Fish Biodiversity, Endemism, Threats and Conservation in the Qiantang River, China

Wen Xiong1*, Shengao Chen2, Dong Xie3, Qiang Wang4, Yanxia Li5, Lei Pan6, Xiaolei Ren7*, Wei Tang8*, Kang Chen9 and Ross N. Cuthbert10

1College of Life Sciences, Hubei Normal University, Huangshi Key Laboratory of Lake Biodiversity and Environmental Conservation, Huangshi 435002, China

2College of Animal Science, Tarim University, Alar, 843300, China

3Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China

4School of Ecological and Environmental Sciences, East China Normal University, Shanghai 200062, China

5School of Tourism and Event Management, Shanghai University of International Business and Economics, Shanghai 201620, China

6Faculty of Resources and Environmental Science, Hubei University/Regional Development and Environmental Response, Key Laboratory of Hubei Province, Wuhan 430062, China

7Wuhan Yongyesaiboneng Planning Survey Co. Ltd., Wuhan 430070, China

8 Water-Environmental Nanotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China

9College of Life Sciences, Zaozhuang University, Zaozhuang 277160, China

10GEOMAR, Helmholtz-Zentrum für Ozeanforschung Kiel, Kiel, Germany

Wen Xiong and Shengao Chen contributed equally to this study and share first authorship.

ABSTRACT

Freshwater fish diversity is imperiled by multiple stressors with global change, including invasive species and habitat loss. There is an urgent need to establish synthesized baseline information pertaining to current ecological communities to quantify future change and identify habitats to protect. The Qiantang River is the largest river in the Zhejiang Province, located in the southeast of China, with extensive fishery and aquaculture sectors. However, synthetic information on freshwater fish biodiversity and invasions in this region is lacking, impeding conservation efforts. We compile published information and empirical surveys to comprehensively discern the fish community of the Qiantang River. There are 184 (167 native and 17 non-native) freshwater fish species or subspecies, belonging to 15 orders, 38 families and 105 genera in the Qiantang River, including species listed as among the ‘100 world’s worst invasive species. Therein, 24 species are endemic to China and 14 species are classed as endangered by the IUCN. We identify and discuss habitat loss, pollution, sand mining, over-fishing and non-native species as the major threats to freshwater fish biodiversity in this system. Thus, we propose that protected areas and bans on fish introductions, should be adopted and better enforced in this and other freshwater systems.

Article Information

Received 10 April 2022

Revised 15 May 2022

Accepted 07 June 2022

Available online 06 October 2022

(early access)

Published 21October 2023

Authors’ Contribution

WX, SC, DX, QW, YL, LP, XR, WT, KC contributed in the investigation of the research work, methodology, formal analysis, software, data curation, writing the original draft of the manuscript, review, editing, and visualization. WX and XR contributed in the statistical analyses, software, formal analysis, writing review, editing type face, and data curation. WX and WT have contributed in review and editing of the manuscript, visualization and validation. WX, SC, XR and RNC contributed to conceptualization, methodology, resources, supervision, project administration, funding acquisition, and review and editing of the manuscript.

Key words

Biodiversity conservation, Fishery resource, Freshwater fish, Global change, Invasive alien species

DOI: https://dx.doi.org/10.17582/journal.pjz/20220401010414

* Corresponding author: chinaxiongwen@gmail.com, lzurenxl@126.com, tangwei@ihb.ac.cn

030-9923/2023/0006-2877 $ 9.00/0

Copyright 2023 by the authors. Licensee Zoological Society of Pakistan.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

Introduction

Rivers are important freshwater habitats, which comprise some of the most biodiverse areas on the planet (Reid et al., 2019). However, multiple anthropogenic pressures, such as invasive species and habitat loss or fragmentation (e.g., from dam construction, levees, weirs), threaten most lotic habitats (Grill et al., 2019; Haubrock et al., 2021). As a result, over one fifth of freshwater fish species have been listed as endangered or extinct, mainly due to flow modification, overfishing, pollution, and non-native species (Dudgeon et al., 2006). Urgently, monitoring efforts are needed to establish comprehensive community composition information for key rivers, to inform future conservation efforts and quantify invasion risk (Guo et al., 2019).

