The effect of electric pulse stimulation to juvenile cod and cod of commercial landing size

The first pilot study on the effects of electric pulse stimulation on larger cod carried out in 2008 was based on a single nominal setting of the Verburg-Holland UK153 pulse system with the intention to determine the range of pulse characteristics with which injuries to the fish occurred. This study was designed to obtain a more detailed view on the effects of the pulse characteristics and to investigate if a specific pulse parameter has a key role in the effects. Lower pulse amplitudes with longer pulse width and higher frequency could induce different effects than pulses with higher amplitudes, shorter pulse width and lower frequency. In this way the effects can be related to a specific pulse parameter and its threshold value. Another aim of major importance is that this research also carried out on the electrically exposed fish that would normally escape through the cod-end meshes with unknown longer term effects. This was already recommended after the first experiment in 2008

The effect of pulse stimulation on biota - Research in relation to ICES advice - Progress report on the effect to cod

In response to questions asked by ICES on the effects of pulse stimulation in commercial beam trawling on components of the marine ecosystem a number of preliminary studies were undertaken in the period between 1 September 2008 and 1 March 2009. These activities involved the exposure of cod to a simulated electric pulse under laboratory conditions and observation of behaviour, including the foraging response, and monitoring mortality and possible internal injuries such as vertebral damage by X-ray photography

Pulse trawl fishing: characteristics of the electrical stimulation and the effect on behaviour and injuries of Atlantic cod (Gadus morhua)

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