1. Disease development in fish

2. Incidence of disease
The incidence of disease is due to the breakdown of the delicate balance between host, pathogen and environment(Snieszko in 1970).
Irresponsible use of chemical disinfectants and antibiotics is a potential environmental hazard.
In fish, stress is usually related to stocking density, environmental quality, handling or transport

3. Incidence of disease in fish
Environ-
ment
Pathogen
Fish

4. Role of water quality in fish diseases
Maintenance of good water quality by making inlet water free from toxic substances and pathogens is one of the integral parts of the health management in aquaculture.

5. Important steps for low dissolved oxygen
Increasing aeration,
reduction of feeding rates,
control of phytoplankton bloom and
water flow management

6. Water quality criteria for optimum fish health management of warm water and cold water species of fish (mg/l, except pH)
Characteristic
Cold water
Warm water O2
5-Saturation Ph
6.5-8
6.5-9
Ammonia (un-ionised)
0-0.02
Calcium
4-160
10-160
CO2
0-10
0-15
H2S
Iron (total)
0-0.15
0-0.5
Manganese
0-0.01

7. Contd…. Characteristic Cold water Warm water Nitrate 0-3.0 Phosphorus
Zinc
0-0.05
Total Hardness (CaCO3)
10-400
10-200
Total alkalinity (CaCO30
Nitrogen (gas saturation)
< 100%
<100%
Total solids
0-80
1-500

8. Four major groups of diseases are generally identified in terms of epidemiology
Sporadic disease: which occur sporadically in comparatively few members of a population
Epizootics: which are large scale out breaks of communicable animal disease occurring temporarily within limited geographical areas
Panzootics: which occur in large areas
Enzootics: which persist or re-occur as low level out breaks in certain areas.

9. Three basic types of culture systems
Intensive culture system, in which animals are raised in high density, examples are intensively managed tanks and ponds
semi intensive systems in which fish or shrimps are raised in moderate densities in ponds , cages or tanks with some management of the system practised

10. Contd…..
extensive systems where they are grown in low intensity ponds or pens in natural bodies of water and where little or no management is practised.

11. Thanking you