This document discusses therapeutants and pesticides used in aquaculture. It outlines various compounds used as drugs, disinfectants, herbicides, insecticides, fungicides, anesthetics, and more. Specific compounds are discussed in detail, including their mechanisms of action, recommended dosages, and effects on fish and aquatic life. A wide range of chemicals are presented, along with factors to consider for safe and effective use in aquaculture operations.

1. R. K. Brahmchari
Assistant Professor
College of Fisheries, Dholi
(RPCAU)
Muzaffarpur, Bihar
Therapeutants
in
Aquaculture

2.  All aquaculture operations have a demand for drugs,
biologics, and other chemicals
 This may include:
1) compounds that one would typically think of as drugs
— antibiotics and other therapeutic compounds
2) disinfectants as part of biosecurity protocols,
3) fish sedatives and anesthetics
4) herbicides and pesticides used in pond maintenance,
5) gender manipulators
6) spawning aids,
7) Immunostimulants & vaccines as biologics

3. Pesticides used in Aquaculture

4.  Pesticides are applied in aquaculture to control:
 Aquatic Weed - Herbicides
 Parasite - Insecticides
 Fungi –Fungicides
 Pesticides are beneficial chemicals:
(1) relatively easy to apply,
(2) generally cost-effective and,
(3) the only practical method of control in some
situations.

5. Herbicides
Herbicides often are directly applied to ponds to
control:
 nuisance growths of algae,
 submersed water grasses,
 floating water plants and
 emergent water plants

6. 1. Copper sulfate (Bluestone):
 are used to control algae, not rooted aquatic plants.
 However, copper is a toxic metal that is long-lived
(persistent)in the environment.
 Copper sulfate can be toxic to fish and aquatic animals at
concentrationsnear levels used to control algae, especially in
soft water (alkalinity values less than 50 mg/L).
 Copper toxicity increases as water hardness decreases.
 Dose for algal control: 0.5 to 1 mg/L per 100 mg/L total
alkalinity (as CaCO3 )

7. 2. Fluridone
 perhaps the safest of the registered herbicides to use in
fish ponds.
 It is expensive and will not kill algae, but effectively
controls submersed aquatic plants.
 It is a persistent, slow-acting herbicide.
 residue may persist for a period of 2 to 12 months, and
results may take 30 to 90 days to be noticeable.
 There are no restrictions for fishing, swimming, or
livestock or human consumption.

8. 3. Glyphosate
 best used for control of emergent and shoreline weeds.
 It is usually applied to the plant and not directly to the
water.
 It has no waiting period or withdrawal restrictions for
irrigation water, livestock water, fish consumption,or
swimming.
 Use only those glyphosate products labeled and specially-
formulated for aquatic systems.
 Some glyphosate products contain additives that are toxic
to aquatic organisms.

9. 4. 2,4-D
 effective for controlling emergent/floating aquatic
plants.
 These compounds rapidly and completely decompose
in about 3 weeks.
 Toxicity of these herbicides increases as pH decreases.
 They are less effective at pHs greater than 8, and more
toxic in acidic waters (pH<6).

10. 5. Diquat
 wide-spectrum herbicide that can be used to control
algae and submersed weeds, but it is not especially
effective on emergent weeds.
 A 14-day waiting period is required by law before diquat-
treated water can be used for livestock consumption, crop
irrigation, or drinking.
 There are no restrictions for fishing, but a 1-day waiting
period is required before swimming.
 Diquat is rarely found in treated water after 10 days.

11. Insecticides
 Insecticides too are directly applied to ponds to control
ectoprasitic crustaceans.
 Two main types of agricultural insecticides used today in
aquaculture are
 Pyrethroids – Deltamethrin, Cypermethrin etc
 Organophosphates - dichlorovos, dipterex etc

12. Fungicides
 Fungicides, like herbicides, generally are not as highly
toxic to fish and aquatic animals as insecticides.
 Trifluralin (Treflan) - Fungicide used in bath treatments
in shrimp aquaculture

13. Disinfectants

14. Disinfectants
 Disinfectants are common disease management tool for
aquaculture sector.
 It can be both a routine bio-security practice to prevent
specific diseases
OR
a routine sanitation process to reduce overall occurrence of
disease.
 Disinfectant formulations often contain surfactants.
 The following overview of disinfectants is provided by the
FAO used in aquaculture.

