Pathological and physiological effects of nicking on brown crab (Cancer pagurus) in the Irish crustacean fishery

Nicking is used in fisheries to immobilize claws of brown crab (Cancer pagurus) in order to prevent cannibalism and fighting during storage. Nicking fractures the apodemes creating an open wound and damage to the internal claw tissues, which is the most valuable product of brown crab. In turn, this results in a reduction of quality of product and possibly compromises the host's defence mechanisms to other physiological challenges experienced throughout the post-harvest process. This study assessed the effects of nicking on the physiology and pathology of brown crab from the Irish fishery over 7 days. Results showed significantly elevated levels of muscle necrosis (P = 0.005), total pathologies (P = 0.022) and encirculating granulocytes in nicked crab compared to non-nicked crab. Mean glucose (212.0 μg/mL ± 108.4), lactate (36.52 μg/mL ± 38.74) and RI (11.05n ± 1.78) levels were higher in nicked crab indicating increased stress levels. Overall, histology results showed a significantly higher (P = 0.022) occurrence of pathologies, such as melanised nodules, in nicked animals. In addition to an observed reduction in the quality of claw muscle, nicked crab also showed significantly higher (P = 0.005) levels of necrosis in claw muscle. From the results of this study it is recommended that alternative retention methods are used.

Highlights► We assessed the pathological status of nicked crab compared to non-nicked crab. ► We examined temporal changes in haemolymph chemistry and tissue pathology. ► We predicted that nicking would reduce the quality of meat and compromise survivability. ► Nicking had a negative impact on the haemolymph chemistry and pathology of crabs.