The key word is sustainable. If 10k wild returning fish is enough to sustain or grow the pop of a system and 11k fish come back you could have a C&R season. If the mortality rate is less than 1000 fish as a product of catch and release. It makes no sense to have a C&R season if a system is not meeting recovery goals. Does not matter how the fish are killed in my opinion it needs to have shutdown limits to insure recovery.