15. 1. Lime
 Liming is considered an integral part of pond management.
 These include improvement of soil chemistry – like ↓ soil
acidity, ↑ total alkalinity, neutralizing sulfides and acids,
precipitating suspended organic material, ↓ BOD, and
improving nitrification
 There are several types of lime that are used in grow-out
ponds - most common is Agricultural lime (CaCO3).
 To disinfect, 100-300 kg/ha is applied in fish ponds during
the culture period

16. 2. Formalin
 Formalin has a very old history as an aquatic chemotherapeutant.
 The first recorded use of formalin in the treatment of fish disease
was in 1909 (Alderman and Michel 1992).
 Formalin kills microorganisms by condensing with amino acids to
form azomethines.
 It is active against a wide range of organisms, including fungi,
bacteria and ectoparasites.
 However, its action is slow.
 At a concentration of 5,000 ppm, 6-12 h is required to kill bacteria
and 2-4 d to kill spores.
 It is also ineffective againstinternal infections.
 Formalin has been approved by most of countries including US
FDA for use in treatment of food fish.

17.  The recommendeddosage rates are 150 ppm for a 1 h bath
and 25ppm for long-term treatment.
 Formalin is also applied directly in ponds at rates varying
from 10-25 ppm, especially during protozoan outbreaks, as a
cure-all remedy.
 However, formalin also causes oxygen depletion and this
excess can be deleterious in the long run

18. 3. Chloramine T (N-chloro-p-toluene sulphonamide)
 Widely used for the disinfection of tanks and equipment.
 Used for the treatment of bacterial gill disease (BGD) in
fish.
 It also has some effect on protozoan ectoparasites on skin
and gills.
 The active component is chlorine (available chlorine =
20%).
 Although chloramine-T is not licensed in the United States
for use with fish intended for human consumption.
 Effective treatment of BGD in freshwater or marine
aquaria, garden ponds, or other aquatic systems at
concentrations ranging from 6.5 to 10.0 mg/L.

19. 4. Hypochlorite (Sodium or calcium hypochlorite)
 Used world-wide for disinfection of tanks and equipment.
 Hypochlorites act by releasing hypochlorous acid, which is
the primary active ingredient.
 The active component is chlorine, which is highly toxic to
aquatic life.
 They are particularly effective in acidic conditions. For
example, the bactericidal effect of hypochlorite is 10 times
greater at pH 6 than at pH 9.
 At pH 7.0, a 0.1-0.25 ppm hypochlorite solution will kill most
organisms within 15 to 20 sec.

20.  Hypochlorites are too toxic to be used directly on tissues
and therefore cannot be used for treatment or prophylaxis.
 Both products, however, are used extensively as
disinfectants.
 In ponds, hypochlorites have been traditionally used as
piscicides. However, a more recent use has been their
application to disinfect incoming water.

21. 5. Iodophores
 Iodophores are a stabilised form of iodine and are used
world-wide as disinfectants for aquaculture equipment.
 They also are used to disinfect fish eggs and are effective
against a wide range of bacteria and viruses.
 An example of this class is Povidone.
 It is lethal to microflora and to viruses, which are killed
within 15 min in a 50 ppm solution
 Used as a fish egg disinfectant at rates of 50 mg/L for 30
minutes during waterhardening and 100 mg/L solution for
10 minutes after water hardening.

22. 6. Benzaklonium Chloride (BKC)
 BKC is a cationic compound that, like formalin, is toxic to a
wide range of bacteria, fungi, and viruses.
 Unlike formalin, it is non-irritating to tissue and has a rapid
onset of action.
 BKC has been recommendedas a bactericide and fungicide
in hatcheries.
 Suggested dosages are 1-1.25 ppm.

