Dedicated To Tribal Aquaculture Programs | ||||||
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 | June 2008 ~ Volume 64 | ||
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Topics of Interest:
Genoa NFH Upgrades Coaster Egg Incubation System
UWSP - Annual Field Days/Workshop
By Greg Fischer, Facility Manager, Northern Aquaculture Demonstration Facility
The UWSP Aquaculture Demonstration Facility will be hosting its Annual Field Days/Workshop coming on June 12-13, 2008. The focus this year will be on practical aquaculture skills and use of equipment. Some of the topics planned to be covered are Fish Health and testing on the farm, feeding, pond weed control, disinfection, water quality, aeration, fish sampling/grading, larval fish feeding/feed training, and use of nets.
There will also be updates on NADF projects and extension/outreach work. Interested folks can contact Ron Johnson at 715-779-3189 or ron.johnson@uwsp.edu or Sarah Kaatz at 715-346-3037 or skaatz@uwsp.edu for more information.
2.5 HATCHERY TIPS
Greg Fischer, NADF Facility ManagerHATCHERY TIP #1: FREE OXYGEN FOR YOUR FISH !!
Well water and some spring water is often naturally low in dissolved oxygen
and higher in other gases such as nitrogen. Heating cold water can also cause higher nitrogen gas levels in water. Sending this water directly into your fish
rearing tanks and ponds can potentially cause issues. Water that is saturated with gases
can actually be over 100% saturated and may not show any visible signs such as bubbles. If the gas saturation in the water reaches 102% or greater, some species of fish are negatively affected and may go off feed or worse die. Different species of fish are affected in separate ways by gas super saturation.A fairly easy and inexpensive way to potentially correct super saturation and add oxygen to your incoming water is to run the water through a degassing/aeration column. To correctly size and build a degassing/columns for a large volume of water does require some engineering design, but you can build smaller units for your tanks that do work without an engineering degree. Fairly effective, small, degassing/aeration columns can be constructed using corrugated PVC drain pipe or similar material that is 36-48 inches long and 4-8 inches in diameter (the exact diameter pipe to use depends on the flow). Attach a plastic or noncorrosive screen at one end of the pipe and fill the pipe ¾ full with bioballs, koch rings, (Aquatic Ecosystems) or plastic screening to break up the water. Leave the other end open for the water inlet. Hang or suspend this from the ceiling and run the water through it into the rearing tank. This should cause an increase in the oxygen levels and a lowering of the total gas saturation of the water.
There are many variables to consider in how effective these simple degassing/aeration columns can be, but they are fairly inexpensive to build and are a good place to start with dealing with super saturation or low oxygen levels in your water. Remember happy fish start with good water quality and a proper rearing environment.
HATCHERY TIP #2
NADF has been experimenting with early life stage larvae feeds for lake herring with some success. The projects final results will be presented at a later date but we wanted to share the experimental diets with folks in the industry. While visiting NADF this winter, Rick Goetz of the WATER Institute observed larval herring feeding on these diets and has tried one with some success for early feeding of yellow perch. One commercial grower is also trying these diets with yellow perch this spring. NADF is planning on investigating the use of these diets in the spring with several species. These diets may be useful for other species such as walleye and yellow perch. The diets that NADF have been utilizing are Proton manufactured by INVE Aquaculture Inc. (801-956-0203) (www.inve.com) and Artemac manufactured by Aquafauna BioMarine (310-973-5275) (www.aquafauna.com). Both these diets are specially formulated with highly specific material and are aimed at replacement of live Artemia. These diets are fairly expensive, but usually only need feed larvae fish a short time before converting them to a less expensive commercial feed. These diets may potentially help bridge the gap of first feeding larvae fish which would be very beneficial to commercial growers out there. Please feel free to contact us with any questions, comments, or trials that you run with these feeds.
