective in preventing growth of saprolegnia on  eggs. A 2% treatment would require 2.5 pounds of salt for each gallon per  minute flow for the 15 minute period. If water could be adequately aerated and  recirculated for 15 minutes, a 2% treatment would only require 2.67 ounces of  salt for each gallon of water. If fungus is established, treatment for a longer  period of time will be needed. A treatment of 5% for up to one hour on  alternate days may be required to halt an existing infection on eggs. Do not  allow sac fry to be exposed to this concentration of salt. When Using Formalin - A prior salt treatment will reduce the  chances of mortality of fish and increase the effectiveness of the formalin  treatment for parasite control. A salt flush immediately following the formalin  treatment will help to recondition the damaged gills and reduce the chances of  delayed mortality. One pound of salt for every four gallons per minute water  flow should be adequate for both treatments.
  Acid Rain Relief - A sudden drop in pH creates stress in  trout. The fish usually act very nervous and even try to get out of the raceway  or pond in order to escape the irritating effects on their gills and skin. When  this condition is seen during or after a rainstorm, the immediate addition of salt  will help to relieve stress. When fish have been damaged from acid rain the  continuous use of white salt blocks (with no additives) at the head of the  system for two or three days will assist in recovery. Salt blocks used during  rainstorms when acid rain is a potential problem will be helpful in providing  the fish with needed ions, as well as providing relief from some of the stress  on the gills. If problems become critical, you may need to install a system at  the head of your farm to add a buffer, such as hydrated lime.
  Muddy Water Relief - If water becomes muddy during a heavy  rain or if it is stirred up during cleaning, a salt flush treatment will aid in  the removal of foreign particles on the gills. One pound of salt for every four  gallons per minute should be adequate.
  Grading and Inventorying For Stress Relief - A salt flush  just prior to grading, inventorying, and other handling of fish will help to  calm the fish and better prepare them for the handling stress. Salt relieves  the gills of excess water and stimulates the release of ammonia and nitrates  from the blood. It is especially beneficial to trout grown in soft water by  assisting with the salt balance needed in their blood and tissues.
  Hauling Stress Relief - The use of salt in transport tanks  is a common practice to reduce stress. Concentrations as high as 0.8% (6.4  pounds/100 gallons of water) can be used safely for extended periods. In soft  water, many biologists also recommend the addition of gypsum (3.3 ounces/100  gallons) to increase calcium hardness and baking soda (2.7 ounces/100 gallons)  to help prevent the pH from dropping. After the fish are delivered to raceways  or ponds, the use of salt blocks for several hours will help prevent fish  health problems from hauling and handling stress.
  Gill Problem Control - One of the major problems of early  feeding fry in hatcheries is the accumulation of uneaten feed and fecal  material on the gills. This frequently leads to environmental and bacterial  gill problems. Salt treatments administered at least weekly help rid the gills  and skin of excess mucus containing foreign material and organisms.
  Low Oxygen Relief - When fish are gaping at the incoming  water due to low oxygen, a salt flush will quickly relieve stress and reduce  chances of mortality. One pound of salt for every four gallons per minute  should be adequate. For extended relief, the use of salt blocks will be  helpful.
  Ice Control - Salt can be poured on your intake screen to  help melt ice, to reduce ice problems on raceway screens and even to help keep  pipes open during severe cold. It is also beneficial when sprinkled on icy work  areas.
  Algae Control - Salt sprinkled on filamentous algae in  shallow areas around the edge of ponds will help keep the algae under control.  Several applications will probably be needed during the year.
