Our mitigation strategies help to prevent accidental otter casualties.
Unintentional otter mortality can occur on roads or when otters become entangled and trapped in fishing gear such as fyke nets and crayfish traps.
We were funded by the Trunk Roads Agencies in Wales to produce reports highlighting priority areas for mitigation on roads (areas with multiple mortalities or evidence of breeding). Reports were produced for North, Mid and South Wales.
Road traffic accidents
Otters can travel several miles in a night, and often cross roads where rivers are culverted or bridged. Road traffic accidents cause a significant number of casualties. We typically receive around 200 otters per year, of which 80-90% have been killed as a result of road traffic accidents. The death of otters on roads can have a serious impact on populations in some areas, particularly where population densities are low or where danger-spots impact on breeding females.
Suitable mitigation measures are described in reports by Grogan (2001) and by Liles and Colley (2000, 2001), and include the installation of dry culverts or bolt on ledges, in combination with fencing to guide otters to the safe passage point.
Fyke nets and crayfish traps
The Environment Agency stipulate that both fyke nets and crayfish traps must be securely fitted with an otter guard if their entrance is greater than 95mm in diameter. In fyke nets this guard must be fitted to the funnel leading to the first chamber of the net or trap.
Regulations by the Environment Agency state that the guard must consist of:
- tightly stretched flexible netting with a mesh size measured when wet of not more than 75mm knot to knot or 300mm round the perimeter; or
- a rigid square grid with bars separated by not more than 85mm; or
- a rigid ring with internal diameter of not more than 95mm.