HATCHERY TIP #2.5
As spring approaches many coolwater and warmwater fish facilities will be preparing for egg collection and incubation. A common problem with incubating eggs is fungus or Saprolegnia infections. These infections are usually identified to the eye as a white cottony growth. As with all fish health issues your first step should be to provide hatchery conditions as favorable as possible to the incubating eggs. This includes sufficient oxygen, correct temperature, appropriate pH, and removal of dead eggs. If fungus is evident or continues to present an issue, a known hatchery method for chemically treating fungus (Saprolegnia) infections is formalin at 1667ppm for 15 minutes. Some common trade names of approved for fish use formalin are Paracide-F(Argent Chemicals 800-426-6258) and Parasite-S (Western Chemical 800-283-5292).
A note of caution with using any of the above formalins. Store at recommended temperatures of 59°F and do not expose to direct sunlight. Do not allow to freeze and avoid prolonged storage. Cold and freezing cause the formation of paraformaldehyde, which is toxic to fish. Paraformaldehyde can be recognized as a white precipitate in the container. When in doubt throw it out. Also, remember to order sufficient formalin in the warmer months as it cannot be shipped to us in the cold months.
Genoa NFH Upgrades Coaster Egg Incubator
By Nick Starzl, Fishery Biologist , Genoa National Fish Hatchery, Genoa, WI.
A new recirculating egg incubation system was constructed at the Genoa National Fish Hatchery (NFH) to facilitate coaster brook trout production. The new system incorporates a chiller which allows for the manipulation of the egg incubation temperature. Slowing the growth rate of some egg lots is especially important during the start of the coaster brook trout production cycle at the Genoa NFH. Brook trout eggs are taken throughout the entire spawning season at the Iron River NFH in order to ensure genetic conservation of the brook trout strains. The eggs are then shipped to Genoa NFH in late December through early January. At this time, the growth rate of the early egg lots are slowed by chilling the water, while the later lots are allowed to catch up developmentally over a period of a month. This process allows the entire brook trout production lot to be pooled together, resulting in an increased efficiency of time and space as well as reducing cannibalism and therefore increasing survival.
Cost was kept to a minimum by utilizing existing materials, including the pump and chiller from the previous system, and by constructing the system in house by using the talents of Jeff Lockington in order to weld the aluminum frame and water reservoirs. It’s estimated that a similar system would have cost $6,300.00 if the system would have been bought new, but by using the above cost savings methods the price was about $2,200.00 including staff labor. The main expense for the project was the purchase of two new MariSource vertical egg incubators.
Coaster brook trout produced at the Genoa NFH are part of an ongoing Great Lakes multi-agency restoration effort involving the U.S. Fish & Wildlife Service, the National Park Service and the states of Wisconsin, Minnesota and Michigan. The "coaster" strain of brook trout is endemic to the Great Lakes and other drainages along the Atlantic coast. The species is threatened due to over-fishing, competition with non-native species, and habitat loss throughout its range. Each year, the Genoa NFH distributes thousands of brook trout to restore populations along the northern shores of Lake Superior. Genoa's 2008 production of “brookies” is scheduled to include 30,000+ stockable fish ranging in size from 2" to 9", and also to provide a backup brood source for the Iron River NFH.
Calculation of Disease Treatments
By Michael Masser and John Jensen, Southern Regional Aquaculture Center
* Water treatments are based on water volume. A specified amount of chemical is added to a known quantity of water for a specified time. If too little chemical is added the treatment will be ineffective; if too much is added or if the fish are left in contact with the chemical too long, they may become stressed or die.* Feed treatments and fish injections are based on fish weight. A specified amount of chemical is added to the feed or injected into the fish. Improper doses may result in an ineffective treatment or mortalities.
* Aquaculturists should compute the volume of each culture unit (e.g., pond, tank, and raceway) before a problem occurs, preferably when the system is designed or filled with water for the first time. The information should be stored so it is immediately available when needed. Practice calculations should be done so the culturist is comfortable and familiar with the computation procedure. A useful text is "Handbook for Common Calculations in Finfish Aquaculture" by Gary Jensen. Culturists are strongly encouraged to obtain and use a copy of this or a similar work book.
