Here's how slot limits "hurt" a fishery. Let's say I am a not particularly good fisherman (easily believable), and I am going to catch and keep the first 5 fish that come into the boat. I catch a 15, 15, 17, 20, and 25 inch limit of eyes. If there's a slot that says I can only keep 17-20" fish, I have 3 fish that I need to throw back. So I get lucky and catch 3 in the slot to fill out my limit before I call it a day. I have now caught a total of 8 fish with 3 released. Tagging studies show conclusively that there is only about a 30-50% chance that my released fish will ever be caught again. Most likely reason is because they died due to having been caught, improperly handled, and unceremoniously tossed back into the water. Hell, I see 12" walleyes floating in the river every year in the middle of a swarm of boats.
S0...how many fish did I kill that day? Science would suggest I killed something over my limit. Probably 6 total fish, maybe even 7 just to keep my limit of 5. The tighter the slots, the more this happens.
If you want a way of reducing human mortality on fish, you need to implement a "first 5 over the gunwale" limit. Meaning, you keep what you catch until you have your limit and then you are done. This is kind of similar to NDGFs paddlefishing rules (seriously, who thinks they'd have a C&R day if it weren't for political reasons?). For years they had a "you hook it, you keep it" rule in place.
