As a condition of the CR1 trapping licence the Environment Agency dictates the maximum size for entrance apertures on traps at 95mm. This restriction is to prevent larger creatures, especially otters, from entering the traps. However, due to various quirks in UK law, tens of thousands of crayfish traps with larger (illegal) entrances have been sold in recent years across the UK. 
It seems that illegal-to-use traps can be sold  openly and the onus is on the purchaser to know the law and not to use them. With so much effort and expense put into conserving and reintroducing otters it seems strange, yet typical, how UK trade law effectively leaves the ultimate fate of our otter population in the hands of a few fishing-tackle importers. 
The NICT are assured by one leading importer that they have, at last, adjusted the sizes to comply with environmental concerns and we hope that the others do the same.

The traps in question are the collapsible spiral wire and netting type: manufactured in the Far East and imported by the container-full. They are cheap and efficient at catching crayfish. Fish are also often caught and survive until being released. Unfortunately they are equally effective at catching otters and have put a serious dent in the otter population over the last five years. The otter sees a crayfish or fish inside the trap and dives, maybe several times, until crashing through the entrance and becoming caught. It may even enter through curiosity alone. 

Our first concern is that none of these illegal traps are used without otter guards being fitted. A simple remedy is to shorten the existing wire and tie it off firmly at the legal size. Better still cut 90mm pipe into rings or form rings from stiff wire. 

When buying a new trap the best thing to do is check the entrance size and act accordingly. 

Also of some concern to the NICT is that unscrupulous anglers are believed to use these traps specifically to catch otters, knowing that they can blame the crayfish trapper. 

The threat to otters is so serious that the Environment Agency now takes a very tough line with those caught using illegal traps. 
Be warned!