Comparison of benthic fauna of two beels under different management system

Abstract

A comparative study of benthic fauna between Rajdhala beel and Padmai beel ofNetrakona District under different management system was carried out from July 1999 toJanuary 20OO. An average number of 1113 and 1175 organisms/m2 were obtained fromRajdhala heel and Padmai beel respectively. A total of 22 taxa belonging to 8 diversegroups, Oligochaetes, Chironomids, Molluscs, Ceratopogonids, Diptera (other thanChironomids and Ceratopogonids), Ephemeroptera, Leeches and Crustaceans wererecorded. Oligochaetes were dominated and constituted 46% and 49% ofthe total benthicpopulation in Rajdhala heel and Padmai beel respectively. The next dominant group wasthe Chironomids, which constituted 31% and 30% of the total benthic population inRajdhala beel and Padmai beel respectively. The highest number 1279 and 1437individuals/m2 of benthic fauna was recorded in December from Rajdhla beel andPadmai bee! in respectively. The lowest number of benthic fauna 869 and 914 individuals/m2 were found during September and July from Rajdhala beel and Padmai beelrespectively. Monthly variation of benthic fauna among two beels were found statisticallysignificant (p<0.05). The numerical distributions of benthic fauna was found to bevaried with depth ranges. However, the depth wise variation of total benthic faunabetween two heels was not found statistically significant. Fish yield of Rajdhala beel (488 kg/ha/yr) was appreciably higher than the Padmai beel (250 kg/ha/yr).