Bycatch and Trawl Efficiency Series
How fuel costs could be reduced by >30% and bycatch by >90%

As part of the ACPF and FRDC funded project to explain bycatch reduction and trawl efficiency research results in fisheries, Steve Keneally, Matt Broadhurst and Steve Eayrs share options to reduce bycatch and trawl efficiency.

Please note that in episode 1 a summary of findings is given first.
Further episodes to come are:

  • Bycatch globally
  • Bycatch in Australia
  • Bycatch reduction and codend – BRDs
  • Fuel efficienct bycatch reduction – front end (rig config, boards, sweeps)
  • Fuel efficient bycatch reduction – net mechanics (mesh size, net shape, knot direction)
  • Fuel efficient bycatch reduction – ground gear (ground gear & fish excluders)
  • What are fisheries interested in?
Bycatch and trawl efficiency

SUMMARY RESULTS

Bycatch and Trawl Efficiency Series | Episode 1: Fuel costs and bycatch reduction

Bycatch Innovation: Fuel costs and bycatch reduction summery

PRESENTATION POINTS: A protocol for LIFE prawn trawling

Bycatch and Trawl Efficiency Series | Episode 1: Fuel costs and bycatch reduction

1.

Select the most appropriate multi-net configuration

  • Choose a conventional configuration with more sleds, less otter boards including: single beam, triple- or quad-rigged trawls.

  • Explore the potential for installing SAFEs between spreading mechanisms and low-impact ground gears.

  • Explore the utility of low-impact ground gears.

2.

Reduce otter-board Angle of Attack (AOA) to ~20 degrees

  • Choose conventional configurations with the lowest stable operating AOA.

  • Explore the potential of retrofitted modifications to existing designs for reducing AOA.

  • Explore the potential for novel designs like the batwing.

3.

Minimise twine area

  • Optimise mesh size and twine diameter for the targeted catches and then reduce trawl body to the shortest practical length by maximising side taper and minimising wing height.

  • Explore the potential for increasing lateral mesh openings at strategic positions, via T45 (square mesh) or T90 panels, as a means for reducing unwanted catches.

  • Explore the potential for minimising twine area via alternative trawl designs like tongue or W-trawls and/or high-order multi rigs.

4.

Optimise spread ratio (SR)

  • Optimise the SR within a defined range for the desired trawl system.

5.

And Slow down!!

  • Towing speed has a huge impact on drag & fuel use.

Through a sequence of trying existing technologies, it should be possible to modify prawn trawls and spreading mechanisms to reduce fuel costs by >30% and bycatches (key fish and small prawns) by >90%.