If you lose or gain a decimal point on a sample problem, you get the answer wrong. If you lose or gain a decimal point in real life, your treatment will likely be ineffective and your fish will continue to die or you may actually kill your fish with the treatment!
Sample Calculations
To provide the culturist with an opportunity to become familiar with the methodology used to calculate fish disease treatments, three hypothetical situations are presented. For each example, there are several ways to correctly compute the amount of chemical to add or the drug to use. Calculations and steps are shown in detail for one method.
Example 1
You have a raceway with rainbow trout that are infected with the parasitic protozoan. You elect to treat with chemical XYZ. The raceway contains 5,000 gallons of water with an alkalinity of 75 milligrams per liter (mg/L or ppm). How much XYZ would you use?
- Determine from your diagnostic laboratory or from aquaculture literature the proper chemical concentration that should be added to provide a safe treatment (an example may be similar to Table 1).
Table 1. Treatment concentration of XYZ in water of various alkalinities
(mg/L = ppm)
Alkalinity of water (mg/L
Permissible Treatment (mg/L)
0-49
Test for toxicity before use
50-99
0.5-0.75
100-149
0.75-1.00
150-200
1.00-2.00
200+
Ineffective
You know that the alkalinity is 75 mg/L. Therefore, an appropriate treatment concentration for XYZ is 0.5 mg/L.
2) Determine the quantity of XYZ to be added to the raceway to achieve the 05 mg/L concentration.
2a) Convert the volume of the raceway from gallons (gal) to liters (L).
(5,000 gal) x (3.8 L per gal) = 19,000 L in the raceway2b) Determine a correction factor for the proportion of chemical (XYZ) that is active ingredient. (100%) / (100% active ingredient) = correction factor = 1.0
NOTE: Percent active ingredient is the purity of the chemical or the amount that is effective in the treatment of the disease. If the chemical is not 100% active, a correction factor must be generated.
2c) Compute the amount of chemical (XYZ) that should be added to the raceway.
(volume of raceway) x (dosage of XYZ) x (correction factor) (19,000 L) x
(0.5 mg/L XYZ) x (1.0) = 9,500 mg XYZ2d) Convert milligrams (mg) XYZ to grams (g).
(9,000 mg) / (1,000 mg/ 1.0 g) = 9.5 g XYZ added to the 5,000 gallon raceway
NOTE: Because some protozoan’s have a complicated life cycle that must be considered in its treatment, applications of some chemicals should be made frequently.
Example 2
1) Obtain from your diagnostic laboratory a recommended treatment concentration for formalin. An appropriate dose is often 25 mg/L (or 25 ppm formalin)
2) Determine the quantity of formalin to be added to the raceway to achieve the 25 mg/L (25 ppm) concentration.
2a) Convert the volume of raceway from gallons (gal) to liters (L). (5,000 gal) x (3.8 L per gal) = 19,000 L in the raceway
2b) Determine a correction factor for the proportion of chemical (formalin) that is active ingredient.
NOTE: Although formalin is 37% formaldehyde gas dissolved in water, for fish treatment purposes formalin is considered to be 100% active.
(100%) / (100% active ingredient) = correction factor = 1.02c) Compute the amount of chemical (formalin) that should be added to the raceway. (volume of raceway) x (dosage of formalin) x (correction factor)
(19,000 L) x (25 mg/L formalin) x (1.0) = 475,000 mg formalin2d) Since formalin is a liquid it is desirable to convert milligrams (mg) to milliliters (mL). (475,000 mg formalin) / (1,000 mg / 1.0 g) = 475 g formalin 1.0 g formalin = ~ 1.0 mL formalin, so 475 g formalin = 475 mL formalin added to the 5,000 gallon raceway
Example 3
You have carp in a garden pond with a diagnosed bacterial (Aeromonas hydrophild) infection. The pond contains 10 fish that weigh an average of 2 pounds each, for a total of 20 pounds offish. The bacterium is sensitive to terramycin. How would you prepare the treatment?
