Minimise the time the fish is out of water, and handle it as little as possible. Covering the head of the fish with a wet cloth or piece of wet netting will help keep it calm and stop it flapping. Note that deep-hooked fish should survive if the hook cannot be removed. Cut the line as far into the mouth as possible. Do not pull hard on the line and always release the fish immediately.
Eels are particularly vulnerable if deep hooked, as all their vital organs are close to the throat.
Do not hold eels tightly around the throat. For easy handling of eels turn the fish onto its back, cover its head and hold still for 30 or 40 seconds. This will leave it lying completely still, ready for unhooking. Barbel and grayling may have a particularly long recovery time. Respect all fish regardless of size or species.