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Effects of pulse trawls: checking the facts Presentation by prof. dr. A.D. Rijnsdorp, Wageningen University

Prof. Dr. Adriaan D. Rijnsdorp informed the Members of the European Parliament this evening with scientific evidence about the effects of Puls Trawl on the Marine Ecosystem.

15 January, Strasbourg

CONCLUSIONS

Available scientific evidence shows:

Pulse trawls have a smaller ecological impact on the marine ecosystem (footprint, seabed disturbance, benthic impact, discard survival) than beam trawls.

Experiments on the effect of pulses (worst case exposure) did not found adverse effects. The few indications for adverse effects found require further research.

Clear adverse effects have been observed for cod and whiting (fractures). Further research is required to study other species and effect of body size.

THE DISCUSSION

OR

What do we know?

Time trend in fishing effort

Effects of mechanical disturbance

Effects of electrical stimulation

Benthic impact reduced by 50%

Effects of electricity

Five research projects on effect of electricity:

  • 2 PhD-projects Univ Gent (completed);
  • 2 PhD-projects ongoing (Wageningen, NIOZ);
  • Experiments WMR/IMARES

Exposure (worst case) to commercial sole pulse:

  • Fractures induced in cod, but not in other fish species (plaice, sole, dab, sea bass)
  • No lesions found in dab
  • No effect of food detection (catshark)
  • No effect on mortality of worms and shrimps
  • No effect on development / mortality in 6 out of 8 egg/larval stages of cod

Injury rate in commercial samples:

  • ~10% cod; ~2% whiting
  • 0% plaice, sole, dab, sea bass

Survival experiments (Dutch vessels)

Survival of discards (much) better than in tickler chain beam trawl.

Effects on catch efficiency and selectivity

Catch Efficiency = kg fish/m3 trawled area

Catch efficiency pulse / beam trawl (tickler)

  • Higher for sole
  • Lower for plaice and other fish species
  • Much lower for benthos

Logic consequence

  • Bycatch of pulse trawl smaller than beam trawl per kg sole quotum

Size selectivity uncertain

Fact Check

Conclusions

Available scientific evidence shows:

  • Pulse trawls have a smaller ecological impact on the marine ecosystem (footprint, seabed disturbance, benthic impact, discard survival) than beam trawls.
  • Experiments on the effect of pulses (worst case exposure) did not found adverse effects. The few indications for adverse effects found require further research.
  • Clear adverse effects have been observed for cod and whiting (fractures). Further research is required to study other species and effect of body size

Research project: Impact Assessment 2016-2019

Costs: 2.5 m Euro

Marine organisms (Wageningen University)

Response of selected marine organisms to pulse exposure

Benthic ecosystem (NIOZ)

Effect of pulse trawling on functioning and biogeochemistry of benthic ecosystems (short-term and long-term effects)

‘Sea bed’ (Wageningen Marine Research)

Effect of pulse trawling on the fish stocks and benthic ecosystem (North Sea scale)

Synthesis (Wageningen Marine Research)

Effect of transition of tickler chain beam trawl fleet to pulse trawl fleet on bycatch and adverse effects on benthic ecosystem?

Contact:

VisNed: Pim Visser 0031 653146220

Nederlandse Vissersbond: Durk van Tuinen 0031 642408572

Credits:

Flying Focus

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