Using otolith trace elements as biological tracer for tracking larval dispersal of black porgy, Acanthopagrus schlegeli and yellowfin seabream, A. latus among estuaries of western Taiwan

To understand if the trace elements in the otoliths can be used as a biological tracer for tracking natal origin and dispersal of larval black porgy (Acanthopagrus schlegeli) and yellowfin seabream (A. latus) among estuaries, the fish larvae in 1997, 1998, and 2005 and water samples in 2005 were collected from 3 estuaries on the western coast of Taiwan. The elemental composition in both otoliths of the larvae and water samples were analyzed by a solution-based inductively coupled plasma mass spectrometer (ICP-MS). Temporal and spatial differences were found in some of the measured 12 element/Ca ratios in the larval otoliths. The water elemental composition was also significantly different between estuaries and between flood and ebb tides. 87. 5-100 % of the larvae of both species could be successfully assigned to their sampled estuaries. However, only 20 % of the black porgy collected from TT in 1998 could be successfully assigned to TT and the rest to GST and TK. The low assignment might be due to the mixing by the tidal current because the flood tide comes from the direction of TK in the south and GST in the north and merged in the middle of Taiwan Strait nearby TT. This study demonstrated that the trace elements in the otoliths of the fish have the potential to detect the temporal and spatial variation of environmental conditions in the estuaries and subsequently can be used for tracking the origin of the larvae from different estuaries and their dispersal rate.