Distribution of Cheumatopsyche species and environmental factors in Tamagawa River system

Abstract

Distribution of Cheumatopsyche spp. and environmental factors were studied in the Tama-gawa River system, Tokyo. The bentic fauna and the environmental data of sampling stations were already published (Tokyo, 1994-1999b), but larvae of Cheumatopsyche were now examined. Three species of Cheumatopsyche larvae (i.e., C. brevilineata, C. infascia and Cheumatopsyche sp. 'sato') were recognized. However, only three larvae specimens of Cheumatopsyche sp. 'sato' were collected from one station. The other two species were dominant with C. infascia occurring in wide reaches on the upper stream, while C. brevilineata occurring in wide reaches of the lower stream. The overlap of their altitudinal distributions was recognized between about 100-150 m above sea level. In this area, the BOD, COD, EC and biological pollution index in the stations inhabited by C. brevilineata were higher than those inhabited by C. infascia. Finally, the restrictive factors of their distribution were considered in relation to water temperature and water quality.