I think its pretty naive to say the 1 fish limit will destroy the fishery. C&R mortality has a much larger impact. I give a reference below for 16%. Even at 5, the multi weekend c&r warrior has a far bigger impact on the fishery. If you catch and release 25, you likely kill 3-4. My guess, the decline will likely be as a result of increased fishing pressure because the new harvest rules will attract more anglers, which will mean more C&R focused on walleye, and thus more mortality. An angler who releases 10 walleye to find a keeper 1-2 times per year, does far less damage than a CR angler catching 50 walleye a day 5-6 times a year.
There are lots of estimates on C&R mortality out there. This one from Ontario cites 16% mortality rate and I like it because its a review of about 110 scientific papers on the topic
https://www.ontario.ca/page/catch-an...-fish-handling :
"The impact of mortality caused by catch-and-release practices is often underestimated by both anglers and fishery managers. From a review of 118 catch-and-release studies (Appendix 1), which, in total, involved over 120,000 fish, the average mortality associated with catch-and-release angling was 16.2%. Thus, while many anglers may assume that by practising catch-and-release they are having no impact on the fish population, a significant number of released fish may die. Additionally, many anglers will continue to fish after they have caught their limit under the premise that they will release all further fish caught, however they often do not take into consideration the number of fish which will inadvertently be killed as a result of this practice."