81% decline in migratory fish populations - but there is (some) hope

Freshwater migratory fish populations have declined by 81% from 1970 to 2020, according to the 2024 Living Planet Index published by WWF in May 2024.

Unfortunately, this comes as no surprise, with Atlantic salmon and now sea trout populations understood to be in decline.

This blog post from the Freshwater Blog offers some hope that river restoration, and in particular, barrier removal (dams, weirs and culverts) can help, as a key driver of migratory fish declines is the fragmentation of rivers and the blockage of migration routes due to dams, weirs and other barriers.’

It’s worth remembering that resident’ brown trout also migrate up and downstream to complete their lifecycle (as do many invertebrates) so barriers affect them too. 

Here at the Wild Trout Trust, we are doing what we can to remove barriers and reduce fragmentation of habitat so that rivers and their wildlife can function naturally and be more resilient to the insidious pressures of poor water quality, drought and flood.

Two recent examples of large scale weir removals are on the River Nidd in Yorkshire and the River Ecclesbourne in Nottinghamshire. It’s not only big weir projects: we also remove lots of smaller barriers that might be passable for a big sea trout or salmon but not by smaller, river resident fish trying to reach spawning gravels. 

Engineered fish passes tend to be expensive to install and maintain — so our preference is to remove the barrier wherever possible. It’s more cost effective and delivers a better result for the river and all its wildlife rather than only large migratory fish.

There is lots more information about the effect of weirs, culverts and barriers on this web page, and more about the trout lifecycle for both sea and brown trout on our About Trout’ pages

Snake lane weir after A1
Snake lane weir before A1
The weir at Snake Lane on the River Ecclesbourne