Scottish Marine and Freshwater Science Volume 5 Number 14: Electrofishing for Razor Clams (Ensis siliqua and E. arquatus): Effects on Survival and Recovery of Target and Non-Target Species

Executive Summary

Trawling and tank based trials were conducted to assess whether electrofishing (which is currently prohibited under EU regulations) for razor clams ( Ensis siliqua and E. arquatus) affects survival and behaviour patterns in Ensis spp. and non-target species.

Boat trials in a number of areas identified that the main non-target species most likely to be affected by this fishery are starfish species, crab species (predominantly hermit crabs), flatfish and sandeels. No mortalities were recorded as a direct result of the fishing equipment or electric field generated and any induced behavioural responses in non-target species were exhibited for a maximum of 10 minutes following exposure. However, during this time stunned animals may be vulnerable to predation.

Tank trials indicated that exposure to an electric field typical of that generated through electrofishing by the vessels involved in this project did not affect short term (5 days) survival in razor clams, surf clams, starfish or hermit crabs.

These results suggest that electrofishing for razor clams does not have immediate or short term lethal effects, or prolonged behavioural effects, on vertebrate or invertebrate species exposed to the electric field generated. Further research is required to determine medium and long term effects. However, as electrofishing has a very low short term impact on non-target species and the seabed it warrants consideration as a viable fishing method for the commercial razor clam fishery in Scotland within sustainable limits.

This project set out to examine the electrofishing process and the potential localised effects on associated fauna. The study did not address the broader question of long term sustainability of razor clam populations under various levels of commercial fishing activity. This report does not offer any advice on the amount of fishing effort which could be applied in the different areas supporting razor clam populations. The authors recognise the need for such assessments to take place and recommend that the next stage should be quantitative assessments of stock size towards the development of a sustainable fishery scaled to the size of the resource.