15. Some Lampreys

A. are catadromous

B. are anadromous

C. have a mutualistic (+,+) relationship with trout

D. have no larval stage

Some Lampreys are anadromous from their lake and they migrate up rivers to spawn.

Explanation:

If the adult fish live in the sea and migrate into fresh water to spawn is known as anadromous and if the adult fish live in fresh water and migrate into salt water to spawn is known as catadromous.

An anadromous fish like salmon, smelt, shad spends most of their life in the sea and returns to fresh water to spawn. A catadromous fish like eels lives in fresh water and enters salt water to spawn.

Sea lamprey brings nutrients into fresh water and provide a source of food for various birds, fish, mammals and people. The newly transformed lamprey can live only for few months in fresh water.

The females deposit a large number of eggs in nest made by males in the streams with strong current. Spawning is done by death of the adults