|Towards a scientifically informed decision : Effects of electrical pulse stimulation on bioirrigation and movement activity patterns of Arenicola marina in the context of pulse trawling|
Portier, J. (2019). Towards a scientifically informed decision : Effects of electrical pulse stimulation on bioirrigation and movement activity patterns of Arenicola marina in the context of pulse trawling
. BSc Thesis. NIOZ Netherlands Royal Institute for Sea Research: Yerseke. 50 pp.
The experimental fishing method of pulse trawling was initially developed to decrease fuel consumption rates of flatfish fisheries in the North Sea targeting common sole (Solea solea). By replacing tickler chains with electrodes, the targeted fish is immobilised until it enters the net by using electrical pulse stimuli. The adaptation to this new technique reduced fuel consumption rates by 40-50%, while decreasing seabed damage and bycatch (Poos et al., 2013; van Marlen et al., 2014). However, the commercial use of this method was met with significant resistance by environmental organisations, as possible adverse effects on marine life had been documented. Earlier studies reported spinal injuries in Atlantic cod (Gadus morhua) as a result of exposure to electrical pulse stimuli (de Haan et al., 2016; Soetaert et al., 2016). This type of exposure may affect burrowing invertebrates, which may otherwise avoid the mechanical trawl disturbance. However, this area of research remains unexplored, though it is important to investigate as electrical fields can penetrate the seabed. As part of the Impact Assessment of Pulse trawl Fisheries (IAPF), this study aimed to assess the possible effects electrical pulse stimuli may have on bioirrigation and movement activity patterns of lugworm (Arenicola marina). In a laboratory setting, seven A. marina specimens were subjected to a worst-case pulse exposure scenario using the electrical pulse parameters used in common sole (S. solea) pulse fisheries, to study their behavioural reaction, recovery, and the potential changes in oxygen dynamics related to this. These changes were compared to six control specimens of A. marina. All specimens were analysed using porewater pressure recordings and a selected group with additional oxygen consumption rate measurements to detect changes in behaviour and respiration respectively. Planar optode imaging was used to visualise the changes oxygen dynamics induced by macrofaunal activity inside the sediment in experimental setup. A significant increase in both burrowing (2.24%) and defecation (0.33%) was observed in the exposure group, as opposed to pumping activity, which showed a reduction of 2.59%. Pumping of water by the lugworm into its burrow caused oxygenation at depths of 19 cm (39 – 52%). However, after exposure to an electrical pulse stimulus, oxygen saturation values inside the gallery decreased rapidly (13 – 26%). Oxygen consumption rates were higher in the control group, which may predominantly be influenced by microbial activity. Though, the difference was not significant between the two sample groups. Our research suggests that exposure to an electrical pulse stimulus can cause alterations to the ecosystem functioning of A. marina in terms of bioadvection, while possibly increasing the vulnerability of the species towards predators such as flatfish.