Spatio-temporal distribution, food intake and growth of cod (Gadus morhua L.) in the Western Baltic Sea

• Main Author: Funk, Steffen
• Other Authors: Möllmann, Christian (Prof. Dr.)
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Staats- und Universitätsbibliothek Hamburg Carl von Ossietzky 2020
• Subjects: Habitatnutzung; Mageninhaltsanalysen; Nahrungszusammensetzung; cod; habitat use; stomach analyse; diet composition; 570 Biowissenschaften; Biologie; 42.81 Pisces; 42.94 Meeresbiologie; Ostsee; Kabeljau; Nahrungsaufnahme; Wachstum; ddc:570; Gadus morhua; kabeljau
• Online Access: http://nbn-resolving.de/urn:nbn:de:gbv:18-104144; https://ediss.sub.uni-hamburg.de/handle/ediss/8379

The present thesis deals with patterns in depth and habitat use, seasonal and depthspecific food intake and growth of cod (Gadus morhua L.) in the Western Baltic Sea (WBS). Cod is the commercially most important demersal species in the WBS and therefore also of pronounced scientific interest. Despite decades of research and stock monitoring important knowledge gaps still remain, limiting our understanding of the ecology of cod in the WBS. The results presented in this thesis reveal the important role of shallow water habitats in the seasonal depth use of cod in the Western Baltic, their essential role for the seasonal food intake and thus, their important impact on the seasonal growth of cod. Furthermore, the effect of extreme summer periods in relation to habitat selection and resulting negative effects on seasonal growth are discussed. Finally, it is shown that the methods presented in the study such as (a) using fishers’ knowledge to reveal patterns in depth use, (b) using different fishing methods to enhance depth and habitat coverage in stomach sampling in order to analyze depth-specific patterns in food intake, and (c) using individual-based bioenergetic growth models to detect seasonal patterns in growth, can enhance our ecological knowledge not only for cod in the Baltic Sea, but provide practical approaches to be used also in other ecosystems and for other species. Die vorliegende Dissertation befasst sich mit Mustern in der Tiefen- und HabitatNutzung, der saisonalen und tiefenspezifischen Ernährung sowie dem Wachstum des Dorsches (Gadus morhua L.) in der westlichen Ostsee. In der westlichen Ostsee ist der Dorsch die kommerziell wichtigste, demersale Fischart und daher von einem großen wissenschaftlichen Interesse. Trotz jahrzehntelanger Forschung und jährlichem Bestandsmonitoring bestehen immer noch wesentliche Wissenslücken im Verständnis der Ökologie des Dorsches in der westlichen Ostsee. Die Ergebnisse der vorliegenden Arbeit veranschaulichen die große Bedeutung von Flachwasserhabitaten in der ...