China is a country with very high aquatic biodiversity, supporting as very rich diversity of freshwater fish (He et al., 2020). In the past one hundred years, many researchers have investigated the freshwater fish biodiversity in China. These efforts have resulted in the identification of hotspots with high fish biodiversity, such as the Pearl River (He et al., 2020), Yangtze River (Fu et al., 2003), Hainan Island (Xiong et al., 2018b) and Leizhou Peninsula (Xiong et al., 2019a). However, ecological information for many regions and systems is lacking, such as Qiantang River, hampering present and future conservation efforts (He et al., 2020).

Qiantang River is the largest river in the Zhejiang Province of China, and is an important freshwater fishery and aquaculture area nationally (Chen, 1990). Since 1930s, investigations into the fish fauna in the Qiantang River have reported information on fish biodiversity; however, the results have been equivocal and are dated, with the number of fish species in the Qiantang River varying considerably among studies, with values of 32 (Wu, 1964), 86 (Lin, 1936), 50 (Mao, 1959), 112 (Lu et al., 1960) reported. However, in recent years, over 300 new species of fish have reported in China (He et al., 2020) and 439 non-native freshwater fish species have been introduced in China (Xiong et al., 2015), necessitating more up-to date accounts of the conservation and invasion status of key freshwater systems. Currently, synthesis, analysis and assessment of fish biodiversity and fishery resources are limited, which in turn limits conservation of freshwater fish and the sustainability of fisheries in the Qiantang River and elsewhere. In this study, we thus compiled and analyzed comprehensive fish data in the Qiantang River. Our main purpose were to (1) provide an updated inventory of fish species in the Qiantang River; (2) identify the endemic and threatened species in the Qiantang River; and (3) to review the main threats to fish biodiversity and provide conservation recommendations.

Materials and Methods

Study area

The Qiantang River is situated in the northwestern part of the Zhejiang Province, China (117°30′- 120°30′E, 28° 00′-30°30′N). The Qiantang River has two important sources: a south source and a north source. The south source is Lan River, originating from the Lianhua Mountain (located at the junction between the Kaihua County of Zhejiang Province and Xiuning County of Anhui Province), and is 530 km in length. The north source is Xin’an River, originating from the Huangshan Mountain, which is over 600 km in length. These two important sources (Lan River and Xin’an River) confluence in the Koumen as Qiantang River and flow north through the Hangzhou Bay, and eventually drain into the East Sea (Fig. 1).

 

The geographical range of the Qiantang River basin is divided into three sub-basins. The upstream from the Meicheng comprise the upper reaches, with a narrow valley and rocky channel and a high gradient. The middle reaches are from Meicheng to Fuyang, and the main stream broadens out from Long River. From Fucheng downward to the estuary of the Qiantang River are the lower reaches; the total area of the Qiantang River is 54349 km2.

The prevailing climate around the Qiantang River is subtropical monsoon, with annual mean temperature of 17℃ and annual precipitation approximately 2000 mm; over 60% of rain falls in the April to September period. Furthermore, interannual fluctuations in precipitation are marked, with ‘wet’ and ‘dry’ years varying by two-to-three times.

Sources of information

We collected and collated information about fish biodiversity in the Qiantang River from field investigation and comprehensive literature review. On the one hand, we conducted over 20 fishery surveys in different seasons from 2010 to 2018. Fish samples were collected with gillnets, cage nets, and electrofishing. Detailed sampling methods are presented in Xiong et al. (2017). On the other hand, the information about fish in the Qiantang River was mainly obtained from two database: We searched for combination of words “freshwater fish” and “Qiangtang River” in the Web of Science (ISI, http://www.isiknoledge.com) and the China National Knowledge Infrastructure (http://www.cnki.net). Furthermore, we opportunistically collected information from Chinese books, such as Fish Resources of Qiantang River (Chen, 1990). These field investigations and literature reviews allowed for the inventorying of the fish species in the Qiantang River. Threatened species were identified according to the red list categories of the International Union for Conservation of Nature (IUCN, www.iucnlist.org) and the China’s Red List of Biodiversity: Vertebrates, Volume V, Freshwater Fishes (Zhang and Cao, 2021).

