The Elbe estuary is subject to constantly changing abiotic factors such as salinity, water temperature, oxygen content, turbidity and river runoff. In estuarine food webs, keystone fish species are considered suitable indicators for the assessment of ecosystem quality. With climate change and other human impacts, such as channel management, wastewater sewage and nutrient inputs, the Elbe estuary has faced several anthropogenic stressors in the past and present. Within the past four decades, severe alterations of the ecosystem occurred. With regard to changing abiotic factors, the aim of this study is to check whether these influences have led to significant changes in the fish fauna of the Elbe estuary. Data from research catches with stow net vessels over four time periods (I: 1984-1986, II: 1994-1995, III: 2009-2010 and IV: 2021-2022) were standardized. The composition of the fish fauna at five main channel stations along the salinity gradient of the Elbe estuary was compared during all four seasons. The highest total fish biomasses per haul were recorded in periods II and III (75.36 and 119.46 kg/Mio m³, respectively), whereas biomasses were much lower in periods I and IV (39.09 and 16 kg/Mio m³, respectively). These changes are mainly related to changes in abundance and biomass of O. eperlanus, the most important fish species in the Elbe estuary. Between periods III and IV the abundance of A. fallax, P. flesus, G. cernua and other species declined, while abundance of two marine estuarine opportunists (C. harengus and M. merlangus) increased.

Primary Presenter: Jesse Theilen, University of Hamburg (jesse.theilen@uni-hamburg.de)

Authors:

Victoria Sarrazin, University of Hamburg, Department of Biology, Biodiversity Research – Hamburg, Germany   (victoria.sarrazin@uni-hamburg.de)

Elena Hauten, University of Hamburg, Institute of Marine Ecosystem and Fishery Science – Hamburg, Germany  (elena.hauten@uni-hamburg.de)

Raphael Koll, University of Hamburg, Institute of Cell- and Systems Biology of Animals, Molecular Animal Physiology –Hamburg, Germany  (raphael.koll@uni-hamburg.de)

Christian Möllmann, University of Hamburg, Institute of Marine Ecosystem and Fishery Science – Hamburg, Germany  (christian.moellmann@uni-hamburg.de)

Andrej Fabrizius, University of Hamburg, Institute of Cell- and Systems Biology of Animals, Molecular Animal Physiology –Hamburg, Germany  (andrej.fabrizius@uni-hamburg.de)

Ralf Thiel, Leibniz Institute for the Analysis of Biodiversity Change, Centre for Taxonomy and Morphology – Hamburg, Germany  (R.Thiel@leibniz-lib.de)