SLU Aqua actively contributes to the global efforts to conserve and utilize freshwater crayfish. Join our crayfish experts, Lennart Edsman and Patrik Bohman, as they participate in strategic meetings in Spain, conduct study visits with Finnish researchers and fishermen in Lake Hjälmaren and Lake Vättern, and represent Sweden at the world's largest crayfish conference, held this year in Zagreb.
In May this year, a meeting was held in Seville with participants from all Spanish regions as well as from universities, national authorities and the Ministry of the Environment. Attending the meeting was Lennart Edsman from SLU Aqua and the Institute of Freshwater Research. The meeting was about developing a strategy for the conservation of the country's only native species of freshwater crayfish, the endangered white clawed crayfish, Austropotamobius pallipes, which is a sister species to our critically endangered noble crayfish here in Sweden. The work to develop the strategy has been going on for a long time, but the conservation program has met massive resistance from the commercial fishing of the introduced American invasive species red swamp crayfish in southern Spain. This species, like our introduced signal crayfish, is a carrier of the disease crayfish plague, which is fatal to European freshwater crayfish.
– I was invited to the meeting to present for more than an hour our 25 years of work on the crayfish action program in Sweden and the Nordic countries. I pointed out that although it is just a document on paper, it is absolutely necessary to have an established program of measures to be able to demand more resources and carry out the necessary practical measures. I also gave tips on how to work with effective methods such as insect poison and shock liming to eradicate invasive crayfish species and how to limit or stop the free trade of live crayfish. I hope my participation helped a little. In any case, on September 19, the Spanish Minister of the Environment finally signed the strategy for the conservation of the white clawed crayfish, says Lennart.
In August, Patrik Bohman and Lennart Edsman from SLU Aqua welcomed a group of researchers and fishermen from Finland for a study trip to Lake Vättern and Lake Hjälmaren. They were interested in learning more about the gear and methods used in commercial fishing for signal crayfish in Sweden, and are working, among other things, to develop a sorting grid to quickly sort out crayfish below the minimum size directly on the boat.
- During the study visit, we accompanied fisherman Rolf Gustavsson to lift and empty crayfish traps on a bumpy Lake Vättern. The group photographed and discussed gear such as the sorting grid and trap lifter, the methods of post-harvest handling of their catch and further details of the equipment. Already in the afternoon, one of the participants ordered 100 traps of the type used by most of the commercial fishermen on Lake Vättern, for onward delivery to Finland. Hopefully he got a discounted price, says Lennart.
The group also visited Hans Johansson who is a professional fisherman in Hjälmaren.
- Hans offered lunch and demonstrated how he and his son fished crayfish in the lake, and a lot of tips and advice were exchanged. The discussions were also, besides crayfish, about the common interest in fishing for fish, Lennart continues.
When the study visit was over, Lennart followed the Finnish friends to the Finnish boat at Stadsgården in Stockholm and waved them off.
- Everyone was very happy with the trip and the exchange, and plans for a Swedish study trip to Saimaa next year have already begun, Lennart concludes.
Every two years, the world's freshwater crayfish stakeholders gather for an international conference. In September, the Crayfish Conference was held in Zagreb, Croatia, with over 220 participants from all corners of the world. Everyone, ranging from researchers, managers and fishermen to farmers and administrators participated. SLU Aqua's Patrik Bohman and Lennart Edsman were there.
- I gave the opening speech on the crayfish situation in Fennoscandia with the role of crayfish as endangered, invasive, mythical, traditional, commercial, tasty and ecologically central in freshwater. I also gave a presentation on the problem of dwarf populations, says Lennart.
- My presentations were about the project to develop the best methodology for environmental DNA and crayfish and how to estimate population density with dive surveys and using submersibles. I also had a poster on how to track crayfish in Lake Vättern with acoustic telemetry, says Patrik.
The conference featured more than 100 presentations over five days, as well as two excursions and a city tour.
- What impressed us was how new molecular methods such as eDNA, metabarcoding and genomics are widely used in the studies. But what impressed us most was the high quality of the talks given by the students compared to those given by the senior researchers. The prize for the best oral presentation was consequently awarded to a brand new master's student who didn't even know if she would continue with her PhD, Lennart concludes.
The committee to award the prize for the best spoken paper in Zagreb meets under the chairmanship of Lennart.
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Participants in the Swedish-Finnish knowledge exchange after the fishing trip on Lake Vättern. From right, Joonas Häkkinen fisherman in Finland's largest lake Saimaa, Timo Ruokonen researcher Natural Resources Institute Finland (LUKE), Lennart Edsman, Rolf Gustavsson fisherman Vättern, and Japo Jussila researcher University of Eastern Finland. Photo Patrik Bohman.
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There were many questions and comments after Lennart's presentation in Seville on 25 years of crayfish conservation work in the Nordic countries.
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Lennart Edsman, Researcher
Department of Aquatic Resources, Institute of Freshwater Research, SLU
lennart.edsman@slu.se, +46 70 510 36 43
Patrik Bohman, Environmental Monitoring and Assessment Analyst
Department of Aquatic Resources, Institute of Freshwater Research, SLU
patrik.bohman@slu.se, +46 10 478 42 17