I have heard that some people leave lines attached to the banks of rivers, with a strong monofilament, barbed hook, and a large split shot 12" from the hook and a bundle of worms.
I presume that having baited such a contraption, they then visit later on in the day, perhaps in darkness and retrieve their quarry.
It would seem that in order to be prolificc, multiple lines would need to be set.
Never seen it my self
Matt