R.J. Kloosterboer

Welfare aspects of live chilling and freezing of farmed eel (Anguilla anguilla L.): neurological and behavioural assessment

Abstract The overall objective of the study was to evaluate a slaughter method of eels, which consisted of chilling until their body temperature was Firstly, 19 eels with an average live weight of 758±44 g were restrained and equipped with EEG, ECG electrodes and a temperature sensor inside the body. Then, they were placed in the ice water. Indices for the induction of unconsciousness and insensibility were the appearance of theta and delta waves and no response on pain stimuli, which disappeared at a body temperature of 8.0±2.1 °C after 12±5 min in 15 eels. The responses to pain stimuli did not disappear in three eels. Within a confidence level of 95%, the percentage of eels that is not effectively stunned during the procedure in ice water of n =14) to 7±4 ( n =11) and became irregular during cooling down. When placed in the brine water of −18 °C, the EEG showed rapid and extreme depolarisation of the membranes, which started after 27±17 s ( n =18). The ECG showed fluttering of the heart in all eels. None of the eels recovered after this procedure. For 10 eels with an average live weight of 128±27 g, it was observed that the body temperature decreased from 17.1±0.6 to 4.0±0.5 °C in the ice water. After 15 min in the brine water of −16.1±2.2 °C, the body temperature decreased to −3.1±2.3 °C. Finally, three groups of seven eels and eight single eels were placed in ice water of −0.0±0.1 °C. The observation of unrestrained eels revealed four phases. Animals were (1) swimming around in the water, (2) attempting to escape from the ice water, (3) pressing their nose to the wall or corner while showing clonic muscle cramps, and finally (4) breathing only, while all other muscle activity was totally suppressed. Afterwards, they were transferred to cold brine at −18 °C, and none of the eels recovered. The eight control eels, which were transferred to water at 18 °C, swam around, except for one that was lying in an S-shape position at the bottom. After 570 and 605 s, two eels tried to escape from the box. The obtained results show that the eels, which were transferred from water at 18 °C to ice water, might be stressed, a specific behaviour and an irregular heart rate were observed. From an animal welfare point of view, it is therefore not recommended to stun eels by live chilling. Moreover, at least 5% of the eels will not be stunned at a body temperature of

Evaluation of captive needle stunning of farmed eel (Anguilla anguilla L.): suitability for humane slaughter

Abstract In the study, 53 eels with a live weight of 700 to 800 g were restrained and equipped with EEG and ECG electrodes before stunning. The eels were mechanically stunned by a captive needle pistol using a shooting pressure of 8 bar and an air injection of 3 bar during 1.5 s. The behaviour was observed during and after stunning. Indices for the immediate induction of unconsciousness and insensitivity were the appearance of theta and delta waves tending to an iso-electric line, i.e. no brain activity. The duration of these waves averaged 11±8 s ( n =32) on the EEG. Another nine animals showed directly after stunning no brain activity. Due to severe clonic cramps five animals were stunned twice. The ECG showed fluttering of the heart configuration immediately after stunning in all eels. It was concluded that within a confidence level of 95%, taking into account the number of animals with a reliable EEG ( n =42), at least 93% of the eels were effectively stunned by a correctly positioned captive needle pistol. It was easy to stun eels with a captive needle pistol using air pressure; however, more research is needed for the development of a restraining and stunning device suitable for use in practice.