A project developed in Denmark helps there be a hundred times more fish of some species
The fishermen had overtaken them and now science corroborates it: Reefs, whether natural or artificial, promote marine biodiversity. Hence the convenience of preserving them and, where appropriate, restoring them. A study carried out in Denmark has concluded that The placement of new reefs can help there be a hundred times more fish of some species.
Just six months after the National Institute of Aquatic Resources at the Technical University of Denmark (DTU Aqua) and several local organizations established new reefs in Bredgrund, in the south of the country, researchers recorded a hundred times more cod than usual.
Original reefs have shrunk in Denmark after decades of human activities. In the last 100 years alone, 8.3 million cubic meters of stone have been removed to expand the country’s ports and produce concrete, said Christina Tækker, Head of Communication at the DTU.
According to a study by this university, these figures correspond to the removal of at least 55 square kilometers of habitats for plants and animalsan area approximately the size of the Bermuda Islands and almost double the surface area of the Canary Island La Graciosa.
The disappearance of stones causes a lack of hiding places for marine animals and places where species such as algae or mussels can attach.. And if the algae disappear, there are often fewer small sea creatures and fish, such as cod, left.
Concrete reef being tested in Copenhagen’s inner harbour.
| Wolfgang Kunther / DTU
The absence of stone reefs and kelp forests means that cod have fewer places to hide from predators like cormorants and seals. The conclusion is clear: it is necessary to restore the stone reefs.
Expensive and complicated construction
With the aim of restoring the reefs, DTU Aqua, in harmony with local actors, has initiated a series of projects that investigate the compounds of rocks, mussels, concrete, etc.
One of the projects analyzes whether reefs can protect the coast and encourage more marine life. The answer is yes, help increase biodiversityto improve fish spawning and growth areas already create value for sport fishermen and divers.
“We are in the middle of a biodiversity crisiswhere species are going extinct at about the same rate as when the dinosaurs went extinct. “That’s why I’m pleased with the results of the study, which reveal that cod thrive around rock reefs and are better able to hide and feed than before,” said lead researcher Jon C. Svendsen.
“We are currently in a pilot phase, developing and testing various reefs and documenting how they work. We are moving in the right direction, but progress is slow because stone reef construction is expensive and complicated“, Add.
Artificial reef installed in the bay of Santander.
| University of cantabria
Reef creation began in Denmark 15 years ago. Nowadays, more attention is paid to reefs throughout Europe, because the member states of the European Union (EU) are obliged to protect and restore them that have disappeared according to the Habitats Directivewhich protects them in Natura 2000 areas.
There are two types of reefs. One is the ‘geogenic‘, which is made up of rocks. To recreate these reefs, rock is extracted from quarries and transported by boat to the chosen location. The other type is ‘biogenic‘, is made up of living organisms, such as oysters or mussels, and provides important habitats for a variety of fish species.
Protection against climate change
Another DTU project, called Barreef, seeks to determine whether artificial reefs can be used, in addition to promoting biodiversity, to protect the coast. DTU is testing the first coastal protection reef in the North Sea. Researchers believe it will have a stabilizing and restorative effect on the coast.
The project incorporates two sustainability principles: ‘nature-inclusive design’ and ‘nature-based solutions’. “Taking these two principles into account, in the future it would be good to build reefs that also serve as coastal protection and be better prepared as sea levels rise due to climate change“, highlights Svendsen.
A concrete reef. Scientists hope it creates a natural breeding ground for sea creatures, because it is similar to coral reefs and seashells.
“The expectation is that the construction industry can take advantage of the experience gained in future coastal protection projects, bridges, tunnels and offshore wind farms, which perhaps can be optimally designed to provide new habitats for fish, mussels, algae… Because it is necessary to act now,” explains Svendsen.”
Installation of an artificial reef on the Valencian coast.
| EFE / Valencia City Council
Before we saw the sea as an inexhaustible chamber, where we caught the fish we wanted and dumped a lot of wastewater. Also we have eliminated key living conditionsin the form of stone reefs, which fish and small marine creatures use as habitat,” he says.
“Every year, we cause oxygen depletion in the sea and extract sand from the seabed for coastal protection and construction. We have reached the point where we can no longer take from the sea. We need to give back, gain better knowledge and be more careful. Otherwise, we could end up with a lifeless ocean“, warns Svendsen.
130 artificial reefs in Spain
In Spain, the beginning of the installation of artificial reefs dates back to the early eighties of the last century. This activity begins with the installation of the pioneer reefs of the “Escorpora” Project (1981) and Sa Riera-Begur (1982), both in Catalonia.
During the rest of the decade a slow take-off takes place with the installation of ten new reefs: three in Catalonia (L’ampolla, Salou, and Medas), three in Valencia (Santa Pola, Tabarca and Torrevieja), two in the Canary Islands (Tazacorte and Arguineguin), one in the Balearic Islands (Cap Regana) and one in Andalusia (Conil).
During the nineties, artificial reefs were definitively consolidated as fisheries management measure, installing 93 in the entire decade. In this way, there are currently 133 reef initiatives recorded, 17 of them under the responsibility of the Government of Spain and the rest of the autonomous communities.
The priority line of action in Spain corresponds to artificial protection reefs. Artificial reefs developed in other countries generally associate the double function of protection and production to the same type of modules since, evidently due to its volume and weight, a production reef also constitutes a drag deterrentdetails the Ministry of Agriculture, Fisheries and Food.
The University of cantabria manufactured three years ago in its laboratories, with a 3D printer and within a European program, a total of 36 artificial reefs that were placed on the seabed of the bay of Santander and three other locations in France, the United Kingdom and Portugal.
–Artificial reefs managed by the central government: https://www.mapa.gob.es/es/pesca/temas/proteccion-recursos-pesqueros/arrecifes-artificiales/arrecifes-artificiales-instalados-por-la-sgp/default.aspx
–List of artificial reefs managed by the autonomous communities: https://www.mapa.gob.es/es/pesca/temas/proteccion-recursos-pesqueros/aa_ccaa_tcm30-278059.pdf
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