The dynamics of a natural population of zooplankton in Lough Neagh, Northern Ireland

Abstract

Zooplankton populations in eutrophic Lough Neagh, Northern Ireland were sampled during the period October 1979 to November 1981.

Instar analyses of the copepods Cyclops abyssorum and Eudi aptomus gracilis, the dominant zooplankters in the lake, revealed that seven cohorts of the former are associated with one year, as opposed to five cohorts of the latter. Two generations of either species may complete
development within one year.

Embryonic development of C. abyssorum and E. gracilis was found to be slightly more rapid at lower temperatures than has been recorded for other lakes. Prolongation of postembryonic development was observed at various times of the year and is thought to be food controlled. An index to quantify this effect is described; and is used in conjunction with computer models designed to simulate copepod populations.

Seasonal variation in mean body length is observed in both C. abyssorum and E. gracilis as is seasonal variation in reproductive effort. A skewed adult sex ratio in C. abyssorum suggests elective predation of adult females. E. gracilis does not s how such a phenomenon to a similar extent.

Although the standi ng crop of C. abyssorum generally exceeds that of E. gracilis, the P/B ratio of the latter frequently.

Date of Award	1986
Original language	English