Uppvandring av ålyngel i Viskan: årsrapport för 2025

Södra Cell Värö is a pulp mill that has been in production since 1971. The mill’s damming of river Viskan pose a migration barrier for migrating juvenile eel. The eel management plan of Viskan is an agreement formed between Södra Cell Värö paper mill, Varberg municipality, the former Swedish Board of Fisheries and several hydro power plant owners along Viskan. The eel management plan was formed in 1980 to facilitate the migration of eels by collecting eels at the dam by the mouth of the river and relocating them upstream within the drainage basin of Viskan. The migration of juvenile eel has been monitored by collecting juvenile eel from four eel collectors at the river mouth of Viskan from May to early October 2025. New this year is that one stationary eel collector was replaced by an ELFI (Elver finder), which is a portable collector for juvenile eel. Data on the weight and number of eels were collected two to three times a week during this period. This data is compared to data along the entire sample time series starting in 1971. The number of migrating juvenile eel has decreased over time since the monitoring started, but slightly increasing levels can be seen during the past twelve years. The total catches in 2025 were 80,83 kg (approximately 239 711 individuals) which closely resembles last year’s catch.