{"id":5174,"date":"2026-08-19T13:08:41","date_gmt":"2026-08-19T13:08:41","guid":{"rendered":"https:\/\/improveaquaticlife.se\/2026\/08\/19\/the-sea-lamprey-is-fighting-for-its-survival-in-the-river-atran-watch-the-video-clip\/"},"modified":"2026-08-19T20:29:06","modified_gmt":"2026-08-19T20:29:06","slug":"the-sea-lamprey-is-fighting-for-its-survival-in-the-river-atran-watch-the-video-clip","status":"publish","type":"post","link":"https:\/\/improveaquaticlife.se\/en\/2026\/08\/19\/the-sea-lamprey-is-fighting-for-its-survival-in-the-river-atran-watch-the-video-clip\/","title":{"rendered":"The sea lamprey is fighting for its survival in the River \u00c4tran\u2014watch the video clip"},"content":{"rendered":"

It has existed on Earth for more than 400 million years. But today, the sea lamprey is one of Sweden\u2019s most endangered fish species. In this video segment, we tag along on surveys in the River \u00c4tran. Here, we find out how this rare fish is faring\u2014and whether the conditions still exist for the species to reproduce in the river. <\/strong><\/p>\n

In previous news reports, we\u2019ve covered how biologists have used electrofishing to survey the riverbed of the River \u00c4tran, primarily to locate sea lamprey larvae, which are buried in the sediment. Now you can watch a video clip where we dive below the surface and also chat with biologist Daniel Wendesten, who is conducting the survey. <\/p>\n

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Using electrofishing, biologist Daniel Wendesten is surveying the lake bottom of River \u00c4tran.
Photo: Nicka Hellenberg<\/p><\/div>\n

\u201cIn most cases, electrofishing is done in flowing water to catch fish that move freely. The larvae of the sea lamprey, on the other hand, are buried in sediment banks, so the method has to be adapted accordingly,\u201d says biologist Daniel Wendesten in the film. <\/p>\n

Several different species were found
\n<\/strong>During the survey in Falkenberg, not only sea lampreys were found. River lampreys and brook lampreys were also caught, as were eels. The larvae of the different species are very similar to one another and can be difficult to tell apart. <\/p>\n

The species has disappeared from many of the rivers where it was once found.<\/p><\/blockquote>\n

For the sea lamprey, the situation is particularly serious. The species has declined dramatically in Sweden. In the River \u00c4tran, the population was estimated at around 1,500 individuals around 2010. Later surveys paint a completely different picture. In 2025, a total of 28 sea lampreys were recorded in the River \u00c4tran, according to the Halland County Administrative Board. <\/p>\n

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While Daniel Wendesten, a biologist with the Swedish Anglers Association, is electrofishing, Mathias Arnham films the mysterious life beneath the surface.
Photo: Nicka Hellenberg<\/p><\/div>\n

Dependence on Large Fish
\n<\/strong>A significant portion of the sea lamprey\u2019s life is spent in the ocean. There, adult individuals live as parasites on other fish. The availability of large fish is therefore crucial to the species\u2019 survival. <\/p>\n

At the same time, the sea lamprey needs functioning rivers in order to reproduce. When the fish migrates upstream from the sea, it seeks out suitable bottoms for spawning. The larvae then live buried in the sediment for several years. <\/p>\n

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A sea lamprey larva is measured and recorded before being quickly released back into the water.
Photo: Nicka Hellenberg<\/p><\/div>\n

Dams and other barriers to migration can prevent fish from reaching their spawning and nursery areas. Furthermore, regulating water flow can wash away the fine sediment that the larvae need. <\/p>\n

The River \u00c4tran has historically been an important river for the sea lamprey. However, the species has disappeared from many of the rivers where it was once found. The County Administrative Board notes that the sea lamprey has gone from being present in 20 rivers in Halland in 2015 to only three by 2024. In 2025, the species was recorded in four rivers in Halland. <\/p>\n