Declawing of crabs is the process whereby one or both claws of a crab are manually detached before the return of the live crab to the water, as practiced in the fishing industry worldwide. Crabs commonly have the ability to regenerate lost limbs after a period of time, and thus declawing is viewed as a potentially more sustainable method of fishing. Due to the time it takes for a crab to regrow lost limbs, however, whether or not the practice represents truly sustainable fishing is still a point of scientific inquiry, and the ethics of declawing are also subject to debates over

pain in crustaceans Pain in crustaceans is a scientific debate which questions whether they experience pain or not. Pain is a complex mental state, with a distinct perceptual quality but also associated with suffering, which is an emotional state. Because of this c ...

. While not always fatal, declawing can substantially alter the chances of a crab's survival in the wild. Declawing is a controversial practice; some jurisdictions have banned it partially or completely, while others only allow the crab's claws to be harvested commercially.

Procedure

Declawing is done by hand. To ensure a clean break along the natural fracture plane, one finger is placed on the basal

cheliped A chela ()also called a claw, nipper, or pinceris a pincer-like organ at the end of certain limbs of some arthropods. The name comes from Ancient Greek , through New Latin '. The plural form is chelae. Legs bearing a chela are called chelipeds. ...

joint. A rapid and firm downward motion is then applied as the claw is fully extended, breaking the claw at the basi-ischum between the coxa at the base of the leg and the merus. Particularly for crabs whose whole bodies are not consumed by humans, declawing is an attractive practice. Claw removal can facilitate storage and transport of crab meat, eliminate cannibalism within storage tanks, and make handling easier for crew.

Effects of declawing

Crabs that survive the initial declawing face potential disadvantages in feeding, mating, and self-defense. The most immediate impact of declawing, however, is possible death. In an experiment using commercial techniques, 47% of

Florida stone crab The Florida stone crab (''Menippe mercenaria'') is a crab found in the western North Atlantic, from Connecticut to Colombia, including Texas, the Gulf of Mexico, Belize, Mexico Jamaica, Cuba, The Bahamas, and the East Coast of the United State ...

s that had both claws removed died after declawing, as did 28% of single-claw amputees. 76% of these casualties occurred within 24 hours of declawing. Declawing also affects the ability of a crab to feed, as crabs generally use their claws to facilitate the capture and consumption of their prey. Declawed stone crabs are forced to scavenge as opposed to actively hunt and forage. Stone crabs in controlled experimental settings still consumed the same amount of food, but altered their feeding habits after declawing, eating fish instead of bivalves, normally an important part of their diet in the wild, because bivalves must be opened with the crab's muscular claw. Outside experimental settings, where declawed crabs must actively compete for food, mortality from starvation poses a significant danger. Research on Jonah crabs by Carloni and Goldstein (2016) found that declawed individuals were much more likely to refuse food altogether.Carloni, Joshua, and Jason S. Goldstein. "Claw removal and its impacts on survivorship and physiological stress in Jonah crab (''Cancer borealis'') in New England waters." Report submitted to the Atlantic States Marine Fisheries Commission. January 25, 2016. https://www.asmfc.org/uploads/file/56ba03f1AmLobsterTC_JonahCrabReport_Jan2016.pdf Ultimately, different species of crabs respond in different ways to limb loss, with heterochelous crabs facing particular difficulties. Additionally, declawed crabs show significantly lower activity levels than

negative control A scientific control is an experiment or observation designed to minimize the effects of variables other than the independent variable (i.e. confounding variables). This increases the reliability of the results, often through a comparison be ...

s, and may have difficulties attracting mates. McCambridge, Dick, and Elwood (2016) demonstrated that brown crabs that had autotomized (detached their own claws) fared better in mating than manually declawed crabs, which were much less likely to successfully attract females. Effects on mating appear to vary by species; studies on the green crab and the velvet crab demonstrate that the loss of limbs impair mating chances, but evidence of such an effect among the Atlantic blue crab is mixed.

Pain and stress caused by declawing

Whether

crustaceans Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean gro ...

are capable of feeling pain is a topic of ongoing scientific discussion and debate. It has been argued that because crabs can autotomize their claws, manual declawing along natural fracture planes might not cause pain. Patterson, Dick, and Elwood (2007), however, found that declawing heightened physiological stress responses measured through analysis of

haemolymph Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod (invertebrate) body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which ...

in declawed crabs more so than in autotomized ones.

Regulation

The regulations on crab fishing varies across the globe based on region and species of crab, and not all crabs caught are declawed. The United Kingdom prohibited declawing for 14 years, from 1986 to 2000. In the United States, different states have adopted a variety of measures regarding declawing. Regulations on the Alaskan king crab fishing industry do not make any mention of declawing, and implicitly assume the entire crab will be taken. Some

Gulf Coast The Gulf Coast of the United States, also known as the Gulf South, is the coast, coastline along the Southern United States where they meet the Gulf of Mexico. The list of U.S. states and territories by coastline, coastal states that have a shor ...

states such as Florida and Louisiana prohibit the harvesting of whole stone crab, allowing for declawing only. In contrast, declawing Jonah crab in Maryland was banned after 2015 unless a vessel could prove it had historically conducted the practice and was registered in a state where the practice was allowed.''Maryland Register'' Vol. 34, No. 12. Proposed Action on Regulations, Title 08 Subtitle 02, Department of Natural Resources Fisheries Service: Notice of Proposed Action. 8 July 2016. https://services.statescape.com/ssu/Regs/ss_8587336159857509982.pdf. 2017 Sarasota Mar Vista Stone Crab 1 FRD 6870

2017 Sarasota Mar Vista Stone Crab 1 FRD 6870

Sustainability

The central argument for declawing is that because crabs can regenerate lost limbs, it is inherently more sustainable than the capture of whole crabs. Yet claws are a large portion of a crab's biomass, ranging from 20% to over 50% of some species' total weight, and thus regeneration can be highly energy- and time-consuming. The empirical occurrence of regenerated claws in fishery harvests is low, with studies on stone crabs calculating from less than 10% (Davis et al., 1978), to 13% (Florida Fish and Wildlife Conservation Commission, 2011). Larger, older crabs generally do not survive long enough to regrow their claws, as they are near the end of their lifespan.

References