• Saltwater fish"It starts right here, in Maldives" is Copyrighted by Flickr user: nattu (Nattu) under the Creative Commons Attribution license.
  
  

How fish get infested

• "Snorkel Flyby" is Copyrighted by Flickr user: jurvetson (Steve Jurvetson) under the Creative Commons Attribution license.
  
  You must know the life cycle of these parasites to understand how they get into fish. Like many other parasites, worms require different hosts at different times in their life cycle.
  
  

Big Fish

• Large fish carry the adult forms of parasitic worms in their stomachs. Phocanema and Anisakis worms often live in the fish's belly flaps. Parasite eggs are expelled into the sea with the fish's excreta.
  
  

First Hosts

• After hatching the worm, larvae are eaten by tiny euphasiid crustaceans. These tiny shrimplike animals become the worm's first host. They in turn are eaten by small fish.
  
  

Bigger Fish

• Little fish get eaten by bigger fish. The bigger fish are then infested by worms as well. Because big fish eat more than small fish they will also have more worms in their gut.
  
  

The Circle Closes

• These larger fish are in turn eaten by even larger predators. These predators get the adult worms in their stomachs and the cycle is repeated. That is how saltwater fish get worms.