Question

Parents of ammocoetes larva show
(a) Paired fins
(b) Placoid scales
(c) Catadromous migration
(d) Anadromous migration

Answer 1

Hint: This is a type of migration in which adult fish live in the sea and migrate into freshwater to spawn, and whereas the other one, the adult fish live in freshwater and migrate into saltwater to spawn. Marine forage fish often makes large migrations during their spawning, feeding, and nursery grounds.

Complete step by step answer:
An anadromous fish is the fish that is born in freshwater, spends most of its life in the sea, and returns to freshwater to spawn. For example, Salmon, smelt shad, striped bass.
 While Catadromous fish spend most of their lives in freshwater, then migrate to the sea to breed. Examples include American eel, European eel, inanga, shortfin eel, longfin eel.
Ammocoete is known as the larval stage of the primitive lamprey. For breeding, the lamprey migrates upstream in rivers. Males make a nest in sand and gravel in which females lay eggs and males fertilize them.
In about 3 weeks, eggs hatch into ammocoete larva that lies buried in sand and feeds on detritus. The fully-grown larvae go downstream and enter the sea. Examples of anadromous fishes are sea trout, three-spined stickleback, sea lamprey, and shad.
So, the correct answer is, ‘Anadromous migration.’

Note: The basic causes of fish migration:
- Marine forage fish often make large migrations during their spawning, feeding, and nursery grounds. - Movements are related to ocean currents and with the supply of food in several areas at different times of the year.
- Adults move to the spawning grounds, then return to the feeding grounds. Migratory patterns of fish are related to oceanographic factors and currents. Adult movements thus are directional rather than passive, and the fish respond to environmental conditions, for example like climate.