REDUCING THE BY-CATCH OF JUVENILE FISH (MULLOWAY ARGYROSOMUS-HOLOLEPIDOTUS) USING SQUARE-MESH PANELS IN CODENDS IN THE HAWKESBURY RIVER PRAWN-TRAWL FISHERY, AUSTRALIA

The numbers of prawns and small fish (mulloway) caught by two designs of prawn-trawl codends with square-mesh panels were compared in a mani pulative field experiment in the Hawkesbury River prawn-trawl fishery. Compared with a conventional codend, catches from a codend made entir ely of square meshes showed a 52% reduction in the mean weight of praw ns caught and a 95% reduction in the numbers of mulloway caught. A cod end with the posterior half made of diamond-shaped meshes and the ante rior half made of square-shaped meshes showed no significant differenc e in the catches of prawns compared with the control, but reduced to 4 6% the mean numbers of mulloway caught. There were no differences in t he sizes of prawns and mulloway caught by the half-square and the cont rol codends. The codend made of all square meshes did not catch the sm allest prawns and mulloway available. The results are discussed in ter ms of the probable behaviour of prawns and mulloway in trawls and the possibilities for future developments of these fishing gears. It was c oncluded that there is great potential for square-mesh panels in coden ds to reduce the by-catch of fish such as juvenile mulloway in the Haw kesbury River prawn-trawl fishery while maintaining catches of prawns.