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Non-native fishes are widespread in Hong Kong and many are likely to be established. Extensive field
surveys, literature reviews, and citizen science data were used to determine the diversity, geographic distribution,
potential introduction sources, and known impacts of non-native freshwater fishes in Hong Kong. In total, 95
species, including five...
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... The difference between the numbers of nonnative species present (530) and those that are established (200) could be an indication of the large potential 'introduction debt' China would face if all non-native species became established. In comparison, 49 non-native fishes have found breeding populations in Hong Kong alone (Chan et al., 2023). While the potential introduction debt of that relatively small (~1000 km 2 ) territory is far less than China, 100 non-native species (including five hybrids) have been recorded from Hong Kong, far exceeding the number of natives fishes (65 species; Chan et al., 2023). ...
... In comparison, 49 non-native fishes have found breeding populations in Hong Kong alone (Chan et al., 2023). While the potential introduction debt of that relatively small (~1000 km 2 ) territory is far less than China, 100 non-native species (including five hybrids) have been recorded from Hong Kong, far exceeding the number of natives fishes (65 species; Chan et al., 2023). Furthermore, half of the nonnative species in Hong Kong are breeding in the wild; if the same thing occurred across the rest of China,~270 species might become established, suggesting that there may be a sizeable introduction debt. ...
Globally, population declines of freshwater animals have been consistently greater than counterparts in other realms, making fresh waters hot spots of endangerment—particularly for larger species. Furthermore, biotas have become increasingly homogenized as invasions by non‐native species proceed. These trends are particularly evident in Anthropocene China, where humans have profoundly altered freshwater ecosystems, with serious consequences for fishes and other aquatic vertebrates. Here, I examine the prospects for ‘bending the curve’ or reversing the trend of freshwater fish biodiversity loss in China, focusing on examples from the Yangtze and further south. Much of China's rich fish biodiversity is threatened, but a lack of contemporary surveys means that the conservation status of many species is uncertain, and ~40% of fishes are data deficient. Although nutrient pollution of major rivers has abated recently, poor water quality remains a concern, and the widespread proliferation of emerging contaminants and microplastics can be expected to have unpredictable (but detrimental) effects on the biota. Warmer temperatures will exacerbate the toxicity of micropollutants, and facilitate the spread of non‐native species that have been supplanting native fishes. Extensive dam construction has fragmented major rivers, and has blocked fish migrations, preventing access to spawning sites and leading to population extirpations. Dams limit the ability of fishes to adjust their ranges to compensate for global warming, with increased drought severity and frequency under climate change representing an existential threat. Overexploitation will be reduced by the recent introduction of a 10‐year fishing ban in the Yangtze basin, but dams, flow regulation, emerging contaminants and continuing habitat degradation will stymie any population recovery or significant recovery of biodiversity as a result of the ban. Furthermore, captive breeding and release programmes have failed to restore populations of threatened fishes because poor management of breeding stock has allowed inbreeding or hybridization leading to genetic pollution of wild populations. Other anthropogenic activities, such as large‐scale mining of river sand on the Yangtze flood plain—exacerbated by the sediment‐trapping effects of upstream dams—are persistent obstacles to reversing the trend of fish biodiversity loss in China.
... [HKSAR]) listed 28 diadromous fishes (Chan et al., 2023), 8 more than that reported for the mainland (Xing et al., 2016). Undoubtedly, widespread overexploitation and pollution , extensive transformation of coastal habitats (Tian et al., 2016), and proliferation of dams (98,000 according to Song et al., 2022) will have reduced populations of diadromous fishes in China. ...
... Nonetheless, small barriers have been consistently shown to impede fish passage (see Holmquist et al., 1998;Jellyman & Harding, 2012;Rolls, 2011), but studies of their effects in Asia are limited, with most research undertaken in Japan (e.g., Katano et al., 2006;Morita et al., 2009). Evidence from Japan (Katano et al., 2006) and New Zealand (Baker, 2003;Doehring et al., 2011;Franklin & Gee, 2019) indicates that low barriers can be highly deleterious for small-bodied diadromous fishes; this is significant because the relatively diminutive gobies, eleotrids, and kuhliids constitute the majority of diadromous species in Asia (Chan et al., 2023;Chou et al., 2020;Xiong et al., 2018;Yuma et al., 1998). ...
