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Researcher breaks new ground to improve sustainable fishing

“My field of research covers fish and other aquatic organisms, both salt water and fresh water. I primarily work with sustainable fishing, ranging from how fishing affects sea organisms and the ocean beds to resource utilisation, EU directives and strategies for fishing and the marine environment, but I also work with studying and protecting aquatic life in our local streams and lakes and, of course, the Limfjord” Niels Madsen explains. He is currently collaborating with a number of fishing organisations on improving fishing technologies and legislation to heighten the sustainability of the fishing industry.

He is currently collaborating with a number of fishing organisations on improving fishing technologies and legislation to heighten the sustainability of the fishing industry.

- “At the moment, the majority of my work is focused on the question of discard survival rates – in other words, how many fish of a specific species survive if they are returned to the sea when caught because they are smaller than the minimum catch size limit. The EU recently introduced a ban on discarding fish, but that creates huge problems for the fishermen, since they only get a fraction of the price for these fish as they can only be sold for industrial purposes. In addition, if the smaller fish are returned to the sea, they can, one, grow to a larger size and have larger value if caught later, and two, contribute to the continued reproduction of the species if allowed to grow to spawning age” Niels Madsen says.

Some species of fish can tolerate getting caught and then re-released into the sea, and the EU are working on an amendment to the directive that will permit discarding small fish of certain species – as long as there is scientific evidence that these species have a high discard survival rate.

- “The first question to ask is of course, how do we prove the survival rate of species such as plaice and sole, for whom we expect a high survival rate? What we will be doing in practice is to collect fish from the fishing boats and place them in underwater cages to study their survival for a specific period of time. Once we have data on the survival of these species, we will work on getting approval for exempting these species from the discard ban. In other words – our results and data will be used for re-evaluation of the ban at EU level” Niels Madsen elaborates.

Cross-disciplinary collaboration enables new fishing technologies

While working on documenting discard survival rates is one way to improve sustainable fishing, research on sorting fish according to size and species before they even enter the fishing nets takes up another major part of Niels Madsen’s time. And in this work, he looks to both companies and other departments at Aalborg University to find specialised expertise and new technologies.

- “In one project, I collaborate with the Funen company Sonos Aqua, who, with help from Faroese investors, have developed an acoustic system capable of encouraging fish to swim in a certain direction. Different fish species hear sound at different frequencies, which means that we can use sound to either discourage certain species from entering the net or encourage certain species to enter the net, depending how we point the acoustic waves. We will be testing this system at the Faroese Islands in November” Niels Madsen explains.

Underwater cameras give access to unique data

Another technological advance that Niels Madsen has high hopes for is introducing new, intelligent technologies in the latest underwater cameras.

I collaborate with Professor Thomas Moeslund at the Department of Architecture, Design and Media Technology here at AAU on automating the recognition of species of fish by intelligent camera technology. The potential idea is that intelligent underwater cameras can use image recognition to trigger a signal to the fisherman, so as to, say, assist the fisherman to optimise his fishery in terms of fuel savings and optimised haul, as he will be able to target his fishing to areas where the fish are present in large numbers

Niels Madsen

As a first step in the use of underwater camera technology, Niels Madsen is getting information from experience and recordings from 50 cameras handed out to fishermen all over Denmark in order to assess the potential of the technology. “We are hoping the researchers at Media Technology can help us in the future to find an automatic way to identify which parts of the hours of hours of footage that show fish to ease the process of sorting through these data as well” Niels Madsen says with a smile.

In addition to aiding the fishermen optimise their fishery, such underwater cameras and cross-disciplinary collaboration may also give the researchers access to crucial new data on the general state of oceans and fjords:

- “The Kattegat and the Limfjord are very important in terms of protecting unique and sensitive areas, but there is a lack of full pictures of the state of the fauna on the sea bed floor out there. Research vessels are very expensive to use, so we are also pursuing new approaches in the shape of collaboration with the drone researchers at the Department of Electronic Systems on developing camera-bearing unmanned vessels that can sail either on the surface or underwater” Niels Madsen says.

- “In general, it is very important to me to work cross-disciplinarily, and I am happy to have experts within for instance camera technology or drone technology so close that I can practically just drop by their offices” he adds.

Increased focus on local aquatic systems

In addition to his work on aquatic environments at sea, Niels Madsen is also working on creating a bigger focus on the local fjord, both in his own research and in his students’ project work.

Having access to the Limfjord and the streams that lead into it from all over Northern Jutland, as well as the nearby lakes, is a gift to the students here at AAU. I collaborate with a range of the owners and managers of property along the fjord, including the Aage V. Jensen foundations and the Danish Nature Agency, on various problems within their areas

Niels Madsen

One such problem is an imbalance at the lake Vilsted Sø near Nibe, which is filled with algae. As part of their fieldwork, a group of Bachelor’s students supervised by Niels Madsen set out test nets to gain data on the composition of fish species in the lake.

- “On the basis of their work, the students offered not just an explanation but also concrete suggestions for how to restore the balance” Niels Madsen says and adds: “The opportunity to collaborate with our students is being noticed all over the region: I have been working here at AAU for a little over a year, and already the local organisations have noticed how our students carry out valuable work. They have started contacting us if they have relevant problems or questions concerning aquatic life in the area, because they know we potentially have the manpower, laboratories and equipment that enable us to look into the issues thoroughly.”

The researcher also hopes the local fieldwork will create value for the region for many years to come:

- “This local focus in our student projects has the added benefit that our graduates often get employment locally, which means that in a few years from now, we will have a strong network of biology and environment graduates working in the Northern Denmark municipalities who already have a deep hands-on insight – theoretical as well as practical – into the areas they will be responsible for. I hope this will benefit not only our collaboration with the local municipalities and nature organisations but also the Northern Denmark aquatic nature as a whole” he finishes.

To further this close local collaboration, the Department of Chemistry and Bioscience organised a conference on ensuring a sustainable Limfjord in the future in December 2017. The conference brought together relevant actors such as organisations, municipalities, researchers, property owners and managers of the Limfjord and adjacent nature areas with the purpose of furthering and coordinating future research and development activities along the fjord.