Relative engineering and catching performances of paired penaeid-trawling systems

Industrial double rig trawl fisheries in the southeastern and southern Brazil: characterization of the fleet, nets and trawl simulation

“…As long as advances are made in the measurements of fuel consumption of the fleet (i.e., using flow meters), it will be possible to associate that consumption to the hydrodynamic resistance (Broadhurst et al, 2013), and thus to have the specific figures of the technological improvements (i.e., reduction in yarn diameter) on the reduction of the used fuel by trawl hour or swept area.…”

Modifying penaeid-trawl spreading mechanisms to improve environmental efficiency

“…Even slight reductions in impacts are potentially beneficial, considering that otter boards leave the most discernible track marks from trawl configurations . However, from a catching perspective, one concern with minimising otter-board bottom contact is that a lower AOA could reduce substrate disturbance and negatively affect catches because penaeids mostly reside in the substrate 2013a;. Further, otter boards are known to herd fish (Wardle, 1989), either through visual or tactile stimuli, and so even subtle variation in their design and AOA might influence species selection by the trawl.…”

“…For example, in an experiment comparing optimised single-, double-, triple-and quad-rigs in a single fishery, Broadhurst et al 575 (2013b) showed that even with the greatest SR, triple rig had lower otter-board and therefore total system contacts (by 29-55% and 2-6%, respectively) than double-and quad-rigs. Similar benefits can be realized by substituting double-with dual-rig (Broadhurst et al 2013a) or using a penta rig, which maintains the triple-rig theme to a higher order.Within any spreading mechanism the sweeps potentially can also impact the substrate (i.e. the 580 sweep connected to the ground gear, which typically operate at an oblique angle of 15-25 o ), with the amount depending on their length and attachment height (usually several cm above the seabed).…”

“…Early configurations (all with the same cumulative headline length) and found that compared to single rig, the multi-trawl configurations reduced drag by 7, 11 and 10%, respectively. In related work, Broadhurst et al (2013a) observed that a dual rig had 24% less drag than a double-rig configuration.These observations also support broad differences proposed by Sterling and Eayrs (2010) When Sterling and Eayrs (2010) first field tested the batwing, the overall drag reduction was assessed as 13% with 5.5% greater SR. Based on these results, it was expected that a later version would require 20-25% less fuel than conventional double-rigged otter boards for the same SAR performance. Subsequent comparative trials by McHugh et al (2015c) support these estimates with 690 mean drag and fuel up to 18 and 14% less than conventional flat-rectangular, kilfoil and cambered otter boards for the same SR and speed.…”

“…by >16% of a double rig); a 830 modification shown to reduce some teleost catches in other trawls (e.g. Rose and Nunnallee 1998).Reduced headline height also reduces drag, while Broadhurst et al (2013a) observed that fewer otter boards may translate to fewer small fish being herded into the trawl.Quad rig encompasses the same three-wire bridle configuration as dual rig, and might return similar benefits in terms of bycatch reduction. One limitation of quad-or penta-rigs is the need for up 835 to five codends, which can increase on-board handling and BRD maintenance.…”