Meta‐analytic assessment of physiological markers for decapod crustacean welfare

Abstract

Decapod crustacean welfare is not only an ethical consideration for legislative purposes. Under culture and fishery settings, poor environmental conditions and operator practices can cause stress, which compromises the immune system and increases the risk of disease. For finfish, there are established environmental and animal (group, individual) welfare indicators. This is not the case for crabs, lobsters or shrimp. While environment‐based indicators like temperature, pH and oxygen levels are easily transferable, there is no consensus for a common measure of stress to monitor welfare in decapod crustaceans. To address this shortcoming, we conducted a meta‐analysis of the primary literature to test for relationships between haemolymph (blood) condition, for example, levels of glucose, L‐lactate, haemocytes (n = 8), and sources of physical stress, for example, handling, trawling, emersion and transport (n = 12). Despite variations in effect sizes (n = 459), generalised liner mixed models repeatedly ranked L‐lactate (followed by urea and glucose) as the most significant physiological predictor of stress in the haemolymph, with trawling followed closely by emersion as the most impactful stressors. Duration post (stress) exposure, sex (male, female), water temperature and moult stage (pre‐, inter‐, post‐moult) were not associated significantly with stress prediction using the selected biochemical and cellular parameters, however, moult status was undefined in ~48% of literature sources and should be interpreted with caution. We present evidence that quantitating L‐lactate levels in the haemolymph represents a physiologic operational welfare indicator of decapod crustaceans, which complements existing condition/vigour indices.

Towards Shrimp and Prawn Welfare in the Wild‐ Caught Fishing Industry: A Global Review and Recommendations for Research and Policy

“…Firstly, it is possible to improve the welfare of shrimp at capture and slaughter. This can be supported by studies that identify and validate welfare indicators (Albalat et al 2022;Conneely and Coates 2023). Secondly, it is possible to reduce the number of shrimp or other animals caught.…”

“…Before turning to a discussion of potential animal welfare interventions, we believe it is important to recognise that the global shrimp fishing industry is closely related to a number of challenges related to human rights and justice. There is widespread recognition that policies aiming to improve animal welfare and other areas of sustainability must understand these dimensions of human wellbeing (Wrenn and Johnson 2013;Rodriguez 2018;Coghlan et al 2021;Reisman et al 2022;Conneely and Coates 2023). Here, we will summarise three key challenges, focusing on shrimp fisheries in developing countries.…”

“…Trawling, like other harvest methods, can be very stressful for crustaceans (Albalat et al 2022;Conneely and Coates 2023). Trawling can crush carapaces, cause collisions with other animals, and drive shrimp to exhaustion as they try to escape the net (Gillett 2008;Conneely and Coates 2023). One solution could be to reduce the duration of trawls (Crustacean Compassion).…”

“…When on board, shrimp may experience oxygen deprivation and/or inappropriate air temperatures (Birch et al 2021;Conneely and Coates 2023). Shrimp may become stressed and eventually die from asphyxiation, which is typically considered inhumane (Lewit-Mendes et al 2022;Conneely and Coates 2023). Shrimp may also experience stress if directly exposed to rain (Lavallee et al 2000;Saraswathy et al 2021).…”

“…Suffering from oxygen deprivation may be minimised by optimising handling processes and improving on-board logistics where possible to reduce the amount of time that shrimp spend out of water. Shrimp could plausibly be delivered to recovery tanks rather than directly onto the deck in situations where this is practicable (Conneely and Coates 2023).…”