Differences in Otolith Elemental Composition of the Larval Rhinogobius giuhnus (Perciformes, Gobiidae) among Estuaries of Taiwan: Implications for larval Dispersal and Connectance among Metapopulation

摘要

Trace elements in otoliths can be used as biological tracers to identify fish populations, their migratory environmental histories, and larval origins because the elemental composition of otoliths of fish reflects that of the ambient water. The goby Rhinogobius giurinus is one of the dominant species in estuaries of western Taiwan. The seasonal occurrence of larvae of this goby was found to be delayed from south to north. To understand if gobies of different estuaries come from the same population, 89 larvae were collected from the estuaries of Gongshytyan Creek (GST), Tatu River (TT), and Tongkang Creek (TK) in western Taiwan during the period Mar.-Aug. 1998. Ages of the larval goby were examined by examining daily growth increments in otoliths, and the ratios of 12 elements with the Ca concentration of otoliths were analyzed by solution-based inductively coupled plasma mass spectrometry. The daily ages ranged 12-22 d, total lengths 6.37-7.64 mm, and growth rates 0.321-0.548 mm/d, and none of their means significantly differed among estuaries (p > 0.05). On the other hand, however, the majority of ratios of elements to Ca measured in otoliths of larvae significantly differed among estuaries and between months (one-way ANOVA, p = 0.036 to < 0.0001). Jackknife classification using otolith elemental composition indicated that 93.75% -100% of larvae could be successfully assigned to their original estuary and birth month. These results indicate that R. giurnus maintains self-sustaining populations with minimal connection among the estuaries of Taiwan examined. http://zoolstud.sinica.edu.tw/Journals/47.6/676.pdf