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Gemeinschaftsstudie zu den die Herkunft von clupeiformen Fischen steuernden Prozessen in verschiedenen Regionen

Das Projekt "Gemeinschaftsstudie zu den die Herkunft von clupeiformen Fischen steuernden Prozessen in verschiedenen Regionen" wird vom Umweltbundesamt gefördert und von Stiftung Alfred-Wegener-Institut für Polar- und Meeresforschung e.V. (AWI) durchgeführt. Objective: The central activity of the project will be the Sardine Anchovy Recruitment Project (SARP) type study as originally conceived by the Intergovernmental Oceanographic Commission (IOC) for the International Recruitment Project (IREP). Despite the potential benefits from such a study it has never been carried out because of the scale of resources requiring considerable international cooperation. 2 main objectives are pursued: to identify processes controlling the annual variability of recruitment of sprat (Sprattus sprattus), sardine (Sardina pilchardus) and anchovy (Engraulis encrasicholus) by developing and refining quantitative methods for the measurement of larval condition and relating larval survival to oceanographic conditions and food availability; - and to develop effective sampling strategies for the prediction of recruitment strength where there is a significant environmental influence during the larval stage. General Information: Application of the SARP methodology to the present programme involves firstly a series of larval surveys to determine the seasonal distribution of abundance of the small larvae over time intervals (e.g. 2 week periods) over the whole spawning season. Follow up cruises to sample juveniles will take place later in the season. A comparison of the age distribution of the juveniles, from otolith daily growth ring counts, with the larval abundance distributions will indicate which groups of larvae were relatively successful or unsuccessful in terms of survival. Having identified groups of larvae with particularly good or poor survival the determining factors can then be examined. This will involve inspection of oceanographic conditions and food availability during the larval phase in relation to larval condition measured by a range of biochemical and histochemical techniques. Larvae for these analyses will have been collected routinely during the earlier larval surveys together with measurements of food abundance and relevant oceanographic data which might influence survival. The conclusion of the study will have identified the time during the early life history of the particular species studied at which significant mortality has taken place and the most probable causative agents of this mortality.

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