Spawning in the Wild
Using her tail like a fan, the female trout clears away gravel to create
a series of shallow nests or egg pockets, collectively referred to
as a redd.
A male joins her and fertilizes the eggs as she lays them. As she begins digging
a new egg pocket, gravel is carried downstream by the current and covers the
previous one. The covered egg pocket is then protected from predators and oxygenated
as water courses through the gravel.
Incubation time varies based on water temperature, but on average the eggs will
hatch in 21 days. After hatching, the fry stay protected in the gravel nest until
their yolk sac is absorbed.
Once the yolk sac is absorbed, the young trout swim out to slow water along the
stream's edge and shelter among rocks and plants.
They first feed on microscopic organisms and move on to aquatic insects as they
grow.
Unlike brown trout, rainbow trout have become established and reproduce naturally in a few of Missouri’s coldwater streams. From December through mid-March, mature females select spawning sites or redds near the downstream ends of pools, just above riffles.
In as quickly as 3 years, a trout will grow to a spawning size of 14 inches. However, because of predation, flooding and other natural causes, less than 1 percent of the young trout will survive to adulthood. In contrast, approximately 80 percent of hatchery-raised trout survive from hatching to stocking.
