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Title: Fishery sustainability and welfare of the edible crab, Cancer pagurus
Author: McCambridge, Claire
ISNI:       0000 0004 6057 1948
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2016
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Manual declawing of Cancer pagurus before return to the sea and during storage aboard fishing vessels has been legal in Northern Ireland (NI) since the revocation in 2000 of the Crab Claws (Prohibition of Landing) Order (1986). However, the paucity of objective data on this fishery practice has raised concerns for the sustainability and welfare of C. pagurus. Feeding ability of edible crabs was examined by either inducing autotomy or manual declawing of a walking leg, one or both chelae, before crabs were offered prey items. Crabs were offered mussels, Mytilis edulis, to assess if having one or no chelae results in a reduced ability to feed on hard shelled prey for which its crushing chelae are adapted. Crabs that had a walking leg removed ate significantly more mussel mass than crabs that had one or two claws removed, with no difference between crabs that had one claw or two claws removed. This suggests that induced autotomy and manual declawing of C. pagurus has a detrimental effect on the ability of crabs to feed on readily available prey, and that other feeding opportunities must be found The physiological stress response to manual declawing of both claws, in males and females, was assessed by extracting lactate over 24 hours following claw removal. All manually declawed crabs died within 14 days, whereas all others survived for +23 days. Lactate concentrations in crabs that had both claws manually declawed increased significantly, compared to autotomized and intact crabs, and remained high for 24 hours. Thus, manual double declawing results in a prolonged stress response and high crab mortality, leading to the recommendation to cease this practice, or perhaps develop induced autotomy techniques as a more sustainable fishery practice. Fighting ability during contests for resources (female and a shelter) was investigated in crabs that had either 1 claw manually declawed, 1 claw autotomized or the crab remained intact. Contests involved an intact crab and an autotomized crab, or an intact crab and a manually declawed crab. Intact and autotomized crabs were motivated to fight for the female and won more contests than the manually declawed crabs. Manually declawed crabs displayed more submissive and defensive behaviour than the other crabs and were less motivated to fight for the female. More manually declawed crabs competed for and won the shelter than intact and autotomized crabs. The findings of these experiments provide an insight into realistic scenarios facing manually declawed crabs once returned to the sea, and raise serious concerns regarding sustainability and animal welfare.
Supervisor: Dick, Jaimie ; Elwood, Robert Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available