博士 / 國立臺灣大學 / 漁業科學研究所 / 96 / In order to understand the dispersal of the fish larvae among estuaries in the coastal waters of western Taiwan, the daily growth increments and elemental composition in otoliths of both river-origin amphidromous goby and estuarine-dependent marine sparids were analyzed. Including 10 species of larval gobies in Gongshytyan Creek (GST) in 1997, larval Rhinogobius giurinus in the estuaries of Gongshytyan Creek, Tatu River (TT), and Tongkang Creek (TK) of western Taiwan, larval black porgies Acanthopagrus schlegi in the same three estuaries in 1997, 1998, and 2005, and larval yellowfin seabream A. latus in GST and TT in 1998 and 2005 were collected by Fyke net set against flood tide during night-time spring tide. The water temperature, salinity, and water samples were also measured and collected in both flood and ebb tide during sampling in 2005. 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). Jackknife classification analysis was used to clarify the dispersal and connectance of the metapopulations among estuaries. The results of the findings were listed as follows:
(1) The otolith elemental compositions were significantly different among 10 species of larval gobies. According to the result of PCA, the grouping of the larvae was different from the migratory type of the adults. This indicated that the larvae used similar microhabitat as nursery area, irrespective of different migratory type of the adults. It was also found that some individuals dispersed away from the common habitat. Some vagrant individuals might have drifted away from the population''s normal migratory circuit.
(2) The mean total length, daily age, and growth rate of the larvae including larval R. giurinus, A. schlegi, and A. latus were all not significantly different among estuaries (p > 0.05) except the total length of larval A. schlegi in TK which was shorter than that in GST and TT (p < 0.001).
(3) The discriminant function analysis of otolith elemental composition indicated that 93.75-100% of larval R. giurinus could be successfully assigned to their original estuary and birth month. These indicate that R. giurnus is a self-sustained population with minimum connection among estuaries of Taiwan.
(4) Similarly, 87.5-100 % of the larvae of black porgy and yellowfin seabream could be also successfully assigned to their original estuaries. However, only 20% of the black porgy collected in TT in 1998 could be successfully assigned to TT, the rest 80% were from both GST and TK. The low assignment might be due to the mixing by tidal current because the flood tide came from both TK in the south and GST in the north and then merged in the coast of central Taiwan nearby TT.
(5) Eleven elements (Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb, Ca, Sr, and Ba) in the water samples were detected. The elemental composition of the water samples was significantly different between GST and TT, and between flood and ebb tides, indicating that the water elemental signature is river-dependent and changes with time.
In conclusion, the differences in elemental signature in otolith of the larvae among estuaries may reflect the water chemistry of the estuaries and thus the otolith signature can be used as tracer to track their estuarine origin and dispersal among estuaries. Through the analysis of otolith elemental composition by Jackknife classification of discriminant function analysis, the larvae can be successfully assigned to their estuarine origin. This can help us to delineate the habitat conservation and fisheries management unit of the fish in the coastal waters of Taiwan.
| Identifer | oai:union.ndltd.org:TW/096NTU05451005 |
| Date | January 2008 |
| Creators | MEI-YU CHANG, 張美瑜 |
| Contributors | 曾萬年 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 112 |
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