Fish
Content
Fish Diseases, B. V. Sc. & A.H. 7th Sem.
Non-infectious disease
Disease caused by
Environmental problem Nutritional deficiency Genetic disorder
Environmental disease Asphyxiation Cause : oxygen deficiency in water Time : early morning commonly but O2 deficiency occurs at any time cloudy weather death of an algal bloom pond turnover Oxygen requirement: varies species to species most fish >5 mg/L (suitable), <0.5 mg/L (lethal) trout >8 mg/L (suitable), 3 mg/L (lethal) Causes of low DO - algal bloom and bulk respiration - algal die offs and consequent decomposition - addition of rotting/decomposing organic - matter - high temperature Symptoms Fish comes to the surface Gulps air Gathers at water inlet Fish dies with mouth open, opercula wide
Compiled and Edited By: Suraj Subedi, Yanamani Nepal, Nirajan Bhandari
Page 1
Fish Diseases, B. V. Sc. & A.H. 7th Sem.
Treatment and control Aeration by beating water, swimming, boating Mechanical aeration (Aerator, Blower) Water exchange (out bottom deoxygenated water and in fresh cool oxygenated water) Adjustment of temp. Stop fertilizing Gas Bubble Disease Causes - super-saturation of oxygen in water - phytoplankton bloom >110 saturation problematic, >140 saturation fish kill In eye, skin, fin (non-fatal) and sometimes in heart, liver and brain also (fatal) Problem: eye blindness due to damage of lens and retina, bacterial secondary infection due to disruption of bubble Symptoms Development of large external gas filled bubbles in the eye, fin, lip Visible externally Lose balance due to large gas filled bubbles Fish swims at an angle of 450 with head pointing downward However, fish remains active and feed also Treatment and control Add fresh water or water exchange Remove excess green algae Stop adding nitrogenous fertilizer Remove the fish from ponds and keep in the new ponds with appro priate oxygen level (saturation) at that temp. Temperature Effects Fish are poikilotherms. Alterations in temperature affects Temperature sensitive and prone to Metabolic rate and consequent disease Every species has optimum range for excreted metabolites Oxygen production and consumption temperature eg. carps : 28-320C Cold water species : 10-200C Growth Gets thermal shock and also death Warm water species : 20-280C when there is sudden change in (temperate) 0 Warm water species : 28-35 C temperature by 3-40C because fish (tropical) can¶t tolerate this difference and Importantly, defensive mechanisms Beyond this range fish get stressed and antibody formation
Compiled and Edited By: Suraj Subedi, Yanamani Nepal, Nirajan Bhandari
Page 2
Fish Diseases, B. V. Sc. & A.H. 7th Sem.
Management and control Should not place fish in too cold or hot water Follow proper stocking procedure Provide shade in hot weather Cut off vegetation around in cold weather Water exchange Hydrogen Ion concentration pH suitable range for fish: 6.5-9 Fish gets stressed/died beyond these range pH 4 ± acidic death point, pH 11 ± alkaline death point Many toxic substances becomes more toxic at high or low pH levels Growth and reproduction ceases beyond optimum range Irritation of skin and gill at low pH Gill damage at low pH Cornea and lens damage at high pH Nutritional diseases develops as a result of - deficiency (undernutrition) - excess (overnutrition) - imbalance of nutrients present in their food - Disease signs develop only when supply of vitamins and minerals falls below critical level Disease caused nutritional deficiency
Cracked head Cause: Vitamin C deficiency Signs Cracked head hemorrhage beneath head deformed body Loss of appetite Treatment 1 g/kg of feed for 5-7 days Aflatoxicosis
Caused by aflatoxin, a kind of mycotoxin produced by fungi Aspergillus flavus and Aspergillus parasiticus Found in oil seed crops eg. Cotton seed, peanut meal, corn, wheat, soybean, fish meal, feed (main source of infection to fish) Gets infected when feed contaminated with aflatoxin is eaten by the fish Fry are more susceptible than adults
Factors that increase the production of aflatoxins in feeds environmental temperatures > 27°C (80°F)
humidity levels > 62% moisture levels in the feed > 14% Improper storage
Compiled and Edited By: Suraj Subedi, Yanamani Nepal, Nirajan Bhandari
Page 3
Fish Diseases, B. V. Sc. & A.H. 7th Sem.
