Spawning and Raising Trout
Using a needle, oxygen is gently injected into the body cavities of female
trout so that their eggs are discharged.
Male trout are gently squeezed until they expel milt into containers
of eggs. The milt contains sperm and fertilizes the eggs.
Fertilized eggs are placed in incubator jars where they are kept suspended
in flowing water.
Trout feeding at a hatchery raceway.
To prepare for stocking, fish are sorted by size using either screens
or grading boxes.
After sorting, catchable-sized trout are netted and loaded into distribution
trucks.
Fish are stocked in trout parks during each night of the season from
March 1 to October 31.
Autumn signals the start of of spawning time at the trout hatcheries. The process begins with the separation of males and females into different raceways.
The female trout are checked for eggs. Females that are ripe with eggs are pulled out for spawning.
At 57 degrees Fahrenheit, the eggs will hatch in 21 days. Newly hatched trout have yolk sacs on their abdomens and are called sac fry.
Once the yolk sac is absorbed, the fry are ready to begin feeding on a commercially prepared trout food. When the trout reach 3 inches, they are moved outside to hatchery raceways.
At the hatcheries, trout are divided into pools based on their age. Hatchery workers carefully monitor the growth, health and number of fish in each pool.
By weighing a few fish every month, the workers can calculate the feeding rate and readiness of the fish for stocking in streams. Depending on the rate of feeding, water temperature and flow, raising a catchable-sized trout can take anywhere from 12 to 18 months.
To deter predators like herons and kingfishers, fishing line or netting are hung over the pools and raceways.
Missouri’s five trout hatcheries work together to produce trout, so the trout you catch may have been hatched at one hatchery and raised at another.