1) Determine from your diagnostic laboratory or from aquaculture literature the proper treatment concentration. Terramycin is frequently used at 2.5 grams (g) active ingredient per 100 pounds (lb) of fish per day for 10 days. The drug is then mixed with the feed and fed to the fish.
2) Determine the quantity of terramycin needed for the 10 day treatment.
2a) Determine a correction factor for the proportion of chemical (Terramycin) that is an active ingredient.
NOTE: Terramycin premix is often supplied as a 50% active mixture. Always check the label of a specific package. (100%) / (50% active ingredient) = correction factor = 2.02b) Compute how much Terramycin is to be fed each day. (dosage of Terramycin) x (lb of fish in pond) x (correction factor) (2.5 g Terramycin / 100 lb fish) x (20 lb fish) x (2.0) = 1.0 g terramycin per day
2c) Compute the quantity of terramycin fed for 10 days. (1.0 g Terramycin / day) x (10 days) = 10.0 g Terramycin
3) Determine the amount of food that you will feed to the fish during the 10 day treatment period.
3a) Ornamental fish, such as carp, might reasonably be fed at a rate of 1% of their body weight per day. (20 lb fish) (1.0% / 100 %) = 0.2 lb food per day
3b) Compute feeding rate for 10 days. (0.2 lb food / day) x (10 days) = 2.0 lb food
4) Prepare medicated feed and present it to the fish.
Commercially prepared, medicated feeds are available and can be used. Alternatively, medicated feed can be prepared by mixing the 10 grams of Terramycin with two pounds of feed. The antibiotic may be mixed in a vegetable or fish oil. It is then spread on the feed pellets which become coated with a thin film of the antibiotic-laced oil. Regardless of the source, 0.2 pounds of the medicated feed are provided to the carp each day for 10 days.NOTE: Treating any fish by mixing your own feed/chemical, assumes you are able to obtain an even mix of the product and that the fish can consume the correct amount of chemical needed.
The Role of Stress in Fish Disease
R.W. Rottmann, R. Francis-Floyd, and R. Durborow, Southern Regional Aquaculture CenterStress
Physiological stress and physical injury are the primary contributing factors of fish disease and mortality in aquaculture. Stress is defined as physical or chemical factors that cause bodily reactions that may contribute to disease and death. Many potential fish disease pathogens are continually present in the water, soil, air, or fish. In nature fish are often resistant to these pathogens, and they are able to seek the best living conditions available. Food fish reared under commercial aquaculture conditions are confined to the production unit and are weakened by stress conditions including:
- increased fish density and poor water quality (i.e., low dissolved oxygen, undesirable temperature or pH, increased levels of carbon dioxide, ammonia, nitrite, hydrogen sulfide, organic matter in the water);
- injury during handling (i.e., capture, sorting, shipping);
- inadequate nutrition; and
- poor sanitation
These conditions can result in decreased resistance by the fish, resulting in the spread of disease and parasite infestation.
Stress and injury initially trigger an alarm reaction (fight or flight response), which results in a series of changes within the fish. A blood sugar increase occurs in response to hormone secretion from the adrenal gland as liver glycogen is metabolized. This produces a burst of energy which prepares the animal for an emergency situation. In addition, the inflammatory response, a defense used by fish against invading disease organisms, is suppressed by hormones released from the adrenal gland. Water balance in the fish (osmoregulation) is disrupted due to changes in the metabolism of minerals. Under these circumstances, freshwater fish absorb excessive amounts of water from the environment (over-hydrate); saltwater fish lose water to the environment (dehydrate). This disruption increases energy requirements for osmoregulation. Respiration increases, blood pressure increases, and reserve red blood cells are released into the blood stream.
