Egg Hatching
As the eggs develop, you can see trout ova develop within them. This is called the ‘eyed ova’ stage. How quickly the eggs will hatch depends on water temperature – colder water means slower development in the egg.
At 46.0 °F (7.8°C) the eggs will hatch in 60 days but at 40.5°F (4.7°C) they will take 97 days to hatch. Generally, it is assumed that most eggs hatch in February and the age of a trout is measured from this ‘birthday’. How many eggs hatch varies enormously depending on quality of the water and gravel – it can be as low as 4%, or, at the top end, exceed 80% where conditions are really good.
The newly hatched trout are called alevins, and they live in the gravel, feeding off the remaining yolk that is attached to their body for 14-30 days, again temperature influencing their rate of development.
