Dedicated To Tribal Aquaculture Programs September 2007 ~ Volume 61 Coordinator: Frank G. Stone  (715-682-6185) Ext. 12 U.S. Fish and Wildlife Service Email: Frank_Stone@fws.gov

Topics of Interest:

Portable Fish Rearing Facility

Fish Health Advisory ~ VHS

Stress and Fish Health

Treatment of Fish Diseases

Calculating Treatments for Ponds and Tanks

Pond Fertilization Basics

Aquatic Animal Drug Approval Partnership Program Update

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Portable Rearing Facility and Spawning Habitat Reclamation
Aid Remnant Lake Sturgeon
Aaron Paquet, Environmental Scientist, Northern Environmental, Lansing, MI.  1-517-702-0470

Lake sturgeon (Acipenser fulvescens) are an ancient, long-lived, and hardy fish that were once abundant throughout the Great Lakes.  Sadly, as Europeans settled in the region and altered its landscape through logging, commercial fishing, and development, the Great Lakes largest fish declined precipitously in abundance.  Today, lake sturgeon remain in only low numbers and their populations exist in only a small fraction of the historic range. 

Over fishing and other human-induced pressures drove the sturgeon into decline.  However, it is diminished reproduction resulting from these low population numbers and a lack of available and/or accessible spawning habitat that has perpetuated their suppression.  The Little River Band of Ottawa Indians (the Tribe) recognizes the importance of this very unique species and is leading efforts to protect and restore it.  Their first objective was to help the genetically distinct, remnant population of sturgeon that spawns in the lower Manistee River.  In a given year, less than 90 members of the population are believed to spawn, and only a small fraction of those are female.

Recognizing the immediacy of this small, remnant populations need, the Tribe initiated a concerted effort to bolster successful reproduction.  In 2004 the worlds first portable streamside sturgeon fry rearing facility, custom built on behalf of the Tribe by Northern Environmental Technologies, Incorporated (Northern Environmental), was put into operation along the lower Manistee River.  Rearing fry in a streamside facility, as opposed to in offsite hatcheries, is expected to maintain the natural imprinting of the young sturgeon to the Manistees unique physiochemical characteristics. This is essential to preserving the distinct genetic identity of the Manistee Rivers spawning population by encouraging high fidelity to the sturgeon's stream of origin.  This may also protect other small, remnant populations by minimizing the straying of Manistee River sturgeon into other systems. Since inception, the portable facility and rearing process have undergone numerous refinements, ultimately rendering the robust and adaptable platform for streamside fish hatching and/or rearing thats available today.  Following the success of the Manistee River rearing facility, the Tribe and a coalition including the Great Lakes Fisheries Trust Wisconsin Department of Natural Resources, U.S. Fish and Wildlife Service, Michigan Department of Natural Resources, and Northern Environmental collaborated to place four additional portable streamside sturgeon rearing facilities around the Lake Michigan basin.  Installed at locations on the Milwaukee and Manitowoc Rivers in Wisconsin and the Cedar and Whitefish Rivers in Michigan, this initiative is intended to restore or bolster sturgeon reproduction in tributaries around Lake Michigan that historically hosted spawning. Increasing successful reproduction through streamside rearing is only a starting point for sturgeon restoration.  The key to ensuring their long-term recovery and sustainability in the Great Lakes will be restoring and reclaiming suitable spawning and rearing habitats in tributary rivers and streams.  Although sturgeon spawning habitat has been created in some Great Lakes states, the method used (i.e., armoring river banks with stone rip rap) can be detrimental to long-term stream stability and the habitat of other organisms.  With that in mind, the Tribe set out to find a better way.  During 2005, the Tribe and Northern Environmental once again collaborated.  This time, both the Manistee Rivers primary sturgeon spawning site (an man made deposit of stone in a reach locally known as Suicide Bend) and the documented conditions of other North American sturgeon spawing habitats were evaluated.  The findings were then contrasted to the conditions of a reach (locally referred to as Tunk Hole) immediately adjacent to Suicide Bend.  Our goal was to determine what factors contribute to, and limit, suitable spawning habitat at Tunk Hole.  By combining strategies developed from the gathered information with contemporary stream habitat restoration tactics, we developed an ecologically, culturally, and aesthetically-sound manner for creating sturgeon spawning habitat at Tunk Hole was discerned.  This effort has laid the groundwork for reclaiming Tunk Hole.

 

Fish Health Advisory ~ VHS
By: Wisconsin Dept. of Agriculture

Click here to view this pdf document (484KB)

 

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Stress and Fish Health
Reprinted from: Introduction to Fish Health Management
La Crosse Fish Health Center
Edited By: Becky Lasee, USFWS

Stress is a major contributing factor in disease outbreaks. Seyle (1950) defined stress as "the sum of all the physiological responses by which an animal tries to maintain or reestablish a normal metabolism in the face of a physical or chemical force."

