Boulder Reef Restoration in Bredgrund |The effect of reef type on fish

Jon C. Svendsen (Author), Bo Mammen Kruse (Author), Tim Wilms (Author), Pauli Nordfoss (Author), Oliver Luk (Author), Gesine Ramm (Author), Charlotte Bourdon (Author), Jes Dolby (Author)

Research output: Non-textual formSound/Visual production (digital)Communication


Here, DTU Aqua presents a short film explaining the artificial boulder reef project in Bredgrund, investigating the effects of different types of boulder reefs on fish abundance and diversity in southern Denmark.

The project uses unbaited underwater cameras to monitor fish at six different locations in Bredgrund. The locations are: two sand control sites, two large reef sites, and two several small reef sites.
The large reef sites consisted of one large reef whereas the small reef sites consisted of 16 small reefs. To test which reef type is more economical, each of these reef types were made of the same amount of material. i.e. the one large reef was made of 300m³, and the 16 small reefs combined were also made of 300m³. The sand sites had no boulder coverage.

Footage was collected from each of the sites in 2016 before reefs were input, in 2018 after the reefs were input, and again in 2020.
Analyses examine if fish abundance and diversity change with the type of reef. Data from the artificial boulder reefs will be compared against the data collected before the reefs were constructed, the sand control sites, and each other. Data will be used to see which reef type is most efficient, the large reef or the several small reefs? Analyses will also reveal differences between fish species and fish body sizes recorded using unbaited cameras.
Results from this study will be used to determine how future artificial reefs should be built in the most economical and efficient manner.
Original languageEnglish
Publication date2019
Media of outputYouTube video
Publication statusPublished - 2019


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