Effects on sharks and rays

Rays and sharks (elasmobranchs) possess electro-sense organs to detect food, which may make them particularly sensitive for pulse fishing. To analyse the effects on elasmobranchs, two different experiments have been conducted on the small-spotted catshark, Scyliorhinus canicula as model organism.

First round of experiments on catsharks

During the first round of experiments, de Haan et al. (2009) exposed three groups of 16 fish to a series of 4 pulse bursts at maximum amplitude at three different distances from a conductor pair, while a fourth group was used as a control. Fish in all tested groups started feeding normally directly after the exposures. Fish were kept in husbandry for 9 months after the exposure and produced eggs in numbers varying between 5-39 per group, while the control group did not produce eggs.

Second round of experiments on catsharks

During the second round of experiments, Desender et al (2017) studied how pulse stimuli affected the electro-detection ability of catsharks. The electro-response to an artificially created prey-simulating electrical field was tested before and after exposure to the pulsed electrical field used to catch flatfish and shrimp. No statistically significant differences were noted between control and exposed animals, both in terms of the number of sharks exhibiting an electro-response prior to and following exposure as well as regarding the timing between onset of searching behaviour and biting at the prey simulating dipole. These results indicate that, under the laboratory circumstances as adopted in this study, the small-spotted catshark are still able to detect the bio-electrical field of a prey following exposure to PDC used in pulse trawls.