In other words, stress occurs when the fish is faced with environmental or other factors that extend the stabilizing (or homeostatic) processes beyond the fish's normal limit.

A stress factor or stressor is an environmental change that is severe enough to require a physiological response on the part of the fish. If the response of the fish is sufficient to reestablish a satisfactory relationship with the changed environment, then adaptation to the stressor will occur.The physiological changes that occur following a stressor have been termed the general adaptation syndrome (GAS) or stress response. GAS has been described as consisting of: (1) an alarm reaction; (2) a stage of resistance during which adaptation occurs; and (3) a stage of exhaustion if adaptation does not occur because the stress was too severe or long lasting. There are many environmental stressors associated with intensive culture of fish. These include poor water quality (i.e. high ammonia, nitrate, or pH, low dissolved oxygen and high levels of organics), rapid environmental changes (i.e. fluctuating water temperatures) and poor nutrition. Additional management practices, such as handling, seining, sorting, grading, vaccinating, therapeutic treatments, fright, anesthesia, crowding and transport also contribute to stress in fish. Stress induced by environmental and management practices can result in reduced growth (due to poor food conversion or weight loss), impaired spawning, altered behavior, increased susceptibility to disease and even death. Examples of the effects of stress on disease resistance include development of columnaris disease following handling of fish in warm weather and outbreaks of fungus in the winter. Outbreaks of most parasites and other types of bacteria can also occur following stress. Many of the stressors that occur in intensive culture can be controlled through changes in management practices. The following recommendations will assist in decreasing hatchery related stressors:

• Reduce handling of fish. Use proper handling and hauling procedures when moving fish.If there is a seasonally to disease outbreaks, avoid handling fish two to three weeks prior to and during the expected time of usual outbreaks.Avoid handling and crowding fish during hot weather.Avoid temperature shocks.Stresses can be additive; allow recuperation between stressful situations.Avoid high loading densities.Provide optimal environmental conditions for the species being raised. Maintain water quality within the suggested guidelines. Pay special attention to maintaining optimal oxygen levels and minimal ammonia levels. Test water quality parameters frequently and keep accurate records.Provide food that meets the nutritional needs of the fish under the cultural conditions being used.Maintain cleanliness of rearing facilities. This includes segregated fish handling equipment or strict practices of disinfection of nets and other equipment between lots or rearing units. Fish showing signs of distress and dead fish should be removed.
• Where appropriate, use strains of fish species which show resistance to the specific endemic disease.
  

The fish culturist who has frequent contact with the fish should be the first line of defense against a disease outbreak. The fish feeder sees the fish regularly and should be alert to subtle changes which may indicate severe stress in fish. Fish in good health actively feed and quickly flee from disturbances. Fish in poor health gather near the incoming water supply, do not feed well, are sluggish, swim high in the water column, pipe air at the surface of the water and may flash on the bottom of the holding unit. Changes in normal external and internal appearance should also be observed (such as sores, lesions, and excess mucus or color changes).

 

Treatment of Fish Diseases
Reprinted from: Introduction to Fish Health Management
La Crosse Fish Health Center
Edited By: Becky Lasee, USFWS

Prophylaxis and chemotherapy are two methods used to treat diseases of fish. Prophylactic treatments are preventative and protect against the occurrence of an epizootic. Such treatments are used primarily for ectoparasites and stress related bacterial diseases. Chemotherapeutic treatments are initiated after clinical signs of the disease appear in a population of fish.

 

RULES OF CHEMICAL TREATMENT

1. Fish should be examined to diagnose the disease or problem to be treated. Seek professional assistance if in doubt of the cause.

 

A "shotgun" treatment is poor policy and can lead
to drug resistant microorganisms.

2. Determine general condition of fish. Fish may not be able to with­stand standard treatments. In this case, it is advisable to give serial treatments with progressively higher concentrations of the chemical.

3. Clean holding unit before chemical treatment. Many chemicals are in­activated by organic materials. A holding unit which is not clean often provides a sanctuary for the organ­ism under attack.

4. Remove fish from feeding schedule 24-48 hours prior to treatment. Oxy­gen consumption is reduced when fish are taken off feed and fish are more apt to withstand the treatment. 5. All leaks in the holding unit should be repaired prior to treatment. This rule is important in order to maintain a constant chemical concentration.

6. Auxiliary aeration devices should be on hand and operative. This rule applies more to bath treatments where oxygen depletion is more likely.

7. Determine proper dosage, amount or concentration of chemical to be used. Always double check your chemical calculations. Determine the correct method and route of application or administration. Accurately determine withdrawal time of chemical.

8. Compare economic value of fish with cost of treatment. If cost of desired treatment is greater than the value of the fish, it may be worth changing your choice of chemicals or even abandoning the treatment.

9. Always check the route of chemical discharge at the facility. It is possible that the chemical in use may cause environmental damage after it leaves the unit being treated.