... Immigration of catadromous eels (Kawakami et al., 1998;Itakura & Wakiya, 2020), kuhliids (Oka & Tachihara, 2008), and anadromous puffer fishes (Yang & Chen, 2008) occurs at this time. It is also the active period for amphidromous gobies, which are a major component of the diadromous fish fauna in Hong Kong (Chan et al., 2023) and Japan (Yuma et al., 1998). They generally have lower abundance, recruitment, and feeding activity in winter (Iida et al., 2013;Shiao et al., 2015), with peak migration periods during the wet season (Dinh et al., 2017). ...
China has experienced substantial coastal reclamation and damming of rivers. These changes have the potential to impact migrations of diadromous fishes between the sea and fresh waters, but the composition of these fishes and the impacts of barriers to their movement in China have received little attention. We inventoried the species composition and distribution of diadromous fishes, and the impacts of barriers on them, in the Hong Kong Special Administrative Region (HKSAR), southern China. Fish assemblages were surveyed using hand‐nets, supplemented by cast‐netting and single‐pass snorkel surveys, in 24 small coastal streams across three regions. Surveys were undertaken on multiple occasions during the wet and dry seasons to account for the monsoonal tropical climate. Twenty‐eight diadromous fishes were collected, mostly gobies, amounting to over half (53%) of the total richness of primary freshwater fishes; four additional species are known from literature records. Diadromous richness was 48% greater during the wet season, when all species were encountered. Richness varied substantially among streams, from a maximum of 17 (2 streams that were diversity hot spots) to none (3 streams). The most widespread diadromous fish was Glossogobius giuris (71% frequency of occurrence), followed by Mugil cephalus (58% occurrence) and Eleotris oxycephala (50% occurrence). The remaining 25 diadromous fishes occurred in fewer than half of the streams; 12 species were confined to a single stream and may be locally threatened. There were conspicuous spatial differences in diadromous assemblages across HKSAR, despite its limited extent (1114 km²), the proximity of the surveyed streams, and the broad geographic distribution of most species. Regional species assemblages were influenced by localized habitat characteristics, with a noticeable distinction between areas with and without large, fast‐flowing, and highly oxygenated streams. The presence of in‐stream barriers (weirs: 0.3–8.7 m high) did not affect spatial patterns in species assemblages, although, on average, diadromous richness was lower in weir‐obstructed streams (4.0 vs. 6.9 species in unobstructed streams). In total, 18 species were confined to unobstructed streams or sections below weirs, whereas the remaining 10 species were recorded both above and below weirs. Only the mottled eel (Anguilla marmorata) and a goby (Stiphodon multisquamus) were able to ascend weirs over 2 m. Although at least 400 m of the lower course of each stream was sampled, diadromous fishes were confined to the first 300 m in 12 of the 13 weir‐obstructed streams. Remarkably, the tally of 32 diadromous species in HKSAR exceeds the 19 known from mainland China, highlighting the need for further research on composition and conservation status of diadromous fishes.
... Over the past ten years, numerous studies have reported the presence of Pterygoplichthys outside of their natural range, some identifying the locations of introductions while others describing the growth of existing populations (Wakida-Kusunoki et al. 2016). Some recent reports are from west Bengal of India, Southern India, Bangladesh, Indonesia, Hongkong, Singapore and Malaysia (Hossain et al. 2008;Das et al. 2020;Patoka et al. 2020;Tan et al. 2020;Chan et al. 2023;Parvez et al. 2023). ...
The non-native vermiculated sailfin catfish Pterygoplichthys disjunctivus (Weber, 1991) is recorded for the first time in eastern Nepal's aquatic systems. Native to South America, the first reports of P. disjunctivus in Asia were recorded in India, with subsequent reports from Bangladesh, Hongkong, Indonesia, Malaysia, Singapore, Thailand and Vietnam. Our findings mark the first known occurrence of a non-native species of sailfin catfish in Nepal. The public, policy makers, researchers, and merchants of ornamental fish all need to be informed critically about the release of non-native fish into natural water systems in light of the concerns. Non-native fish may negatively affect native fish populations if released into natural waters. Therefore, it is imperative that strict measures must be taken to prevent the intentional or unintentional escape of non-native fish into Nepal's natural water systems.
