SCALE-LOSS AND SURVIVAL OF JUVENILE YELLOWFIN BREAM, ACANTHOPAGRUS AUSTRALIS, AFTER SIMULATED ESCAPE FROM A NORDMORE-GRID GUIDING PANEL AND RELEASE FR OM CAPTURE BY HOOK AND LINE

Two laboratory experiments were done to assess the scale-loss and survival of juvenile yellowfin bream, Acanthopagrus australis after (1) simulated escape through the guiding panel of a Nordmore-grid and (2) release after capture by hook and line. In both experiments the total scale-loss on treatment fish was quite low (<3%). In experiment 1, yellowfin bream that were fatigued to exhaustion and forced to pass through a guiding panel showed significantly more scale-loss at, and posterior to, their area of maximum height than fish that were fatigued but did not pass through the guiding panel (60.5% to 80% difference in means). In experiment 2, fish that were hooked and then released lost significantly more scales across their entire body than did control fish (79% to 87% difference in means). There were negligible mortalities over the duration of experiment 1 (30 days). In experiment 2, all fish in four treatment tanks (40 fish) and one control tank (10 fish) died due to hyperplasia and fusion of gill filaments caused by copepods and protozoan parasites. The results are discussed in terms of the likely stresses incurred by fish due to the fishing gears tested in each experiment and the aquarium systems used.