10. Before beginning treatment, check the condition of chemical being used. Some chemicals are altered when improperly stored. This alteration could yield an ineffective or a toxic chemical.

11. Check concentration of the stock chemical. Many treatment recommendations are based on active ingredients.

12. Dilute chemical before applying to the holding unit.

13. Ensure proper mixing and distribution of the chemical in the water column of the holding unit.

14. NEVER leave the holding unit while treatment is in progress.

15. Observe fish closely during treatment. If distress is observed, the treatment should be terminated, or if low dissolved oxygen is the problem, additional aeration should be provided.

16. Periodically examine fish to determine efficacy of treatment.17. Do not stress (by handling, crowding, etc.) treated fish for 24-48 hours after treatment.

Make every effort to determine the predisposing factor or factors for the condition being treated and correct for them if possible. If the predisposing factor is not removed, it is likely that the condition will reap­pear.

 

TREATMENT METHODS

Prolonged Bath Treatment.   For this type of treatment, the inflowing water is cut off, the volume of water is determined and the correct dose of chemical is added to the unit. After the designated length of contact time, the chemical is flushed out of the unit rapidly (no longer than 10 minutes) with fresh water. An advantage of the bath procedure is that a more precise treatment can be given to the fish. The following precautions must be observed with bath treatments in order to prevent serious losses:

♦     Aerators should be available to ensure adequate oxygen if levels are depleted during treatment.
♦     The fish should be observed throughout the treatment regardless of treatment time. Fresh water should be added at the first signs of distress.
♦     The chemical must be uniformly distributed in the unit to ensure equal exposure of all fish to the chemical. No one procedure is used for the distribution of treatment chemicals within a unit. Rather, the method of distribution depends upon several factors including the type of chemical used, type and size of unit receiving the chemical, equipment, labor available and common sense.

Indefinite Bath Treatment
In­definite baths are usually used to treat ponds. The chemical is applied at low concentrations for extended periods of time. The chemical is al­lowed to gradually dissipate or detoxify naturally. This is generally considered a safe method of treatment but there are a few drawbacks. The most significant drawback is that treatments can be expensive because large quantities of chemicals are required. Another drawback relates to the possible adverse effects on the pond environment. Some chemicals are algacidal or herbicidal and may kill enough plants to ultimately cause an oxygen deficit in the pond being treated.

Constant Flow Treatment
Constant flow treatments are used in situations where it is impossible or impractical to shut off the water supply long enough to use one of the bath treatments. The volume of water flowing into the unit must be determined and a stock solution of the chemical is metered into the in­flowing water to maintain a constant concentration. Upon completion of the treatment period, the inflow of the chemical is stopped and the unit is flushed by the continuous flow of fresh water. Constant flow treatments require large quantities of chemical which can become quite costly. Furthermore, irregularly shaped raceways cannot be treated in this manner.

Feeding and Injection
The treatment of certain systemic bacterial diseases requires that the drug be introduced into the fish's body; usually through the feed or by subcutaneous injection. Treatment dosages are based on body weight of the fish. Standard treatments are given in grams of active drug per 100 pounds of fish per day or in milligrams of active drug per pound or kilogram of body weight. Medicated feed is purchased commercially. Once feeding of the formulated medication has begun, it should be continued for the prescribed treatment period. Large and valuable fish, particularly when numbers are small, can be treated effectively by injection of the antibiotic directly into the body cavity (intraperitoneal or IP) or into the muscle (intramuscular or IM). Most antibiotics work more rapidly when injected IP. For both types of injections, particularly IP, caution must be exercised not to damage internal organs.
The most convenient location for IP injections is at the base of one of the pelvic fins. The pelvic fin is partly lifted, the needle placed at the fin base and gently inserted until its tip penetrates the body wall. The needle and syringe should be held on a line parallel to the long axis of the body and at about a 45 degree angle downward to avoid internal organs. Penetration of the body wall is indicated by a sudden decrease of pressure against the needle. As soon as the tip of the needle is in the body cavity, the required amount of medication should be injected rapidly and the needle withdrawn. For IM injections, the best location usually is in the area immediately anterior to the dorsal fin. The needle and the syringe should be held on a line parallel with the long axis of the body and at a 45 degree angle down­ward. The needle is inserted to a depth of about 1/4 to 1/2 inch and the medication slowly injected directly into the muscle tissue of the back. The injection must be done slowly, so that the back pressure will not force the medication out of the muscle through the channel created by the needle.