  Unlike many chemicals, salt can be safely used regardless of  water temperature. However, the use of salt does not replace the need for good  management practices such as keeping raceways and ponds clean, starving fish  before handling or hauling, maintaining proper densities, and avoiding  overfeeding.   Common Salt Is Fungicidal On Trout Eggs **By: Jeffrey J. Rach, Theresa M. Schreier, and Leif L.  Marking****National   Fisheries Research   Center, P.O. Box 818, La    Crosse, WI 54601  (608) 783-6451** Malachite green, the preferred fungicide for fishery use, is  no longer legal for control of fungus on fish or fish eggs. Formalin is an  effective fungicide, but fishery managers are concerned about safety to the  user and effects of effluent in the environment. Other antifungal agents are  needed to maintain healthy fish and eggs in fish culture systems. Salt (sodium chloride) has been widely used by the  aquaculture industry as a therapeutic agent and to reduce stress to fish. Some  fish farmers use salt for routine management purposes without proper knowledge  of how it functions. Salt is commonly used to prevent and treat bacterial  diseases, eliminate external parasites, reduce stress conditions during fish  transport, and reduce toxicity of ammonia and nitrate nitrogen in fish ponds.  Some reports in the literature suggest that use of seawater is effective for  control of the common fungus Saprolegnia sp. on eggs of salmon. Others suggest  that mixtures of sodium chloride and calcium chloride will control fungus on  incubating eggs. We designed experiments to evaluate the effectiveness of  sodium chloride for control of fungal infections on incubating eggs of rainbow  trout. **In Vivo Procedures:** Green eggs of rainbow trout were placed in Heath incubation  trays and maintained in well water with a flow rate of 1 L/minute. Groups of  500 eggs were confined within 15-cm diameter acrylic rings fastened to the  screen of each incubation tray. Eggs were inoculated with fungus (Saprolegnia  parasitica) actively growing on hemp seeds suspended by tea balls in the upper  tray of each duplicated treatment. Infection of eggs generally occurred within  7 days. The infection rate of about 10% in each duplicate series of trays was  obtained by exchanging infected eggs between the trays. Eggs infected at the 0  and 10% level were then exposed to salt solutions for 15, 30, or 60 minutes  every other day for 2 weeks. Treatments ceased when the eggs began to hatch. A  positive control group was inoculated with fungus, but not treated with salt; a  negative control group was not inoculated with fungus nor treated with salt. **Efficacy of Common Salt:** The hatch rate for control groups of eggs was only 12% for  those infected with fungus and 28% for those that were not infected, suggesting  that the infection procedure was successful. These eggs were tested during  August when trout eggs are generally smaller in size and lower in fertility.  The 1.5% salt treatment was ineffective for control of fungus on infected eggs,  but the hatch rate of uninfected eggs improved slightly. The 3% salt treatment  was highly effective for controlling infection in the uninfected eggs; hatch  rates were 65% in 15-min exposures, 66% in 30-minute exposures, and 72% in  60-minute exposures. These hatch rates were considerably higher than the  uninfected control group (28%), confirming the therapeutic value of  prophylactic treatments. Eggs that were infected with fungus at the 10% level  fared much better with 3% salt treatments; infection was controlled in 30 and  60 minute exposures, and hatch rates increased over control groups to 31, 39,  and 64% at the 15-, 30-, and 60 minute exposures. **Feasibility for Use of Salt:** Common salt is readily available and listed as a low  regulatory priority fishery chemical. We have demonstrated that 3% salt  solutions are effective for control of fungal infections and improving hatch  rates of treated eggs. Lower treatment rates may be useful for preventing  fungal infections through prophylactic treatments. Disadvantages of using salt  are the large quantities that would need to be transported, stored, and  administered to static or flow-through aquaculture systems. Perhaps the  solutions could be stored in tanks or ponds and reused during the egg  incubation season. We believe that salt is a viable antifungal agent where it  can be used in a practical manner. We conclude that the 3% salt treatment is the treatment of  choice because it is fungicidal and yet safe for the eggs.   PUMP ALARM SYSTEM **By: Larry Wawronowicz, Fish and Game Director, Lac du  Flambeau Tribal, Fish Culture Program** The Lac du Flambeau Tribal Fish Culture Program pumps water  to all its facilities from two wells and Pokegama Lake.  