2 really great articles that talk about how yeah, in fact, the c&r seasons have impacted the fish populations. Definitely worth the read, but if you skip it, here's the nutshell version:
22 years of study has been completed on closed lakes in Ontario, and the evidence overwhelmingly shows a negative impact on fishing during the spawn. Also, the fishing on the Canadian side of border waters like Erie, St. Lawrence and Niagara is consistently better yielding bigger fish, as evidenced by the tournaments on these waters.
https://www.outdoorcanada.ca/ontario-now-has-the-worlds-best-smallmouth-fishing-heres-why/
https://www.outdoorcanada.ca/fishing-for-nesting-bass/