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Fecundity as a factor controlling the seasonal population cycle in Temora longicornis (Copepoda, Calanoida)
Fransz, H.G.; Gonzalez, S.R.; Klein Breteler, W.C.M. (1989). Fecundity as a factor controlling the seasonal population cycle in Temora longicornis (Copepoda, Calanoida), in: Ryland, J.S. et al. (Ed.) Reproduction, Genetics and Distributions of Marine Organisms: 23rd European Marine Biology Symposium, School of Biological Sciences, University of Wales, Swansea, 5-9 September 1988. International Symposium Series, : pp. 83-90
In: Ryland, J.S.; Tyler, P.A. (Ed.) (1989). Reproduction, Genetics and Distributions of Marine Organisms: 23rd European Marine Biology Symposium, School of Biological Sciences, University of Wales, Swansea, 5-9 September 1988. International Symposium Series. Olsen & Olsen: Fredensborg. ISBN 87-85215-15-5. VIII, 469 pp., more
In: International Symposium Series. Olsen & Olsen: Fredensborg, more

Available in  Authors 
    VLIZ: Proceedings [27047]
Document type: Conference paper

Keywords
    Fecundity; Persistence; Population dynamics; Seasonal variations; Temora longicornis (Müller O.F., 1785) [WoRMS]; ANE, North Sea, Southern Bight [Marine Regions]; Marine

Authors  Top 
  • Fransz, H.G.
  • Gonzalez, S.R.
  • Klein Breteler, W.C.M.

Abstract
    Daily fecundity in the copepod Temora longicornis (O.F. Müller) was measured in the southern North Sea by 24 h incubation of mature females. It was increasing in spring from about 5 eggs per female in Feb to 30 at the end of Apr. It fluctuated between 3 and 30 eggs in May and Jun, and on a low level between 1 to 8 eggs in Aug. Fecundity showed a seasonal pattern reflecting the fluctuations in chlorophyll concentration, but the spring increase may be a response mainly to increasing temperature. This dependency on food level and temperature was confirmed by egg production in cohorts kept at different conditions in the laboratory. Females reared in the laboratory at 5 °C were less productive than hibernating females in the sea at the same temperature.A mathematical model indicated that the three abundant spring/summer generations can maintain a stable population density at the observed levels of daily fecundity, if the mortality level is about 0.10 d-1 before June, and 0.06 d-1 thereafter. The tenfold increase observed in the first generation is possible at a mean mortality rate of 0.07 d-1 It is conceivable that the spring increase in number is the result of the high fecundity and a relatively low level of mortality .The summer decline starting during the second generation will be a resuIt of the reduced fecundity, but also requires an increase of mortality rate to values beyond 0.10 d-1. Low egg production rates in summer seem insignificant, but may nevertheless be essential for the pelagic population to persist during summer and the subsequent hibernation period. The possible role in population persistence of resting eggs accumulating in the bottom sediment, and egg production at low temperature and food levels in early spring, is discussed.

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