Topher, draft nets are quite small nets operated using traditional methods. Typically, one man holds an end of the net on shore, while a small boat goes out, paying the net out behind it, and makes a wide sweep before returning to shore. The net is then hauled in by hand.
These nets operate in the estuary, or even in the tidal stretches of the river, and so only take fish destined for the river(s) that feed that estuary. They are thus much less indiscriminate than the drift netters which operate on the high seas and take salmon heading for any number of rivers including, in the case of the Irish nets, fish destined for other countries. Draft nets may take other estuarine fish, such as mullet or sea bass, but certainly don't kill the numbers of seabirds, dolphins etc that die in drift nets every year. Because the whole process is quite short, I think that anything that is caught in the nets can often be released without too much harm.
Of course, as a rod fisherman, I would ideally like to see an end to all netting. Draft nets can, at certain times of the year and especially in low water conditions, take very large numbers of fish. Nevertheless, the pragmatist in me acknowledges that it remains necessary to have a supply of wild salmon into the commercial market, and as I said to Paul, this seems the least worst system.