AFB1, AFB2, AFG1 and AFG2 are direct contaminants of grains and finished feeds such as cottonseed, peanut meal, and corn, wheat, sunflower, soybean, fish meal Cancer causing agent Symptoms pale gills impaired blood clotting anemia poor growth rates decreased immune system might cause liver and kidney tumor increased mortality may also be observed Management and control Purchase of recently prepared (see date of manufacture) and properly stored feed (mentioned below) Debris must be removed from feed ingredients Complete fish feeds should be stored in an air -conditioned room Feed should be stored off the ground, on platform and at least one foot away from any walls (to avoid condensation) Avoid using feeds that appear discolored, lump together, and smell musty Separate or discard contaminated feed and avoid feeding it to fry, fish Clean feed storage bins and automatic feeders regularly Add a toxin inactivator to the stored feeds Constant monitoring for aflatoxins in the feed will reduce the risk of aflatoxicity in fish Mechanical trauma Trauma leads to fracture, hemorrhage, infection and sometimes death too. Caused by injuries to any portion of the body from a blow, crush, cut, or penetrating wound Often occurs during netting, transport, handling Breaks epidermal and dermal layers and allows invasion of pathogen Prophylactic measures Test and slaughter examine the fish if infection in fish is found of no control then kill entire population and dispose them so that the disease will not be transmitted to others burn and deep bury the carcasses effective for absolute control Applied in whirling disease Sanitation of aquaculture equipments Quarantine and restriction of Parasites and pathogens enter the movement hatcheries and farm through carriers, needs when fish are moved from utensils, feed, water etc. suspected or infected geographical Hands should be washed with areas to no-infected geographical disinfectants area Tools, transport appliances, nets, Quarantine involves holding fish in gears should be cleaned and detention until the incubation period disinfected with disinfectants is over Common disinfectants: chlorine, restriction of movement involves calcium oxide, sodium hydroxide, restricting entire movement of fish salt, potassium permanganate between 2 geographical areas
Compiled and Edited By: Suraj Subedi, Yanamani Nepal, Nirajan Bhandari
Page 4
Fish Diseases, B. V. Sc. & A.H. 7th Sem.
needs strict legislative regulation to control intercontinental, interstate movement of fish
Needs cooperation among stakeholders in Nepal, quarantine exists, active in paper work Systemic Parenteral
Curative measures Dip Bath Dip
Bath
Flush Swabbing
Mix the required amount of drug in a measured volume of water Fish are taken out of culture system in a net and submerge in it for certain period of time Return fish to the culture system short treatment (<15 minutes) for small number of fish High concentration of drug Small volume of water External treatment used for surface infections a ectoparasitic infestations. nd Ineffective for systemic infections Eg. salt Prolonged treatment Calculate volume of water and drug and mix Fish are allowed to remain in disinfectant mixed water for long time (<24 hrs.) Effective and more precise Done in small holding facilities like trough, tank, pond, raceway but water exchange should be shut off during treatment period Fish suffering with respiratory distress becomes anoxic during treatment period At the end, disinfectant should be flushed out of the system which might be time consuming Eg. Salt/formalin bath
Indefinite bath Drug is applied to the culture system at low concentration for indefinite period No water exchange Drug is allowed to dissipate gradually Suitable for pond treatment
Compiled and Edited By: Suraj Subedi, Yanamani Nepal, Nirajan Bhandari
Page 5
Fish Diseases, B. V. Sc. & A.H. 7th Sem.
