EFFECTS OF SQUARE-MESH PANELS IN CODENDS AND OF HAULBACK DELAY ON BYCATCH REDUCTION IN THE OCEANIC PRAWN-TRAWL FISHERY OF NEW-SOUTH-WALES, AUSTRALIA

Two experiments were conducted in the New South Wales oceanic prawn-tr awl fishery, 1) by comparing catch from a conventional codend with tha t from two new codend designs with square-mesh panels and 2) by showin g the effects on catches of a short delay in haulback of trawls with s quare-mesh panels. The two new codend designs incorporated panels of n etting (85-mm mesh) sewn such that the meshes were square-shaped (meas uring 7 x 11 bars) and inserted lengthwise and widthwise into the tops of the anterior sections. Simultaneous comparisons among these design s and a conventional codend showed that both designs performed similar ly by significantly reducing the weights of bycatch that would be disc arded (by 46% and 38%, respectively) without significantly reducing th e catch of the prawn Penaeus plebejus. The second experiment showed th at juvenile red spot whiting, Sillago flindersi, an important commerci al finfish, escaped from the square-mesh panels in the trawl during a 10-15 second haulback delay. Trawls without any haulback delay showed no significant reduction in the bycatch of this species. The results a re discussed in terms of the probable behavior of fish in the modified trawls and in terms of the implications that factors such as haulback delay may have on the survival of fish escaping through square-mesh p anels in codends.