4.1. Distributions of the non-native fishes and their potential
impacts
Non-native fish species appear to be common and widespread in the
freshwaters of South China, as they were recorded in all eight main
rivers (Table 2). Although not all of the 20 species can be classified
as invaders, all the rivers have been colonized by multiple non-native
fish species.
Of the 20 non-native fish species found, the Nile tilapia, redbelly
tilapia, mrigal carp, North African catfish, and suckermouth catfish are
considered the most successful invaders because: (1) they were found in
all of the studied rivers (Table 2); (2) they have established
self-sustaining populations and can be considered as dominant fish (Fig.
3); and (3) they have negatively impacted native fish species and water
quality (Gu, Hu et al., 2018; Yu et al., 2018). The
marble
goby and
jaguar
cichlid appeared to be successful invaders in the NDJ, WQH and CHJ of
Hainan Island, where they have established natural populations and
impact native species through predation (Figs. 3, 7) (Wang et al., 2012;
Yu et al., 2018). These invasive fishes can cause a series of impacts on
the region’s biodiversity and economy. For example, the invasion of
tilapia in Guangdong Province has caused economic losses in the cultured
and capture fisheries, leading to species exaction, biodiversity loss,
and deterioration of the natural aquatic environment (Gu, Yu, et al.,
2019).