Incremental technical refinements were made to a generic Nordmøre-grid to minimise bycatches of the giant cuttlefish (Sepia apama), blue swimmer crabs (Portunus armatus) and various teleosts, while maintaining catches of western king prawns (Melicertus latisulcatus) in an Australian prawn-trawl fishery with Marine Stewardship Council accreditation. The Nordmøre-grid changes involved varying bar spaces, escape-exit areas and guiding-panel lengths. Compared to a control, catches of unwanted teleosts and the targeted prawns largely remained unaffected by any of the technical changes—although the quality of the latter was improved. Maximum reductions in unwanted catches of giant cuttlefish and blue swimmer crabs (both ~90%) were achieved by a Nordmøre-grid with 38-mm bar spaces, a large escape exit (>0.8 m2) and a 2.7-m guiding panel. While the fate of escaping cuttlefish and crabs remains unknown, it is likely their survival would exceed that for discards. Through this study we have identified a potential management tool for reducing unwanted bycatches that could be considered in the context of other existing strategies for this fishery involving spatial/temporal closures and on-board handling.