NEBRASKAland Magazine is dedicated to outstanding photography and informative writing with an engaging mix of articles and photos highlighting Nebraska’s outdoor activities, parklands, wildlife, history and people.
Issue link: https://mag.outdoornebraska.gov/i/377644
The Life Cycle of a Rainbow Trout 1) Egg • An embryo develops inside the egg 10-14 days after eggs are fertilized. • Eggs at this stage are called eyed eggs because the eyes of the developing trout can be seen as two black dots. • Some eggs turn white during development. These eggs are not fertile and will not hatch. 2) Hatch • The time of hatching depends on the water temperature. In Trout in the Classroom aquariums, the water is 52° and eggs hatch between 20-24 days after they are fertilized. • When the eggs are ready to hatch, an enzyme softens the eggshell so that the trout can break through. 3) Alevin • Newly hatched trout are called alevins. They have an attached yolk sac that contains all the nutrients they need as they finish developing. • As their fins develop, they absorb the yolk sacs. • In nature, the alevin remain hidden in gravel so they are protected from predators. In Trout in the Classroom aquariums, they rest on the bottom of the hatching basket. 4) Fingerling • 10-15 days after hatching, the yolk sac is gone, and the alevin swim from the gravel or out of the hatching basket. • At this stage, trout feed on plankton and free- floating organic matter in the water. • As they grow, they develop markings on their sides called parr marks. These marks help camouflage the young trout in vegetation. • Most small trout never become adults. Instead, they become prey to larger fish and other aquatic animals. • Trout in the Classroom fish are released into a natural habitat during this life stage. 5) Adult • Adult rainbow trout eat insects, plankton, crustaceans, fish eggs and sometimes small fishes. • As trout grow bigger, the parr marks fade and are replaced with the small black spots and a pink band that identify them as rainbow trout. • When adult trout become reproductive and are ready to spawn, their coloration becomes more intense. 6) Spawn • In a stream with plenty of clean gravel and flowing, oxygen-rich water, the female trout uses her tail to create a nesting area called a redd. • She releases her eggs into the redd. Then, a male joins her and releases milt to fertilize the eggs. • Once the spawning is complete, the parents abandon the redd. • A completed redd will have many layers of eggs and gravel, and as many as 4,000 eggs. ■ The Nebraska Game and Parks Commission's Fisheries Division receives rainbow trout eggs from neighboring western states and the U.S. Fish and Wildlife Service. Trout are hatched at the Rock Creek and Calamus fish hatcheries and raised to a catchable size of about 10 inches at the Rock Creek and Grove Lake fish hatcheries. Last year nearly 270,000 rainbow trout were stocked into Nebraska waters. PHOTO BY BOB HALLINEN ALASKA DISPATCH NEWS NJ DEPT FISH & WILDLIFE CALIFORNIA FISH & WILDLIFE CALIFORNIA FISH & WILDLIFE PHOTO BY EUGENE SHULER PHOTO BY GRAHAM OWEN In addition to supplementing sustained populations in the cool-water streams of western and central Nebraska, rainbow trout are stocked seasonally into warmwater fisheries statewide to provide cool season fishing opportunities. Trout stocked in these waters cannot survive the summer months and are intended to be caught and harvested before the water gets too warm. OCTOBER 2014 • NEBRASKAland 53