Caddisflies (Trichoptera) in benthic communities of southern Sakhalin rivers, Far East Russia

During one year we studied caddisfly assemblages in benthic macroinvertebrate communities of mountain (Frikena River) and piedmont (Partizanka River) reaches of the Lyutoga River Basin. For most of the year in the mountain reaches, the scraper Neophylax ussuriensis Martynov dominates. Maximum caddisfly density (403 ind./m(2)) and biomass (14,441 g/m(2)) was recorded in July before mass emergence of that dominant species. The density of caddisflies in the benthic community was more significant in November (32%), and caddisfly biomass was most significant in July (69%). In the piedmont reaches of Lyutoga River Basin in various seasons, Rhyacophila (Hyporhyacophila) sp., Hydatophylax sp., Hydropsyche orientalis Martynov, and Stenopsyche marmorata Navas dominated. Maximum density and biomass of caddisflies (451 ind./m(2), 1,576 g/m(2)) were recorded in 5 September. The density of filterers H. orientalis and S. marmorata occurs in the salmon spawning season and seems to be correlated with the increased abundance of suspended organic substances in the water column as salmon spawn. In the piedmont reaches the role of caddisflies are the most significant in September (49% of total macroinvertebrate density and 56% of biomass).