A photo of a young turbot just before it is released into Roskilde Fjord has won the DNRF’s Photo Competition 2020

24. April 2020
  • THE PANEL'S REVIEW:

    The Panel’s Review:

     

    The small turbot inside the hand expresses a fundamental human care for our fellow creatures. Thus, the picture addresses an important topic at a time when the biological diversity of the earth is threatened. Therefore, it represents the underlying research project in both an empathic and aesthetically engaged way.

     

    The Panel:

     

    • Christine Buhl Andersen, Chair of the New Carlsberg Foundation
    • Louise Wolthers, Research Manager/Curator at the Hasselblad Foundation
    • Minik Rosing, Professor at GLOBE Institute, vice chair of the DNRF board and board member at Louisiana Museum of Modern Art

The first prize in this year’s DNRF Photo Competition goes to a photo of a young turbot, which shortly after the photo was taken, was released into Roskilde Fjord. In Denmark, fish are released into the waters to create sustainable populations, and the adapted genetics of the fish are crucial to their survival. At the same time, the research behind the photo is important for the protection of fish in Danish waters.

The winning picture in the DNRF's Photo Competition 2020 shows a young turbot, which will soon be released in Roskilde Fjord.
The winning picture in the DNRF’s Photo Competition 2020 shows a young turbot, which will soon be released in Roskilde Fjord. Photo: Mads Christoffersen, senior consultant, DTU Aqua, Technical University of Denmark

For the third year in a row, researchers from all over the country submitted their best research photos to the Danish National Research Foundation’s Photo Competition 2020, and the winners have now been chosen. This year’s winning photo shows a young turbot that barely covers two fingers of the hand that is gently lifting the fish above the water. In the background, beneath the water’s surface, countless other small turbots are swimming around.

“The small turbot in the photo is not much more than half a year old, and the picture was taken just before we released the small fish and all its brothers and sisters into Roskilde fjord. It is part of a major release program, where we release large quantities of fish in Danish waters every year,” explained Mads Christoffersen, senior consultant at DTU Aqua at the Technical University of Denmark and the person behind this year’s winning photo.

Christoffersen and his colleagues at DTU Aqua have primary responsibility for monitoring fish stocks in Denmark and are responsible for fish farming and fish release. The reason why fish are released into Danish waters is that several fish stocks are not necessarily sustainable, even with healthy regulated recreational and commercial fishing. If you want to fish for recreation in Denmark, you must pay for an annual fishing license. Part of the income received from the sale of Danish fishing licenses finances the breeding and release of fish. As a result, fisheries help to finance and maintain sustainable fish stocks in Danish waters.

“As fish biologists, we naturally would prefer that the fish reproduced in such large numbers that there was no need to release them. But in Denmark when nature is unable to sustain certain species such as turbot and scrub, then it is a nice model that funds from the fishing licenses help to maintain the stocks so that they are sustainable through release. With the release of fish, we focus on raising the stocks so that fishermen can catch fish in the future, and naturally, we hope that the stocks can reproduce themselves sufficiently over time,” said Christoffersen.

Fish are genetically adapted to specific habitats

Niels, a local angler, is pictured. He and several other volunteer fishermen from the Gershøj Recreational Fishing Association helped release the turbots.
Niels, a local angler, is pictured. He and several other volunteer fishermen from the Gershøj Recreational Fishing Association helped release the turbots. Photo: Mads Christoffersen.

A few years ago, the researchers started to use local parent fish for breeding the fish fry that will be released. The changed practice is due to the realization that genetics play a major role in whether the fish thrive. In this connection, the researchers at DTU Aqua are very dependent on so-called citizen science, where volunteer forces contribute to the project to ensure that local fish are used for breeding.

“It is important that the fry we release in an area are bred by fish originating in the same area. Fish like the turbot in the photo are simply genetically adapted to the individual areas. Therefore, we are also very dependent on the great volunteer help we get from fishermen who catch parent fish for us in the selected areas at exactly the right times, shortly before the fish are ready to spawn,” explained Christoffersen.

The biological consequences of not using fish from local areas for breeding and release would be enormous and create a kind of put and take fishing in Danish waters, whereby fish are released only to be caught again.

“There would be no future in such a model, because fish that do not belong to the habitat in which they are released may not be able to spawn. And if they are, then their offspring probably won’t succeed because the physical conditions don’t fit the fish’s genetics. In this way, we would spend a lot of resources and money on one generation of fish, instead of creating a reproductive generation that may eventually create generations that can manage on their own,” said Christoffersen.

He also points out that fish released without taking genetic adaptation into account can, in the worst case, risk destroying and eradicating the natural fish stock in the area.

“We have seen it with trout stocks, where the naturally adapted trout spawn early in the season, after which the trout that do not belong naturally risk spawning in exactly the same breeding grounds. It can cause the first spawn to detach, and back are the spawn that do not create sustainable offspring. In this way, the natural ecosystem is destroyed,” said Christoffersen.

The researchers are monitoring the state of the fish in the waters

Part of Christoffersen’s work is also to tag fish with small individual inactive tags, which are often implanted in the fish or attached to the fish’s back. If the fish are then caught again, data on the fish can be collected. Depending on the purpose, the fish can also be tagged with electronic transmitters. However, the electronic tags are more expensive and are therefore often used for more focused studies for which some specific detailed data is requested, while the cheaper inactive tags are used to a much greater extent to obtain more general data on fish stocks.

“If fish with inactive tags are recaptured, it gives us data on how much the fish has grown since it was released, so that we can, for example, calculate the average growth rate per day. Furthermore, we get data on the fish migration from where it was released to where it is caught, but noting more precise than that. With electronic tags, on the other hand, we can see where the fish have been throughout the period with a margin of error of a few meters. So which tags we use depends a lot on purpose versus resources available,” explained Christoffersen.

The data collected also form the basis for research articles on the different fish species in Denmark. In the articles, the researchers use the different data to identify the areas in which the fish migrate and where they prefer to spawn in Danish waters. In this way researchers get a picture of the life cycle of the fish, which is essential if we are to protect the animals in the future.

“There is a lot of activity at sea, such as offshore wind farms, rale suction, etc., that we would like to avoid, because it harms the fish. With our data, we try to provide our input for marine planning by mapping the so-called essential fish habitats. These are areas that are very important for the survival and life cycle of a particular fish species. Therefore, as far as possible, we try to publish our data so that we can refer to it when we have to argue why certain fish habitats in Danish waters should be protected,” concluded Christoffersen.

Much more info about the research and fishcare in Denmark can be found at Fiskepleje.dk

More photos and information about the competition can be found here