Capture Related Stress in Mackerel #2
In Norway, 1.3 million tonnes of fish were landed by commercial purse seiners in 2017. However, during the capture and slaughter process, fish are exposed to stresses such as crowding, hypoxia and rapid temperature change. Such stressors have the potential to negatively impact upon the animals’ short and long-term welfare. The purpose of these experiments is to increase our understanding of how current purse seine capture and slaughter practices affect the behaviour, physiology and resulting meat quality of Atlantic mackerel (Scomber scombrus). Mackerel supports an important purse seine fishery in Norway, but is a delicate species that is highly susceptible to stress. By understanding how mackerel responds to stress we hope to promote welfare friendly fishing practices that maximise: 1) survival potential if the catch is to be released and: 2) meat quality if the catch is to be retained, contributing towards a more sustainable and profitable Norwegian fishing industry.
This application is in support of the FHF project “Fangstkontroll in Notfiske”. Three replicates of three small schools of mackerel (consisting of 100 individuals in aquaculture net pens) will be exposed to typical purse seine capture crowding densities of either ~50 kg/m3 or ~180 kg/m3 (achieved by reducing the volume of the net pen) or a control (no crowding) for either 15 or up to a maximum of 60 minutes. Resulting behavioural, physiological and meat quality responses will be determined using camera observation, as well as blood, tissue and meat quality sampling. Mortality outcomes will be monitored in the control and ~50kg/m3 crowded groups.
The effect of slaughter method on meat quality will also be investigated after stressor treatments for subsamples of 10 fish taken from the net pen. Slaughter methods investigated will be: 1) a blow to head followed by brain spiking; 2) immersion in cold hypoxic seawater and 3) electrical stunning followed by immersion in cold hypoxic seawater. These experiments will also be replicated three times. Optimal field strength and duration for effective mackerel electrical stunning will be determined by examination of behavioural and reflex responses on 25 additional fish post stunning.
The number of mackerel involved in all experiments will total 900. Simulation of commercial conditions during capture and slaughter of pelagic fish can be regarded as “Considerable distress” as fish are exposed to hypoxic environments, rapid temperature changes and crowding to relatively high densities, inducing a level of distress and perhaps death. As we intend to study physiology and behaviour, there is no replacement for the use of live animals. We have therefore focused on reducing the number of animals required to an absolute minimum, by use of power analysis. Furthermore, as much data as possible will be collected from each experimental subject. The project will also reduce the severity of the experiments by avoiding chronic and acute suffering, by defining early stage endpoints. For the development of effective future legislation, these experiments are required in order to reveal, understand and compare the implications of current commercial fishing practices upon animal welfare.
This application is in support of the FHF project “Fangstkontroll in Notfiske”. Three replicates of three small schools of mackerel (consisting of 100 individuals in aquaculture net pens) will be exposed to typical purse seine capture crowding densities of either ~50 kg/m3 or ~180 kg/m3 (achieved by reducing the volume of the net pen) or a control (no crowding) for either 15 or up to a maximum of 60 minutes. Resulting behavioural, physiological and meat quality responses will be determined using camera observation, as well as blood, tissue and meat quality sampling. Mortality outcomes will be monitored in the control and ~50kg/m3 crowded groups.
The effect of slaughter method on meat quality will also be investigated after stressor treatments for subsamples of 10 fish taken from the net pen. Slaughter methods investigated will be: 1) a blow to head followed by brain spiking; 2) immersion in cold hypoxic seawater and 3) electrical stunning followed by immersion in cold hypoxic seawater. These experiments will also be replicated three times. Optimal field strength and duration for effective mackerel electrical stunning will be determined by examination of behavioural and reflex responses on 25 additional fish post stunning.
The number of mackerel involved in all experiments will total 900. Simulation of commercial conditions during capture and slaughter of pelagic fish can be regarded as “Considerable distress” as fish are exposed to hypoxic environments, rapid temperature changes and crowding to relatively high densities, inducing a level of distress and perhaps death. As we intend to study physiology and behaviour, there is no replacement for the use of live animals. We have therefore focused on reducing the number of animals required to an absolute minimum, by use of power analysis. Furthermore, as much data as possible will be collected from each experimental subject. The project will also reduce the severity of the experiments by avoiding chronic and acute suffering, by defining early stage endpoints. For the development of effective future legislation, these experiments are required in order to reveal, understand and compare the implications of current commercial fishing practices upon animal welfare.