23. 7. Acriflavine
 Acriflavine is a mixture of 3,6-diamino-10-methylacridinium
chloride and 3,6-diaminoacridine, Known also as
Trypaflavine.
 It has been used extensively in egg disinfection; as an
antiseptic for treating wounds, ulcers, and bacterial lesions;
and in protozoan and monogenean infections.
 Acriflavine is normally used as a long-term bath and is
known to kill plants.

24. 8. Malachite Green
 Malachite green is the common name for p,p-
benzylidenebis-N,N-dimethyl aniline.
 It was originally developed in the 1920s as a textile dye.
 Malachite green has been extensively used in controlling
infections due to bacteria, fungi, protozoans and
monogenetic trematodes on eggs, fry and adult fish.
 In recent years, however, there have been strong moves
against malachite green application, especially with respect
to its use in food fish.
 This is because the chemical has a moiety that is known to
be carcinogenic.

25.  It is usually applied at 1-2 ppm for short exposure, and for
long baths at 0.01 ppm for fry/fingerling/PL and 0.1 ppm
for juveniles.

26. 9. Copper Sulphate
 Copper sulphate is a broad-based disinfecting agent used in
fish/ shrimp farms.
 It is effective against a wide range of organisms including
blue-green algae, bacteria, fungi, protozoans, digeneans,
leeches and monogeneans.
 Copper sulphate is used at a rate of 1:2000 with water/acre
or 0.5 ppm in freshwater ponds.

27. 10. Potassium permanganate (KMnO4)
 KMnO4 , is a oxidizing agent that will react with any organic
matter in a pond including algae, bacteria, fish, and organic
bottom sediments.
 It has been used in fish ponds to treat common fish
pathogens such as gill parasites and external bacterial and
fungal infections.
 Contrary to some reports, KMnO4 does not add significant
amounts of oxygen to water and actually decrease dissolved
oxygen concentrationsby killing algae that produce much of
the oxygen in ponds.
 Common treatment rates are 2 ppm or mg/L for an
indefinite pond application or 10 mg/L for a 10-minute tank
treatment.

28. 11. Organophosphates
 Organophosphate pesticides are used in both freshwater fish
ponds and marine shrimp hatcheries to control infections by
crustaceans, and monogeneans and ciliates, respectively.
 The main organophosphatesused are Malathion, Dipterex,
Dichlorvos, and Dursban.
 In many freshwater fish farms, these organophosphates are
also used to control aquatic insects that prey upon fish fry,
such as dragonfly larvae.
 Dosage is usually about 0.5-1 ppm for 3 to 7 day.

29. 12. Sodium chloride (Salt)
 Used as a 0.5-1% solution for an indefinite period as an
osmoregulatory aid for the relief of stress and prevention of
shock.
 Used as a 3% solution for 10-30 minutes as a parasiticide.

30. Anesthetics in Aquaculture

31. In aquaculture, anesthetics are used during
transportation to prevent physical injury and
reduce metabolism (DO consumption and
excretion).
Also used to immobilize fish so they can be
handled more easily during harvesting, sampling
and spawning procedures.

32. Characteristics of ideal anesthetic
 An ideal anesthetic should induce anesthesia rapidly
with minimum hyperactivity or stress.
 It should be easy to administer and should maintain
the animal in the chosen state.
 When the animal is removed from the anesthetic,
recovery should be rapid.
 The anesthetic should be effective at low doses and
the toxic dose should greatly exceed the effective dose
so that there is a wide margin of safety.

33. Stages of Anesthesia
 Induction
 Most anesthetics can produce several levels or stages of
anesthesia.
 Stages include
 sedation,
 anesthesia,
 surgical anesthesia and
 death.
 The stage achieved usually depends on the dose and the
length of exposure.

