Abstract
ABSTRACTThis paper addresses the relationship between fish and environmental variables from the Seti Gandaki River Pokhara, Nepal. The water bodies previously had higher abundance and distribution of fishes, which are declining probably due to deterioration of abiotic characteristics and degradation of habitat. Five study sites were: three along the main channel and two along the tributaries. Water sampling was conducted fortnightly and fish sampling was done monthly. Altogether 30 species of fishes belonging to 5 orders, 9 families and 24 genera were recorded. The redundancy analysis (RDA) revealed significant correlations between fish assemblage and environmental variables. The first two axes accounted for 44.15% of the variation of which RDA1 explained 30.32% and correlated with conductivity, pH, dissolved oxygen, free carbon dioxide, ortho-phosphate, nitrite and silicates; while RDA2 explained 13.83% and correlated with depth, width, discharge and nitrates. Likewise, RDA1 revealed a gradient from species that require more oxygenated waters of upstream sites (Schizothorax richardsonii, Pseudecheneis eddsi, Naziritor chelynoides, Garra annandalei, Schistura rupecula and Lepidocephalichthys guntea) to less oxygenated urban and downstream sites (Puntius sophore, Pethia conchonius, Barilius bendelisis, Barilius vagra, Garra gotyla, Mastacembelus armatus and Channa orientalis). RDA2 revealed the gradient from species inhabiting urban and downstream sites to upstream sites.
Highlights
There has been a growing global concern among freshwater biologists about the alteration of aquatic ecosystems, rapid deterioration of water quality, destruction of riverine environment, and significant decline in the species diversity and abundance of stream fishes (Shrestha 2008; Zhao et al 2011)
Spatiotemporal variations of abiotic characteristics such as dissolved oxygen (DO) and pH are often higher at upstream but lower at urban and downstream reaches in contrast to free carbon dioxide (F-CO2), conductivity, and compounds of phosphorus (P) and nitrogen (N), which were lower at upstream reaches but higher at urban and downstream reaches due to environmental pollution (Osmundson et al 2002; Kannel et al 2008; Bu et al 2010)
A total of 30 fish species belonging to 5 orders, 9 families and 24 genera were recorded from the Seti Gandaki River Basin (Table 1)
Summary
There has been a growing global concern among freshwater biologists about the alteration of aquatic ecosystems, rapid deterioration of water quality, destruction of riverine environment, and significant decline in the species diversity and abundance of stream fishes (Shrestha 2008; Zhao et al 2011). Most freshwater ecological studies have strongly suggested biological monitoring of waterbodies along with the environmental characteristics (Dudgeon 1999; Wetzel 2001; Wu et al 2011). Spatiotemporal variations of abiotic characteristics such as dissolved oxygen (DO) and pH are often higher at upstream but lower at urban and downstream reaches in contrast to free carbon dioxide (F-CO2), conductivity, and compounds of phosphorus (P) and nitrogen (N), which were lower at upstream reaches but higher at urban and downstream reaches due to environmental pollution (Osmundson et al 2002; Kannel et al 2008; Bu et al 2010). Fish assemblage structure in several studies was best correlated usually with the environmental variables stream size, discharge and free carbon dioxide (Koel and Peterka 2003; Fernandez and Bechara-Conicet 2010; Negi and Mamgain 2013), with.
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