Ecological interactions between cod and flounder in the Baltic Sea

Last changed: 08 June 2023

There is a major knowledge gap of the ecological interactions between the two commercially important species cod and flounder, both dwelling in benthic habitats in the Baltic Sea. The BENTHFISH project at SLU Aqua is investigating the interactions between the two fish species and will serve as a basis for an ecosystem-based fisheries management.

Preliminary analyses have revealed that these two species feed on similar prey suggesting potential strong competition for benthic food. This competition may have intensified during the past years as benthic prey have become scarcer due to the deoxygenation of the deep waters.

The recent increase in the Baltic flounder stocks’ abundance could therefore be one of the causes of the enduring low body condition, as well as low abundance, of the cod. If confirmed this would imply an important trade-off between cod and flounder with direct implications for fisheries management.

The research project BENTHFISH

Our project intends to resolve the interplay between the commercially exploited species cod and Baltic flounder and hence be of help in management decisions.

The project will

  1. characterise and quantify the trophic interactions between cod and flounder in the Baltic Sea using newly collected diet data and
  2. apply the results into a novel ecosystem model to investigate the trade-offs between the two species under different scenarios of climate change and fishing pressure.

Project manager for the BENTHFISH project is Michele Casini, Department of Aquatic Resources, The Swedish University of Agricultural Sciences (SLU).


Project name

Fish interactions in the marine benthic habitat: a knowledge gap in Baltic Sea fish ecology and multispecies fisheries management (BENTHFISH), 2019-2021.

Project partners

The Swedish University of Agricultural Sciences (SLU) and Linköping University.

Funding agency

Swedish Research Council Formas

Ecosystem-based fisheries management

Ecosystem-based fisheries management (EBFM) is a pillar of responsible fisheries and environmental EU legislations. EBFM aims to a sustainable management of marine resources which recognizes and account for the critical ecological interactions among key species and ecosystem components.


Michele Casini, Professor
Department of Aquatic Resources, Institute of Marine Research, SLU, +46 10 478 40 16, +46 761-26 80 07