Selectivity and catch efficiency
A better understanding of the response of fish to electrical stimuli and the characteristic of the pulses used, will allow for a better understanding of size selectivity of pulse gear. The available evidence shows that the pulse trawl has a higher selectivity to catch sole as compared to the conventional tickler chain beam trawl. All comparative fishing experiments have shown a higher catch efficiency for sole than for plaice or other demersal species.
Changes in catch efficiency
Whether the absolute catch efficiency of the pulse trawl has increased is currently being investigated. It is well known that the catch efficiency of a fishing gear may increase over time due to technological developments and improved skills of the fishermen, in particular when new techniques are introduced (Eigaard et al., 2014).
Inconclusive data on changes in size selectivity
The available data are inconclusive whether pulse trawls may have a better size selectivity, e.g. catching fewer undersized fish. The promising results reported by van Marlen et al (2014) were not corroborated in a later study (van der Reijden, in preparation).
A better understanding of the response of fish to electrical stimuli and the characteristic of the pulses used, will allow us to give a mechanistic interpretation of the size selectivity of the pulse gears used in the commercial fishery and could potentially guide us to improve the pulse stimuli to increase the length threshold for the cramp response.