Flush Done in raceway, trough, tank, pond etc. having direct flow through system Similar to dip but fish are not handled/removed from culture system A high concentration of disinfectant is flushed in from upper end and fish are exposed to drugs and flush out from lower end of the culture system
Swabbing Topical treatments are less practical and applies only to treat open sore in broodfish involves application of drugs in high concentration For better convenience it is desirable to immobilize the big -sized fish prior to swab application. Swabbing with antibiotics and disinfectant can be effective Involves handling and exposure to anesthetics Stressful to fish Eg. Acriflavin, iodine Parenteral Can be effective but applicable to only high value fish such as broodfish and ornamental fish Because needs individual fish injection Intramuscular and intraperitoneal Mass treatment is impractical Systemic Mixing drugs in feed and feeding fish Problems: leaching of drugs y Short shelf life mainly of sinking pellets, loss of drugs to bottom before eaten by fish y Fate of water soluble antibiotics? y Diseased fish may not consume fish y Unpalatability due to drug itself Precautions Indiscriminate feeding of low levels of antibiotics will remove only those bacteria most sensitive to the drug and can lead to the development of drug resistant strains. Therefore treatment with antibiotics should be only at prime need. It is better to stop feeding 1±2 days prior to medication through feed. Never treat the fish within 4 hours after feeding. Always watch for signs of stress a unexpected toxicity. Monitor D.O. levels before and during treatment. Calculations for dilutions of the drug should always be rechecked.
Compiled and Edited By: Suraj Subedi, Yanamani Nepal, Nirajan Bhandari Page 6
Compil d and Edi d B Suraj Sub di, Yanamani Nepal, Nirajan B andari
Antibiotics s ch s T mycin which is a water soluble and may leach out of the feed unless preventive steps are taken. It is best to suspend such drugs in oil when preparing medicated feed. The daily ration of feed can then be coated with oil/antibiotic mixture.
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Page 7
¤¦¥ ¤ ¤ £ ¡ ¢¡
Fish is
s sBV
&A
7
th
Non-infectious disease
Disease caused by
Environmental problem Nutritional deficiency Genetic disorder
Environmental disease Asphyxiation Cause : oxygen deficiency in water Time : early morning commonly but O2 deficiency occurs at any time cloudy weather death of an algal bloom pond turnover Oxygen requirement: varies species to species most fish >5 mg/L (suitable), <0.5 mg/L (lethal) trout >8 mg/L (suitable), 3 mg/L (lethal) Causes of low DO - algal bloom and bulk respiration - algal die offs and consequent decomposition - addition of rotting/decomposing organic - matter - high temperature Symptoms Fish comes to the surface Gulps air Gathers at water inlet Fish dies with mouth open, opercula wide
Compiled and Edited By: Suraj Subedi, Yanamani Nepal, Nirajan Bhandari
Page 1
Fish Diseases, B. V. Sc. & A.H. 7th Sem.
Treatment and control Aeration by beating water, swimming, boating Mechanical aeration (Aerator, Blower) Water exchange (out bottom deoxygenated water and in fresh cool oxygenated water) Adjustment of temp. Stop fertilizing Gas Bubble Disease Causes - super-saturation of oxygen in water - phytoplankton bloom >110 saturation problematic, >140 saturation fish kill In eye, skin, fin (non-fatal) and sometimes in heart, liver and brain also (fatal) Problem: eye blindness due to damage of lens and retina, bacterial secondary infection due to disruption of bubble Symptoms Development of large external gas filled bubbles in the eye, fin, lip Visible externally Lose balance due to large gas filled bubbles Fish swims at an angle of 450 with head pointing downward However, fish remains active and feed also Treatment and control Add fresh water or water exchange Remove excess green algae Stop adding nitrogenous fertilizer Remove the fish from ponds and keep in the new ponds with appro priate oxygen level (saturation) at that temp. Temperature Effects Fish are poikilotherms. Alterations in temperature affects Temperature sensitive and prone to Metabolic rate and consequent disease Every species has optimum range for excreted metabolites Oxygen production and consumption temperature eg. carps : 28-320C Cold water species : 10-200C Growth Gets thermal shock and also death Warm water species : 20-280C when there is sudden change in (temperate) 0 Warm water species : 28-35 C temperature by 3-40C because fish (tropical) can¶t tolerate this difference and Importantly, defensive mechanisms Beyond this range fish get stressed and antibody formation
Compiled and Edited By: Suraj Subedi, Yanamani Nepal, Nirajan Bhandari
Page 2
Fish Diseases, B. V. Sc. & A.H. 7th Sem.
