Crab claw cropping.... Sustainable or barbaric ?

The stone crabs Menippe adina and M. mercenaria are found from North Carolina to Mexico’s Yucatan Peninsula. Most (probably 90%) is caught in Florida waters and most landings occur off the southern half of Florida’s west coast. (pic is of Alaskan Snow crab claws)

Fishermen haul up their pots, pluck a stone crab out, tear off one claw, and toss it back to grow another claw. If the claw has a length of at least two inches, one or both may be removed from a male or non-egg-bearing female. In the U.S. fishery, only one claw at a time may be removed from the crab – a system unique to the stone crab fishery and created by the fishermen to keep the population sustainable. Some scientists expressed concern over the high mortality of stone crabs following declawing, but regulations were changed to increase survival rate.

In about one year, a larger stone crab can regenerate a claw that’s about two-thirds its original size. A smaller crab can take three years to grow a claw that just meets the legal market size. Surveys of crab buyers indicate that about 20 percent of the claws purchased from fishermen are from crabs that had already been declawed once.

Stone crabs have quite astonishing reproductive rates, spawning up to 13 times a year. Minimum claw size regulations make it possible for female stone crabs to go through one or two breeding seasons before they are caught.

Recent landings of Florida stone crab have been below historical levels, about 2,700 MT (six million pounds). Due to insufficient data, biologists are uncertain why landing numbers are down, although the decrease is believed to be caused by more fishing by both recreational and commercial fishermen. To combat the problem, Florida fishery managers are adopting measures to reduce fishing effort by decreasing the number of pots currently being used.

In the U.S. fishery, only one claw at a time may be removed from the crab – a system unique to the stone crab fishery and created by the fishermen to keep the population sustainable. Some scientists expressed concern over the high mortality of stone crabs following declawing, but regulations were changed to increase survival rate.

IIn the UK both claws may be removed from the Edible Crab. Now Bob Elwood Professor of Animal beaviour at Queen's University belfast ( Marine Biology DOI:10.1007/s00227-007-0681-5)** reports that crabs with one claw removed show greater stresss (measued by glucose and lactate into the blood) - than crabs allowed to shed claws natrally.

Of 28 crabs with one claw removed 5 died and none did after narural claw shedding.

As the claws are critical to survival for defence and also for food foraging this appears not only to be primitive but also ultimately non sustainable.

"There is a suggestion that the practice makes the fishery sustainable but the data on mortality would put this into doubt," says Elwood.

** Abstract here and details of the publication

Abstract We examined physiological stress responses in the edible crab, Cancer pagurus, (Edible crab - see pic) subjected to the commercial fishery practice of manual de-clawing.

We measured haemolymph glucose and lactate, plus muscular glycogen and glycogen mobilisation, in three experiments where the crabs had one claw removed. In the first, crabs showed physiological stress responses when ‘de-clawed’ as compared to ‘handled only’ over the short term of 1–10 min.

In the second, de-clawing and the presence of a conspecific both increased the physiological stress responses over the longer term of 24 h. In the third, de-clawing was shown to be more stressful than ‘induced autotomy’ of claws.

Further, the former practice caused larger wounds to the body and significantly higher mortality than the latter.

Since the fishery practice is to remove both claws, the stress response observed and mortality data reported are conservative.

Uggghhhh!!!