Ensis sp. fishery in Scotland

Also known as razor shells, razor clams and “spoots” Vessels were often “multi purpose” Light trawl, scallop diving, dredges, lobster and crab pots etc. Recent regulation has licensed vessels specifically for Ensis fishery Diving operations usually in depths 4 – 10m. The main market for Ensis spp is as a live export to southern Europe and Asia (in particular China, and Japan) Emphasise mult task under old regulations. Refer to Compliance for further details re licensing. Animals need to survive for 10-12 days.

Distribution and landings by ICES rectangle (2005- 2014) Updated map required Normally inshore sheltered waters. Data prepared by Rui Catarino MS-S

Landings (Tonnes) 1997 - 2014 Landing values approach £3 million pounds

Ensis sp. Burying mechanism

Description of burying mechanism The digging cycle of Ensis sp. The broken lines between adjacent valves indicate movement of the shell in relation to the sand (stippled). A, foot probing downward, siphons and fourth pallial aperture (4) open (i); B, siphons closed, valves adducting, water ejected from mantle cavity, maximum pressure in pedal haemocoele (iii); C, adduction complete, maximum dilation of the foot (Schwellform), retraction commencing (iii)-(iv); D, retraction complete, siphons reopened, ejection of water from 4th pallial aperture, slight withdrawal of foot from sand, leaving cavity below (s) (iv)-(v); E., relaxation of adductors complete, valves held firm in sand as foot probes (vi);  movement of shell, including opening of valves; O ejection of water from mantle cavity; <<, probing of foot; <, hydrostatic pressure of haemocoale derived primarily from adduction, secondarily from retraction; >--<, contraction of adductor of retractor muscles. [Source: Trueman, 1967] Emphasise the requirement for muscular control to either bury or unbury. Unlike tetanising/paralysis of shrimps and fish in European fishery.

Harvesting techniques and rates Intertidal hand collection by digging. <100 per hour Intertidal hand collection by saline. 1000+ per tide Hand collection by divers by digging. <100 per hour Hand collection by divers by saline. 3000+ per tide Hydraulic dredge. 5000+ per day Divers using electro gear. 5000+ per day. Introducing saline into the environment is a consideration. Data from Seafish report SR652

Scottish fishing rig (anecdotal)

Case Studies for ensis South and West Wales. Previously un-fished area. Ensis present. Control and worked areas. Environmental impact study on non-target species. Post survey inspections for up to 28 days. Southern Ireland. Inshore diving for shellfish is banned. Mechanical collection of ensis using electrical stimulus in front of dredge rather than fluidising seabed using hydraulic system.

Effects of Electrofishing for Ensis spp Effects of Electrofishing for Ensis spp. on benthic macrofauna, epifauna and fish species Dr. Andrew Wooler (1), Evonne Maxwell (1), William Lart (2) Salacia-Marine Sea Fish Industry Authority June 2011 Prepared for the South and West Wales Fishing communities Ltd as part of Electrofishing for Razorfish (Ensis spp.) Project (FIFG 57437) Seafish report SR652 ISBN-978-1-906634-58-2 www.seafish.org

Generator ( AC plus DC welding)

Comparison between positive (left) and negative (right) electrodes after several hours use DC systems will deposit metal, evolve hydrogen, chlorine gas and NaOH into the environment in significant quantities. Chlorine compounds are toxic to marine organisms and this technique is used in cooling pipes for power stations.

Fishing trials Four trial areas of 100m * 100m were selected as having suitable sediment type for razorclams and also large diversity of other species. Areas had not previously been fished as in “protected area”. Areas were randomly divided (N/S) One half of each area was subjected to intensive coverage with electro-rig energised. The four ”control areas” were not fished in any way. Standard experimental/ control scenario.

Fishing trials (cont) Cameras on electro-rig recorded reactions to electric field. Observer on vessel monitored bird, mammal and cetacean interaction with electro-rig. Details of system performance (current and voltage), vessel location, weather conditions etc recorded in tow log.

Species observed in electric field 4 species of crustacea. 5 species of Mollusca 3 species Echinodermata 8 species of fish Collected data includes type of effect, description of behaviour and recovery time. Short term (1 day post fishing) and long term (up to 28 days post fishing) studies of macrofauna, epifauna and fish carried out in all areas. Fish Species include: Rays, Dover Sole, Dab, Plaice, Sand eel, Rockling, goby, wrasse.

Conclusions (Heavily paraphrased.) “At the currents and voltages used in these trials Ensis spp can be effectively harvested without serious negative effects on the epifaunal and macrofaunal benthic community.” “Given the commonly reported negative effects of alternative approaches, toothed and hydraulic dredges. The results of this study suggest further development work is warranted to develop less disturbing fishing gears”.

BIM pulse dredge trials Stimulus. “ Pulsed” AC or DC at 20 volts ~ 100 Amps. 4 or 6 electrodes. Dredge penetration 1 to 5 cm. 15 minute tows Dredge stationary for 40 – 60 seconds to stimulate ensis. Dragged though patch and then halted. Overall 18% of retained razors damaged. ( 8 – 28% by haul) Comparison with published results ( Fahy and Carroll 2007) for hydraulic dredge. 3 bar water pressure to fluidise the sediment to a depth up to 30 cm. 60% of retained razors damaged. No specific information available on the stimulus. Not convinced that “ pulsed” would have been possible without purpose built kit. No one available to give info. By catch included hermit crabs, crangon, pipefish, dab, Goby.

BIM collector rig Short electrodes nesc as handling long ones with the dredge would be unfeasible on anything but large vessels. Stop start trawling very difficult in any weather.