The seasonal abundance of the copepodite stages ofCalanus helgolandicusandPseudocalanus elongatusoff Plymouth

Abstract

The relative abundance of the six copepodite stages (CI-CVI) ofCalanus helgolandicusClaus (Copepoda: Calanoida) andPseudocalanus elongatusBoeck (Copepoda: Calanoida) was recorded at a station in the English Channel throughout 1989. There was a pronounced seasonal variation in the abundance of the early stages. Increased recruitment from the nauplii corresponded in both species to rising primary production early in the year, producing small CI abundance peaks in March. The major period of naupliar development occurred after the April/May spring bloom. During seasonal peaks the CI and CII stages typically formed 40% of the copepodites of these species but were scarce at other times. The body carbon weight ofCalanusandPseudocalanusCIs decreased by 38% and 21% respectively from May to August, indicating an increase in food limitation for the nauplii. Summer was passed predominantly in the CIV and CV stage at low abundances.