These nets were tested last year in Puget Sound by the (i think) Suquamish tribe, and the results were quite encouraging.
With the right incentives, the tribes should be willing to switch to the less lethal nets, but as you've said they are more labor-intensive. The biggest incentive I see is that the fish are alive at the time of harvest, and therefore fresher to the market place, perhaps commanding a higher price.
The down side is that the new nets are considerably more expensive.
Which Tribes are netting in the Columbia?