ACCEPTABLE USE OF CHEMOTHERAPEUTICS
The basic principal of chemotherapy is one of selective toxicity. The drug must destroy or eliminate the pathogen by either bactericidal or bacteriostatic action, without having side effects on the host. Numerous drugs and chemicals have been used successfully for the control of fish diseases. However, many have not yet been registered by the U.S. Food and Drug Administration (FDA) for use in fish aquaculture. Uses of therapeutics in aquaculture and their registration status is listed in Table 10.1 / 10.2 . It is up to the user to deter­mine whether a particular product is approved for an intended use in aquaculture because the status of drugs and chemicals is always subject to change due to research findings or regulatory agency rulings.Chemicals purchased for hatchery use should be of United States Pharmaceutical (USP) grade, if possible. The chemical formula should be on the label. Treatment compounds must be stored as directed on the label. Lids or caps should always be tight. Chemicals that develop an abnormal color, texture, etc. or are held after the expiration date should be disposed of properly. Hazardous chemicals should be handled only with proper safety precautions.

Chemotherapeutics Added to the Feed
Two drugs have been cleared by the FDA and are currently available for use in treating systemic bacterial infections in hatchery fish. These are Terramycin and Romet 30. There are other drugs which have not yet been cleared for use but are identified here in the event that they are registered in the future.

Terramycin (Qxytetracycline). APPROVED FOR USE BY FDA
Terramycin is approved for control of bacterial hemorrhagic septicemia and pseudomonas disease in catfish and approved for control of ulcer disease, furunculosis, bacterial hemorrhagic septicemia and pseudomonas disease in salmonids.
The drug is usually available in the form of TM-50 or TM-50D, the latter being a formulation containing a water dispersible carrier. TM-50D can be used in starter diets or with pellets that require fine particles for processing. Terramycin, TM-50 and TM-50D are trade names of Pfizer, Inc. for their oxytetracycline products. TM-50 and TM-50D contain 50 grams of oxytetracycline hydrochloride per pound of product. In other words, each 9 grams of TM-50 or TM-50D contains 1 gram of Terramycin. Terramycin has been a useful drug in treating systemic bacterial infect­ions which have developed a resistance to sulfa drugs. However, Terramycin resistant strains of bacteria have also been encountered.

Dosage rate: Terramycin fed at the rate of 2.5-3.75 grams per 100 pounds of fish per day for 10 days is usually effective. Terramycin often stimulates the appetite of trout, but salmon may find it distasteful. Terramycin should not be fed on a prophylactic basis because resistant strains of bacteria may develop.

Romet_30. APPROVED FOR USE BY FDA
Romet 30 is only available as a preformulated medicated feed from commercial feed manufacturers. Romet 30 is approved for control of Aeromonas salmonicida infections of trout and salmon, and Edwardsiella ictaluri infections in channel catfish. The active drug is a combination of two medications (Table 10.1 / 10.2 ) which compliment each other's antibacterial action. In addition, the chemical nature of these compounds reduces the risk of bacterial resistance.

Dosage rate: Medicated feed is administered for 5 consecutive days to provide approximately 23 mg of active ingredients per pound (50 mg/ kg) of live body weight of fish per day. Salmonids must be withdrawn from treatment at least 42 days prior to stocking or slaughter; catfish require a 3 day withdrawal period.

Sulfamerazine. APPROVED FOR USE BY FDA BUT NOT PRE­SENTLY AVAILABLE BY SPONSOR
Sulfamerazine is a sulfonamide that is effective for treating infections caused by both Gram negative and Gram positive bacteria. It is approved for control of furunculosis in rainbow, brook and brown trout. The action of the drug within the fish is basically bacteriostatic (it is the defensive mechanisms of the fish that ultimately kill the bacteria).

Sulfonamide toxicity may occur when high dosages (10 grams per 100 pounds of fish per day or more) are fed to sensitive fish. If high dosages are required, a combination of two sulfa drugs totaling the desired rate should be fed. Toxicity usually results from the formation of complex sulfa crystals in the renal tubules. Signs of drug toxicity include abnormal bloating of the stomach (dropsy) and a chronic susceptibility of the gills to fungus (in salmon). Exophthalmia, swollen kidneys and death occur in acute cases.

Dosage rate: Sulfamerazine incorporated in processed diets is fed at the rate of 10 grams per 100 pounds of fish per day for 10 days (a 21 day withdrawal is required). This therapy should produce a blood level of the drug of 9 to 12 mg per 100 ml of blood.

Furazolidone. NOT APPROVED FOR USE BY FDA
Furazolidone (Furox 50) is one of a large number of related drugs in the nitrofuran group. The name Furox 50 is the trade name of a product developed by the Norwich Pharmacal Company for a formulation containing 11% Furazolidone. This drug has provided good results in the treatment of furunculosis and enteric redmouth in trout and against other Gram negative rods in other fish species (especially in cases where there is drug resistance against the sulfonamides and Terramycin).

Dosage rate: Furazolidone has been effective when mixed in the diet at the rate of 2.5 grams of pure drug per 100 pounds of fish for 3 days followed by a 20-day course of a 1.0 gram level per 100 pounds of fish.

