POPULATION STRUCTURE AND DRIFTING PATTERN OF AQUATIC MITES IN RANDI GAD, A TRIBUTARY OF RIVER ALAKNANDA IN GARHWAL HIMALAYA, UTTARAKHAND, INDIA

Abstract

The present paper deals with the population structure and temporal drift pattern study of aquatic mites in Randi gad, which is a third order spring fed tributary of river Alaknanda in Garhwal, Uttarakhand, India. The mites contribute significantly to the structure and function of a stream ecosystem as it is a preferred food of fish and insects. To significantly analyze the drift strength of mites in a stream, a new index, Dobriyal Bahuguna Drifting Index (DBDI) has been developed which is based on the density of mite population in nature and number of drifting individuals in unit time. The maximum mite population in the stream was observed in January (51 units.m-2 ) and minimum in October (35 units.m-2 ) with 7 species. It was found that the mites perform specific monthly and diel drift pattern. Various factors like current velocity, breeding, colonization, habitat disturbance and protection from predators are responsible for it. The DBDI value for different mite species was observed highest in February (0.264) and minimum in November (0.227). It was also observed that maximum drift was preferred during late morning hours (8-12 hrs).