Generally speaking, the brook trout population will start preparing for their spawning season as soon as the water temperature starts falling from its summer highs, with the spawning season starting as the fall sets in.
What Months do Brook Trout Spawn?
Spawning will usually begin somewhere in early October, peak in November, and will end in December. However, this range is subject to differences due to the geographical location of the spawning grounds.
Brook trout inhabit coldwater streams and lakes across the Eastern United States and eastern Canada. As this covers a lot of territories, the spawning season range can vary depending on geographical location.
Waters of the northern habitat borders will see trout spawning as early as August, due to shorter summers and cold weather.
On the other hand, waters of the southern habitat borders will see the spawning season beginning into December, as only then the water will be cold enough and days short enough to trigger the spawning instincts!
Most Relevant Brook Trout Spawning Factor
We can agree that falling water temperatures are the most general factor triggering the spawning season – and there is a story full of interesting details behind this! To start, why do brook trout spawn when summer starts turning to fall?
Brook trout spawning season will go into full effect once the water temperature range hits an optimum of 40-49° F – if it happens during the right time of the year. This temperature decline after warmer summer months is a signal for the trout that the feasting days are at an end, and it is time to think about the offspring and survival of species.
It takes around 95 – 100 days for the eggs to incubate, and after that fry will emerge and start seeking food and shelter. For them to survive, conditions need to be optimal in terms of water temperature and available food.
If, for example, spawning was to take effect during summer, fry would hatch at the beginning of winter, facing a lack of food and extremely cold water. These harsh conditions are not suited for the survival of small and fragile brook trout fry!
Spawning season kicking in with fall and taking full effect when winter is at the doors means timing is perfect for meeting optimal conditions for the fry.
Fry will hatch somewhere between February and April (depending on geographical location), meeting the slowly growing water temperature and abundance of food that will allow them to feed, grow, and mature.
If the conditions are optimal, some brook trout will even be ready for their spawning season in their first year of life (especially in small streams).
Other Brook Trout Spawning Factors
Apart from falling water temperatures, more factors will affect the offset of brook trout spawning season.
The most important, and also most easily observed factor is the gradual decrease in daylight.
Even if the water temperature has not fallen enough, and is somewhere in the upper range of acceptable or even outside of it, shorter days and longer nights will trigger the brook trout spawning season.
This is an important survival instinct, that prevents a delay of spawning season due to prolonged summer temperatures. When summer turn to fall and days begin to shorten, brook trout will start spawning.
There is also a question of water levels. It is known that rising water levels are connected with summer turning into fall (with fall bringing rain). This change is also a trigger for brook trout; they will use the opportunity of rising water column to scale the rapids and obstacles that are unscalable when the water levels are low.
This upstream migration is triggered by strong spawning instincts shared by almost all migratory fish species. They will always start swimming upstream when instincts kick in, heading for grounds where they were hatched.
Apart from instincts, this migration had a deeper meaning. When fry emerges from eggs, they will be too small and too weak to travel upstream. The only direction they can take is downstream – and the further they hatch upstream, the more room for growth will be available when traveling downstream.
This means that trouts who travel the furthest will have the biggest chances of having successful offspring! And therefore, rising water levels are an essential factor of a successful spawning season.
Time of day
Brook trout spawning takes effect on so-called ‘’redds’’ (shallow nests built on sandy and gravel bottom). It is always performed during daylight – but it is interesting that this only applies to brook trout living in rivers.
By contrast, brook trout living in lakes spawn only during the night!
Brook Trout Spawning Problems
If for any reason water temperature starts rising after the brook trout population already started with their spawning, it will most likely cause a delay in the process. The chances for such occasion will grow with the length of the increased water temperature period, especially if the temperature rises to 55 F.
This delay might seem like a minor issue, but it can have a very negative effect on the survival of offspring. Fry will hatch later in the spring and will face a much shorter timeframe needed to obtain the weight necessary for the survival of the first winter.
Brook trout spawn early to mid-fall. During this time the water temperature drops to spawning levels which is 40-49° F. Spawning season will run until December with the peak of the season being thought November.