Question

Oceanodromous fishes migrate from
A. Fresh to fresh water
B. Fresh to marine water
C. Marine to freshwater
D. Marine to marine water

Answer 1

Hint: Anadromous fishes are found throughout the world's ocean and these fishes live and spend their whole life in salt water and there are other fishes too which migrate differently.

Complete answer:
If we look at options, option A is Fresh to fresh water. Those fishes which migrate from fresh water to freshwater are not anadromous fishes but these are called potamodromous fishes. Oceanodromous fishes are those fishes which migrate from marine to marine water and therefore this option is incorrect and it gets eliminated.
Moving to option B which is Fresh to Marine water. Those fishes which migrate from fresh water to marine water are not anadromous fishes but these are called catadromous fishes as Anadromous fishes are those fishes which migrate from marine to marine water and therefore this option is incorrect and it gets eliminated.
Moving to option C which is Marine to Freshwater. Those fishes which migrate from marine water to freshwater are not anadromous fishes but these are called anadromous fishes. Oceanodromous fishes are those fishes which migrate from marine to marine water and therefore this option is incorrect and it gets eliminated.
Last option D is Marine to marine water. This option is the correct one since those fishes which migrate from marine water to marine water are called Anadromous fishes and that is what has been asked in the question, therefore this option is the correct one.

Thus, the correct answer is option D i.e., marine to marine water.

Additional information:
There are many fishes which are anadromous but they are termed as highly migratory species and they migrate in search of food.

Note:
Oceanodromous fishes are migratory fishes which migrate in order to search food and they are found wholly in sea due to which they migrate from marine water to marine water and from all the options, D is the correct one because of this. Those fishes whose migratory route is different or you can say their migratory route is not marine to marine water are not anadromous fishes.