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Low impact trawling

Explore the potential of semipelagic trawling as a sustainable alternative to demersal trawling for cod, focusing on adjustable trawl doors, catch regulation, and low-impact practices. Discuss the results and implications of on/off experiments, catch efficiency, and ground gear testing. Highlight the need for future advancements in adjustable trawl doors and effective communication systems.

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Low impact trawling

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  1. Semipelagic trawling/behaviour(PhD) Ground gear Adjustable trawl doors Catch regulation Low impact trawling

  2. Semipelagic trawling/behaviour Can semipelagic trawling be an alternative to demersal trawling for cod- thus reducing seabed impact and energy consumption

  3. Semipelagic trawling/behaviour(PhD) • On/off(doors/sweeps) experiments-2012/2013 • 2012; 7 pairs, high turbidity, cod shoaling/high density, temperature 0.6 C • 2013; 8 pairs, low turbidity, cod close to seabed, low density, 1.6 C

  4. Catch efficiency of semi-pelagic trawl for cod (Gadus morhua) Doors OFF Doors ON Trawl circumference 50 % 10 m 50 % 22 m Seabed Cod are twice as concentrated when the doors are on the seabed, both years

  5. Semipelagic trawling/behaviour(PhD) • Catch 2012; In total 15% higher with doors/sweeps off • Catch 2013: In total 33 % less with doors/sweeps off • Higher horizontal herding(cod entered mainly in the center of the net mouth both years) with doors and sweeps on the seabed, both years • The way forward ?

  6. Ground gear • Objective: Reduce bottom impact • Tested a roller ground gear(2013-2015) onboard research vessel and fishing vessels • The roller gear ”caught” too many stones • Way forward ? –Start with a ”new” concept- adjust existing rockhopper ground gear ?

  7. Adjustable trawl doors • Objective: Manouver pelagic trawl doors vertically and horisontally by opening/closing hatches above and below the towing point(2013-2016) • Obtain optimal rigging of trawls • Obtain same distance from seabed with both doors during semipelagic trawling • Same doorspead with different warp lengths- sampling trawls

  8. Adjustable trawl doors • Results; Pelagic trawl doors can be manouvered both horizontally and vertically by opening/closing the hatches • The way forward; • Need a robust communication system between vessel and the doors

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