Zooplankton of Lake Ainslie, Cape Breton, Nova Scotia, 1979

Seasonal abundance and succession of zooplankton were examined in Lake Ainslie, Cape Breton, N.S., from 9 May to 29 September, 1979. The major species were Daphnia retroeurva, Boemina sp., Diaptomus minutus, Cyclops sp., Asplanchna priodonta, Keratella cochtlearts, and Polyarthra vulgaris. At most stations seasonal abundance of zooplankton reached a peak in June, with a maximum of 266 pl at Ainslie Village. Zooplankton density declined during July and remained low throughout August. A rise in zooplankton abundance occurred in late September. A distinct seasonal succession was evident with Diaptomus the dominant species in May (<113.1 L⁻¹), Bosmina (<116.1 L⁻¹), and Daphnia (<53.1 L⁻¹) in June-July, and Bosmina, Cyelops (<34.1 L⁻), and Asplanchna (16.1 L⁻¹) in August. Bosmina was the dominant zooplankter (<65.0 L⁻¹) at every station on 29 September. Cyclops (<22.0 t⁻¹) was also present in considerable numbers. These changes in abundance and species composition of the zooplankton are being con- sidered in relation to the presence of large numbers of planktivorous alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis) adultgand juveniles.