THERAPEUTICS ADDED TO THE WATER

Tricaine methanesulfonate. APPROVED FOR USE BY FDA
Also known as Finquel™ (or MS-222). It is used as an anesthetic at 15 to 330 ppm (mg/L) for ictalurids, salmonids, esocids and percids. For other aquatic organisms it is used at 1:1,000 to 1:20,000. A 21 day withdrawal time is required.

Acriflavin. NOT APPROVED FOR USE BY FDA
Acriflavin has been used in the transport of warmwater fish to combat delayed mortalities caused by aeromonad and pseudomonad infections. Water in the transportation tank must be maintained at 4.0 ppm Acriflavin for the duration of the trip.

Chloramine T. NOT APPROVED FOR USE BY FDA
Chloramine T can be used in the treatment of various bacterial, fungal, protozoan and monogenetic trematode infect­ions. It has been used as a bath treatment at 7-15 ppm for 1 hour. Efforts are currently in progress to register this drug.

Copper Sulfate. NOT APPROVED FOR USE BY FDA
At 0.5 ppm, copper sulfate (CuSO4) has been used to control external parasites.

Di-n-Butyl Tin Oxide. NOT AP­PROVED FOR USE BY FDA
This chemical is used to treat a variety of internal helminths. The dosage rate is 250 mg/kg (114 mg/lb) mixed into the food for 3 days. This is toxic to fry but not to adult largemouth bass.

Diquat. NOT APPROVED FOR USE BY FDA
Diquat has been registered only as an aquatic herbicide for use in ponds and ditches. Diquat has been sold as a liquid containing 35.3% active ingredients. Fish culturists using Diquat to control filamentous algae also found the chemical to remedy bacterial gill disease, especially in earthen ponds. The chemical is expensive and muddy water or heavy accumulations of fish wastes may reduce its effectiveness. It appears to have low toxicity to fingerling salmon. Diquat has been used to treat salmonids at 2.0 ppm of active Diquatcation (1:500,000) (8.4 ppm from the bottle) for 1 hour. Applicators should use rubber gloves and respirators to avoid contact with the chemical. Because Diquat is a potent herbicide, fish culturists should avoid using Diquat whenever the treated water might later be used for irrigating crops.

Formalin. APPROVED FOR USE BY FDA
Formalin (Paracide-FTM Formalin-FTM, Parasite-STM) is probably the most widely used therapeutic agent in fish culture. It is the common name for a solution containing 37 grams of formaldehyde in 100 grams of water. Methyl alcohol or calcium salts may be added to prevent chemical changes in formalin. Formalin is corrosive and may turn rusty if stored in drums with scratched linings. Neither the rust nor the stabilizing chemicals added to formalin have an effect on formalin for treatment purposes. Old formalin or formalin exposed to cold temperatures may form a white precipitate of paraformaldehyde. 

Formalin is effective against the majority of external parasites, with the possible exception of Saprolegnia fungal infections. Formalin should be used at 167 to 250 ppm for one hour in troughs, tanks, raceways and rectangular concrete ponds. Water temperature is extremely important (refer to Table 10.1 / 10.2 ).  Salmonids are somewhat sensitive to higher concentrations of formalin above 7-10°C. As a rule of thumb, use 167 ppm formalin for 1 hour if temperatures exceed 10°C. Repeat the treatment two or three times on succeeding days if the parasites have not been removed. In earthen ponds, which cannot be flushed following treatment, use an indefinite treatment of 25 ppm formalin. If rearing ponds are heavily loaded with either fish or phytoplankton, try a treatment of 15 ppm of formalin and repeat if necessary at 5-10 day intervals.

Fish treated with formalin may suffer delayed mortality 5-6 hours post-treatment. This occurs frequently with rainbow trout yearlings, especially if they have had no prior formalin treatments. Experience has shown that if rainbow trout were treated with formalin when they were young, they become resistant to formalin with age. The cause of formalin sensitivity is not known.

Formalin at 1667 ppm is effective against fungus which attacks incubating eggs. Use 15 minute treatments, repeated as often as is necessary to prevent fungal growth. Formalin is highly toxic (and per­haps carcinogenic) to humans! The strong odor and the eye irritation usually warn of its presence. Long term exposure to low level formalin fumes is hazardous to human health.

Nitrofurazone (FuracinTM). NOT APPROVED FOR USE BY FDA
Furacin is a nitrofuran antibiotic that acts against bacterial organisms. It comes as a water mix and has been widely used in the sorting and transfer of bait minnows. Furacin dosage is 75 mg/kg (3.4 g/100 lb) of fish per day for 14 days. Repeated use has not been reported to harm fish.

Hyamine 3500. Hyamine 1622 and Boccal. NOT APPROVED FOR USE BY FDA
These are quaternary ammonium chloride compounds that were originally developed for disinfection in the dairy, food and restaurant industries. They are potent antimicrobial agents and their value as therapeutic agents have been recognized by the aquaculture society. Work is in progress for registering these compounds.

