AP BIOLOGY

Detailed explanation-1: -Anadromous fishes, including many salmonids, lampreys, shad, and sturgeon, spend most of their lives in the sea and migrate to freshwater to reproduce.

Detailed explanation-2: -Adult salmon spawn in freshwater, where female salmon lay thousands of eggs that are fertilized by male salmon. Spawning can occur in spring, summer, fall, or winter and depends on the salmon species. After spawning, adult salmon die and their bodies provide nutrients for the freshwater ecosystem.

Detailed explanation-3: -Salmon are born in freshwater rivers, spend most of their lives in the ocean and then return to the place they were born to lay their own eggs. Salmon swimming upstream is both a form of migration and a way to ensure that their young survive long enough to hatch and grow into adults.

Detailed explanation-4: -Salmon come back to the stream where they were ‘born’ because they ‘know’ it is a good place to spawn; they won’t waste time looking for a stream with good habitat and other salmon. Scientists believe that salmon navigate by using the earth’s magnetic field like a compass.