There are numerous sources that show the ecological cycle of the anisakids. For example:
From Science and Nature – Natural History of Anisakids:
To complete their life cycle, anisakid worms must pass through three very different hosts:
2. Inside the egg, a tiny larva undergoes a period of development before hatching. Eggs containing larvae, or hatched larvae, are eaten by tiny sea animals such as krill (shrimp-like crustaceans) as they sink toward the ocean floor or drift in the current. (Some are eaten only after settling on the bottom.)
5. If the fish dies, the capsule breaks down and the larva moves away from the place where it has lain dormant. If the fish has been eaten by another fish, the larva simply moves to a location in the new host and becomes dormant again. If the fish dies but is not eaten, the larva may move from the abdominal organs into the muscles. If the fish is eaten by a marine mammal, the larva breaks free in the stomach and develops to an adult worm.
6. Worms that reach adulthood and mate in the stomach of a marine mammal produce eggs that are released into the water to start the cycle over again.
7. Larvae that are accidentally swallowed alive by a human usually cannot mature but typically cause a painful illness called anisakiasis, or anisakidosis. (Anisakiasis refers specifically to infection with A. simplex; anisakidosis is a more general term meaning infection with one of the anisakid worms.) Anisakiasis was first diagnosed in the 1950s.
The larva’s ability to move within a dead fish, or from one fish to another has important implications for the spread of the parasite:
The largest whale, the blue whale, eats tons of tiny krill in a day.