There are a plethora of potential modifications to ground gearsthat might address one or more of the above stated historical con-cerns surrounding penaeid trawling; ranging from simple adjust-ments within existing configurations (e.g. minimising the size andweight of chains) to completely new rigging arrangements. Amongthe latter, one novel ground gear that may have application wasoriginally described by Rose (1999) to test the injury rate of red kingcrab, Paralithodes camtschaticus passing under conventional groundgears in Alaskan benthic fish trawls. This configuration compriseda buoyed footrope supporting an array of vertical chains (expiredU.S. patent number 5517785), and was subsequent refined and pre-liminarily tested (termed the ‘soft-brush’ ground gear) by Sterlingand Eayrs (2007). Intuitively, unlike conventional ground gears thatare dragged in a concave shape across the bottom, the soft-brushground gear and derivatives should have considerably fewer habi-tat impacts because there is no such scraping action. However, aprerequisite to quantifying the extent of any habitat benefits isestimating the engineering and/or catching efficiencies—since anyreduction in either or some standardized index of functional per-formance would preclude industry adoption. We sought to addressthese latter questions here, by testing the hypothesis of no differ-ences in the catching efficiency and engineering performance of ageneric penaeid trawl rigged with three examples of conventionalground gears, and a version of the soft-brush.Prior to staring the work, one consideration that we recognisedwith testing different ground gears is that their attachment viadrops to the trawl effectively precludes obtaining isolated dragmeasurements and removes independence, which could confoundcomparisons. For example, any difference in performance might bedue to altered trawl geometry (i.e. different vertical and horizontalopenings; Broadhurst et al., 2014), rather than the treatments ofinterest. A way to avoid such confounding is to ensure the groundgear remains independent of consistent system geometry; achieved