Fish are able to adapt to stress for a period of time; they may look and act normal. However, energy reserves are eventually depleted and hormone imbalance occurs, suppressing their immune system and increasing their susceptibility to infectious diseases.
Defense against infection
Mucus
Mucus (slime layer) is the first physical barrier that inhibits entry of disease organisms from the environment into the fish. It is also a chemical barrier, containing enzymes and antibodies which can kill invading disease organisms. Mucus also lubricates the fish, aiding their movement through water, and is important for osmoregulation. Injury as a result of handling (i.e., capture, transport, etc.) and certain chemicals in the water (i.e., poor water quality, disease treatments) remove or damage the mucous layer, reducing its effectiveness as a barrier against infection at a time when it is needed most. This damage decreases the chemical protection of the slime layer and also results in excessive uptake of water by freshwater fish and dehydration by saltwater fish. Decreased lubrication causes the fish to expend more energy to swim at a time when its energy reserves are already depleted.
Scales and skin
Scales and skin function as a physical barrier which protects the fish. These are injured most commonly by handling, rough surfaces of tanks or cages, and by fighting caused by overcrowding or reproductive behavior. Parasite infestations can also result in damage to gills, skin, fins, and loss of scales. Damage to scales and skin of the fish can increase the susceptibility to infection. It also causes excessive uptake of water by freshwater fish or loss of water from marine species (osmotic stress). Fish which are heavily parasitized may die from bacterial infections which gained initial entrance to the fish’s body through damaged areas in the skin.
Inflammation
Inflammation is a natural immune response by the cells to a foreign protein, such as bacterium, virus, parasite, fungus, or toxin. Inflammation is characterized by swelling, redness, and loss of function. It is a protective response, an attempt by the body to wall off and destroy the invader.
Any stress causes hormonal changes which decrease the effectiveness of the inflammatory response. Temperature stress, particularly cold temperatures, can completely halt the activity of the immune system, eliminating this defense against invading disease organisms. Excessively high temperatures are also extremely detrimental to the fish’s ability to withstand infections. High water temperature may favor rapid population growth of some pathogens. High temperature also reduces the ability of the water to hold oxygen and increases the metabolic rate and resulting oxygen demand of the fish.
Antibodies
Unlike inflammation and other nonspecific forms of protection, antibodies are compounds formed by the body to fight specific foreign proteins or organisms. The first exposure results in the formation of antibodies by the fish which will help protect it from future infection by the same organism. Exposure to sublethal concentrations of pathogens is important for fish to develop a competent immune system. Animals raised in a sterile environment will have little protection from disease. Young animals may not have as effective an immune response as older animals and therefore, may be more susceptible to pathogens in the environment. Stress impairs the production and release of antibodies. Temperature stress, particularly rapid changes in temperature, severely limits the fish’s ability to release antibodies, giving the invader time to reproduce and overwhelm the fish. Prolonged stress reduces the effectiveness of the immune system, increasing the opportunities for disease-causing organisms.
Disease prevention
Numerous books and articles have been written on the diagnosis and treatment of specific fish diseases; however, prevention through good management practices is the best control measure to minimize disease problems and fish kills. Good management involves maintaining good water quality, preventing injury and stress during handling providing good nutrition, and using sanitation procedures. The following are management practices that help prevent stress and the resulting fish kills.
Water quality
1. Do not exceed carrying capacity of fish in ponds and tanks.
2. Monitor water quality parameters. Maintain dissolved oxygen levels above 5 mg/L. Sub-optimum levels of dissolved oxygen, while not immediately lethal, may stress fish, resulting in delayed mortality.
3. Prevent the accumulation of organic debris, nitrogenous wastes (ammonia and nitrite), carbon dioxide, and hydrogen sulfide.
5. Maintain appropriate pH, alkalinity, and temperature for the species.
Handling and transporting
1. Use capture methods that minimize physical injury and stress.
2. When possible, use knitted mesh nets rather than knotted nets to reduce injury and scale loss.
3. Speed and gentleness when handling fish are of utmost importance.
4. Minimize the number of times the fish are lifted from the water, and work as quickly as possible when transferring fish.
