Fig 1.
Multiple net configurations: engineering efficiency is progressively increased with an addition of smaller size nets.
The proposed ‘W’ trawl in twin rig configuration (e) is hypothesised to be a progressive development beyond the quad rig (d).
Fig 2.
Net plans for Florida flyer (top) and ‘W’ trawl (bottom).
Fig 3.
‘W’ trawl attached to the Trawl Evaluation Rig (TER) and placed in the mid-stream section of the flume tank.
Fig 4.
Stretched netting sewn down the centre line with a hanging ratio of 0.707
Table 1.
Tested conditions for flume tank sessions.
Table 2.
Flow speeds tested.
Fig 5.
Otter boards and sled used with the small nets; (a) Florida flyer board, (b) ‘W’ trawl board, (c) ‘W’ trawl sled.
Table 3.
Otter board and sled particulars.
Fig 6.
Drag and in-pull with 95% confidence intervals for standard flyer (SF) and ‘W’ trawls with respect to spread ratio.
Fig 7.
The proportion of drag-transfer through the centre line of the ‘W’ trawl with 95% confidence intervals versus spread ratio.
Fig 8.
Predictions of total drag for standard flyer (SF) and ‘W’ trawl systems, with 95% confidence intervals [from flume tank data].
Fig 9.
Total drag standardised by swept area rate for standard flyer (SF) and ‘W’ trawl system [from flume tank data].
Fig 10.
Total drag for standard flyer and ‘W’ trawl systems with 95% confidence intervals [field results].
Fig 11.
Estimated mean spread ratio with 95% confidence error bars [field results].
Table 4.
Performance of the ‘W’ trawl relative to the standard system, concluding with standardised drag, and 95% confidence intervals.
Fig 12.
Predicted mean catches per tow by mass and numbers for Tiger and Bay prawns, with 95% confidence intervals.
Fig 13.
Predicted mean by-catch weight per tow, with 95% confidence intervals.