National Invasive Species Week takes place from May 20-26, raising awareness of the harm that some non-native plants and animals can cause indigenous species, their economic cost and how their intrusion can be prevented. 

Some of the most problematic species are familiar to anglers: killer shrimp, signal crayfish, Chinese mitten crab, quagga mussel, Himalayan balsam and giant hogweed. 

Some species have Alert status and if anglers spot them, they should be reported to the website  

Among these are the topmouth gudgeon, water primrose, ruddy duck, black bullhead and marble crayfish. Asian hornets have received much public attention, notably for the threat they pose to honey bees. But the hornet has an eclectic diet and eats many other fly species, including mayflies and caddis. 

The overriding message for fly-fishers to prevent the spread of invasive species is Check, Clean and Dry: 

Check your gear after leaving the water for mud, aquatic animals or plant material. Remove anything you find and leave it at the site. 

Clean everything thoroughly as soon as you can, paying attention to nets, waders, and areas that are damp and hard to access. Use hot water if possible.  

Dry everything for as long as possible before using elsewhere as some invasive plants and animals can survive for two weeks in damp conditions.