... Over the past ten years, numerous studies have reported the presence of Pterygoplichthys outside of their natural range, some identifying the locations of introductions while others describing the growth of existing populations (Wakida-Kusunoki et al. 2016). Some recent reports are from west Bengal of India, Southern India, Bangladesh, Indonesia, Hongkong, Singapore and Malaysia (Hossain et al. 2008;Das et al. 2020;Patoka et al. 2020;Tan et al. 2020;Chan et al. 2023;Parvez et al. 2023). ...
The non-native vermiculated sailfin catfish Pterygoplichthys disjunctivus (Weber, 1991) is recorded for the first time in eastern Nepal's aquatic systems. Native to South America, the first reports of P. disjunctivus in Asia were recorded in India, with subsequent reports from Bangladesh, Hongkong, Indonesia, Malaysia, Singapore, Thailand and Vietnam. Our findings mark the first known occurrence of a non-native species of sailfin catfish in Nepal. The public, policy makers, researchers, and merchants of ornamental fish all need to be informed critically about the release of non-native fish into natural water systems in light of the concerns. Non-native fish may negatively affect native fish populations if released into natural waters. Therefore, it is imperative that strict measures must be taken to prevent the intentional or unintentional escape of non-native fish into Nepal's natural water systems.
... Over the past ten years, numerous studies have reported the presence of Pterygoplichthys outside of their natural range, some identifying the locations of introductions while others describing the growth of existing populations (Wakida-Kusunoki et al. 2016). Some recent reports are from west Bengal of India, Southern India, Bangladesh, Indonesia, Hongkong, Singapore and Malaysia (Hossain et al. 2008;Das et al. 2020;Patoka et al. 2020;Tan et al. 2020;Chan et al. 2023;Parvez et al. 2023). ...
The non-native vermiculated sailfin catfish Pterygoplichthys disjunctivus (Weber, 1991) is recorded for the first time in eastern Nepal's aquatic systems. Native to South America, the first reports of P. disjunctivus in Asia were recorded in India, with subsequent reports from Bangladesh, Hongkong, Indonesia, Malaysia, Singapore, Thailand and Vietnam. Our findings mark the first known occurrence of a non-native species of sailfin catfish in Nepal. The public, policy makers, researchers, and merchants of ornamental fish all need to be informed critically about the release of non-native fish into natural water systems in light of the concerns. Non-native fish may negatively affect native fish populations if released into natural waters. Therefore, it is imperative that strict measures must be taken to prevent the intentional or unintentional escape of non-native fish into Nepal's natural water systems.
Dam construction has fragmented and substantially altered streams globally, obstructing migrations between coastal and freshwater habitats by diadromous animals. We undertook a territory-wide survey of decapod species (shrimps and crabs) in Hong Kong, southern China, examining spatial and seasonal variability in assemblage composition, and the impacts of barriers, across 24 lowland streams. Thirteen diadromous and 10 primary (i.e., non-migratory) freshwater decapod species were recorded, considerably more than reported elsewhere on the Chinese mainland. While some decapods are proficient climbers, six diadromous species were confined to unobstructed streams. Dams (0.3–8.7 m high) reduced total richness, but had stronger effects on diadromous species (mean richness fell from 4.9 to 3.2 species). Mean species richness of both total and diadromous decapods were lowest in streams with dams > 2 m tall (reductions of 6.4 to 3.8 and 4.9 to 2.2, respectively). Decapod assemblage structure was significantly different above and below dams, reflecting the restriction of primary freshwater species to reaches above dams, and diadromous species to reaches downstream of dams. Our findings underscore the need for improved knowledge of the diversity of diadromous animals in China and tropical East Asia, as well as better understanding of mitigation measures to improve dam passage by these animals.
