Brook trout is a member of the salmon family; it is often referred to as a trout, but it is actually a salmon. Members are Arctic salmon, lake and bull trout, and Dolly Varden. This fish is native to streams and lakes and can be found as far north as Canada, as far west as Eastern Iowa, and as far south as Georgia in the Great Lakes region as far north as Hudson Bay. Brook trout range in color from marbled green to brown with red spots and blue halos. The leading edge of the fins is white and the belly is red.

The Brook Trout has a relatively short life span, rarely surviving more than four to five years. Its diet includes frogs, crustaceans and small marine mammals such as voles, insects and worms. Brook trout are preferred prey for the seven-gill eel, and they are also preyed upon by many seabirds. Brook trout prefer relatively cold, clean water and are very sensitive to pollution. Although most brook trout are freshwater fish, some will actually swim to the sea to live for a while before returning to the river to spawn. Brook trout usually spawn in late summer or early fall, when they migrate and females form a depression in the river bottom with their tails. This is called a redd. once the female places her eggs in the redd, several males will fertilize the eggs and then the female covers them with gravel, using her tail again. a 29 inch brook trout was caught in Manitoba, Canada in 2006, but its weight was not recorded and their short life span dictates that they, cannot grow to a very large size.

It takes about 100 days for the eggs to hatch. The temperature requirements are relatively stringent, with normal incubation at 6-7°C.

Many anglers are controversial about when to fly fish for brook trout, some believe in fishing before the spawn and some believe in fishing after the spawn, I personally prefer after the spawn so that the females can hatch more young.

Before the spawn the females will prepare for the spawn and go to feed as much as possible, as opposed to this time when it is easier to fly fish for brook trout.

When in Montana?

Brook trout were first introduced to the area during the 1800s. They have since made their way into the cooler headwaters.

The redd spawns every year from September to October. Once the eggs have been laid, they will be fertilized and eventually emerge around February. The young will then stay out of sight until they are big enough to feed.

When in Colorado?

The spawning period for the Brookies in Colorado is similar to that of the brown trout. The ideal time to catch these fish is late September to early October.

The leaves on the trees begin to change to golden amber as the seasons get colder. This is the time of year when bass and big bow fishing are most likely to be successful.

When in Wyoming?

In my mind, Wyoming is a spoiled place for choice when it comes to fishing. There are so many different species to choose from, and the fish can be left to spawn in peace with the abundance.

When in Michigan?

 In Michigan, the spawning period for the Brookies begins in October to November. The temperature needs to cool down in order for the fish to start developing their bodies. Hens will start emerging redds with their tail. Male fish will then join at a later stage.

 Article refer:
1.How we guard brook trout？
2.Trout Fly Fishing: 3 Bad Habits to Break
3.The Complete Guide to Fly Fishing for Brown Trout
4.A guide to catching aggressive fall brown trout
5.Triploid Trout(Why so Big!) 
6.Four Best Tailwater Trout Fisheriesof the Region's