Question

Which is an anadromous fish?
A. Hippocampus
B. Petromyzon
C. Exocoetus
D. Anabas

Answer 1

Hint: Most of the fish migrate on the regular basis, ranging from, daily to annually and the time ranges from days to a few months and sometimes, it is a few years, most fish are migrating either for the food or to reproduce.

Complete answer:
Migration involves the movement of the fish on a large scale.
When coming to the classification of the migration, they are:
Anadromous: This type of fish originated in the freshwater and they live in the seawater, but they again migrate to the freshwater for the reason of spawn, examples for anadromous fish are salmon, striped bass, Petromyzon.
Catadromous: These are the fish that are migrated from the freshwater to the saltwater, to spawn. Examples include eels, hippocampus, Exocoetus, Anabas, etc.
Diadromous: These are the group of fishes which are migrated between the blue sea and the freshwater.
Amphidromous: This type of fish is. Migrated from the freshwater to the sea, but not for breeding.
Potamodromous: These fishes are also undergoing migrations, but only in the freshwater.
Oceanodroma: This type of fishes are also undergoing migrations which are only in the seawater.
Some fish such as tuna are used to migrate from north to south and vice versa based on the temperature gradient.

So the correct answer is Petromyzon.

Note:
Salmons hatch in freshwater streams, and from there they travel to the sea water, where they live for 2 to six years, and when they mature they again return back to sea water to hatch. Salmons have the capability of going 100 kilometers in the sea.