The sea lamprey is one of the most threatened fish species in Sweden. It is listed as Endangered (EN) on the 2020 Swedish red list. Inventories in the 2020s indicate that the annual breeding population at present does not exceed 100 individuals. This can be compared with an estimated spawning population size of 1500 as recently as in 2008.
Sea lamprey. Illustration: Linda Nyman
The present breeding range extends along the Swedish west coast from the Norwegian border to northwestern Skåne. As with all anadromous species the sea lamprey has suffered from the establishment of hydropower and other barriers in rivers. It cannot pass traditional pool-and-weir fishways, and the distribution is therefore restricted to the lower parts in exploited rivers. During the parasitic life-stage at sea it is assumed to suffer from the consequences of over-fishing, notably the lack of large marine fish.
Conservation actions are urgently needed. A Swedish single species action plan has been decided upon for the period 2020−2024. The work is jointly led by the County Administrative Boards in Halland, Västra Götaland, and Skåne, with support from the Swedish Agency for Marine and Water Management and SLU Swedish Species Information Centre. An international Sea lamprey network has been founded in order to exchange knowledge and information on conservation issues.