34. Stage Condition Behaviour/Response
I Sedation Motion & breathing reduced
II Anesthesia Partial loss of equilibrium
Reactive to touch stimuli
III Surgical anesthesia Total loss of equilibrium No
reaction to touch stimuli
IV Death Breathing & heart beat stop
Overdose - eventual death

35. Maintenance
 Once the desired degree of anesthesia is reached, it may be
desirable to maintain fish in that state for some time.
 Because drug dose and exposure time are often
cumulative, it is difficult to maintain a uniform depth of
anesthesia.
 One reason for this is that levels of anesthetic may continue
to accumulate in the brain and muscle even after blood
levels have attained equilibrium.
 A desired level of anesthesia can usually be maintained by
reducing the dosage.

36. Recovery
 During the recovery stage the anesthetic is withdrawn and
fish return to a normal state.
 To reduce recovery time, induction should be rapid and
handling time should be minimal.
 Initial recovery may take from a few seconds to several
minutes, depending on the anesthetic administered.
 Typically, the animal will attempt to right itself and will
begin to respond to noise and other sensory stimuli.
 Full recovery can take minutes to hours, depending on the
species and drug used.

37. Factors affecting anesthesia
 These can be divided into biological and environmental
factors.
 Often, the rate at which anesthetic drugs become effective
is related to the gill area to body weight ratio, which can
vary considerably among fish species.
 Aquatic species also have different metabolic rates that
affect the rate at which chemicals are absorbed and
anesthesia is induced.
 For example, cold-water species seem to respond to lower
concentrationsof anesthetic than warm-water species.
 Larger individuals generally require a greater concentration
of anesthetic than smaller individuals.

38. Anesthesia of fish
1. MS-222
 Chemical name - Tricaine methanesulfonate.
 Comes as a white, crystalline powder that can be dissolved
in water at up to an 11% solution.
 It lowers the pH of water, creating an acidic condition that
can irritate fish and cause harmful side effects.
 To prevent problems, the stock solution can be buffered
with sodium bicarbonate (baking soda) to achieve a pH of 7.
 One of the major drawbacks of MS-222 is that even when
fish are deeply anesthetized, handling still increases levels
of plasma cortisol concentrations,an indicator of stress.

39.  Induction is rapid and can take as little as 15 seconds.
 Carps are quickly anesthetized when immersed in 100 to
250 mg/L.
 Anesthesia can be maintained at 25-50 mg/L.
 Recovery is usually rapid and equilibrium can be expected
to return after only a few minutes.
 A recovery time longer than 10 minutes suggests that too
much anesthetic is being used or that the exposure time is
too long.

40. 2. Benzocaine
 Benzocaine, or ethyl aminobenzoate, is a white crystal that
is chemically similar to MS-222.
 However, benzocaine is almost totally insoluble in water and
must first be dissolved in ethanol or acetone.
 The standard approach is to prepare a stock solution in
ethanol or acetone (usually 100 g/L) that will keep for more
than a year when sealed in a dark bottle.
 In solution, benzocaine is neutral (pH 7) and therefore
causes less hyperactivity and initial stress reaction than
unbuffered MS-222.

41.  Benzocaine is effective at approximately the same doses
as tricaine.
 It is not safe for exposureslonger than 15 minutes.

42. 3. Quinaldine
 Quinaldine is a yellowish, oily liquid with limited water
solubility that must be dissolved in acetone or alcohol
before it is mixed with water.
 While it is an effective anesthetic, it is an irritant to fish,
has an unpleasant odor, and is a carcinogen.
 The low cost of quinaldine has made it a popular tool for
collecting tropical fish for the aquarium trade, as well as in
the bait and sport fish industries.
 Quinaldine sulfonate is a pale yellow, water-soluble
powder; it is more costly than quinaldine or MS-222.

43.  Quinaldine solutions are acidic and are usually buffered
with sodium bicarbonate.
 Induction takes 1 to 4 minutes and may cause mild muscle
contractions.
 Recovery is usually rapid.
 The effective treatment concentration of quinaldine
solutions varies with species, but is generally 15 to 60
mg/L.

