Fish were measured (nearest 0.1 cm TL) and weighed (nearest 0.1 g), then fish were preserved
in 90% ethanol for further otolith daily increment analysis, which assumed due to the occurrence of daily
rings (Morales-Nin, 1989; 1992). At the laboratory, sagittae (i.e., the largest otolith) of individual fish were removed, washed, measured (nearest 0.1 mm) and kept dried in the vial. Then each sagitta was embedded in resin and cut by the low speed diamond saw (South Bay Technology Inc., model: 650). After cutting, each sagitta was polished by sand paper (grit size ranging from 600 to 1500) until the primodium (i.e. core) was seen, then it was further polished to be more transparent by diamond polishing compound, i.e. diamond-pate, for making a clear visibility for “daily ring” to be counted. The numbers of daily ring of each sample was counted under the light microscope with high power (1000x)
by three readers, whom had no information on size of the sample fish.