Management and control Should not place fish in too cold or hot water Follow proper stocking procedure Provide shade in hot weather Cut off vegetation around in cold weather Water exchange Hydrogen Ion concentration pH suitable range for fish: 6.5-9 Fish gets stressed/died beyond these range pH 4 ± acidic death point, pH 11 ± alkaline death point Many toxic substances becomes more toxic at high or low pH levels Growth and reproduction ceases beyond optimum range Irritation of skin and gill at low pH Gill damage at low pH Cornea and lens damage at high pH Nutritional diseases develops as a result of - deficiency (undernutrition) - excess (overnutrition) - imbalance of nutrients present in their food - Disease signs develop only when supply of vitamins and minerals falls below critical level Disease caused nutritional deficiency
Cracked head Cause: Vitamin C deficiency Signs Cracked head hemorrhage beneath head deformed body Loss of appetite Treatment 1 g/kg of feed for 5-7 days Aflatoxicosis
Caused by aflatoxin, a kind of mycotoxin produced by fungi Aspergillus flavus and Aspergillus parasiticus Found in oil seed crops eg. Cotton seed, peanut meal, corn, wheat, soybean, fish meal, feed (main source of infection to fish) Gets infected when feed contaminated with aflatoxin is eaten by the fish Fry are more susceptible than adults
Factors that increase the production of aflatoxins in feeds environmental temperatures > 27°C (80°F)
humidity levels > 62% moisture levels in the feed > 14% Improper storage
Compiled and Edited By: Suraj Subedi, Yanamani Nepal, Nirajan Bhandari
Page 3
Fish Diseases, B. V. Sc. & A.H. 7th Sem.
AFB1, AFB2, AFG1 and AFG2 are direct contaminants of grains and finished feeds such as cottonseed, peanut meal, and corn, wheat, sunflower, soybean, fish meal Cancer causing agent Symptoms pale gills impaired blood clotting anemia poor growth rates decreased immune system might cause liver and kidney tumor increased mortality may also be observed Management and control Purchase of recently prepared (see date of manufacture) and properly stored feed (mentioned below) Debris must be removed from feed ingredients Complete fish feeds should be stored in an air -conditioned room Feed should be stored off the ground, on platform and at least one foot away from any walls (to avoid condensation) Avoid using feeds that appear discolored, lump together, and smell musty Separate or discard contaminated feed and avoid feeding it to fry, fish Clean feed storage bins and automatic feeders regularly Add a toxin inactivator to the stored feeds Constant monitoring for aflatoxins in the feed will reduce the risk of aflatoxicity in fish Mechanical trauma Trauma leads to fracture, hemorrhage, infection and sometimes death too. Caused by injuries to any portion of the body from a blow, crush, cut, or penetrating wound Often occurs during netting, transport, handling Breaks epidermal and dermal layers and allows invasion of pathogen Prophylactic measures Test and slaughter examine the fish if infection in fish is found of no control then kill entire population and dispose them so that the disease will not be transmitted to others burn and deep bury the carcasses effective for absolute control Applied in whirling disease Sanitation of aquaculture equipments Quarantine and restriction of Parasites and pathogens enter the movement hatcheries and farm through carriers, needs when fish are moved from utensils, feed, water etc. suspected or infected geographical Hands should be washed with areas to no-infected geographical disinfectants area Tools, transport appliances, nets, Quarantine involves holding fish in gears should be cleaned and detention until the incubation period disinfected with disinfectants is over Common disinfectants: chlorine, restriction of movement involves calcium oxide, sodium hydroxide, restricting entire movement of fish salt, potassium permanganate between 2 geographical areas
Compiled and Edited By: Suraj Subedi, Yanamani Nepal, Nirajan Bhandari
Page 4
Fish Diseases, B. V. Sc. & A.H. 7th Sem.
