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Ecological effects of electrofishing for Ensis spp.

in Scotland.Fiona Murray1,3, Phil Copland2, Phil Boulcott2, Mike

Robertson2 and Nick Bailey2

1 Razorclam Fishermen’s Forum. 2 Marine Scotland Science. 3 Present address Heriot-Watt University

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Overview• Previous razor clam study in Scotland

• Aim of this project

• Sea trials

• Tanks trials

• Conclusions and implications

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Hydraulic dredge

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Electrofishing• https://www.youtube.com/watch?v=Z02KhkOgfVQ

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Aims of this project: Sea Trials

• Record recovery rates of Ensis spp. • Identify non-target species which may be affected

by Ensis electrofishing

• Record the recovery of non-target species

• Determine if electrofishing may cause mortalities in sandeels

• Observe the impact of the electric rig on the seabed

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Sea trials

• Electrodes dragged over seabed• Quadrats placed for 30 min

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• F99,96, p = 0.004

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• Pictures of all animals identified

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• Non-target results and sandeels

F34 = 2.375 p = 0.043

Sandeels

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• Determine the properties of the electric field generated by electrofishing

• Record the behavioural response to, and recovery from exposure to, an electric field in E. siliqua and 3 non target species

• Monitor the short term survival of E. siliqua and 3 non target species following exposure to an electric field

Aims of this project: Tank Trials

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Tank trials

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Ensis siliqua• https://www.youtube.com/watch?v=o1gcuYmPK6

w

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Non-target species• Pagurus bernhardus

• Spisula solida

• Asterias rubens

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Conclusions• Electrofishing (using this system) is a potentially

low impact method of harvesting razor clams.

• The impact on the seabed is minimal in comparison to conventional dredge and trawl fisheries.

• Immediate effects on non-target species are non-lethal and effects on invertebrate behaviour are short term.

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Suggested next steps• Initial stock surveys – ideally while derogation is

sought• Surveys by chartered commercial vessels using

electrofishing technology linked to quantitative camera based system. Candidates for IFG coordination with industry input to design?

• Assuming derogation granted – allow commercial fishery based on initial survey findings. Vessels participate in data gathering

• Reassess stocks with knowledge provided by fishery and survey

• Adjust scale of fisheries as required and set catch opportunities

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Thanks for listening

F.Murray@hw.ac.uk