Poutès dam completed in 2022

The new Poutès dam on the upper Allier, costing 18.3 million euros, was completed in 2022 after a three-year construction period that began in 2019. The dam, originally built in 1941 and standing 20 meters high with a reservoir spanning 3.5 kilometers, was reduced to 7 meters in height, with its reservoir now covering only 400 meters.

Fish migration and salmon numbers

Two central gates remain open for three months each year to allow fish migration. Despite these modifications, the number of spawning males reaching the spawning grounds in 2024 was 38, according to the Migrateurs Loire indicator, the worst year in the series. In 2025, the number increased slightly to 48, but it still represents only 6.6% of the maximum observed in 2003.

Salmon counts and data adjustments

The 38 figure for 2024 was derived from recorded passes at the Vichy station, with summer mortality subtracted based on radio tracking data from 2006 and 2009. Raw counts from the Vichy station were higher, with 96 salmon recorded in 2023 and 55 by May 20, 2024, according to Logrami data.

Factors affecting salmon decline

The decline in salmon populations is attributed to reduced river flows, rising water temperatures, predation by catfish and great cormorant, and overfishing of krill at sea. The dam itself is not listed as a cause of decline in the Official Journal, which cited these other factors. AFP reported in June 2025 that the Loire-Allier stock salmon is in a "catastrophe" state.

Conservation efforts and fry release

Conservation efforts include a fishing ban, fish passes in areas where low water levels make the river impassable, and the Chanteuges nursery in Haute-Loire, which has released nearly 1 million fry annually in its early years but has since reduced its output by 70%. In 2025, 580,169 fry were released across the Loire basin, with 84.7% in the Allier, marking the first increase since 2021.

Fry production and reproduction challenges

The production of fry in 2025 was estimated at 259,312 on the explored sectors of the Loire basin, the highest since 2020. However, Migrateurs Loire described the estimated egg laying for the 2025 reproduction in the Allier as poor, down compared to the average of the last five years. Young salmon that left after the dam's commissioning in 2022 could begin returning in 2024, but none of the consulted sources quantify the dam's specific impact on these numbers.