1. Kanjana Payooha*, Amonrat Rangsiwiwat, Buakaew Vongamnat and Achara Jutagate Department of Fisheries,Faculty of Agriculture, Ubon Ratchathani University, Ubon Ratchathani Thailand kanjanapayooha@yahoo.com

2. Introduction

3. Ubon Ratchathani province is the most Tilapia cage culture in Thailand 724 fish farmers 7,317 cages along the Mun river, tributary of Mekong river 14,630 tons of annual production 29,260 tons of fish feed have been used

4. Introduction The overloading of organic matter from uneaten feed, waste from fish play important role for the deterioration of water quality in the Mun river. The high intensity of ectoparasites in cultured Tilapia lead to high mortality although there is no bacterial infection.

5. Objective To determine the correlation between the occurrence of ectoparasites and water quality

6. Methodology Fish and water sampling were conducted monthly between August 2013-April 2014. There were two sampling stations in the Mun river where Tilapia cage culture have been high intensity. Two hundreds and seventy fish were examined for ectoparasites. Water quality analysis were conducted for dissolved oxygen, pH, temperature,nitrite- nitrogen and ammonia-nitrogen.

7. Sampling Sites 2 1

8. Results Gyrodactylus sp.Dactylogyrus sp. Trichodina sp.

9. Results

11. Unionized ammonia (mg-N/L ) Mean of tatlal parasite (ind./fish)

12. Discussion and Conclusion High temperature and high ammonia nitrogen contribute to the abundance of ectoparsites in farmed Tilapia Farmers should avoid stocking fish during summer to prevent high mortality causing from ectoparasites.

13. In order to decrease nitrite-nitrogen and unionized-ammonia,the number of cages should be controlled The stocking density of fish in each cage should be reconsidered The plan for setting cages in each area should be monitored for better of current movement. Discussion and Conclusion

14. Acknowledgements Thailand International Cooperation Agency (TICA) Ubon Ratchathani University.