Blue-Estuaries: Feeding ecology and growth of fishes - a contribution to the analysis of functional diversity and food webs in the Elbe and Oder estuaries

As the most important vertebrate group in estuaries, fishes are in their role as top predators of great importance in the food web. The estuaries of the Elbe and Oder are important feeding and nursery areas for many planktivorous and benthivorous fish species, which link lower trophic levels with piscivorous fishes and birds. Key fish species in the estuarine food web are considered suitable indicators for assessing the status of estuarine ecosystems. Due to the great importance of fishes in estuarine food webs, detailed analyses of feeding ecology and growth of estuarine key fish species are necessary to clarify the food web relationships of the important biota in the estuaries of the Oder and Elbe and to assess the possible effects of stressors. In the project of the UHH, juvenile and older life stages of typical pelagic and benthic fish species will be purchased from commercial fishermens in both estuaries from stations that are little and severely affected by stressors. Fish larvae will be caught on own research trips. Daily rings on the otoliths of the fish larvae and the annual rings on the otoliths or scales of older life stages will be analyzed and growth rates will be calculated as indicators of food availability and habitat quality. To identify the prey of fishes and of their role in the food web, analyzes of the food in the digestive tracts of the animals are carried out using microscopes. The food biomass consumed, the abundance and frequency of occurrence of the prey organism taxa, an index of the relative importance of the prey components and the consumption index are determined as parameters of feeding ecology. The work performed and the results obtained in the project of the University of Hamburg will contribute to the joint BMBF-project Blue Estuaries. 

Funding party: Bundesministerium für Bildung und Forschung (BMBF)

Project manager: Prof. Dr. Ralf Thiel

Period: 2020-2023