COEXISTENCE OF FISH AND LARGE HESPERODIAPTOMUS SPECIES (CRUSTACEA, CALANOIDA) IN SUB-ALPINE AND ALPINE LAKES

In western Canada, the large diaptomids Hesperodiaptomus arcticus and (or) H. shoshone (>2.5 mm) usually coexist with fish in large subalpin e and alpine lakes located 1800-2455 m above sea level, but not in sma ll lakes with area 2-16 ha and maximum depth 4-16 m. The char (Salveli nus) and trout (Oncorhynchus) species that inhabit these lakes are usu ally caught at depths of <10 m and feed near shore. The profundal and offshore pelagic habitats of the large lakes provide a refuge from sal monid predation, permitting coexistence of large zooplankton and fish.