Water temperature determines

In March, the salmon eggs under the gravel have grown eyes. We can see the eyes of the fry inside the roe grain. We call it eye roe. The speed at which the little life inside develops from when the roe is laid in the gravel in the fall until it hatches in the spring depends on the temperature of the river water. Development is slower in cold water than in warm water. Hatching occurs earlier in the rivers in the south of the country than in the rivers in the north. But of course there are exceptions. In the west, there are rivers that get their water from glaciers. These are cold, and development is slower here. But one thing is certain: Nature has arranged it so that the fry emerge from the egg at the perfect time. The growth and life cycle of the benthic animals that feed the fry in the early stages is also governed by the temperature of the river water. So by the time the yolk sac fry have used up their food package, the amount of benthos in the river is at its peak. Isn't that great?