Electric pulse fishing
What do we know and what is the research agenda?
17-11-2014, A.D. Rijnsdorp & M.M.M. Rasenberg
mascha.rasenberg@wur.nl
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
1988
2001
2007
2011
2014
No. of pulse trawlers in the Netherlands
Number of active vessels
90
84 licences
80
70
60
50
40
30
20
10
Experimental phase
0
Targeting flatfish & shrimp
isolator
conductor
Electric field: non homogeneous
V/m
Isollator
Conductor
V/m
V/m
Pulse parameters
 Pulse type
● Delmeco
● HFK
 Amplitude (V)
 Frequency (Hz)
 Pulse width (ms)
DELMECO
Pulse width
(µs)
HFK
 Current settings
 40-80 Hz, 120 V
Frequency (Hz)
Amplitude
(V)
Concerns
 Possible adverse effect of electricity on
● Mortality
● Injuries
● Ulcers
schar
% dab withZweren
ulcersop(Belgian
coast)
4,5
4
% Voorkomen
marine organisms
3,5
3
2,5
Totaal letsels zweren
(ILVO: Devriese, L., 2014)
2
1,5
1
0,5
0
No evidence that this is caused by the pulse technique
 Increase in fishing efficiency and risk of
over-exploitation
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)
1.34
1.26
94%
Sole (kg/hectare)
0.59
0.61
103%
Landings
(baskets / hectare)
0.10
0.08
81%
Discards
(baskets / hectare)
0.59
0.25
43%
Van Marlen et al. 2014
Selectivity (plaice & sole):
lower by-catch undersized flatfish
Schol
Catch
per unit area swept
Pulse / Tickler chain
Puls higher
Tong
1:1
Van Marlen et al. 2014
Puls lower
Catch composition
 Self-sampling & observer program
 December 2011 - March 2013
 25 pulse trawl vessels
Type of
fishery
Plaice
Sole
L
DC
%DC
L
DC
%DC
Pulse selfsampling
37
27
42%
35
6
15%
Pulse
observer
61
66
52%
32
4
10%
Beam trawl
(DCF)
90
87
49%
29
6
17%
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 response
Escape (<20 Hz)
Cramp (>20Hz)
Epileptic (120V)
Injuries
Fractures
Haemorrhages
Mortality
No
Feeding
Resume normal
feeding
Escape (<20 Hz)
Cramp (>20Hz)
Epileptic (extreme)
None
No
Resume normal
feeding
Dog-fish
Escape
None
No
Shrimp
Jump (<20 Hz)
Cramp (>20Hz)
None
No
Resume feeding;
deposition viable
eggs
-
Nereis
movement
None
No
-
Cod
Sole
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
1.1 Catch efficiency
& selectivity
1.2 Discards
monitoring
(part of DCF)
1.3 Distribution
(logbook data, VMS)
2. Effect of electricity on marine organisms
and the marine ecosystem
2.5. Field strength
measurements in
situ
2.1. PhD-1
Lab experiments
fish & benthos
2.2. PhD-2
Ecosystem
functioning
2.4. Field
experiments:
Effect on seabed
ecosystem
2.3. PhD-3
Modelling fleet dynamics
& ecosystem functioning
Sub-project 2: Effect of electricity on marine organisms and the ecosystem
3. Development of the pulse technique
 Pulse technique is still under development
 Changes must be monitored
2.5. Field strength
measurements in
situ
2.1. PhD-1
Lab
experiments
fish & benthos
2.2. PhD-2
Ecosystem
functioning
2.4. Field
experiments:
Effect on seabed ecosystem
2.3. PhD-3
Modelling fleet
dynamics & ecosystem
functioning
Sub-project 2: Effect of electricity on marine organisms and the ecosystem
Synthesis: Impact assessment of the Dutch North Sea pulse
trawl fishery targeting flatfish
Sub-project 1: Change in by-catch of undersized fish
1.1 Catch
efficiency &
selectivity
1.2 Discards
monitoring
(part of DCF)
1.3 Distribution
(logbook data,
VMS)
Sub-project 3:
Monitoring the
development of
the pulse
technique
Questions or feedback?