|Title / Titel||Population dynamics and reproduction of the European perch Perca fluviatilis L.|
|Abstract (PDF, 14 KB)|
|Original title / Originaltitel||Populationsdynamik und Laichbiologie des Barsches (Perca fluviatilis L.) im Zürichsee|
|Summary / Zusammenfassung||Population dynamics:
Population fluctuations in perch are estimated by standardized counting and measuring of egg masses collected in spring from four test sites in the lake. We found that the number and size of egg masses provide a reliable picture of the population structure of adult females.
Survival, growth rate, habitat choice and migrations of perch larvae are monitored by pelagic pushnet sampling. Population fluctuations seem to be caused by the development of occasional strong year classes, which is enhanced by favourable environmental conditions in some years, whereas unfavourable conditions in other years (e.g. cold water temperature, low food supply) will cause low larval survival and lead to weak year classes. Natural population fluctuations may be reinforced by strong fishing efforts, which allow females to spawn only once before being captured.
The spawning behaviour of perch is studied by a video survey in a natural habitat in the lake. We investigate sperm allocation strategies of perch males. Our results show that the small males perform a sneaker strategy, mid sized males an opportunistic strategy, and large males perform territorial defence. We found that the number of males and the size of ejaculates vary strongly between spawning acts. We try to find out on which criteria the ejaculate size depends (e.g. female quality, number and size of competing males, individual sperm supplies of the males).
|Publications / Publikationen||Egloff, M. (1998): Life history aspects of swim bladder inflation in the European perch Perca fluviatilis L. PhD thesis, University of Zürich.Egloff, M. (1996): Failure of swim bladder inflation of perch Perca fluviatilis L. found in natural populations. Aquat. Sci. 58: 15-23.Heldstab, H. & Katoh, M. (1995): Low genetic variation in perch (Perca fluviatilis L.) from three major European drainage systems in Switzerland. Aquat. Sci. 57: 14-19.|
|Keywords / Suchbegriffe||Freshwater fish, Perca fluviatilis, population structure, population fluctuations, mating strategies, spawning, sperm limitation, sperm allocation, fertilization success, larvae, larval survival, growth rate.|
|Project leadership and contacts /
Projektleitung und Kontakte
|Other links to external web pages||http://www.uzh.ch/zoolmus/zmneu/forschung/ribi_georg.html|
|Funding source(s) /
|Other Public Sources (e.g. Federal or Cantonal Agencies)
Swiss Agency for the Environment, Forests and Landscape (BUWAL)
|In collaboration with /
In Zusammenarbeit mit
|Duration of Project / Projektdauer||Apr 1987 to Dec 2005|