1. Egg Stage:
* Spawning: Adult rainbow trout migrate to spawning grounds, typically in rivers and streams with clean, cold water. Females deposit eggs in nests (redds) built in gravel beds.
* Incubation: The eggs are fertilized by males and incubated in the gravel for 30-60 days, depending on water temperature.
* Hatching: The eggs hatch into fry, which are tiny fish with a yolk sac for nourishment.
2. Fry Stage:
* Yolk sac absorption: The fry absorb their yolk sac and begin to feed on plankton and other microscopic organisms.
* Development: The fry rapidly grow and develop their fins, scales, and coloration.
* Emergence from gravel: After a few weeks, the fry emerge from the gravel and disperse into the surrounding water.
3. Parr Stage:
* Parr marks: Young trout develop characteristic dark vertical bars called "parr marks," which help camouflage them.
* Growth: Parr continue to grow and develop, feeding on insects and other small aquatic organisms.
* Migration: Some parr may migrate to larger lakes or reservoirs, while others remain in the stream where they hatched.
4. Smolt Stage:
* Smoltification: As they reach a certain size, parr undergo physiological changes known as smoltification, preparing them for saltwater life.
* Silvering: Their coloration changes, becoming silvery to camouflage them in open water.
* Seaward migration: Smolts migrate downstream to estuaries and eventually into the ocean.
5. Adult Stage:
* Ocean residence: In the ocean, adult rainbow trout feed on fish, squid, and other marine organisms.
* Spawning: After several years in the ocean, some adults return to freshwater rivers and streams to spawn.
* Life cycle completion: After spawning, some trout may survive and return to the ocean, while others die.
Note: This is a simplified overview, and the specific stages and timelines can vary depending on factors like water temperature, food availability, and genetics.