Abstract
Condition index, reproduction and feeding of three non-obligatory riverine Mekong cyprinids namely Hampala dispar, Hampala macrolepidota and Osteochilus vittatus were examined. The samples were from the Nam Ngiep (NN) River and Bueng Khong Long (BKL) Swamp, which are the representative of the lotic- and lentic-environments, respectively. These two habitats lay in the same geographical area but on the opposite banks of the Mekong mainstream. The samplings were conducted between May 2017 and April 2018. There were 365 H. dispar, 259 H. macrolepidota and 298 O. vittatus samples in this study. The condition index of all three species were beyond 90% implying they can live well in both lotic and lentic environments. Reproductions of all three species were taken place in both environments with two peaks at the onset and end of rainy season. The samples from BKL showed early maturation than NN samples in all three (3) species. Feeding plasticity, though dominant by insects, was observed in Hampala spp., while O. vittatus can utilise any available detritus in both environments. Results clearly show that all the three selected non-obligatory riverine fish species can live very well in either lotic or lentic environments and imply that they can adjust themselves to reservoir environment.
Highlights
Non-obligatory riverine fishes are fish species that can adjust their life history strategy to both lotic and lentic environments (Kruk & Penczak 2003; Kruk 2006)
This study aims to investigate the differences in well-being and life history traits, i.e. reproduction and feeding, of three non-obligatory riverine cyprinids viz., Hampala dispar, Hampala macrolepidota and Osteochilus vittatus
This study examined 922 individuals of three Cyprinids, i.e. 365 H. dispar, 259 H. macrolepidota and 298 O. vittatus both in Bueng Khong Long (BKL) and Nam Ngiep (NN) (Table 1)
Summary
Non-obligatory riverine fishes are fish species that can adjust their life history strategy to both lotic and lentic environments (Kruk & Penczak 2003; Kruk 2006). These fishes are reported to be more resistant to changes in flow regimes due to damming and dam operations (Kruk 2006). The potential impact of damming of rivers on disappearance of obligatory riverine fishes is of special importance for the Lower Mekong Basin (LMB), where 11 mainstream dams are planned and at least 71 projects in the tributaries are expected to be operational by 2030 (ICEM 2010). The freshwater fish catch in this basin is about 2 million tonnes annually and accounted for almost 20% of the world’s freshwater capture fish (ICEM 2010)
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