At each stage of life, blue crabs are susceptible to a different class of predator, though their most consistent predator is the human being. During the larval stage, blue crabs' most common predators include small species of fish and jellyfish. In their adult, developed stage, larger fish, birds and even many species of mammals will prey on blue crabs.
Commercial crabbing and human destruction of blue crab habitats have dramatically decreased the blue crab population globally. Particularly in the Chesapeake Bay area, blue crab populations have dropped drastically since the 1990s.
Several species of large fish prey on the blue crab in its adult state. When crabs are molting, their bodies are soft and exposed, making them particularly vulnerable to these fish predators. Some types of fish that prey on blue crabs regularly include red drum, croakers, striped bass, eels and even sharks.
Birds prey on blue crabs in coastal bodies of water and tidal rivers. They typically eat offshore crab larvae, small growing crabs and adult crabs in seagrass beds or marshlands. Examples of birds that prey on blue crabs include herons, egrets and diving ducks.
Many sea turtles are also a common predator, with the sole exception being the green turtle, which sustains itself on a vegetarian diet. The Atlantic Ridley and loggerhead turtle prey on crabs.
It is also noteworthy that the blue crab species is highly cannibalistic, and adults have been seen devouring their own offspring in the larvae stage.