Spawning migration of adult European flounder (Platichthys flesus) and implications for marine fisheries




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The aim of this project is to understand the spatial ecology of adult European flounder to inform fisheries management. Specifically, the aim is to determine if adult flounder perform spawning emigration from a shallow estuary during 2019-2020 or if the fish exhibit residency and therefore potentially spawn locally. Local spawning activity may benefit future flounder recruitment in the area. This study will build upon a similar study a year ago, and useful data and knowledge can be used from this.  



Flounder is a marine species that inhabits shallow inshore areas, including brackish and freshwater environments. Flounder has a wide salinity and thermal tolerance and is the only species of flatfish to be found in freshwater in Europe.

Flounder is the most commonly distributed fish in Danish coastal waters and it is a highly valued fish in recreational fisheries.

Even though it is widely distributed, we still do not know much about their migration routes.

For example, is flounder performing a spawning migration in the winter period, or do they spawn in their local estuarine waters? Previous foreign studies have indicated that flounder may perform late autumn or winter emigrations and may leave coastal locations prior to spawning.

Assessing the diversity of flounder migration patterns helps us to understand the ecology of the species and provides useful information for fishery and coastal environmental managers.


The project will map flounder migration in the Roskilde Fjord near Copenhagen using acoustic telemetry. Tiny transmitters will be surgically implanted into the body cavity of adult flounder such that the individual fish can be tracked using acoustic receivers. Stationary acoustic receivers are positioned strategic places in the fjord to detect the movements of the fish. Fish are going to be tagged in autumn 2019.

Also otoliths from fish in the same area will be used to look for salt (Kattegat)/brackish (fjord) water migration.

The student will assist in the field work, both with tagging the fish, retrieving data from the acoustic receivers and then carry out analyses of the data to reveal the movements of the tagged fish. Several environmental variables are measured and may be used to explain the movements of the fish (e.g. water temperature and salinity). 


Field work will be carried out in the period October 2019-April 2020, followed by analyses of the data taking 2-3 months and then 2-3 months for write-up.

It is preferable, but not expected, one student can participate the entire period.


Mads Christoffersen  

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DTU Aqua


Mads Christoffersen





Kandidatuddannelsen i Akvatisk Videnskab og Teknologi


Mads Christoffersen


Bachelorprojekt, Fagprojekt, Kandidatspeciale, Specialkursus


DTU er et teknisk eliteuniversitet med international rækkevidde og standard. Vores mission er at udvikle og nyttiggøre naturvidenskab og teknisk videnskab til gavn for samfundet. 10.000 studerende uddanner sig her til fremtiden, og 5.700 medarbejdere har hver dag fokus på uddannelse, forskning, myndighedsrådgivning og innovation, som bidrager til øget vækst og velfærd.

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