Masoten (Dylox). NOT APPROV­ED FOR USE BY FDA
Masoten (80% active ingredient) at 0.25-0.50 ppm as an indefinite treatment is used to treat monogenetic trematodes and copepod parasites. Masoten should be applied in early morning and at water temperatures above 29°C. Protective clothing should be worn as this chemical can be absorb­ed through the skin.

Potassium permanganate. NOT APPROVED FOR USE BY FDA
Potassium permanganate (KMnO₄) is a strong oxidizing agent that has been used to treat Gyrodactylus infestations and other external para­sites. Use potassium permanganate at 2-4 ppm for 1 hour on 3 successive days. This chemical also has some value in treating bacterial gill disease (at 3.0 ppm it alleviates gill tissue proliferation).

Sodium chloride (Salt). LOW REGULATORY PRIORITY DRUG BY FDA
It is unlikely the FDA will object to using salt and other low regulatory drugs as long as the following conditions are met: (1) they are used as direct­ed; (2) they are used at prescribed concentrations; (3) they are used according to good management practices; (4) the drug is an appropriate grade for use in food fish; and (5) there is no likelihood of an adverse effect on the environment. Salt is administered at a 0.5 to 1.0% solution for an indefinite period to reduce stress or a 3% solution for 10-30 minutes as a parasiticide. Salt is useful for ridding fish of excess mucus, a common host response to external parasites. Not only is salt one of the oldest and most commonly used hatchery chemicals, it is also one of the most overlooked.

Calcium chloride. LOW REGULATORY PRIORITY DRUG BY FDA
Calcium chloride can be used, up to 150 ppm, to increase water hardness for reducing stress when holding and transporting fish. It is also used to increase water calcium concentrations to ensure proper egg hardening.

Acetic acid. LOW REGULATORY PRIORITY DRUG BY FDA
Use as a 1,000 to 2,000 ppm (mg/L) dip treatment for 1 to 10 minutes to remove external parasites.

Hydrogen peroxide (H2O2). LOW REGULATORY PRIORITY DRUG BY FDA
Use at 250-500 ppm (mg/L) (100% active ingredient) for 15 minutes as an effective fungicide for incubating eggs and 250-500 ppm (30-60 minutes) for treating fish with external parasites. Other drugs considered low regulatory priority include calcium oxide, carbon dioxide gas (as an anesthetic), garlic, onion, ice, magnesium sulfate, papain, potassium chloride, sodium bicarbonate (as an anesthetic), sodium sulfite and urea in combination with tannic acid.

Egg Water Hardening and Disinfection
The disinfection of fish eggs began in trout culture because of concern about the spread of furunculosis. There is little evidence that furunculosis can be spread via eggs; how­ever, vertical transmission has been demonstrated for IPN virus, IHN virus and BKD. Egg disinfection is effective in con­trolling the spread of IHN virus with eggs, but is not useful for controlling vertical transmission of IPN virus and BKD, which are carried inside the egg. Nevertheless, fish culturists routinely disinfect trout and salmon eggs during or after water hardening (prior to shipment or upon arrival).

Erythromycin phosphate. NOT APPROVED FOR USE BY FDA
Erythromycin phosphate at 2.0 ppm for 1 hour has been used during the water hardening of salmon eggs to prevent BKD egg transmission. Although mixed results were obtained with regard to eliminating BKD from eggs, treatments did result in improved rates of eye-up and fry survival. It was suggested that erythromycin treatments removed bacterial contaminants such as those that cause coldwater disease.

Providone Iodine Compounds (BetadineTM). Low Regulatory Priority Drug by FDA
Use at rates of 50 mg/L for 30 minutes (at pH 6-7) during water hardening and at 100 mg/L solution for 10 minutes (at pH 6-7) after water hardening. If alkalinity of water used for disinfection of eggs is below 100 mg/L total alkalinity, the disinfection solution should be buffered by adding sodium bicarbonate (NaHCO₃) at a rate of 0.01 percent to prevent low pH drift. Listed below are quantities of 1 percent iodine or sodium bicarbonate needed to obtain the solutions required by these guidelines.

• To   get   100   mg/L   active   iodine solution:
  Add 37.8 ml organic iodine solution/ 3.78 L water (=1 gallon).
  Add 283.20 ml organic iodine solution/28.32 L water (=1 ft3).
  Add 4.54 ml organic iodine solution/ 454 g water (=1 lb).
• To   get   50   mg/L   active   iodine solution;
  Add 18.90 ml organic iodine solution/ 3.78 L water.
  Add 141.60 ml organic iodine solution/28.32 L water.
  Add 2.27 ml organic iodine solution/ 454 g water.
• To get 0.01% sodium bicarbonate:
  Add 0.378 g NaHCO3 /3.78 L water.
  Add 2.83 g NaHCO3 /28.32 L water.
  Add 0.045 g NaHCO3 /454 g water.