44. 4. 2-Phenoxyethanol
 2-Phenoxyethanol is an opaque, oily liquid. This drug is
moderately soluble in water but freely soluble in ethanol.
 The solution is bactericidal and fungicidal and is, therefore,
useful during surgery.
 It is relatively inexpensive and remains active in the diluted
state for at least 3 days.
 2-Phenoxyethanol has a relatively large margin of safety and
has been reported to produce a range of effects from light
sedation to surgical anesthesia at concentrations of 100 to
600 mg/L.
 Concentrations of 300 to 400 mg/L are useful for short
procedures, and lower concentrations of 100 to 200 mg/L
are considered safe for prolonged sedation, such as during
transport.

45. 5. Clove oil
 Clove oil has been widely used as an anesthetic in human
dentistry and as a food flavoring.
 The major constituent (70 to 90 percent by weight) is the oil
eugenol.
 It is an effective anesthesia in carp (Cyprinus carpio) at 40
to 120 mg/L.
 Recovery time increases with higher doses and longer
exposure time.
 Clove oil is also an effective anesthetic for crustaceans at
doses of 100 to 200 mg/L.

46. Hormones in Aquacultre

47.  Hormones in aquaculture are used for artificial
reproduction and sex reversal.
 The first sustains the production chain with the
constant production of seeds.
 The second is used when the growth rate and/or gain
weight are different between the male and female.
 The use of hormones in food producing animals faces
different legal regulations in different countries.

48. i. use of hormones in fish farming - Sex reversal
 The use of hormones in fish farming for sex reversal aims at
the production of monosex population to increase growth
rate or weight gain.
List of Sex reversalhormones in Aquaculture
Hormone Fish Species
17ß – Estradiol Rainbow trout (Salmo gairdneri),
Atlantic salmon (Salmo salar)
17ɑ-Ethynylestradiol Tilapia (Oreochromis aureus)
17α-Methyltestosterone Brook trout (Salvelinus fontinalis),
Nile tilapia (Oreochromis niloticus)
Tilapia (Oreochromis mossambicus)

49. ii. Hormone for induced spawning of fish
Why Induce Fish to Spawn?
 produce hybrids that are different from the parent species;
 produce sterile polyploid fish (for example, sterile triploid
grass carp for aquatic weed control);
 synchronize reproduction of large numbers of fish for
simultaneous spawning, thereby simplifying production and
marketing of the fish;
 produce fry outside the normal spawning season for
maximum hatchery production and to provide fish when
the price and market demand is greatest; and
 maximize survival of fry under controlled hatchery
conditions.

50. Synthetic Hormones
 Salmon GnRH analogue (sGnRHa)
 Ovaprim
 Ovatide
 Gonopro etc
 Human Chorionic Gonadotropin (HCG)
 Luteinizing Hormone — Releasing Hormone

51. Flesh Colour Enhancer

52.  Fish ‘skin’ has chromatophores, a type of cell that contains
color pigments.
 These pigments utilize carotenoids to bring forth shades of
yellow (Xanthophylls), red and orange (Carotenoids), and
brown and black (Melanin).
 The diet of fish impacts the actual pigment.
 Xanthophylls and carotenoids are the most important
classes of pigments for fish and crustaceans.

53.  Yellow and Red shades are the two colors most effectively
influenced by color enhancing foods, which utilize the
chromatophores.
 However, protein and foods such as seaweed are effective
with the chromatophores to produce brilliant blues,
purples and greens in fish.
 Recent review papers on carotenoids and salmonids, with
special emphasis on astaxanthin and canthaxanthin in
salmonid pigmentation

54. Sources of carotenoids
 Variety of carotenoids, both synthetic and naturally
occurring products, are available for use in aquaculture.
 Included are synthetically produced astaxanthin (3,3'-
dihydroxy-P, Pcarotene-4,4'-dione) and canthaxanthin (p,
p-carotene-4,4'- dione)
 and natural materials such as krill, Spirulina, crustacean-
meals, marigold, Capsicum, and other xanthophyll-
containing vegetable meals.
 Added to this list are commercially available products of
the astaxanthin-rich yeast rhodozyma.
 Another microbial source being considered is the
microalga Haemafococcus pluvialis.