AP BIOLOGY

Detailed explanation-1: -In case of salmons, it has been theorized by Wisby and Hasler that they imprint on the unique odour of the natal water and as adults follow the same odour cues to their birth homes for spawning. Hence the correct answer is ‘Imprinting’.

Detailed explanation-2: -Scientists believe that salmon navigate by using the earth’s magnetic field like a compass. When they find the river they came from, they start using smell to find their way back to their home stream. They build their ‘smell memory-bank’ when they start migrating to the ocean as young fish.

Detailed explanation-3: -When salmon are young, the theory goes, they imprint on the pattern of the Earth’s magnetic field at the mouth of their native river. Years later, when the salmon head back home to spawn, they home in on that pattern.

Detailed explanation-4: -Generally, 1 in 1000 eggs will actually be able to return to its natal stream as a spawning salmon.

Detailed explanation-5: -Anadromous fishes are those that spawn in fresh water, migrate to the ocean to forage and mature, and return to fresh water to spawn and begin the cycle again.