 

Calculating Treatments for Ponds and Tanks
Michael P. Masser and John W. Jensen
Southern Regional Aquaculture Center, August 1991

Every fish farmer has to occasionally use chemical treatments to remove fish, alter water quality, cure disease and control aquatic vegetation.  The fish farmer must follow treatment directions carefully, know the proper amount or concentration of chemical to use and know the pond area and/or volume.  For information on calculating area and volume request SRAC No. 103 - Calculating Area and Volume of Ponds and Tanks.  Regulation and/or approval of chemicals for aquatic use is confusing to fish farmers and fisheries professionals, alike. Aquatic chemicals are regulated federally by the Environmental Protection Agency (EPA) and the Food and Drug Administration (FDA). An oversimplified statement of their missions would be that the EPA regulates chemicals applied to water while FDA regulates chemicals applied to fish.  The fact that approved chemicals can be used only for purposes stated on the label (including the specific target species) is commonly misunderstood. Chemicals approved for water treatment cannot be used for therapeutic purposes nor can a therapeutant approved for one species be used on another. The above is true even of chemicals given GRAS (Generally Recognized As Safe) status. The FDA and/or EPA can approve treatments using unregistered chemicals on a case by case basis. For information on special approval contact the appropriate federal agency.  Several chemicals commonly used in fish culture have never been properly registered. Many chemicals will soon be reviewed and either approved or barred for specific uses. Check with your county Extension office or fisheries specialist for recent developments on approved fisheries chemicals. 

Precautions when making chemical treatments
Chemicals can react quite differently in water depending on its quality and on the target species.  For example, less copper sulfate should be used in water of low alkalinity than in water of high alkalinity.  To be effective, more potassium permanganate is needed as organic content increases.  Furthermore, fish already weakened by stress or disease may succumb to even a normal chemical dose.  To avoid overdosing fish with a chemical, a simple bioassay should be conducted
In a bioassay a small sample of fish from the pond is treated, in the ponds water, with the proposed chemical dosage to determine its safety and effectiveness.  Check oxygen concentrations carefully and be prepared to aerate after chemical treatments, particularly after using potassium permanganate, copper sulfate or formalin.  Use accurate, sensitive scales to weigh chemicals when treating small volumes of water such as the amounts in hauling or holding tanks, hatching troughs and cages.  If a suitable scale is not available, commonly available measuring spoons and cups can be used.  Cups and spoons are not the best way to measure chemicals, but are better than using inaccurate scales or eyeballing the dosage. Accurate spoon and cup measures must be used. Purchase only utensils labeled U.S. Standard Measure or ask a pharmacist to check the volumes of your measuring devices with his accurate measures. 

Inaccurate chemical measurements can harm or kill fish or fail to do the intended job.

Conducting a simple bioassay
A simple on-site test can be done to determine if an approved chemical could be toxic under specific pond conditions. The test should be run using both fish and water from the pond to be treated.  The test exposes a few fish to the concentration of the proposed chemical treatment while other fish are confined in the same type of environment as the fish in the treatment, but without any chemical exposure (called a control).  Tests can be done in plastic buckets, aquaria, or in plastic bags suspended in the pond. Dissolved oxygen and other water quality conditions must be maintained as closely as is practical to that of the pond. Aeration and water replacement (before the test is started) may be required to maintain water quality.  Do not overcrowd the fish in the treatment containers. A safe level of crowding would be to keep fish weight at or below one thousandth of the weight of the water used in the test (i.e., 1 pound of fish to 1,000 pounds of water).  Tests should be run in duplicate or triplicate so that a chance error or mistake will not be misinterpreted.  It is best to observe the fish in the test containers for at least one day before treatment to reduce the chance of deaths caused by handling. The test should be run for 24 to 96 hours. If the chemical is known to detoxify in 24 hours or less, the test can be concluded after 24 hours. If the toxicity of the chemical is unknown, its best to run the test for 96 hours. Follow the basic procedure described below to conduct a bioassay.

♦ Place fish (minimum of 10) in each container. Use at least two containers for the treatment and two for controls.♦ Observe for at least 24 hours.♦ Add chemical at desired concentration to the test containers; add nothing to the control containers.

♦ Observe for 24 to 96 hours.  Record mortalities.

If fish are still alive after the test, it should then be safe to treat the pond. If some fish die, you must decide if some mortalities are acceptable. Chemical treatments may kill fish that are already severely stressed. Pond Fertilization Basics

• Fertilization regimes can be used to improve the food base for cultured fish.

  Fertilizers are categorized as inorganic or organic.

  Inorganic fertilizers are granular or liquid, and are used to increase phytoplankton abundance (algae), or the "bloom".   They are applied by formula and goal ratios.

  Organic fertilizers can be hay, meals, or manure. Amount of nutrients supplied varies due to the composition of the fertilizer.

