not fully on topic but kinda is just not on trout but i have caught skate missing their tail a recent stingray zac caught also was missing its tail which i believe commercial trawlers do to them. caught kahawai missing parts of their tails and cod also. along with various other fish missing part of gill plates have chunks taken and bite marks which look to have healed. it is a tough one it just comes down too are you willing to risk it and then the feeling of will it actually survive which well no one really knows for sure some may while others wont. a few of the kahawai i got over my xmas break i intended on releasing but they were bleeding alot so kept. i know this isnt too do with trout but in general it is a similar practice.