Health Management

HEALTH MANAGEMENT IN AQUACULTURE

Introduction:

Disease is one of the major problems in carp culture system in Assam. Fish suffer ill health from a variety of reasons like Environment (water), Fish (host) and pathogens, which are all inter-related. Any fragile imbalance between the fish and environment causes the disease outbreak. Interaction of host, pathogen and environment affects the disease state of the fish. So, improving water quality, adopting scientific methods of fish culture and maintaining eco-friendly environment will reduce the disease outbreak.

To avoid the disease problem one has to take care in maintaining a healthy environment during the culture period. One of the best methods to avoid this problem is to follow the scientific method of fish culture, because fish health management starts from the beginning of site selection of pond till the harvesting of fish is a multidisciplinary approach through which we can maintain a good health of fish. The good health management programmes includes such as

1. Proper selection of pond site.
2. Good pond design construction.
3. Preparation of pond before stocking of fish.
4. Stocking of quality fish seed.
5. Right stocking density.
6. Maintaining stable phytoplankton growth through fertilization.
7. Water quality parameters management.
8. Proper feeding with balanced diet.
9. Avoid physical injury while netting and stocking.
10. Avoid frequent netting in winter season.
11. Avoid keeping much organic load in the pond bottom.
12. Random monitoring of health condition of the fish during culture period.
13. Keeping record of events (disease outbreak) happening in the pond.

Main root causes of disease outbreak are:

1. When the pond water become polluted.
2. High stocking density, resulting overcrowding of fish.
3. When cultured fishes are deprived of sufficient amount of nutritious feed.
4. When the fishes are attacked by pathogens (parasites, bacteria, fungi and virus) in the ambient.
5. High organic load in the pond bottom.
6. Introduction of exotic fishes (new arrival).

Behavioural signs of healthy fish:

1. Clean body with shining.
2. Fins are kept in erected condition.
3. Bright body colour.
4. Faster movement.
5. Fins and skins remain in intact conditions.
6. Gills are reddish in colour.
7. Show defensive struggle.
8. Movement of eyes is faster.

Behavioural changes of unhealthy fish:

1. Irregular swimming movements.
2. Swimming out of water.
3. Rubbing the body against any rough surfaces.
4. Surfacing on water with shoaling behaviour.
5. Gasping air.
6. Refusal of feed.
7. Excessive mucus secretion on the body surface.
8. Eyes are shrunken.
9. Blackish body colour.
10. Swelling of abdomen.
11. Cyst formation on the body surface.
12. Fins are erected.
13. Very lethargic in movement.
14. Maxillary extension.
15. Head becomes larger.

Treatment strategies to follow:

For any deciding treatments mainly depends on the following factors:

1. Knowledge about the disease development process.
2. Knowledge about the pathogen.
3. Knowledge about the environment.
4. Knowledge about the host.

Essential to know the existence of the pathogen for proper treatment to be followed

1. Whether the pathogen existence in soil?
2. Whether the pathogen existence in water?
3. Whether the pathogen existence in the surface of the body?
4. Whether the pathogen existence in gut (endoparasite)?
5. Whether the pathogen is a systemic?

General precautions and remedies are to be followed:

1. Stocking density of fish should be at optimum level.
2. Before stocking fish seed, ensure that pond is free from insects and predators.
3. Lime and fertilizers should be used as recommended, doses as per POP.
4. Provide optimum quantity of feed.
5. Maintain optimum level of PH and DO2 primarily.
6. Do not allow thick growth of plankton.
7. Prevent entry of fish eating birds.
8. Dead and infected fish should be removed immediately.
9. Removal of molluscs from the pond bottom by netting or dewatering.
10. Maintain higher Alkalinity during winter season.
11. Reduce more handling during transportation.
12. Reduce netting during winter season.
13. While stocking fish seed into the rearing pond bath the fishes with 1-2 ppm with KMnO4 (Potash) for 1 minute, then release into the pond.
14. Avoid entry of sewage/drainage water into the pond.

Different types of fish diseases:

1. Parasitic fish diseases (Ecto and Endoparasites).
2. Bacterial fish diseases.
3. Fungal fish diseases.
4. Viral fish diseases.
5. Nutritional related fish diseases.
6. Environmental mediated fish diseases.

Source of infection in cultured fish:

1. Entry of infected fish.
2. Carrier fish (no clinical signs).
3. Contaminated eggs in hatchery operation.
4. Infected water supply.
5. Contaminated feeds.
6. Use of contaminated nets, boats, and equipment.

Treatment of fish diseases:

Several kinds of treatments are available depending on the intensity and type of diseases, a few disease treatments for some common diseases and their treatments are given below:

Table 1: Common fish diseases and their treatment

Epizootic Ulcerative Syndrome (EUS)

It is a freshwater and brackish water fish disease. It is not reported in marine water so far. Occurring in tropical warm water fish mainly in the Indo-pacific region. This disease was first reported in 1972 in Australia, particularly in the Queens land lake. In the year, 1988 it was reported in India in the month of May in Tripura in canals, rivers, ponds and paddy fields, which caused mass mortality of fish.

Definition of EUS: EUS is a seasonal epizootic condition of freshwater and estuarine warm water fish of complex infectious etiology characterised by the presence of invasive Aphanomyces infection and necrotising ulcerative lesion typically leading to granulomatous response.

Species affected: All freshwater species and most prone species are the murrels.

Possible factors in outbreak of EUS:

1. Drop in temperature in freshwater systems.
2. Sudden drop in salinity < 1.5 ppt.
3. Sudden rains and flooding in freshwater systems.

Causative Agent: Aphanomyces invadans

Clinical signs:

• Gradually Red blood blotches are visible on the body surface and later turns into ulcers exposing the bones.
• Surfacing and gasping of air by the affected fishes.
• Fishes die off in large quantities within short period of time.

Control Measures:

1. Quick lime (Cao) @ 100-600 kg/ha depending on the alkalinity of water.

2. KMnO4 @ 1-10 ppm

i) Pond treatment @ 5-10 ppm OR

ii) Bath treatment @ 1-6 ppm for 5 minutes.

3. Bleaching powder @ 1 mg/L OR 5-10 kg/ha/m in pond water.

4. CIFRI package:

i) Quick lime (CaO) @ 50 kg/ha prior to outbreak of disease which areas are prone to disease. (Prophylactic)

ii) Quick lime (CaO) @ 100 kg/ha during outbreak and after 7 days add 1 ppm bleaching powder.

5. Nacl @ 3-4% dip treatment of affected fish for 30 second.

6. CIFAX application: 1 litre/ha/m depth of water initially and second dose after 15 days of interval.

7. Lime and Turmeric powder: Use mixture of lime and turmeric powder 9:1 kg/bigha in pond water.

8. Antibiotics: Oxytetracycline, Erythromycin @ 60-100 mg/kg of fish for 7 days in feed.