The pumped water supplies the 315 jar hatchery, the start tank facility, ten  200' raceways, 14 fish culture ponds, and the fish transport truck filling  depot. Currently on station are approximately 9 tons of trout with brown,  brook, and rainbow trout eggs. Walleye, muskellunge, and forage fish are reared  in the spring and summer. Depending on the time of the year, 1,000 to 5,000  gallons per minute of water is being pumped. In order for hatchery personnel to have some peace of mind,  sleep nights and enjoy the weekends, it was necessary to design andinstall an  alarm system for each pump. The alarm system was designed to alert hatchery  personnel if power was being supplied during normal or emergency situations  (i.e. power outages, switch failure). For example, on Saturday at 7:00 pm a major snowstorm hits  Lac Du Flambeau and the power lines are down. Telephone service is still  available and there is no one on station. The hatchery manager is home when he  receives a telephone call from Silent Knight Alarm (a private company -  715/362-7374) indicating Pump No. 1, 2 and 3 are "down". The hatchery  manager hangs up, puts his pants on and heads to the hatchery. In the meantime,  the emergency generators start and the transfer switches make power available  to the pumps. The system used to call the hatchery manager is diagramed above. The pump and a 110 Volt receptacle are supplied with AC  power by the Delta Control Switch. An AC power sensor is connected to the 110  Volt receptacle. If the Power Sensor does not detect AC power present, it will  send a signal to the Silent Knight Alarm automatic dialer and an alarm will be  received by Silent Knight Security in Rhinelander, Wisconsin through the telephone line.  Subsequently, a 24 hour operator at Silent Knight will call and keep on calling  a list of 9 numbers until someone answers. Note since the 110 Volt receptacles  and the pumps are connected on the same side of the Delta Control Switches, and  if the pumps do not have power the 110 Volt receptacles do not have power.  Also, because each pump has its own system the Silent Knight operator can tell  the person that answers which pump is down. The Power Sensor will also activate  a set of strobe lights located on the roofs of the pump houses so that in the  excitement of the moment, if personnel forget which pump is down, they can see  the lights flashing when driving by the rearing complex. The major disadvantage of this system is the telephone line.  If the telephone line and the power line both went down in the storm, the  hatchery manager would not have been notified. The hardware as described above  can be purchased for $200.00 per system and there is also a quarterly charge of  $105.00 for all units. The system has worked well and has saved production on  numerous occasions.   DISINFECTION OF HATCHERY FOMITES **By: Terrence Ott, La Crosse  Fish Health  Center, La Crosse, WI** Fish diseases are water borne microorganisms that have  plagued the lives of hatchery personnel since the inception of culturing large  numbers of fish in confined areas began. It can be assumed that fish are  continually bathed in an aqueous suspension of microorganisms and these  organisms are easily transmitted from one raceway pond to another by anything  that goes into the water: brushes, nets, seines, and boots. All these  "fomites" can be effectively sanitized by dipping, soaking, and  rinsing in some chemical disinfectant. Proper disinfection practices at your hatchery are an easy  and inexpensive method of disease control in which destruction of a  "link" in the transmission cycle of a potential fish pathogen can be  broken. Sunshine, in itself, is a fine sanitizer, and few fish  pathogens can last very long under the combined assault of drying and sunshine.  Hatchery tools which have come into contact with a stock of fish should always  be allowed to air-dry in the sun, before contacting another stock of fish. If time and sunshine are at a minimum, the raceway walls and  bottom should be thoroughly cleaned by removing fecal material, excess food and  aquatic plants, then treated with a strong solution of HTH (calcium  hypochlorite) by Olin Corporation, Stamford, Connecticut. The quaternary  ammonium compounds, such as Hyamine 1622, Hyamine 3500, and Roccal can be used  at 600 ppm effectively as disinfecting agents. Net-Dip, distributed as Sanaqua  by Aquavet, Mayward, California is a buffered chloride compound  and is a good disinfectant to use in a 30-gallon tub filled with the  appropriate strength and kept in a convenient location for disinfecting  hatchery tools. The strength of the disinfecting solution is based on the  active ingredient as purchased. Fish raceways can be disinfected by using 1  ounce (dry weight) of HTH per 25 gallons of water for 60 minutes. Iodophors, sold under the trade names of Betadine,  Wescodyne, and others, incorporate the disinfecting element of iodine, which is  an oxidizing agent. Wescodyne can be purchased from West Chemical Products, New York, New    York and used at a concentration of 3 ounces to 5  gallons water. HTH is toxic to fish in very low concentrations. Do not  contaminate aquatic habitats by cleaning hatchery equipment or disposing of HTH  waste products into the environment. Apply this product only as specified on  the label. Store HTH in a cool dry place in its original container. As with all  chemicals received at your hatchery read and understand what is in the Material  Safety Data sheets before handling the chemical. Hatchery personnel entering and exiting a hatchery building  can easily eliminate the spread of microorganisms by disinfecting the bottom of  their boots in a footbath. This can be accomplished by placing a rubber grated  mat or large sponge in the bottom of a plastic dish pan. Fill the pan with just  enough disinfectant solution to cover the grated mat or saturate the sponge.  