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Institute of

OF Baltic Sea Fisheries


Gill net fisheries: Development of alternative management approaches (STELLA2)

eingeklebte Acrylperle in einem Stellnetz
© Thuenen-Institut/A.Schuetz

Development and testing of fishing techniques to minimise conflicts between gillnet fishery, nature conservation objectives and protected species in the German Baltic Sea EEZ (STELLA2)

How can by-catches of marine mammals and seabirds be avoided? This question is to be answered as part of a research project by the Thünen Institute of Baltic Sea Fisheries in cooperation with NABU. The project is funded by the Federal Agency for Nature Conservation.

Background and Objective

Bottom-set gillnets belong to the so-called passive fishing gears. This means that their use has less impact on the marine environment, especially the biotic communities on the seabed, compared to active fishing gear that touches the bottom, such as bottom trawls. They are also considered selective for their target species, which in the Baltic Sea are mainly cod, herring and flatfish.

However, the use of gillnets is also not without its critics, as depending on the area of use, they entail the unwanted by-catch of marine mammals, including harbour porpoises, and seabirds.

One way to avoid bycatch of whales and dolphins is to use so-called pingers. The acoustic signals warn and scare away the animals, which can then become a problem if this technique is used in marine protected areas, "closes off" important feeding habitats of the animals or in case of habituation effects. The use of so-called "PALs" (PorpoiseALert) is somewhat different.  Here, porpoise's own sounds are used as a warning to increase the animals' attention. Nevertheless, there is an urgent need for further solutions.

The STELLA2 research project will investigate how bycatch can be reduced. The project will run for a total of three years, from October 2021 to December 2024, and builds on its predecessor project STELLA. Among other things, the so-called "pearl net" was developed. Transparent acrylic glass balls ("pearls") attached to the net make the gillnet "acoustically more visible" and whales orienting themselves by echolocation can perceive it as an obstacle. In addition, fish pots and fish traps were also developed and tested with the support of the fishery.

In the follow-up project STELLA2, the cooperation between fisheries, science and nature conservation is to be deepened in order to further optimise the methods developed so far, to pave the way for an environmentally friendly coastal fishery with low bycatch and thus to come a step closer to the common goal of sustainable fisheries.

In order to minimise not only bycatch of marine mammals but also bycatch of seabirds, alternative fishing gear such as fish pots and fish traps are being (further) developed and tested for their possible use in commercial, artisanal fisheries. Early cooperation with the fishing industry is particularly important here. In this way, the catchability, i.e. how many fish are caught, and the manageability are also to be tested. The goal is to jointly develop practicable solutions that offer a future perspective for nature and fisheries.

In order to bring about a real switch to alternative, environmentally friendly fishing methods, consumers are also involved. One of the goals is that consumers are more likely to buy sustainably caught fish in the future and are also willing to pay a higher price for it. Marketing strategies such as direct marketing, exclusive cooperation with selected restaurants and retailers and creative marketing are to be supported and expanded.


The project is divided into four work packages that are closely linked in terms of time and topics.

Work package 1: Modification of the control network ("pearl net")

This work package deals with the further development and practical testing of the gillnet modification designed in STELLA to reduce harbour porpoise bycatch ("pearl net").

The objectives are to investigate the behaviour of harbour porpoises in relation to the modified gillnet and to assess the actual effectiveness of the modified gillnets in reducing harbour porpoise bycatch. Furthermore, the catchability of the pearl net in relation to different target species will be investigated.

In parallel, the possibilities of industrial production through cooperation with net manufacturers will be investigated. Furthermore, ways of financing this development work are to be found.

Work package 2: Alternative fishing gear 1 (fish traps)

This work package deals with the further development and testing of fish pots as alternative fishing gear to avoid bycatch of marine mammals (harbour porpoises and seals) and diving seabirds.

The aim is to develop and test an improved fish pot. Since the relatively poor catch efficiency of fish pots in the Baltic Sea has prevented their introduction into German fisheries, the development and testing will focus not only on avoiding bycatch of marine mammals and seabirds, but also on catchability for the target species and the handling of the fish pots.

Work package 3: Alternative fishing gear 2 (pontoon trap)

The concept of the pontoon trap was already developed in Sweden in 2008 and adapted for use in coastal waters. Further technical adaptations will follow to enable its use at the open coasts of the Baltic Sea and to expand the range of target fish species.

The aim is to further develop and test the pontoon trap so that, at the end of the project, the fishery can be provided with a trap that is as catch- and cost-efficient as possible and can act as an alternative to the gillnet.

Work package 4: Communication

Close and transparent communication between all stakeholders (fisheries, science and nature conservation) is the basis for achieving the common goal of nature-friendly fisheries. In several workshops, discussions and constructive cooperation are to be encouraged and the exchange of information on current and international findings is to be ensured.

At the same time, the public and thus the consumers will be involved and informed about the status of the project via websites, social media and other channels. Furthermore, marketing strategies for sustainably caught fish from regional artisanal fisheries are to be developed and expanded. To ensure that the joint work can also bear fruit, a dialogue forum is planned at the end of the project.

Involved external Thünen-Partners

Funding Body

  • Federal Agency for Nature Conservation (BfN)
    (national, öffentlich)


11.2021 - 12.2024

More Information

Project status: ongoing

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