Many thousands of "spiral" traps (see Illegal traps) have already been sold, and are still commonly available, with entrance holes that endanger otters. 
It is illegal to use these traps to catch crayfish in the UK without adapting them. The penalties can be severe: but they probably didn't tell you this when you bought the trap.

DO SOMETHING PLEASE
You can make your own otter guards by attaching either rigid wire or a slice of drainage pipe (always less than 95mm) to all entrances or, if it helps, the NICT is able to provide wire guards (40 pence each + p&p £1.50). These are easily attached to the inside of the entrance holes and clip together, making the trap safe for otters and legal to use. See photographs.

To order your guards please email your order to otterguard@nict.org.uk.

NUMBER OF GUARDS REQUIRED (2 per trap!)............

NAME.............................................................................

ADDRESS........................................................................

Payment can be made by cheque/ postal order payable to 'National Institute of Crayfish Trappers'.
 
Send to: 
NICT OTTER GUARDS
The Lodge
Little Bayham
Tunbridge Wells
TN3 8BD