Are blue crabs predators or prey?

Answer 1

Blue crabs are omnivores. They eat small fish and thin-shelled animals, as well as plants, so they are predators. They are also prey since they are eaten by humans and other animals (eels, sharks).

Answer 2

Crayfish are both predator and prey, because they both eat other animals and are eaten by other animals. You can see this when you think about a food chain, where the base of the food chain is something that is eaten by something else, but does not prey on anything else: usually plants, but can be algae or cyanobacteria. The key thing is that these species are autotrophic, meaning they can make their own food (which they do either by photosynthesis or chemosynthesis). You can call this level of the food chain producers, since they are the only ones that can produce their own food (i.e., are autotrophic). Everyone else in the food chain is considered to be a consumer, and the set of consumers that eat the producers are called herbivores, also known as primary consumers. Whatever eats the herbivores are known as carnivores, also known as secondary consumers. Some carnivores might not eat herbivores, but instead eat other carnivores: these are called tertiary consumers. You can keep the chain going, adding quarternary consumers (they eat tertiary consumers) but the chain doesn't usually get much longer than that. Now you can imagine that each link in the chain doesn't eat just one thing, and is not eaten by just one thing, so you can start to imagine how several food chains can be linked together to make a food web, which is a much more realistic rendering of what is actually going on. Every organism on earth can be positioned within a food web: some webs are very simple, with only a handful of linkages, and others are more complex, with hundreds of linkages, making a very tangled web! Crayfish are found within a number of different food webs, depending on which species of crayfish and where they are found (for example, Pennsylvania alone has 7 commonly found species). Crayfish are omnivorous, meaning they eat both plants and animals, so the have many linkages in their food webs, not just with other animals, but with plants too.