Effects on invertebrates

Pulse effects on various benthic invertebrates

Smaal and Brummelhuis (2005) exposed a variety of benthic invertebrates to a Delmeco sole pulse for 10 seconds. Some species showed a response to the electrical stimulus by closing their shells (bivalves), withdrawing themselves in their shell (whelk, hermit crab) or showing a tail flip response (decapod shrimps), while other species (polychaetes, Echinodermata) did not show a visible response. The experiments did not suggest that electrical stimulation affected the filtration rate of bivalves or the mortality as compared to the control group. Because the company providing the pulse generator did not disclose the details of the pulse characteristics, the results are only indicative for the possible effects.

Pulse effects on shrimps and ragworms

To detect the safe range of pulse parameters, Soetaert et al. (2014) exposed brown shrimps and ragworms to a homogeneous electric field for up to 5 seconds and studied their behaviour, 14-d mortality rate, gross and histology. Pulse setting included the commercially applied frequency and field strengths. No adverse effects were detected except for an increase in a virus infection (IBV) in the hepatopancreas in shrimps exposed to the maximum field strength (200 V/m).

In a follow up experiment studying the effects of repetitive exposure in shrimps, however, this result could not be corroborated. In this experiment, brown shrimps were exposed 20 times during 4 days to either the sole pulse or the shrimp pulse. The survival, egg loss, moulting and the degree of IBV infection was compared shrimps exposed to electrical pulses, shrimps exposed to mechanical disturbance mimicking the conventional shrimp trawling and a control group. The sole pulse treatment gave a significant lower 14-day survival as compared to the control group, while moulting was reduced by mechanical disturbance.