|
阅读理解：
Some fish spend all their lives in the place where they were born．Salmon do not．Born in the fresh water of rivers, they migrate(迁徙)to the ocean when young, then go back to the rivers as adults．
When fall comes, it is time for salmon to spawn(产卵)．They leave the ocean and travel to the beginning of the river where they were hatched(孵化)．Sometimes these trips are more than 2,000 miles．On the long journey they have to fight against the current of the stream．Sometimes they even jump up waterfalls．When they reach the beginning of the river, they are often very tired from their long and difficult journey．
But they cannot rest．The mother fish makes a nest in the sand on the bottom of the river by slapping the sand with her tail．In this nest the mother lays her eggs and the father leaves his sperm．Then the mother covers the nest with sand leaves the baby fish to hatch．
The young fish hatch in the winter．Some species(种类)of salmon start the journey down the river to the ocean when they are a few inches long．They seem to be swimming backwards, but they are really carried downstream by the current．Others live in the river for two or three years before going to the ocean．All of these salmon, however, will make the trip back to where they first lived．
| 