For paddlers, anglers, swimmers and other river users, this means you may encounter Rotary Screw Traps (RSTs) at a small number of locations across Wales during the spring months. These structures are temporary, carefully managed, and clearly signed, but they do introduce additional considerations when navigating the river.

This blog brings together all current information for three river catchments where rotary fish traps will be present, explaining how they work, when they operate, and what river users can expect at each site.

What Are Rotary Screw Traps?

Rotary Screw Traps (RSTs) are temporary fish traps designed to capture juvenile salmon and sea trout (smolts) as they migrate downstream. The fish are briefly held for monitoring, tagging and data collection before being safely released back into the river.

Although RSTs vary in size, they all operate on the same principle:

• A cone-shaped rotating drum is mounted between two floating pontoons
• The drum is positioned in the main flow of the river, half submerged
• Flowing water turns the drum via an internal vane
• Fish entering the cone are gently guided to the rear of the trap
• They are delivered into a holding box for processing and release

RSTs are always manned when in operation, and their use is limited to specific seasons and times of day.

When Do These Traps Operate?

Across all locations:

• Season: Spring (typically mid-March to May or early June, depending on river and site)
• Daily operation: Dusk to dawn only
• Daytime: Traps are either not fishing or moved out of the main flow

Clear warning signage, and in some locations illuminated signs or lights, are used to alert river users to the presence of traps and associated ropes or cables.

River Usk – Mid Wales

In 2026, Natural Resources Wales will operate a Rotary Screw Trap on the main River Usk, between Penpont and Aberbran.

Locations

Two potential sites may be used:

• SN 98114 28812
• SN 98305 28945

(Exact positioning may vary depending on river conditions.)

Operation Details

• Period: Mid March to May
• Timing: Dusk to dawn only
• Staffed: Yes, while fishing
• Signage:
• Warning signs placed upstream
• A line across the river upstream of the trap
• Signage directly on the trap

During operation, the trap will sit in the main flow. Outside of fishing hours, it will not be active.

River Wye – Rectory Pool, Llyswen

A short-term rotary fish trap will also be deployed on the River Wye, at Rectory Pool, approximately 1.2km downstream of Boughrood Bridge, near Llyswen.

Location

• What3Words: ///stitching.historic.dairy

Operation Details

• Duration: Approximately one week
• Timing: Over the Easter period
• Securing method:
• Ropes stretched across the river to hold the trap in place

This is a large piece of equipment, and the presence of tensioned ropes across the river presents a significant hazard if approached at speed or without awareness.

Key Safety Message

River users are asked to:

• Approach the area with extra caution
• Be alert for ropes and fixing lines
• Observe all warning signage, which will be in place for the duration of deployment

River Dee Catchment – North Wales

Within the River Dee catchment, NRW operates Rotary Screw Traps at two known sites:

• Main River Dee at Worthenbury
• NGR: SJ 41646 47503
• River Ceiriog at Chirk (tributary of the Dee)
• NGR: SJ 27673 37007

Important 2026 Update

Only the Worthenbury trap on the main River Dee will be fished in 2026. The Ceiriog site will not be operational this year.

Worthenbury (Main River Dee)

• Season: Spring / early summer (March to June)
• Timing: Dusk to dawn
• Signage:
• Illuminated warning signs 50–200m upstream
• Lights and signage directly on the trap

The Worthenbury site benefits from:

• A straight stretch of river (~100m) upstream
• Clear banks, offering good line-of-sight for approaching river users
• Shallow sections upstream, allowing paddlers to disembark easily under low flows

When not fishing, the trap is moved out of the main flow and positioned close to the left bank (looking downstream). The main channel remains largely unobstructed, though mooring cables and safety lines may still be present, either on, just below, or above the water surface.

River Ceiriog (Chirk) – Context Only

Although not operational in 2026, it’s useful for river users to be aware of this site for future seasons.

• Located in a straight section of river
• Heavily wooded banks, reducing visibility
• Clear upstream signage and shallow disembarkation points under low flows

What River Users Should Keep in Mind

Wherever Rotary Screw Traps are in use:

• Always slow down and look ahead
• Observe warning signs and lights
• Be aware of ropes, cables and safety lines
• Remember traps operate at night, when visibility is reduced
• If unsure, stop well upstream and assess the situation

These traps play a vital role in protecting fish populations and improving river health across Wales, and with awareness and care, they can safely coexist with recreational river use.