Electric pulse fishing What do we know and what is the research agenda? , A.D. Rijnsdorp & M.M.M. Rasenberg

Introduction

Background  Beam trawl fishery for flatfish (sole & plaice) ● Tickler chain impact on sea bed and benthos ● Small mesh  large bycatch of undersized fish ● High fuel cost (heavy gear and high towing speed)  Pulse trawl ● Since 2009 based on temporary licences ● Indications of an increase of sole catches & decrease bycatch (fish and benthos) ● Reduction in fuel costs: about 50% (lighter gear and lower towing speed)

Regulation

No. of pulse trawlers in the Netherlands 84 licences Experimental phase Targeting flatfish & shrimp

isolator conductor

Electric field: non homogeneous V/m Conductor Isollator

Pulse parameters  Pulse type ● Delmeco ● HFK  Amplitude (V)  Frequency (Hz)  Pulse width (s)  Current settings  Hz, 120 V Amplitude (V) Frequency (Hz) Pulse width (µs) DELMECO HFK

Concerns  Possible adverse effect of electricity on marine organisms ● Mortality ● Injuries ● Ulcers  Increase in fishing efficiency and risk of over-exploitation % dab with ulcers (Belgian coast) (ILVO: Devriese, L., 2014) No evidence that this is caused by the pulse technique

What do we know?

Conducted research  Research started in 1998 and focussed on: ● Catch efficiency & selectivity ● Catch composition ● Effect of electricity on marine organisms ● Ecosystem effects

Catch efficiency & selectivity Comparative fishing experiment in 2011: TX36 (HFK), TX68 (Delmeco), GO4 (Tickler chain beam trawl ) Van Marlen et al. (2014) Fisheries Research

Catch efficiency Tickler chain n=33 Pulse n=2*33 Ratio Puls /tickler Plaice (kg/hectare) % Sole (kg/hectare) % Landings (baskets / hectare) % Discards (baskets / hectare) % Van Marlen et al. 2014

Selectivity (plaice & sole): lower by-catch undersized flatfish Van Marlen et al Schol Tong Catch per unit area swept Pulse / Tickler chain 1:1 Puls lower Puls higher

Catch composition  Self-sampling & observer program  December March 2013  25 pulse trawl vessels Type of fishery PlaiceSole LDC%DCLDC%DC Pulse self- sampling %35615% Pulse observer %32410% Beam trawl (DCF) %29617% Rasenberg et al., 2013, IMARES report C122/13

Effects on marine organisms  Lab experiments (ILVO, University Gent, IMARES)  Exposure 2 sec ● Cod & Sole & Dogfish ● Brown shrimp & Nereis  Measurements ● Survival (2 weeks) & behaviour ● Macroscopic ● X-ray & Histology Uni Gent: Marieke Depestele; Maarten Soetaert; Annemie Decostere; ILVO: Hans Polet; IMARES: Dick de Haan; Bob van Marlen

Experiments: effects on COD  Wild cod ● 4% (1/25)  Aquaculture cod ● 0% (0/145) ● 2% (1/53) ● 17% (5/29) ● 48% (125/260) large cod ● 0% (0/122) small cod

Results of the effect studies Behavioural responseInjuriesMortalityFeeding CodEscape (<20 Hz) Cramp (>20Hz) Epileptic (120V) Fractures Haemorrhages NoResume normal feeding SoleEscape (<20 Hz) Cramp (>20Hz) Epileptic (extreme) NoneNoResume normal feeding Dog-fishEscapeNoneNoResume feeding; deposition viable eggs ShrimpJump (<20 Hz) Cramp (>20Hz) NoneNo- NereismovementNoneNo- Depestele et al (in prep); Soetaert et al (2014) ICES JMS; De Haan et al. (in prep)

Effects on dab: experiment to study ulcers  Three groups of 50 dab  Maximal exposure ● DELMECO (60V) ● HFK (70V) ● Reference group (not exposed)  After 1 week killed and examined for lesions, ulcers, wounds, parasites  No ‘injuries’ observed de Haan et al (in prep)

Ecosystem effects compared to traditional beam trawl  Reduction in ● Bycatch of undersized fish ● Bycatch of benthic invertebrates ● Penetration depth  Trawl path mortality ● Under study  Change in distribution pattern ● Consequences to be studied  Upscaling experimental results to fleet level

Change distribution pulse trawlers: consequences for ecosystem effects Tickler chain beam trawls Pulse trawls

What is still unknown?

Knowledge gaps  Effect on physiology marine organisms (what & why!) ● What type of organisms are sensitive? ● Sensitivity of different life stages ● What is long-term effect on organisms that are exposed repeatedly? ● Effect on electro sense organs (rays and sharks)  Effect on geo-chemistry ● Electrolysis (release of nutrients or contaminants)  Effect on functioning benthic ecosystem  Upscaling effects to fleet level and ecosystem level

Management challenges  What is the range of pulse parameters that is safe for marine organisms?  Technological creep and its implications for sustainable management  Application pulse technique in other fisheries  How to control and enforce the application of pulse techniques?

Research agenda I. Governance research II. Economic performances III. Control and enforcement IV. Ecological effects (in relation with the technique)

Ecological effects: impact assessment 1. Effect on the by-catch of undersized fish 2. Effect of the use of electricity on marine organisms and the marine ecosystem 3. The development of the pulse technique

1. By-catch of undersized fish To what extend does the by-catch of undersized fish change when the sole and plaice quota are fished with a fleet of pulse vessels compared to a fleet of traditional beam trawl vessels? Sub-project 1: Change in by-catch of undersized fish 1.3 Distribution (logbook data, VMS) 1.1 Catch efficiency & selectivity 1.2 Discards monitoring (part of DCF)

2. Effect of electricity on marine organisms and the marine ecosystem 2.1. PhD-1 Lab experiments fish & benthos 2.2. PhD-2 Ecosystem functioning 2.3. PhD-3 Modelling fleet dynamics & ecosystem functioning Sub-project 2: Effect of electricity on marine organisms and the ecosystem 2.4. Field experiments: Effect on seabed ecosystem 2.5. Field strength measurements in situ

3. Development of the pulse technique  Pulse technique is still under development  Changes must be monitored

Synthesis: Impact assessment of the Dutch North Sea pulse trawl fishery targeting flatfish Sub-project 3: Monitoring the development of the pulse technique Sub-project 1: Change in by-catch of undersized fish 1.3 Distribution (logbook data, VMS) 1.1 Catch efficiency & selectivity 1.2 Discards monitoring (part of DCF) 2.1. PhD-1 Lab experiments fish & benthos 2.2. PhD-2 Ecosystem functioning 2.3. PhD-3 Modelling fleet dynamics & ecosystem functioning Sub-project 2: Effect of electricity on marine organisms and the ecosystem 2.4. Field experiments: Effect on sea- bed ecosystem 2.5. Field strength measurements in situ

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