Crab is a popular seafood dish amongst humans. But, before we eat them, they have to eat too. So, what do crabs eat?
A crab’s diet can consist of shrimp, algae, worms, and fish. Each species of crabs has its own, specific diet. Most crabs are omnivorous, with some larger crabs being carnivorous. Smaller crabs can be herbivores. Some crabs are scavengers that will eat plants and dead animals.
You may have noticed that a crab’s diet can vary because of size and species. We’ll explain why this is and go into more detail.
If you’d like to find out more about the eating habits of crabs, keep reading. Our guide will walk you through all the information you need to know about a crabs diet.
Let’s dive in.
What do crabs eat?
1. Shrimp
Crabs are omnivorous and like to feed on crustaceans including other crabs. Shrimp is one of many other creatures on the menu for crabs.
Crabs and shrimp often live in the same areas at the bottom of the ocean. They also have similar diets and feed on decaying animals.
The crabs will use their whole body to catch the shrimp. Their long pincers help them to secure the shrimp in their claws.
They will then pull it to its mouth and eat it. They don’t store it and eat it straight after catching it.
Although they can catch the shrimp, sometimes they are too fast and small for the crab. In fact, crabs will eat dead shrimp that they have found if they can.
Shrimp is popular with snow crabs, and makeup 17% of their diets. Shrimp are nutritious for crabs, and contain calcium and omega-3.
They are also a great source of protein for the crabs as well. They also don’t have a lot of fat making them a healthy source of food for the crabs.
Other crabs that enjoy shrimp include blue-legged hermit crabs, giant coconut crabs, red rock crabs, and green crabs. They don’t have any preference for shrimp and will just eat it.
2. Fish
Larger crabs often hunt for small fish, and this can make up to 10% of their diets. Crabs also eat dead fish off the ocean floor during low tides.
Since fish are faster than crabs, crabs have found different ways to eat them. They look for sick and weak fish to capture because they are weaker and aren’t as fast.
Crabs will cut their prey into smaller pieces so they can swallow it, as they have no teeth. They use their pincers to tear the small fish into digestible pieces.
They tend to hunt for smaller fish as they are predated by large fish like salmon. Larger fish often hunt juvenile crabs and crab larvae.
Fish can give lots of energy to crabs and are easy for them to digest. The fish provide the crabs with proteins, vitamins A, D, E, K, and fatty acids.
Since most crabs are scavengers, they aren’t picky about what they find. Some even eat rotten fish, and it is often used as crab bait to capture crabs.
Crabs find their prey by smell and can detect dead animals via smell. They can also prey on the fish using chemoreceptors that sense chemicals released by these fish.
3. Seaweed & Algae
Seaweed is a common meal for herbivorous small crabs. This is an easy meal for many small crabs that are able to hunt for themselves and need to scavenge.
Research has shown that crabs that eat seaweed can contribute to reviving the coral reefs. The Caribbean king crab has been noted to eat large amounts of seaweed, even some that other species in the area would avoid.
An experiment showed that these crabs were able to drop the seaweed cover on the reefs by 50%. This shows that crabs can be very beneficial to their ecosystems.
Another common snack for crabs includes algae. Again, algae are consumed by small herbivorous crabs. Brown, red and green algae are eaten by these crabs.
Crabs in both freshwater and saltwater environments eat these algae. These algae can help remove toxins from a crab’s body and don’t require much effort to hunt and eat.
Algae also help a crab control its molting and benefit its shell. This is when it shed its outer layers to grow, similar to a snake.
They often scrape the algae off rocks with their claws. They can also cut it and pick it to get smaller pieces.
But, algae isn’t always good for crabs, as it can cause poisoning if they eat the wrong type. Too many algae can also lack the essential nutrients a crab needs for survival.
4. Squid
Larger crabs prefer to eat larger marine creatures like cephalopods. Although, since these animals are faster than the crab, they often eat them when they are dead.
Squid is often eaten by crabs like the Dungeness crab or the blue crab. Also, crabs eat whelks alongside squid and other cephalopods.
They provide more protein than other prey such as small fish. Other nutrients they can contain include iron, vitamin C, and calcium.
Crabs don’t hunt squid and will avoid them most of the time. Squid also hunt crabs and are too fast for the crabs to grab, so they eat them dead
Again, they use their pincers to pierce through the skin of the squid. They will cut it into smaller pieces so they can swallow and digest it.
5. Clams
Larger crabs like king crabs will eat small clams and mussels. Sometimes they will eat sea urchins and other hard-shelled organisms as well.
They use their sense of smell to hunt these creatures down. Also, they use their sense of taste and will shift across the ocean floor to find them.
The crab uses its claws to smash open the shell of the clam. They can also slip their claw inside of the shell and crack it from the inside.
Clams can provide crabs with good nutrients to keep them healthy. This includes omega-3, vitamin B12, and essential fatty acids.
6. Crustaceans
Bigger crabs will eat other crustaceans like lobsters, crayfish, and even smaller crabs. This includes blue crabs, king crabs, and snow crabs.
These crustaceans make up around 18% of the snow crab and blue crab’s diet. Cannibalism is common in some species of crabs and helps control the population.
If a female crab is running low on food and unable to find food, she will eat her babies. The mother won’t be able to recognize her children, so she will eat it without knowing or caring.
The number of nutrients that crustaceans provide to crabs can vary for each species. Lobsters can be a source of vitamin A, iron, and calcium.
What do different crabs eat?
Crabs have a varied diet, depending on where they live and what’s available to them. Most crabs are omnivores, whilst others are carnivores.
This table shows what the different species eat:
| Crab | Diet | Main foods |
| Blue | Omnivore | Snails, mussels, oysters, clams, fish, shrimp, crabs, jellyfish, seagrass, seaweed |
| Ghost | Omnivore | Clams, crabs, Sea turtles, seaweed, dune plants, sea plants, insects, carrion, shrimp, barnacles, algae |
| Green | Omnivore | Mussels, clams, snails, shrimp, crabs, sea worms, fish, carrion, plankton |
| Hermit | Omnivore | Microscopic mussels, microscopic clams, dead animals, macroalgae |
| Horseshoe | Omnivore | Clams, snails, sea worms, plankton, crabs, shellfish |
| King | Omnivore | Clams, mussels, cockles, barnacles, snails, sea stars, brittle stars, sea urchins, crabs, shrimp, sea worms, algae, protists |
| Snow | Omnivore | Fish, shrimp, crabs, clams, sponges, brittle stars, sea worms |
What do baby crabs eat?
Baby crabs will eat similar diets to smaller crab species. They will eat particles in the ocean of dead small fish.
As they can’t hunt for themselves, they tend to eat smaller, still prey. This includes plankton, small worms, larvae, and algae.
Once they get older, they’ll begin to learn how to hunt and scavenge bigger meals. Juvenile crabs will live in shallow waters and can’t swim as well.
They will live inside tiny gaps in rocks or in kelp forests. This means it can hunt small snails without being seen and have a source of algae to eat too.
In Conclusion
Crabs have a varied diet, eating whatever they come across. They eat a broad range of foods like plants, crustaceans, and fish.
Each species of crabs has its own diet, suited to its environment and availability.
Juveniles often have a different diet to help them grow and mature. This includes eating other animals for protein.
