Chiers, K.

Decostere, A.

Desender, M.

Polet, H.

Soetaert, M.

Open Marine Archive

Flatfish fishery: impact & challenges 
Soetaert Maarten1,2, Hans Polet2, Annemie Decostere3, Marieke Desender2,3 and Koen Chiers1 
1 Bacteriology & Poultry Diseases, Department of Pathology, Faculty of Veterinary Medicine, Ghent 
University, Salisburylaan 133, B-9820 Merelbeke, Belgium  
E-mail: maarten.soetaert@ugent.be 
2 Institute for Agricultural and Fisheries Research (ILVO), Animal Sciences - Fisheries, Ankerstraat 1, 
B-8400 Oostende, Belgium 
3 Department of Morphology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-
9820 Merelbeke, Belgium 
 
Flatfish are by far the most targeted marine organisms by the Belgian fishermen. Sole (Solea solea) 
and plaice (Pleuronectes platessa) indeed take first place with regard to landings value and landings 
weight, respectively. Both demersal fish species are mainly caught using beam trawls with tickler 
chains. However, this fishing technique has several well known disadvantages including seabed 
disturbance (caused by the deep penetration of the chains in the bottom), excessive discards (due 
to lack of species and size selectivity) and high fuel consumption. Improvements have been made to 
the fishing gear in order to reduce water resistance and to increase selectivity for species and size 
resulting in less fuel consumption and by-catch reduction, respectively. However, these adjustments 
were not assigned as sufficient. Alternative passive techniques such as fly shooting, gill nets or long 
lines are available which are more selective, result in almost no seabed contact and markedly less 
fuel consumption. However, these latter techniques currently are  hardly economically feasible (gill 
nets and long lines) or too dependent on the weather conditions to be fully effective (fly shooting). 
Adequate long-term solutions hence are indispensable to ensure a sustainable and profitable future 
for the flatfish fishery. The most promising alternative meeting both the fisherman’s aspirations 
and the need for ecological progress is pulse fishing. In this fishing technique, the tickler chains are 
replaced by electrodes towing over the sea floor and inducing electrical pulses, which elicit an 
upward movement of the fish enabling its catch without spading the bottom. Pulse fishing, using 
high frequency and voltage pulses, is currently evaluated for catching sole. Hitherto, several plus 
points are discernible in comparison to the classical trawl fishery: marked decrease in seabed 
disturbance, reduction of bycatch of undersized sole and plaice and invertebrate benthos and 
halved fuel consumption (van Stralen, 2005). Unfortunately, also negative effects such as dislocated 
spinal cords, hemorrhages and mortality were observed in certain exposed fish species, especially 
cod (van Marlen et al., 2007; de Haan et al., 2008;). These adverse effects need to be tackled in 
order to be able to define pulse fishing as an environmental friendly fishing technique. Further 
studies hence are needed to define and optimize pulse characteristics for stimulating flatfish that 
are not harmful for (other) exposed marine organisms. 
 
 
References  
de Haan D., B. van Marlen, T.S. Kristiansen and J.E. Fosseidengen. 2009. The effect of pulse 
stimulation on biota. Research in relation to ICES advice. Progress report on the effect on cod. 
Rapport C098/08, Wageningen, Imares. 
van Marlen B., H. van de Vis, D. de Haan, A. van Gool, D. Burggraaf, J. van der Heul and A. Terlouw. 
2009. The effect of pulse stimulation on marine biota. Research in relation to ICES advice. 
Progress report with preliminary results. IMARES rapport C098/07. 
van Stralen M.R. 2005. DE PULSKOR  Samenvatting van het onderzoek naar de ontwikkeling van een 
alternatief vistuig voor de vangst platvis gebaseerd op het gebruik van elektrische stimuli. 
MarinX-rapport 26. 
 
 
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Flatfish fishery: impact & challenges

Flatfish fishery: impact & challenges 
Maarten Soetaerta, Hans Poletb, Annemie Decosterec, Marieke Desenderc, Koen Chiersa 
 aDepartment of Pathology, Bacteriology & Poultry Diseases, Faculty of Veterinary Medicine – Ghent University, Salisburylaan 133 Merelbeke 
bInstitute for Agricultural and Fisheries Research (ILVO), Animal Sciences - Fisheries, Ankerstraat 1, 8400 Oostende, Belgium. 
cDepartment of Morphology, Faculty of Veterinary Medicine – Ghent University, Salisburylaan 133, Merelbeke, Belgium.  
Introduction 
 
Total turnover Belgian fishermen = € 76 million 
• Sole (Solea solea)  
• Plaice (Pleuronectes platessa) 
 
 
 
 
 
 
Mainly caught using beam trawls with  
heavy tickler chains because of their  
high efficiency for sole & plaice 
 
Traditional bottom trawls:  
• seabed disturbance ↗ 
• discards ↗ 
• fuel consumption ↗ 
 
(2010) price (€/kg) catch (10³ kg)  % of turnover 
sole 10.6  3.703 51.4 
plaice 1.3  5.099 8.5 
Alternative fishing methods 
 
Set nets (sole) & flyshooting (plaice)                                                    
• more selective 
• limited seabed contact 
• >50% ↘ fuel consumption 
    
• current fleet is not equipped  
for these techniques 
 
Pulse fishery:  mechanical stimulation  
                    (of tickler chains) 
       
        electrical stimulation (pulses) 
 
• seabed disturbance ↘ 
• bycatch of undersized fish ↘ 
• bycatch of benthos ↘ 
• fuel consumption 50 %  ↘ 
 
Pulse fishery: 2 options 
 
Cramp pulse : currently used for flatfish 
• aims at immobilisation reaction 
• high frequency pulse 
• negative effects such as dislocated 
spinal cords, haemorrhages & mortality 
Step forward but too much side effects? 
 
 
Startle pulse : currently used for shrimps  
• aims at fright reaction 
• elicits an upward movement of flatfish 
• low frequency pulse 
• no negative effects observed till now 
 More acceptable method? 
 
 
Research to be done 
 
Goal:   obtain a low impact startle pulse for flatfish  
 
Step 1:  determine range of ‘safe’ pulse parameters 
• without injuries 
• without mortality 
for sole, cod, brown shrimp & sandworm 
 
 
 
 
Step 2:  finding a ‘safe’ and good scare pulse that 
elicits a great upward movement of the sole 
 
Step 3:  investigate possible negative effects  
(stress & lesions) of this optimized pulse  
on sole, cod, brown shrimp & sandworm 
 
  
Röntgen photo sole 
Take Home Message: 
 
  Beam trawling in its current form is on its return due to a high environmental impact & fuel costs 
  Passive fishery techniques require a total turn-over of the trawl fleet which is unfeasible 
  Pulse fishing can be a great step forward, but the adverse effects need to be tackled first 
 
 
Pulse fishery is the most promising alternative meeting both the 
 fisherman’s aspirations and the need for ecological progress 
Contact: maarten.soetaert@ugent.be 
Acknowledgements: Maarten Soetaert is supported by the IWT 


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