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Improving Water Quality in Fish Passes & River Rewilding Projects
Supporting Salmon & Trout Migration as Part of UK River Recovery Initiatives
Across the UK, fish passage restoration and river rewilding projects are gaining momentum. Driven by organisations like the Environment Agency, SEPA, Natural Resources Wales, and multiple conservation trusts, these efforts aim to restore natural river function, improve biodiversity, and support declining salmon and trout populations.
Water quality remains one of the biggest barriers to successful fish migration—and nanobubble technology is emerging as a valuable tool for river recovery.
The Challenge: Oxygen Depletion in UK Rivers
Many UK rivers experience:
- Low dissolved oxygen (DO) levels, especially in summer
- Nutrient pollution and algal growth
- Sediment buildup in fish passes
- Stagnation at weirs, culverts, and bypass channels
- Organic load from agriculture and urban runoff
- Temperature-related stress on migratory species
These conditions can stop salmonids from moving upstream or reduce survival during spawning migrations.
Nanobubbles: Improving River Conditions for Migratory Fish
Nanobubbles deliver oxygen directly into water systems, remaining suspended long enough to meaningfully raise DO levels and support healthier aquatic ecosystems.
How nanobubbles help river recovery:
- Increase DO at critical migration points
- Improve water clarity and reduce algae
- Enhance natural breakdown of organic matter
- Reduce odours and stagnation in slow-flow areas
- Support healthier macroinvertebrate populations
- Improve spawning habitat quality
Nanobubbles are particularly effective in fish passes, bypass channels, and restored river segments where flow can be limited.
Benefits for Salmon & Trout
- Better energy levels for upstream migration
- Reduced stress during low-oxygen periods
- Higher spawning success
- Improved juvenile survival in nursery habitats
- Enhanced resilience to temperature spikes
A Valuable Tool for UK River Restoration
Nanobubble systems can be installed at:
- Fish ladders and passes
- Weirs and barriers
- Re-naturalised channels
- Urban river corridors
- Canal-river intersections
- Habitat restoration reach projects
For organisations working to revive UK rivers, nanobubbles provide a practical, chemical-free method for restoring oxygen balance and supporting iconic fish species.
