In the North Sea flatfish fishery, electric pulse trawls have been introduced to replace the conventional mechanical method. Pulse trawls reduce the fuel consumption, reduce adverse impact on the ecosystem but cause injuries in gadoids. We describe the design and electrical properties of pulse trawls currently in use and study the behavioural response and injuries in cod exposed to electrical pulses under controlled conditions. Pulse trawls operate at an average power of 0.7 kW m−1 beam length and a duty cycle of ∼2%. The electric field is heterogeneous with highest field strength occurring close to the conductors. Cod were exposed to three different pulse types for a range of field strengths, frequencies, and duty cycles. Two size classes were tested representing cod that escape through the meshes (11–17 cm) and market-sized cod that are retained in the net (34–56 cm). Cod exposed to a field strength of ≥37 V m−1 responded by moderate-to-strong muscular contractions. Some of the large cod (n = 260) developed haemorrhages and fractures in the spine, and haemal and neural arches in the tail part of the body. The probability of injuries increased with field strength and decreased when frequency was increased from 100 to 180 Hz. None of the small cod (n = 132) were injured and all survived. The field strength at the lateral boundaries of the trawl was too low to inflict injuries in cod.

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The objective was to assess neural, behavioural responses and product quality in farmed sea bass (Dicentrarchus labrax) upon electrical stunning in seawater. The electrical sinusoidal 50 Hz or pulse square wave alternating 133 Hz current induced a general epileptiform insult with a current of 3.3 AE 0.2 or 3 A dm À 2 , respectively, for 1s head to tail in seawater. The total duration of the insult was 48 AE 34 and 23 AE 11s. After stunning, the electrocardiogram revealed ¢brillation and ceased or showed malfunction. Product quality was assessed in a group electrically stunned, followed by chilling in ice water and the controls were only chilled in ice water. The pH of the ¢llets was 0.1^0.2 lower (Po0.01) when stunned electrically at days 1, 2, 8 and 10 postmortem, where the colour did not di¡er. The percentage of sea bass e¡ectively stunned using an electrical sinusoidal or pulse square wave current was above 85% within a con¢dence level of 95%. A combination of electrical stunning for 10 s, followed by chilling in seawater with ice £akes resulted in the death of all ¢sh. The former method is recommended to be adapted for implementation in practice. Evaluation of electrical stunning of sea bass in seawater B Lambooij et al.

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