EXAMINATION OF RIFFLE BEDS AND THEIR RELATIONSHIP TO THE NET-SPINNING CADDISFLY (STENOPSYCHE MARMORATA)

Abstract

The objective of the study is to improve the understanding of relationships between multiple spatial scales and the development of micro-habitat as well as its co-dependence with the net-spinning caddisfly (Stenopsyche mamorada). In this study, two target riffles located in the Asa River basin were investigated during the spring of 2006. Three major findings of this research were that; 1. the target specie seems to prefer substrate with median diameters between 3-13 cm because they need medium-sized gravel to create their nests, 2. the abundance of medium-sized gravel in the loose surface layer of riffle bed was observed to be related to the normal flow unit-width discharge because the finer bed material on the surface is washed out during normal flow condition and loose layer is developed, and 3. despite the unstable nature of braided morphology the target specie population was more prevalent and stable because the rough terrain reduce the local shear stress on the riffle bed during small floods.