• If using an inorganic method, it is suggested that you monitor the water quality in your pond weekly, and you will need to know the amounts of:

  • Nitrate (NO₃)

    Ammonia (NH₃)

  • Phosphorous (phosphate, PO₄)

These numbers are used to calculate the amounts of fertilizer that needs to be added. However, the ammonia value may not be needed in the overall calculations, since it can be a very low number.

• Fertilization can be done to maintain a goal ratio, either Culver's 20:1 (TN:TP) or Mischke's 7:1 (NO₃:TP).

  You will also have to monitor pH and dissolved oxygen (DO) on a daily basis.

• It is highly recommended that you have fertilizers analyzed to determine exact concentrations of Nitrogen and Phosphorus and to make sure there is no contamination (extra amounts of fertilizer). 

Basic Pond Fertilization Equations Based on Culver's Method of 20:1 (TN:TP)

Recall, 20:1 is 600ug/L N (microgram per liter) to 30 ug/L P (0.6mg/L N: 0.03mg/L P). A microgram is 1,000 milligrams.

1. To determine phosphorus amounts:

V = (30-Pp) * Vp/ Pf*1,OOO

Where: V = volume of phosphorus fertilizer needed Pp = phosphorus concentration, measured in pond (ug/L) Vp = volume of fish pond (m³) Pf = phosphorus concentration of fertilizer (g/L)

2. To determine nitrogen added by phosphorus fertilizer:

Na = (30-Pp) * Nf/Pf

Where: Na = Nitrogen added by phosphorus fertilizer (ug/L) Pp = phosphorus concentration, measured in pond (ug/L) Nf = nitrogen concentration of phosphorus fertilizer (g/L) Pf = phosphorus concentration of fertilizer (g/L)

3. To determine nitrogen amounts (assuming no phosphorus contamination):

V = (600-Np-Na) * Vp
Nf*1,OOO

Where: V= volume of nitrogen fertilizer needed Np = nitrogen concentration (NO₃+NH₄), measured in pond (ug/L) Na = nitrogen added to pond by phosphorus fertilizer Vp = volume of fish pond (m³) Nf = nitrogen concentration of fertilizer (ammonia, nitrate, and urea)

 

For the following equations use these conversions: Converting between total phosphorus (P) and phosphate (PO₄)Use the Atomic mass of the formulas to create a ratio, as follows:

Atomic weight of P (Phosphorus) = 31
Atomic weight of O (Oxygen) = 16

Atomic weight of P         =   (1*31)
Atomic weight of PO₄   ((1*31) * (16*4))= 31 / 95= 0.3

You can now use this ratio to convert between P and PO₄. If you measure the phosphate in your pond, divide the value by 3 and it will give you the amount of total phosphorus. If you measure total phosphorus, multiply by 3 to get the phosphate.Converting between %P₂O₅ and %P

Use the following equations:

P₂O₅ atomic weight = P*2 + O*5 = (31*2) + (16*5)
= 142 %P    =   P₂/P₂O₅
= (2*31) / 142
= 62 / 142
= 0.44

Therefore, to get the %P from a fertilizer package, multiply the package P value (%P₂O₅) by 0.44.

Converting between %N and %NO₃ (nitrate)

Use the following equations:

N (nitrogen) atomic weight = 14
O (oxygen) atomic weight =16 NO₃ atomic weight = 1*N + 3*O
= 14 + (3*16)
= 62 %NO₃ = 62 / 14 = 4.4

Therefore, to get the %NO₃ from a fertilizer package, multiply the N value by 4.4.

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Aquatic Animal Drug Approval Partnership Program ~ AADAP Updates

Hydrogen Peroxide Removed from FDA's LRP Drug List
The Food and Drug Administration (FDA) announced recently (2 May 2007) the removal of hydrogen peroxide from the list of Low Regulatory Priority Aquaculture Drugs identified in the Program Policy and Procedures Manual Guide 1240.4200.  As a consequence, the only approved hydrogen peroxide product available is Eka Chemicals 35% Perox-Aid, and its use is limited to only those indications on the approved product label. For more information, refer to CVMs Update dated 2 May 2007. Calcein Updates
More pilot immersion marking studies completed:

AADAP has been conducting a few "quick and clean" studies to get some sense of the breadth (species- and life stage-wise) of SE-MARKs effectiveness. In two separate study sets, weve evaluated SE-MARK treatment of channel catfish fingerlings and pallid sturgeon fry. In the case of the former, 2-3" fingerlings marked exceptionally well with or without a pre-treatment salt bath (see picturesabove). However, treatment of 2 to 5-day old pallid sturgeon fry with SE-MARK (without a pre-treatment salt bath) failed to produce an easily detectable mark. A pre-treatment salt bath was not tested as it was felt that it would be much too stressful on this very early life-stage. As opportunities present themselves, AADAP will continue to test other species and life-stages for their "markability."

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