Seasonal change in aquatic insect communities of freshwater streams in southern Thailand
1999
Suparoek Watanasit (Prince of Songkla Univ., Songkhla (Thailand). Faculty of Science. Dept. of Biology)
Aquatic insects in 23 streams of 13 southern provinces of Thailand were collected during wet (October 1944) and dry seasons (March-April 1995) using hand net. Standard time for collection was 20 minutes. The aims of the study were to investigate the composition and distribution of aquatic insects from 23 streams in southern Thailand and to determine seasonal change in the community of aquatic insects. Composition of aquatic insects collected involved 53 families of 9 orders in the dry season. The stream which had the highest total number of individual aquatic insects (636 individuals) was Sutha Lai stream in Yala province whereas the Ton Sai stream in Phuket had the lowest total number of individual insects (11 individuals) in the dry season. On the other hand, 31 families of 8 orders were found in the wet season. Sutha Lai stream was also the highest in total number of individual insects (109 individuals) while the Sibet Chun stream in Surat Thani was the lowest in total number of individual insects (38 individuals) in the wet season. The lowest number of total number of individual insects in Sibet Chun may adversely result from the tourist activity. The effect of seasonal change on total number of families, total number of insects, number of families each order and number of individuals in each order are reported. 1. There was a greater total number of families in the dry season than in the wet season. 2. Total number of insect was also higher in the dry season than in the wet season. 3. Numbers of families of Ephemeroptera, Odonata, Hemiptera, Trichoptera and Diptera were higher in the dry season than in the wet season. 4. Numbers of individuals of Ephemeroptera, Odonata, Hemiptera, Trichoptera and Diptera were also higher in the dry season than in the wet season. In summary, seasonal change influenced the composition, distribution and community of aquatic insects in this study.
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