Lobsters, crabs and shrimps are called "sea scavengers," and unless absolutely fresh are not a desirable food.
"Public School Domestic Science" by Mrs. J. Hoodless
The crabs are the spider-formed scavengers of the sea.
"Toilers of the Sea" by Victor Hugo
The crabs, I was informed, were excellent scavengers, and consumed all the cook's refuse.
"The Cruise of the 'Alerte'" by E. F. Knight