I don't fish in NI at all but do fish in the Outer Hebrides. May of the older anglers were telling me about the "good old days" which in this context would have been the 1980s I guess. They were reporting how much better the catching was then. Recently I looked up the catch stats only to find that many of the places I fish are catching maybe 3 times the number of fish they produced in the 1980s. What would be considered our premier fishery has records going back to the 1880s and their rod catch has declined about 2% since then.
However, I don't dispute that the numbers of fish returning have declined in that the fishery I mentioned previously used to net about 14,000 fish per season on top of their rod catch and this appeared to be sustainable as they'd been doing it for 100 years but now there is no netting so the rod catch represents their total. I don't know exactly how to interpret that as without a counter on the river we just don't know how many fish are actually running, or what the trend is.
If you want some fishing videos then take a look at my youtube channel - most stalking happens at a distance and in the near dark so it doesn't make for good video but I've done a few GoPro type videos of fishing over the last few years and they might brighten up a few winter days for you before the season opens again: