RELATIONSHIP BETWEEN CURRENT VELOCITY, DEPTH AND THE INVERTEBRATE COMMUNITY IN A STABLE RIVER SYSTEM

The relationship between invertebrate densities, current velocity and water depth was studied in the Dan River, northern Israel. Maximum cur rent preferences ranged from 5-120 cm sec-1, and depth preferences ran ged from 5-60 cm. Thirty-five taxa of invertebrates were collected by means of colonization cages. Larval and adult stages of 3 Elmidae (Col eoptera) species were treated separately: Limnius letourneuxi, Grouvel linus caucasicus and Elmis rioloides. Differences in current preferenc e were observed between larval and adult stages of the same species of Elmidae. Taxa were also grouped according to preference for turbulenc e. Wide ranges of depth and current velocity preferences were observed . Most of the taxa were found at between 80-100 cm sec-1 and at depths of less than 30 cm. A correlation between species diversity and curre nt velocity was established. Velocities of 60-80 cm sec-1 contained th e greatest overlap of faunal preference. The sensitivity of selected s pecies to stream flow reduction is discussed.