As you all know, I am not one to lock horns with people on this forum, however, I will have to respectfully disagree with you, Flytosser, though by no means do I mean to offend you. Though there are indeed many factors involved, I will only focus on two of your points. First off, deadfall will not prevent fish, especially trout, from passing through. They can find their way through amazingly tight spaces, like beaver dams for instance. Also, fishing pressure directly affects fish populations, as this is a no-brainer. If people remove fish from a river, especially before they have had a chance to spawn, then you will have fewer and fewer fish in said system. Simple math. Keep taking cookies from the cookie jar and not replace them with more cookies, you will eventually run out of cookies.
To prove this point, my fishing buddy and I hit a popular brook at the beginning of the season, from its mouth to almost its source. Being the first ones through, we caught lots and lots of trout and released all but one 10", though most were quite small yet of legal size. One week later we did the run again. This time there were lots of footprints and empty worm cans for the first kilometer and no trout to be caught except for tiny ones below legal size. Little to no trout were caught until roughly a half kilometer after we stopped seeing footrpints, and then we started catching trout again. Coincidence? Not likely in my opinion, but I'm no scientist.
If the province would put in place a slot limit of, say, 8" minimum to 15" maximum size limit on trout and everything else must be released, in as little as two years I think you would start seeing lots of 7" and another year or two after that you would start seeing lots of 16" + trout in our waters.
Case in point: There is a particular river in NB that I fish every year, and at the most difficult to reach and furthest stretch of this river it is not uncommon to catch average 16-inchers. On a typical day we will easily land twenty plus trout, not counting anything below 8". Why? Because little to no people know about the stretch or bother to trek there, and those that do practice catch and release. Average 16-inchers, with the biggest being 22" so far. However, where access to this river is close to the main road, shortly after the opener there are little to no trout to catch in those places on the same river.
Think about it. Catching big trout could be the case on any river in the province if only the government changed the archaic laws, and if people obeyed said laws and not keep a couple of limits per day, or bring all the members of their family so that dad can catch and keep multiple limits knowing that everyone in his party can keep 5 trout, even little 4 year old Johnny. Yes, this does indeed occur in NB. Like somebody mentioned earlier, some individuals here feel the need to fish for food as opposed to fish for fun. Unfortunately, things will not get better until this reality changes.