Macroinvertebrates of the Tributaries of Upper Baleh River, Sarawak

Studies on Baleh River with respect to aquatic fauna currently remains limited. Hence, this paper presents thespecies richness and composition of macroinvertebrates14 tributaries of Upper Baleh River in Kapit Division,Sarawak. A total of 1,154 individuals from 10 orders, 43 families and 66 genera of macroinvertebrates werecollected. The highest number of macroinvertebrate was taken from Naah River (201 individuals) and the leastfrom Ukit River (15 individuals). The order Ephemeroptera was the most abundant, with 45% of the totalindividuals caught, followed by Trichoptera (23%), Hemiptera (10%), and Coleoptera (9%). Three biologicalindices were used to measure the diversity of macroinvertebrate of which the values of the indices were low:Shannon diversity index (1.54–2.54), Shannon evenness index (0.33–0.89) and Margalef richness index (1.67–4.90). The composition of functional feeding groups varies between first and fourth order streams, which ispossibly an indication of ecological effects of siltation due to logging activities in the area.