Abstract
The introduction of non-native fish species is known to have adverse effects on aquatic ecosystems, but their effect on plateau lakes is not well studied. In this study, we examined the effect of the Japanese smelt (Hypomesus nipponensis) invasion on the fish assemblage in Lake Erhai, a subtropical plateau lake in southwestern China. Through cluster analysis and non-metric multidimensional scaling (NMDS), we found a significant fish assemblage shift: the population of sharpbelly (Hemiculter leucisculus) fell by 67% in catch per unit effort (CPUE) from 2.262 to 0.741; topmouth gudgeon (Pseudorasbora parva) fell by 52% from 0.61 to 0.29; and icefish (Neosalanx taihuensis) plummeted by 88% from 0.736 to 0.088. Meanwhile, the numbers for crucian carp (Carassius auratus) improved by almost 185% from 1.82 to 3.36. A Pearson correlation analysis showed that these four species significantly correlated with the invasion of the Japanese smelt: sharpbelly (−0.71), topmouth gudgeon (−0.71), icefish (−0.62), and crucian carp (0.81). This study documented the expansion of invasive fish and their effects on native species over time, thus providing a case study of invasive fish as well as a theoretical basis for further research into interspecies interactions.
Highlights
Non-native fish are often introduced to enhance aquaculture and fisheries in freshwater ecosystems [1,2], but many come at a significant ecological, evolutionary, and economic cost [3,4,5]
Our results found that the abundance of Japanese smelt, which is highly selective for large Daphnia zooplankton [47], caused a drastic reduction in the catch per unit effort (CPUE) of small, pelagic icefish, which mainly feed on zooplankton [48,49,50]
We found a significant increase in CPUE for crucian carp, which could be due to the reduction of planktivorous fish, which compete for the same food: benthic macroinvertebrates such as chironomidae and oligochaeta [68]
Summary
Non-native fish are often introduced to enhance aquaculture and fisheries in freshwater ecosystems [1,2], but many come at a significant ecological, evolutionary, and economic cost [3,4,5]. Non-native species cause significant changes to an ecosystem’s nutritional structure [12,13]. Understanding the risks non-native fish pose is necessary to determine how to introduce them without damaging the ecosystem [14]. Subsequent censuses establish a baseline against which to compare its effect on native organisms; detection of an invasive species often occurs after the invasive population has reached a critical threshold and begun to alter the ecosystem
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