5. Harvest, handle, and transport fish at times when fish are least susceptible to stress and infection.
6 Transport and holding tanks should be large enough to allow complete freedom of movement of fish and have no sharp corners or edges that might injure the fish.
7. Maintain optimum water conditions while capturing, hauling, and handling fish.
8. A high level of dissolved oxygen is crucial for rapid recovery of the fish from the struggle of capture and handling.
9. Salt (0.3 to 1.0 percent) maybe used in the transport water to minimize osmotic stress and bacterial infection of freshwater fish.
10. Ice may be added to the water during hauling to prevent an increase in water temperature which reduces the ability of the water to hold oxygen and increases the metabolic rate and resulting oxygen demand of the fish.
Nutrition
1. Feed a high quality diet that meets the nutritional requirements of the species.
2. Use proper feeding rate (either over-feeding or starving the fish should be avoided).
3. Store feed in a cool dry place to prevent deterioration. If available, a freezer is ideal for storing fish feed.
Sanitation
1. Quarantine all new fish and observe for mortality. Send samples to a diagnostic laboratory to be examined for parasites and evaluated for viral and bacterial disease.
2. Prevent disease-carrying fish from living in hatchery water supply (e.g., reservoir ponds, springs, streams).
3). Remove all dead fish from a production system as soon as they are observed.
4. Dispose of dead fish properly to prevent spread of disease.
5. Use good sanitation practices resulting in clean equipment, ponds, and tanks. Disinfect containers, nets, and equipment to minimize transmission of parasites and disease from one population to another.
Conclusions
Stress compromises the fish’s natural defenses against invading pathogens. When disease outbreaks occur, the underlying stress factors, as well as the disease organism, should be identified. Correcting stress factors should precede or accompany chemical disease treatments. A disease treatment is only an artificial way of slowing down an infection so that the fish’s immune system has time to respond. Any stress which adversely affects the fish will result in an ongoing disease problem. Prevention of disease outbreaks is more cost-effective than treating dying fish.
The work reported in this publication was supported in part by the Southern Regional Aquaculture Center through
Grant No. 89-38500-4516 from the United States Department of Agriculture.
The Aquatic Animal Drug Approval Partnership Program is a division of the U.S. Fish & Wildlife Service. Its mission is: “Working with our partners to conserve, protect and enhance the Nation’s fishery resources by coordinating activities to obtain U.S. Food and Drug Administration approval for drugs, chemicals and therapeutants needed in aquaculture
AADAP’s new publication series:
The USFWS’s Aquatic Animal Drug Approval Partnership (AADAP) Program recently unveiled two new publication series. Drug Research Information Bulletins (DRIBs) are short bulletins (two pages maximum) describing techniques or observations developed/made at AADAP’s facilities and/or by AADAP staff at partner facilities. DRIBs are intended to provide short study summations of drug approval-related research that fish culturists, INAD investigators, and other aquaculture folks will find useful. Unlike the DRIBs, the Drug Research Reports (DRRs) are longer publications (up to 12 pages or more). The DRRs provide a much more detailed report on studies conducted by AADAP and our partners, which typically will pertain directly to the generation of FDA-required effectiveness or target animal safety data. Access the individual publications below or click here for the program home page.
- Buffering Oxytetracycline Hydrochloride Immersion-Marking Solutions with Sodium Phosphate Dibasic.
- Calculate Amount of Aquaflor® (florfenicol, 50%) to Add to Fish Feed.
- Modeling the Safety of AQUI-S® to Rainbow Trout.
- The Efficacy of Aquaflor® to Control Mortality in Freshwater-Reared Salmonids Naturally Infected with Coldwater Disease.
- Efficacy of Chloramine-T to Control Mortality in Largemouth Bass Naturally Infected with External Columnaris.
Drug Research Reports
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| 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. |
