* High Mortality Rate: Trout eggs and young fry face a high risk of predation from birds, insects, other fish, and even their own siblings (cannibalism). Many eggs never hatch, and even those that do face a constant struggle for survival.
* Environmental Challenges: The environment can be unpredictable, with floods, droughts, and temperature swings that can decimate a population.
* Limited Parental Care: Unlike some species, trout don't provide much parental care after laying their eggs. The eggs are left to fend for themselves, making it essential to have a large number to ensure some survive.
* Life Cycle: Trout have a relatively short lifespan compared to some fish. They need to produce many eggs to ensure the continuation of the species.
Therefore, the thousands of eggs a trout lays are a form of "insurance" against the many threats to their offspring. This strategy helps to guarantee at least some of their young will survive to adulthood and continue the cycle.