Regarding removing the fish I would imagine a boom
boat shocker would do the job well. Care will be
needed to set the current to the water
conductivity conditions. As the job is just a
straight removal exersize you will not have to
worry about constant effort etc.
Re affects on spawning fish see Muth & Roberts
(1996) N.Am.J.Fish.Mgmt 16 (2) pp473-476. I guess
however it all depends on the fish species used.