Population structure, life histories and abundance of copepods in Tjeukemeer, the Netherlands

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Abstract
SUMMARY. The copepod zooplankton of Tjeukemeer was sampled at weekly intervals for 3 years (1969–1971), and ten species were recorded. Five species contributed more than 99% of all individuals collected. Acanthocyclops robustus is the most abundant species (66%), followed by Mesocyclops leuckarti (13%), Cyclops vicinus (11%), Eurytemora affinis (9%) and Diacyclops bicuspidatus (1%).The ecology of the A. robustus population in Tjeukemeer differs from other A. robustus populations in that it dominates the open water zone. This is an additional argument for a taxonomic revision of the A. vernalis‐robustus complex.Seasonal periodicity in abundance of each species was very similar in 3 successive years.All cyclopoid species went into diapause, A. robustus and M. leuckarti during winter, D. bicuspidatus and C. v. vicinus during summer. Most species diapause in a particular copepodite stage.The seasonal variation in the population structure, the fecundity and the sex ratio are described. Both population structure and sex ratio were influenced by diapause and size‐dependent mortality. The fecundity was more influenced by the water temperature and the age structure of the female population than by food situation or size of the females.