Physiological, physical and behavioural responses of sardine to purse seine fishing: Implications for the survival of escapees

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Abstracts / Comparative Biochemistry and Physiology, Part A 146 (2007) S75–S86

hold during ocean transport support a rapid recovery of fish in the live holds. Financial support provided by AquaNet and NSERC Canada. doi:10.1016/j.cbpa.2007.01.097

A2.15 Serotonin as a welfare indicator in teleost fish Ø. Øverli, (Norwegian University of Life Sciences), S. Winberg, (Uppsala University), K.F. Cubbitt, (University of British Columbia), F.A. Huntingford, (Glasgow University) In the CNS, the monoamine neurotransmitter-neuromodulator serotonin (5-Hydroxytryptamine, 5-HT) is critical for maintaining normal cognitive and emotional processes. With respect to animal welfare, it should particularly be noted that 5-HT is paramount in controlling neurogenesis and synaptic plasticity, processes without which learning ability, memory, and mood rapidly deteriorate. In many instances, such as with reactive behaviour seen under chronic stress, the adaptive value of the 5HT controlled responses is clear: Dangerous, unpredictable, and uncontrollable conditions do not generally reward proactive behaviours such as aggression, attempts to feed, or active escape. With regards to emotion, a healthy lack of optimism also aids survival under such circumstances. In other cases, such as in human depression, out of context and dysfunctional changes in serotonin metabolism seem debilitating to normal behaviour, well-being, and survival. In teleost fishes, increased 5-HT metabolism and release occur in response to a wide range of stressors such as social stress, confinement, predators, and parasite infections. Neurochemical measures of 5-HT activity change more slowly than plasma cortisol in response to stress, but are more permanent, not reversed under chronic conditions, and not as easily confounded by sub-optimal sampling procedures. For instance, 5-HT neurochemistry, but not plasma cortisol, gave evidence of dominance hierarchies in Atlantic salmon (Salmo salar) kept under commercial rearing densities, with slower growing fish being subordinate and displaying increased 5-HT turnover. By presenting this evidence, we hope to accentuate a discussion on the pros and cons of using central neuroendocrine measures as a tool to monitor behavioural states and animal welfare. doi:10.1016/j.cbpa.2007.01.720

A2.16 Physiological, physical and behavioural responses of sardine to purse seine fishing: Implications for the survival of escapees A. Marçalo, P. Pousão-Ferreira, (INIAP/IPIMAR-CRIPSul, Portugal); K. Erzini, (Universidade do Algarve, Portugal); Y. Stratoudakis, (INIAP/ IPIMAR, Portugal)

Release of excess/unwanted catch in many commercial fisheries results in some immediate fish mortality and an unknown postrelease fate for most escapees. Observations of the purse seine fishery targeting sardines (Sardina pilchardus) off Portugal demonstrated that while deliberate lowering of the net to allow fish to escape (“slipping”) is occasional, its magnitude is very variable and the contribution to fishing mortality is largely unknown. The analysis of sardine blood and muscle samples collected during ten commercial trips revealed significant linear trends with time spent in the net for most physiological parameters analysed (cortisol and glucose increases, ionic dysfunction and decreases in haematocrit, haemoglobin and ATP), suggesting that the duration of the fishing operation (but not the catch volume) is an important stressor for sardine. Mixed field/laboratory trials involving short-term monitoring after live capture at sea and transfer to captivity are currently used to evaluate the level of delayed mortality and explore its causes. Early results from four trials indicate that post-capture mortality peaks 3–5 days after fishing, and that physical damage is directly linked to survival in the first days after capture, while physiological responses of survivors show inverse temporal trends to those reported during fishing and recovery from blood and plasma acidosis is delayed. Ongoing work aims to identify links between physical and physiological responses to understand the reasons of delayed fish death, while simulations of the capture process in tanks are planned to evaluate the impact of sub-lethal tertiary stress reactions (behavioural impairment) on the survival of escapees. doi:10.1016/j.cbpa.2007.01.099

A2.17 Understanding the welfare of farmed cod under commercial conditions: Integration of physiological, behavioural and physical approaches A. Brown, (Aquatonics Ltd, United Kingdom); A. Bournhill, J. Watson, (Johnson Seafarms Ltd, United Kingdom); T. Wall, (Fish Vet Group, United Kingdom); T. Ellis, (CEFAS, United Kingdom); A.F. Zuur, E.N. Ieno, (Highland Statistics Ltd, United Kingdom) Farming of Atlantic cod (Gadus morhua) in the UK, Norway and Canada offers a means to alleviate pressure on wild stocks, and it is important that systems and practices to achieve good welfare are integral to expansion of this sector. Most studies of fish welfare focus on salmonids, in laboratory-based or small tank studies, and there is limited information on cod. To develop welfare indices relevant to cod farming we are taking a multidisciplinary approach, examining physiological parameters, recording behaviour by video and photography, and assessing physical damage. This is the first study to assess cod welfare on a realistic aquacultural production scale. We assessed normal variability in physical damage and physiological parameters of cod in commercial sea-cages. These data show the benefit of inhibiting gonadal maturation of farmed cod, avoiding the