Straight net traps.
Easy to set up, you reelease what you don't want unharmed.
We use traps to any fish in the cultivating woork.
The 1. link is an american showing differente set ups.
http://web.vims.edu/GreyLit/MDNR/ftm017.pdf?svr=www

This link is to a norwegian wich you can't read but see the principal pics.
http://www.njff.no/portal/pls/portal/docs/1/6182995.PDF


PAUL