Abundance of Aquatic Insects in Spatial Variation of Two Rivers in Perak, Malaysia

Abstract The effect of physical factors on the abundance of aquatic insects has been studied in Kuala Woh and Lata Kinjang Rivers, Perak, Malaysia. The focuses are to identify the aquatic insect families, to compare the abundance of aquatic insects in both sampling areas and to investigate the effect of physical factors (water temperature, depth of water, canopy, and water velocity) of both places on the abundance of aquatic insects. The samples were collected by using aquatic net. Physical parameters; water velocity, water temperature, depth and canopy cover have been measured in situ and recorded. A total of 278 individuals classified into 6 orders and 9 families of aquatic insects were identified from two sampling sites. The largest percentage of samples collected is from order Plecoptera 62.6%, followed by Trichoptera 15.8%, Hemiptera 10.8%, Ephemeroptera 7.9%, Odonata 1.4% and Coleoptera 1.4%. The aquatic insects collected from Kuala Woh have the highest abundance of 214 individuals from 6 orders and 9 families compared to Lata Kinjang which only have 64 individuals from 5 orders and 6 families. Chi-square test value (23.494) indicated significant association between different sampling areas and abundance of aquatic insects, P value = 0.003 (p < 0.05). Kuala Woh has a moderate stream flow (0.17 m/s) of warm water (27°C), with 0.85 m depth and not covered by canopy. Lata Kinjang has faster stream flow (0.84 m/s) with the temperature of 24°C, 0.36 m depth and covered by canopy. The results reveal that the abundance of aquatic insects is high when water temperature increases, low water velocity, deeper water and the area that is not covered by canopy.