PRINCIPLES OF AQUACULTURE (AKU3201)

1. PRINCIPLES OF AQUACULTURE(AKU3201) Fish Diseases

4. Factors affecting fish health HostEnvironment - Stocking density - Poor sanitation • Handling - Changes in pH, salinity - Transport temperature etc. • Chemotherapy • Nutrition • Behaviour Disease agent • Pathogen/ non-pathogen • Opportunistic pathogen Disease agent Disease Env Host

5. 1) Host susceptibility • Physical barrier (skin, scales, exoskeleton, shell, mucous membranes)

6. Physical Signs • Blistered areas • Swollen bellies • Popped-out eyes • Bloody (hemorrhaged) areas on fins • Discoloration or erosion of body parts • Excessive mucus • Growths on the body Behavioral Signs Failure to feed properly Flashing (turning on their sides) Rubbing on the bottom Gathering around the water inflow Reduced vitality Gasping at the surface

7. Physiological defences - Immune system, detoxification by liver • Nutritional well-being • Age (Young more susceptible) • Spawners – stress due to their reproductive functions

8. Sick fish • Unusual behaviour • Scrap body to wall • Coming to surface, gulping for air • Erratic swim • Loss appetite • Physical changes

11. Diseases • Exophthalmia (Pop-eye)

12. Extended belly

13. Haemorrhage

18. 2) Environment • Crucial role in disrupting the balance between host & pathogen • Environmental stress => pathogen & host react = disease occur

19. Stress • Anoxia = absence of oxygen • Fright • Anaesthesia • Temperature changes • Injury • Pollution

20. High stocking density • Restricted spaces – cages/tanks, raceway • Large quantity of concentrated feeds/ fertilizer

21. 2) Environment • Do not exceed carrying capacity – stocking density • Always monitor water quality • Maintain proper DO, pH, alkalinity, temperature • Check accumulation of organic debris, nitrogenous waste (ammonia, nitrite), hydrogen sulfide • Remove pond bottom sludge, dry & lime

22. Temperature changes – fluctuation day & night • Poikilothermic Hatchery • Closed system • If temp. drops, used heater

23. 3) Disease agent • Potential pathogens always present in aquatic environment

24. Disease agent • Parasites (cestodes, nematodes, trematodes & protozoans) • Bacteria (vibriosis, edwardsiellosis, furunculosis) • Viruses (IPN, lymphocystis) • Fungi (saprolegniasis, branchimycosis)

25. Common entry point 1) Wound in skin • Bacteria/viral infections => fungal infection 2)Gills • Pathogen enter body through delicate & thin epithelium • Protozoa establish themselves on them 3) Digestive tract • Bacteria penetrate intestinal lining • Protozoa

26. 1) Parasites • Most common cause of fish mortalities • Especially in larvae & fingerling stages • Multiply rapidly without intermediate host • Attach themselves to the host – special organ such as suckers

27. Penetrate host to multiply & invade vital organs • Invade through ingestion, skin rupture, transgression of gill lamellae, penetration to the egg membrane

28. Protozoan: Ichthyopthirius multifiliis

29. Copepod : Argulus, Lernaea

30. Isopod (Sea lice)

31. Monogenean parasites Dactylogyrus

32. Gyrodactylus

33. Nematode

34. 2) Bacterial disease • Vibriosis - Vibrio harveyi

35. Vibrio anguillarum • Vibrio alginolyticus

36. Quorum sensing

37. 2) Bacterial quorum sensing Monitor the environment & alter behaviour Quorum sensing (QS)

38. 2) Bacterial quorum sensing • Signal molecules AHL AHL BHL (Found in 70 different G- bacterial species) Diseases – controlled by QS

40. Aeromonas • Aeromonas hydrophila • Aeromonas salmonicida

41. Furunculosis

42. Edwardsillosis • Edwardsiella tarda • Edwardsiella ictaluri

43. How to identify bacterial isolates

44. Cotton swab

48. Biochemical test

49. Molecular techniques