Survival and Physiological Recovery after Capture by Hookline: The Case Study of the Blackspot Seabream (Pagellus bogaraveo)

Abstract

Evaluating the survival of discarded species is gaining momentum after the new European Common Fisheries Policy (Article 15 of the European Regulation No. 1380/2013). This regulation introduced a discard ban, with an exemption for those species with demonstrated high survival rates after their capture and release. Candidate species should be evaluated for each fishing gear and geographical area. In this study, we assessed not only survival, but also physiological recovery rates of blackspot seabream (Pagellus bogaraveo) below commercial size captured with a hookline called “voracera” in the Strait of Gibraltar (SW Atlantic waters of Europe). Experiments onboard a commercial fishing vessel were paralleled with studies in controlled ground-based facilities, where the capture process was mimicked, and physiological recovery markers were described. Our results confirmed that hookline capture induced acute stress responses in the target species, such as changes in plasma cortisol, lactate, glucose, and osmolality. However, 90.6% of the blackspot seabreams below commercial size captured with this fishing gear managed to survive, and evidenced physiological recovery responses 5 h after capture, with complete homeostatic recovery occurring within the first 24 h. Based on this study, the European Commission approved an exemption from the discard (EU Commission Delegated Regulation 6794/2018). Thus, the robust methodology described herein can be an important tool to mitigate the problem of discards in Europe.

Economic Improvement of Artisanal Fishing by Studying the Survival of Discarded Plectorhinchus mediterraneus

“…This evidence must be collected for each species, fishing gear and geographical area. Since then, there have been numerous studies focused on evaluating the survival of catches, including teleosts [ 20 , 21 , 22 ], elasmobranchs [ 23 , 24 ], cephalopods [ 25 ] and crustaceans [ 26 , 27 ]. Based on those studies, the European Commission approved the first exemption to this landing obligation (EU Commission Delegated Regulation 6794/2018) for Pagellus bogaraveo caught using the voracera fishing gear in the Strait of Gibraltar (SW Europe).…”

“…It has been reported that capture by fishing is a challenging stressor to aquatic organisms [ 20 , 23 , 28 , 29 , 30 ], and that organisms must react through a series of physiological responses to overcome it. In vertebrates, primary stress responses include the release of catecholamines [ 31 ] and corticosteroids [ 28 , 32 ] to the bloodstream, cortisol being the most important corticosteroid in teleost fish [ 33 ].…”

“…In vertebrates, primary stress responses include the release of catecholamines [ 31 ] and corticosteroids [ 28 , 32 ] to the bloodstream, cortisol being the most important corticosteroid in teleost fish [ 33 ]. Secondary stress responses involve physiological reactions promoted by these hormones, and include changes in the cardio-respiratory system, mobilization of energy metabolites into the blood, changes in the acid-base and hydromineral balance, and in the immune system [ 20 , 25 , 26 , 28 , 34 ]. Glucocorticoids induce the release of glucose (amongst other metabolites, such as proteins and amino acids) after capture, leading to high circulating concentrations of lactate due to an increased anaerobic metabolism [ 21 , 28 , 32 , 35 ].…”

“…The high levels of plasma CO 2 and lactate induced by an acute stressor promoted blood acidification [ 28 , 34 ], counteracted by peripheral tissues. Due to the vasodilation of blood vessels, osmoregulatory disturbances also occur after fishing [ 20 , 28 , 34 , 36 ], and endocrine responses are activated to restore ionic homeostasis [ 28 , 37 , 38 , 39 ]. According to the existing literature, marine animals manage to recover from an acute stress situation caused by fishing in less than 24 h [ 20 , 23 , 25 , 26 , 32 , 40 , 41 ].…”

“…Due to the vasodilation of blood vessels, osmoregulatory disturbances also occur after fishing [ 20 , 28 , 34 , 36 ], and endocrine responses are activated to restore ionic homeostasis [ 28 , 37 , 38 , 39 ]. According to the existing literature, marine animals manage to recover from an acute stress situation caused by fishing in less than 24 h [ 20 , 23 , 25 , 26 , 32 , 40 , 41 ]. If the stressful situation continues over time or if a multiple system failure occurs, tertiary stress responses are triggered, leading to weakened immune responses, reduced growth, reproductive and behavioral impairments, and even death [ 42 , 43 ].…”