Uploaded September 2026 | Updated September 2026, 3 hours ago
As we head into autumn, we enter a key period for migratory fish, with species such as Atlantic salmon returning upstream to their natal spawning grounds.
One concern sometimes raised is that beaver dams could act as barriers, preventing already threatened fish from reaching spawning habitat. But unlike permanent structures such as weirs or hydropower structures, beaver dams are highly dynamic. Water can pass around, through and, during higher autumn and spring flows, completely overtop them, providing routes that fish may use to swim or leap around, through or over these structures.
Beavers build dams to maintain sufficient water depth to move safely through their territory. At some sites, when flows increase, the resident family may make little or no attempt to maintain the dam, allowing its shape, height and structure to change considerably.
This timelapse follows one beaver dam from September to December 2025, showing just how dramatically it changes as river flows rise and fall.
We are funding and working in partnership with a number of organisations across Britain to better understand how beaver dams change over time and what this means for fish passage. We are also working with stakeholders to develop a practical management framework that will allow users to assess beaver dams for fish passage and make informed decisions about whether management may be needed.
Learn more about beaver–fish interactions on our website.
🔗 Link in bio
As we head into autumn, we enter a key period for migratory fish, with species such as Atlantic salmon returning upstream to their natal spawning grounds.
One concern sometimes raised is that beaver dams could act as barriers, preventing already threatened fish from reaching spawning habitat. But unlike permanent structures such as weirs or hydropower structures, beaver dams are highly dynamic. Water can pass around, through and, during higher autumn and spring flows, completely overtop them, providing routes that fish may use to swim or leap around, through or over these structures.
Beavers build dams to maintain sufficient water depth to move safely through their territory. At some sites, when flows increase, the resident family may make little or no attempt to maintain the dam, allowing its shape, height and structure to change considerably.
This timelapse follows one beaver dam from September to December 2025, showing just how dramatically it changes as river flows rise and fall.
We are funding and working in partnership with a number of organisations across Britain to better understand how beaver dams change over time and what this means for fish passage. We are also working with stakeholders to develop a practical management framework that will allow users to assess beaver dams for fish passage and make informed decisions about whether management may be needed.
Learn more about beaver–fish interactions on our website.
🔗 Link in bio
