I would love to be hiking around Shenandoah National Park right now catching brook trout. Any other time of the year I would regularly be getting out there. However, as you may know, brook trout spawn in the fall, typically from late September through December. Everyone who fishes for them hopefully realizes that it is best to leave them alone for a few months until after the spawn.
So what are the reasons for leaving them alone during this time? For one, spawning trout are more vulnerable. They swim upstream into smaller, more open pools with gravel bottoms to deposit and fertilize their eggs. They expend a much higher than normal amount of energy and effort and so are more prone to tiring and are more susceptible to the impacts of stresses associated with being caught, fighting, etc.
Their spawning behavior also makes them much easier to catch. There is always a percentage of fish that die after being caught and released. Even small single barbless hooks typically used in fly fishing, while much less lethal to fish than larger, barbed (or even worse, double and treble hooks), still have a mortality rate up to ten percent according to some studies.
All of this will impact the spawning success of brook trout. Given that these fish are already pressured in nearly all of their range on the east coast by environmental factors such as stream warming, habitat loss and pollution, we should keep this combination of potential problems in mind and leave these guys alone for a few months.