Traditional nets kill the fish they snare, but the drop net keeps them alive, allowing unwanted fish to be sorted out and returned to the sea.
Fishing with barbless hooks is recommended on the trout rivers to aid in releasing, unharmed, unwanted fish.
The longline's drawback is that it offers no control over the size and kind of fish caught, and unwanted fish, which are usually drowned, are wasted.
Even something as simple as reducing the number of unwanted fish caught in nets set for other species would help, he said.
I've got another idea which might work better than trying to unload a pile of unwanted fish.
It is considered an environmentally friendly technique because unwanted fish are released soon after the line is reeled in.
There are also provisions designed to minimize a problem that bedevils fisheries all over the world - "bycatch," the netting and killing of unwanted fish.
In Malaysia an emulsifiable solution of endrin was used to rid mine pools and fish ponds of unwanted predatory fish.
But even with these measures, EU fishing fleets will still catch enormous quantities of unwanted fish which will simply be thrown away, often dead.
In other cases, unwanted fish have been released by aquarists or ornamental fish farmers into the wild.