Lobster larvae are omnivorous and very opportunistic. They eat zooplankton (water fleas, copepods, crab larvae, eggs) and phytoplankton (diatoms, dinoflagellates, filamentous algae).
Postlarvae will eat larvae of crabs and gastropods, copepods, and fish eggs, while in the plankton, and small shellfish, marine worms, small sea urchins and little phytoplankton, once settled on the bottom.
Juvenile and adult diet
Afterwards, lobsters become mainly predators. They feed on crab, shellfish (mussels, clams, scallops), echinoderms (starfish, sea urchins), marine worms (nematodes, polychaetes), and gastropods. They also feed on dead organisms that they come across. Very rarely do they eat algae and aquatic plants. When a lobster captures a prey, it carries it to its shelter to eat it.
When lobsters are small, they are prey for several fish such as cod, tench, flounder, sculpin, wolffish, ocean pout, monkfish, and dogfish. On the other hand, when they are adults, lobsters are much less vulnerable. The only large predator for adult lobster is definitely man. Adult lobsters are especially vulnerable during moulting, when they are still soft. They can then become occasional prey for other predators, but lobsters generally moult inside a shelter for protection.