Fish & Water - Sounds Wild
Aging Crabs

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Aging Crabs

A storm rocks the North Pacific Ocean off the coast of Alaska. Beneath the waves, it's peaceful. Down through the cold, green water at the bottom, a snow crab scuttles across the sandy seafloor. Snow crab support the largest crab fishery in Alaska. This one is an old crab - but how old, and why does it matter?

Determining the age of commercial species is an important part of sustainable fisheries management. For many fish species, accurate ages are determined by looking at scales; or ear bones, called otoliths; which contain banding patterns associated with seasonal fast and slow growth, like growth rings in trees.

Crabs do not have otoliths or scales, and researchers are working on other methods to help determine the age of crab. Crabs molt their shells as they grow, and snow crab go through a terminal or final molt which, from that point on, leaves them in the same shell for the rest of their lives. This "retirement home" shell shows wear, and degrades in color and texture over time, allowing researchers to clearly distinguish actively growing or recently molted newshell crab from oldshell crab that have not molted in some time. Researchers have discovered that hard structures in the crab's stomach called ossicles display age-related banding patterns, and they are developing methods to best extract these ossicles, prepare them for microscopic examination, and use them to determine the crab's age.