SIMULATED ESCAPE OF JUVENILE SAND WHITING (SILLAGO-CILIATA, CUVIER) THROUGH SQUARE-MESHES - EFFECTS ON SCALE-LOSS AND SURVIVAL

Two laboratory experiments were done to assess effects of simulated es cape through square-meshes on the scale-loss and survival of (i) non-f atigued and (ii) fatigued small sand whiting (Sillago ciliata). In exp eriment 1, non-fatigued fish that were forced through square-meshes (t reatment fish) showed no significant difference in scale-loss compared to fish that did not pass through square-meshes (control fish), altho ugh there was a 50% difference in mean scale-loss immediately posterio r to their maximum height. In experiment 2, fish were fatigued to exha ustion by swimming against a current of 0.7 to 0.8 knots for 15 min. F atigued fish that were then forced through square-meshes showed signif icantly more scale-loss across their entire body than did the fatigued control fish (difference in means of between 67% to 84%). In both exp eriments the total scale-loss on treatment fish was quite low (1.4-4%) and there were negligible mortalities (only 2 treatment fish died in experiment 1) over the duration of each experiment (30 days). We concl ude that the composite square-mesh panel currently used to reduce by-c atch in the NSW oceanic prawn trawl fishery is likely to cause negligi ble damage and mortality of small sand whiting. (C) 1997 Elsevier Scie nce B.V.