needs strict legislative regulation to control intercontinental, interstate movement of fish
Needs cooperation among stakeholders in Nepal, quarantine exists, active in paper work Systemic Parenteral
Curative measures Dip Bath Dip
Bath
Flush Swabbing
Mix the required amount of drug in a measured volume of water Fish are taken out of culture system in a net and submerge in it for certain period of time Return fish to the culture system short treatment (<15 minutes) for small number of fish High concentration of drug Small volume of water External treatment used for surface infections a ectoparasitic infestations. nd Ineffective for systemic infections Eg. salt Prolonged treatment Calculate volume of water and drug and mix Fish are allowed to remain in disinfectant mixed water for long time (<24 hrs.) Effective and more precise Done in small holding facilities like trough, tank, pond, raceway but water exchange should be shut off during treatment period Fish suffering with respiratory distress becomes anoxic during treatment period At the end, disinfectant should be flushed out of the system which might be time consuming Eg. Salt/formalin bath
Indefinite bath Drug is applied to the culture system at low concentration for indefinite period No water exchange Drug is allowed to dissipate gradually Suitable for pond treatment
Compiled and Edited By: Suraj Subedi, Yanamani Nepal, Nirajan Bhandari
Page 5
Fish Diseases, B. V. Sc. & A.H. 7th Sem.
Flush Done in raceway, trough, tank, pond etc. having direct flow through system Similar to dip but fish are not handled/removed from culture system A high concentration of disinfectant is flushed in from upper end and fish are exposed to drugs and flush out from lower end of the culture system
Swabbing Topical treatments are less practical and applies only to treat open sore in broodfish involves application of drugs in high concentration For better convenience it is desirable to immobilize the big -sized fish prior to swab application. Swabbing with antibiotics and disinfectant can be effective Involves handling and exposure to anesthetics Stressful to fish Eg. Acriflavin, iodine Parenteral Can be effective but applicable to only high value fish such as broodfish and ornamental fish Because needs individual fish injection Intramuscular and intraperitoneal Mass treatment is impractical Systemic Mixing drugs in feed and feeding fish Problems: leaching of drugs y Short shelf life mainly of sinking pellets, loss of drugs to bottom before eaten by fish y Fate of water soluble antibiotics? y Diseased fish may not consume fish y Unpalatability due to drug itself Precautions Indiscriminate feeding of low levels of antibiotics will remove only those bacteria most sensitive to the drug and can lead to the development of drug resistant strains. Therefore treatment with antibiotics should be only at prime need. It is better to stop feeding 1±2 days prior to medication through feed. Never treat the fish within 4 hours after feeding. Always watch for signs of stress a unexpected toxicity. Monitor D.O. levels before and during treatment. Calculations for dilutions of the drug should always be rechecked.
Compiled and Edited By: Suraj Subedi, Yanamani Nepal, Nirajan Bhandari Page 6
Compil d and Edi d B Suraj Sub di, Yanamani Nepal, Nirajan B andari
Antibiotics s ch s T mycin which is a water soluble and may leach out of the feed unless preventive steps are taken. It is best to suspend such drugs in oil when preparing medicated feed. The daily ration of feed can then be coated with oil/antibiotic mixture.
¤©¨¥ ¤§¤
Page 7
¤¦¥ ¤ ¤ £ ¡ ¢¡
Fish is
s sBV
&A
7
th
