DR Well we used tangle nets broodstocking with success as long as we were out of transition water ( the fish slimed up ) In transition the fish were OK BUT then as the days went on the rubs ( even hand prints from holding ) fungus up and the head area really was a mess. Second when lifting the net if you don't take up the slack and get under the fish you are squeezing the hell out of the fish when you bring it in the boat. Tangle netting in bays or transition water is not all that much better than gill nets.

Beach seining the first issue is location as you have to have gravel bottom. Mud just turns into a soupy mess that the fish run out of DO. If you do mud, yeah they may swim away but they don't recover to spawn.

Then you have loading and by that I mean how many fish are in the net. When you make your sweep you then bring the forward tail in and as the U shrinks the fish become bunched into the bow of the net. The faster you bring in the greater the massing in the bow and the damage to the fish. You need at least 3 ft of water at the bow and you simply sort by had throwing over the net the non target fish. As the load decreases you continue bringing the net in so as to be able to get your hands on the fish. If you dip net then your now adding stress plus hand sort, at greatly increased rate. If your in mud then kiss your ass good bye. In addition if your location lacks reasonable flow ( current ) then time is everything as the mass packed in the bow will run out of DO.

Purse seining? All the above apply minus the mud, just differently. Simply put it matters not if it is seined, hook & line, or whatever if you get Chinook or Coho in the transition between salt and fresh the mortality is huge. Whatever happens it seems you wind their clocks down and they may survive then but most don't survive to spawn. Now we did no in depth studies but captured brood and held them in 100% ideal circumstances and could not get past the mortality. Agency staff working with us did everything they could ( with more experience & skills ) and could not over come this either. Move upstream and the fish slimed up and we went to beach seines and snagging ( much different than your mental image at this minute as it was very specialized with location, tackle, transport ) and dropped down to around a 4% mortality.

Now the agency staff ( if any are still around ) were well aware of all this and this is why I find this selective thing so unreal. If you want to selective harvest their is only one way to do without losses. Fish wheels! They can be designed to sort and return to the stream rather effectively. All this net stuff is about trying to maintain the tradition harvest methodology of the INDIVIDUAL. Better they formed co ops, used restoration money for low interest loans to get a start up, and got it down to ZERO impacts on non targeted species.