Hundreds of thousands of baby eels have been released today as part of a conservation project.
The elvers try to swim upstream where they will grow into adults as our Gloucestershire correspondent Ken Goodwin reports.
The Environment Agency is patrolling the River Severn to watch out for elver poachers.
They're using boats with special imaging equipment so they can see in the dark. Other officers patrol the banks.
The baby eels are a delicacy in the Far East and can command a high price, but fishing is strictly controlled. Anyone doing it without a permit can be prosecuted.
Bill Burleigh is an Environment Agency Fisheries Officer:
Elver fishermen say that the cold weather has delayed the start of the annual migration of baby eels up the River Severn.
Nigel Mott fishes for wild salmon on the Severn using a centuries old method of cages or "putchers".
The salmon swim with the tide and into the traps. But to get them he has to clamber out along a precarious girder and then find his way among the racks of putchers.
His are made of metal, more traditional ones were made from willow.
Mr Mott is wearing a head camera for some of the shots so you can see what he can see.
If what he is doing looks dangerous now, imagine what it is like in the dark, and in a gale. But it is a way of life Mr Mott says he is determined to protect.