Benthic fauna in the Mun river and its tributaries during the opening of the sluice gates of the Pakmun dam
2005
Kanjana Payooha(Ubon Rajathanee University, Ubon Ratchathani (Thailand). Faculty of Agriculture. Department of Fisheries) | Praneet Ngamsnae(Ubon Rajathanee University, Ubon Ratchathani (Thailand). Faculty of Agriculture. Department of Fisheries) | Chaiwut Grudphan(Ubon Rajathanee University, Ubon Ratchathani (Thailand). Faculty of Agriculture. Department of Fisheries) | Thanatip Lamkom(Ubon Rajathanee University, Ubon Ratchathani (Thailand). Faculty of Agriculture. Department of Fisheries) | Tuantong Jutagate(Ubon Rajathanee University, Ubon Ratchathani (Thailand). Faculty of Agriculture. Department of Fisheries)
Taxa richness and abundance of benthic fauna were studied in the Mun river and seven of its tributaries by using Ekman Grab (15x15 cm) from August 2001-June 2002 during the opening all of sluice gates of the Pakmun Dam in Ubonratchathani province. There were 25 sampling stations spread from Phibunmunsahan district (upper reaches reaches of Pakmun Dam) to Khongchium district (lower reaches of Pakmun Dam). The samplings were carried out once a month. Four phylum of benthic fauna were found which included Arthropoda (75.38 percent), Annelida (14.27 percent), Mollusca (10.25 percent) and Nematoda (0.13 percent) and they consisted of 47 families and 87 genera. The most dominant family was Chironomidae (66.5 percent), followed by Family Amblemidae (bivalve) and Family Tubificidae (earthworm), second and third respectively. The average population number of benthic fauna during the study period was 23 individuals/square m. Benthic fauna were found in abundance in May (62 individuals/square m), April (44 individuals/square m), January (29 individuals/square m), December (27 individuals/square m) and March (20 individuals/square m). The least abundance were found in October (9 individuals/square m). The average Diversity Index of benthic fauna was 1.15. The average population number of this study was much less than of the result of 20 years ago which was 120 individuals/square m. In the year 1999-2000, during the period of closing the sluice gates, the average population number was 51 individuals/square m. This suggests that the abundance of natural food of the Mun river had been greatly decreased over time.
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