Rainbow trout fry investigations

Rainbow trout fry investigations

Rainbow Trout are spring spawners, and deposit their eggs in gravel at sites known as redds. The eggs hatch in 4-7 weeks depending on water temperature. After hatching, fish spend up to two weeks as sac fry, remaining in the gravel and absorbing their yolk sac. Once the yolk sac is absorbed, the fry emerge from the gravel to begin feeding. Fry spend the first several months of their life in shallow areas found along the river margins, using vegetation and interstitial spaces between rocks as cover from predators. During this time, they are also easily sampled to estimate population size. Changes in the fry population over time can indicate whether factors such as water quality, flow, temperature, or presence of parasites are affecting survival. Additionally, fry estimates conducted later in the year can be indicative of the number of fish that will recruit to the juvenile and adult populations. Finding ways to increase fry survival in rivers has been the focus of many CPW aquatic research projects.

Colorado Parks & Wildlife

Rainbow trout

Spawning

Fry

Population management

2 pages

2022

Fact Sheet

application/pdf

English