Abstract
Rhinogobius formosanus Oshima, 1919 has long been considered an amphidromous goby. However, a landlocked population recently found in the Jingualiao Creek upstream of the Feitsui Reservoir in Taipei suggests that R. formosanus may complete its life in the river. This study aims to verify the habitat use of the landlocked population of R. formosanus collected from the Feitsui Reservoir and an amphidromous population collected in Malian Creek using otolith Sr:Ca ratio analysis. The hypothesis that early life history varies between the landlocked and migratory gobies was also tested. Genetic analyses show that the Feitsui Reservoir and Malian Creek populations are not genetically different. Rhinogobius formosanus from Malian Creek showed high-to-low otolith Sr:Ca ratios suggesting that these specimens spent a planktonic larval stage in the sea followed by a freshwater life at later stages. In contrast, R. formosanus from the Feitsui Reservoir showed constant lower otolith Sr:Ca ratios, implying a landlocked life history of fish in the creek upstream of the reservoir. In addition, the analysis of growth increments showed a longer pelagic larval duration for the fish in the Malian Creek (58.8 days) than those in the Feitsui Reservoir (38.8). Variation of pelagic larval duration in two genetically homogenous populations implies acclimatization to the reservoir by the landlocked gobies. This study shows that R. formosanus, like some other congeners, is capable of adapting to a freshwater landlocked environment in its early developmental stage and supports the hypothesis that landlocked populations may have a shorter pelagic larval duration.
Highlights
Amphidromy is a diadromous behavior that applies to larvae living in the estuary or sea followed by the post-larvae return to a river where the fish are hatched (McDowall 2007)
A total of 20 specimens of R. formosanus were collected from two creeks in northern Taiwan:Jingualiao Creek, which flows into the upstream area of FR, representing a landlocked population with syntopic congeners R. candidianus and R. similis Gill, 1859; and Malian Creek (MLC), representing an amphidromous population with syntopic congener R. similis, directly connected to the sea (Fig. 2; Table 1)
Molecular analyses show haplotypes of FR and MLC populations are mixed without reciprocal monophyly (Fig. 3), implying that gobies of these two populations are conspecific and the observed otolith differences can be considered intraspecific variations
Summary
Amphidromy is a diadromous behavior that applies to larvae living in the estuary or sea followed by the post-larvae return to a river where the fish are hatched (McDowall 2007). 2400 and 18000 km, respectively (Shen and Tzeng 2002; Hoareau et al 2007; McDowall 2007) The dispersal of the former is documented by genetic homogeneity across the distribution range (Watanabe et al 2006; Ju et al 2013), but the later shows high population structure across the Indo-Pacific Barrier (Lord et al 2012). Endemic species, such as Sicyopterus aiensis Keith, Watson & Marquet, 2004 and S. sarasini Weber & de Beaufort, 1915 have relatively shorter PLD’s of c. Endemic species, such as Sicyopterus aiensis Keith, Watson & Marquet, 2004 and S. sarasini Weber & de Beaufort, 1915 have relatively shorter PLD’s of c. 80 days and do not display genetic structure across their distribution areas in Vanuatu and New Caledonia, respectively (Lord et al 2010, 2012)
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