This will allow wetting only of the bottom of the boot. If the entire boot  requires disinfection, remove the mat or sponge from the pan and add more  disinfectant to raise the level above the ankle. Change the disinfectant  solution in the pan once a week to keep the solution fresh and working. Ponds which have contained fish should receive an  agricultural lime treatment of 2,000 pounds per acre, and be allowed to air-dry  in the sun for several weeks before new stocks of fish are introduced. Another method of keeping the link broken between fish and  potential pathogens is to keep tools used in cleaning raceways separated from  one raceway to the next. Supply each raceway on your facility with its own set  of brooms, brushes, and dip nets. If this is not possible you should at least  keep separate tools used for broodstock from those used for fry and  fingerlings. Broodstock often carry microorganisms, which may not be harmful to  them, but are easily transmitted to, and can be detrimental to, younger fish. Keep in mind while working at your hatchery that good  hygiene is one of the best ways of ensuring a good healthy stock by allowing  normal physiological functioning and a proper balance between the animal and  its environment, thus reducing the influence of harmful agents in that  environment.   Hatching Fish Eggs Out Of Water **Commercial Fisheries Newsline, October 1994** What are you doing to invent the future? Do fish eggs really  need to be incubated in water? Could small amounts of water be heated/cooled  and then sprayed over eggs to speed/retard egg development? Experiments In Hungary on white mice oocytes in an  embryological laboratory have led to the development of a new form of fish egg  incubator. The knowledge that pike-perch eggs can be incubated out of water in  a damp spray, motivated a series of experiments. A small group of researchers,  a geneticist, an electrical engineer, and a fish biologist began investigating  a practical means of fish egg incubation and hatching out of water. Their criteria were that: the new method should involve low  water and energy consumption; survival should be at least equivalent to that  provided by traditional incubators; sterilization should not involve malachite  green, antibiotics or other banned chemicals; labor should be minimal; hatching  should be at an optimal time, and the incubator should work both for freshwater  and seawater fish eggs (preferably for most cultured species). The first experiments used common carp eggs, and established  that incubation did not require water, just moisturized air. The fertilized  eggs were placed on a net with a mesh of about 2/3 of the eggs' diameter. Metal  or plastic nets made of filamentous material proved unsuitable; hard nets were  best. To increase capacity, the optimum number of eggs to be placed on the  net-tray was established. In the case of carp, good results were achieved with  up to 2-3 layers of eggs. Sometimes, usually in batches with low fertilization rates,  infections led to mass mortality. This was mostly when moisture was over 100%  in air, and the water condensed in droplets on the eggs. With relative humidity  lower than 99 percent the eggs were damaged through drying out, which meant  precise temperature-humidity regulation was needed. After a year of  experimentation, this was successfully refined. The problem of sudden infections causing high egg losses  remained. A further year was spent testing several chemicals and treatments to  reduce the losses. A tannic acid solution was the answer, and once the  treatment was perfected, even batches of eggs with less than 10% fertilization  rate were free of external fungal or bacterial infections without using  malachite green or antibiotics. Later versions of the incubator have an automatic feature  for separating the egg shells and larvae after hatching. The latest, and  best, variant is made from material resistant to sea water corrosion. It is  programmable for different species, and has even been tested for hatching the  eggs of Atlantic cod. Survival was no lower than that of the control group. The  fish egg incubator uses 400 liters of water per 60 hours for the incubation of  1,000,000 carp eggs. Before marketing, the machine needs to be tested for other  sea-water fish as well as salmonids, but since Hungary has no sea, this is not  easy, and the company is now seeking a foundation or partner to complete the  job. More information is available from: Mr. Lajos Laslo,  Biochemical Laboratory Service Ltd, H-1165 Budapest, Zselyi Aladar u. 31. Hungary. Tel:  +36-1-271 2602, Fax: +36-1-271 2896.    **Return
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