The biomass of benthos on the littoral and spring spawning grounds of Kurile Lake in the period of low abundance of foraging juvenile sockeye salmon in 1974

Abstract

Characteristics of qualitative and quantitative composition of benthos organisms on littoral and spring spawning grounds of Kurile Lake was given for the first time in 1974. Grounds of the littoral and spring spawning grounds typically consist of intermiting plots of pebble or gravel (clean or covered by biocrust) with permanent sand component, sometime silty. The silt component in the spring spawning grounds in the rivers Srednaya and Kirushutk is more impressive comparing to the lake spawning grounds. Chironomids of the group Crico­ topus aff аlgarum dominated in all sites. In the mid of July the highest biomass of the benthos among the littoral spawning grounds was near the head of the Ozernaya River, at Severnoye Blizhneye and Severnoye Dalneye spawning grounds, the lowest biomass was in the Gavryushka Bay and near the Etamynk River mouth. Spring spawning grounds were extensively different: maximum biomass of the benthos, which almost totally consisted of chironomids, was typically recorded in the Srednaya River, minimum biomass — in the Kirushutk River.