Have you ever wondered about how long different types of crabs live? The decapod crustacean has been around for millions upon millions of years, and over 800 species of crabs continue to thrive all over the world in unique environments to this day. Asking Google this question may get you a quick on-average answer, yet what lies beneath that answer is complicated. Many factors and circumstances affect the lifespan of the crab, including other species (and humans), and the environment. Furthermore, some species of crab have simply evolved to be able to live decades longer than others. 

Continue reading to learn fast facts about the crab lifespan and what negatively and positively affects it.

The Crab’s Life Cycle

Dungeness crabs, for instance, live on average 10 years. They go through quite a few cycles as infants and adolescents and do not fully mature until they are about 3-years old. Here is a quick review of the Dungeness crab’s life cycle:

• The larval phase, which lasts about 4 months, consists of five zoeal and one megalopa stage. This is the time when the crab looks nothing like one; just a little blip floating around trying to grow strong. During this stage, they are only about 1 millimeter long and continue to molt as they increase in size.

• During the megalopa stage (post-larva), the Dungeness crab starts to resemble an actual crab, but very tiny and cute. In the spring and summer, these little guys stay close to shore to stay protected from rough waters and predators. During this stage, they are only about half the size of a dime.

• As the crab continues to molt, it becomes larger and healthier and reaches the juvenile stage of the life cycle, which they will remain in for 2 years. During this time, they will molt up to 6 times! They continue to spend most of their time in shallow waters where it is easy for them to feed and survive. 

A note from the Oregon Department of Fish and Wildlife about molting:

When preparing to molt, a crab’s old exoskeleton separates from the new one beneath. At this time the new exoskeleton absorbs water and becomes larger. This causes a split at their “molt line”, located mid laterally on the carapace. The new and extremely soft crab now has the flexibility to back out of its old shell. During this incredible feat, crabs are extremely vulnerable to predators and for that reason it’s done quickly. 

• The adult Dungeness crab travels out into deeper waters, sometimes up to 2,000 feet, although many are still found near land looking for food and mates. This is the time where guys and gals will find each other and repeat the cycle all over again! 

You can read another blog from Fathom Seafood on how Dungeness crabs mate; it is very fascinating! 

Comparing Crab Species

While over 800 crab species will not be listed in this article, here are the top 10 common species of crabs and their average life expectancy.

1. Dungeness crab: 10 years
2. King crab: 20 to 30 years
3. Snow crab: 20 years
4. Spider crab: 100 years!
5. Blue crab: 4 years 
6. Stone crab: 8 years
7. Bairdi crab: 10 years
8. Coconut crab: 60 years
9. Hermit crab: 30 years
10. Ghost crab: 3 years

There is quite a difference in life expectancy between some of these species. You may be thinking twice now about getting your child a hermit crab as a pet! 

Factors That Affect the Crab Life Expectancy and Population

Predators

Predation is a natural part of life! 

Like most small living things, crabs have multiple predators that they must keep on their radar throughout the day. Taking the Dungeness crab for example, their natural predators include halibut, dogfish, sculpins, octopus, sea otters, and even other species of crab. Salmon also feed on crab larvae. Obviously the crab species are much more vulnerable when they are in the first stages of life until they are considered adult, which is why babies and juveniles tend to stay closer to the shore where they can hide in plants and bury themselves underneath the sand. The good news is that crabs can protect themselves quite well from some predators with the use of their powerful pincers and hard exoskeleton. 

Human Behaviors

Silly humans. We just can’t resist a delicious crab. The harm comes along when overfishing populations of crab take place. While there are laws and regulations put into place to attempt to prevent overfishing from happening, it still occurs. Crabs are also vulnerable from the use of certain fishing gear and vessels, which is obviously used to catch them, but can also ruin habitats and cause poor water quality. 

The Environment

Probably the factor that most greatly affects crab populations is climate change. 

According to research, climate change negatively impacts a crab’s life “including embryo development, timing and length of the spawning period, the duration and quality of the larval stages, the level and spatial distribution of the settlement, growth rates and size of the juveniles, size at maturity, and catchability.”

Sea level rise affects crab habitats and changes in precipitation increase areas of low dissolved oxygen. The lower the concentration, the more stress aquatic life is under. Ocean acidification, or the changes in seawater’s acidity from absorbing carbon dioxide is also a major concern for crab species. This ocean acidity can keep crabs from building new shells and can even dissolve their current shell, as well as stunt their growth. 

Neither of these things are good for the crab population, and 2 out of these 3 factors humans can change via their behaviors, abiding by laws and regulation, increasing technology use, and by continued research.

The Oldest of All The Crabs

Can you guess which “crab” is one of the oldest living fossils? 

A horseshoe crab! They have been living on this earth for over 445 million years and have barely changed and evolved from what they initially were like. However, a horseshoe crab is technically not even a species crab...but it’s still an interesting fact!

Hopefully you learned something interesting and can understand that species depend on human beings to keep their life expectancy stable. While crab will always be caught and sold for delicious meals, there are steps we can take to help their habitats and their livelihood. 

Speaking of meals...are you interested in purchasing live Dungeness crab for your next sustainable meal? Head over to Fathom Seafood and browse their selection!