Results

We identified a total of 184 freshwater fish species or subspecies, belonging to 15 orders, 38 families and 105 genera in the Qiantang River. The full inventory of fish compiled in the Qiantang River is presented in Table I, alongside taxonomic information, non-native species, migratory species, and IUCN statuses. Cyprinidae are the most species rich and endemic families, accounting for 52.1% and 34.7% of total native species and total endemic species of Qiantang River, respectively. More precisely, Psephurus gladius, Formosania stigmata, Niwaella laterimaculata, Acheilognathus imberbis, Acrossocheilus kreyenbergii, Acrossocheilus parallens, Gobiobotia longibarba, Hemiculterella sauvagei, Hemiculterella wui, Pseudorasbora elongate, Saurogobio dumerili, Sinibrama macrops, Salanx longianalis, Rhinogobius cliffordpopei, Siniperca knerii, Siniperca obscura, Siniperca roulei, Siniperca undulata, Hemibagrus macropterus, Tachysurus eupogon, Pseudobagrus albomarginatus, Pseudobagrus ondon, Pseudobagrus tenuifurcatus, and Silurus meridionalis, are endemic to China. Despite the Qiantang River amounting to only 0.5% of the total Chinese land area, it provides suitable habitat for 167 native fishes (about 10% of the total number of Chinese freshwater fishes), including the 24 species endemic to China.

The conservation status of fish species in the Qiantang River has been identified in Table I. A total of 14 fish species are listed as threatened according to IUCN red list criteria or are listed as endangered species in China. We also identified 42 migratory fish species.

In total, we detected 17 non-native fish species, including Cirrhinus molitorella, Cirrhinus mrigala, Labeo rohita, Tinca tinca, Gambusia affinis, Lepomis macrochirus, Micropterus salmoides, Oreochromis niloticus, Oreochromis aureus, Oreochromis mossambicus, Clarias batrachus, Clarias gariepinus, Hypostomus Plecostomus, Ictalurus punctatus, Ameiurus nebulosus, Lepisosteus osseus and Piaractus brachypomus, that occurred in the Qiantang River (Table I). In particular, G. affinis, Oreochromis sp., P. brachypomus, are widely distributed in the diverse freshwater ecosystems of the area (such as wetlands, ponds, rivers, reservoirs and paddies).

Discussion

Threat to fish biodiversity

Freshwater fish species are one of the most threatened animal groups worldwide (Olden et al., 2010; Reid et al., 2019). In China in particular, largely due to habitat loss and biological invasions, freshwater fishes are severely threatened (Xiong et al., 2018b, 2019a); fish biodiversity and fisheries resources have significantly decreased in many waterbodies (Fu et al., 2003; He et al., 2020). The study area, Qiantang River basin, is located in the Zhejiang Province, which is one the fastest growing economic regions in China (NBS, 2020). As a result, many human activities have seriously threatened fish biodiversity in the Qiantang River, including through damming, pollution, sand mining, over-exploitation and non-native species.

The Qiantang River is an important river for many migratory fish species of China. There are 42 migratory fish (36 native and 8 non-native) that have been found in the Qiantang River. Starting with Xin’an Reservoir in 1958 and, nine other large reservoirs thereafter (Fuchunjiang, Wuxijiang, Tongshanyuan, Hengjin, Nanjiang, Chencai, Shibi, Anhua, and Wanyao reservoir), dams were built in the Qiantang River for control flood and the development of hydropower. Then in the 1980s-2000s, a great number of small hydropower stations were built in the upper section of the Qiantang River. These dam and water conservancy projects (sluice gates, dykes, diversion canals etc.) have fragmented the Qiantang River, causing some migratory fish populations to decrease and even go extinct. For example, reeves shad (Tenualosa reevesii) is a high valuable anadromous spawning fish in China; every spring and summer, reeves shad swim upstream from the ocean into the spawning grounds of the Qiantang River for breeding. The highest previous catch of reeves shad was 1574 tonnes in China, however, the catch of this fish species has now reduced to less than 1 tonne nationally and the species has become extinct in the Qiantang River because of damming (Liu et al., 2002). Furthermore, many fish spawning and growth opportunities could be reduced because of low water temperatures (Hao et al., 2017, 2019). For example, the most important Chinese commercial carps (Ctenopharyngodon idella, Hypophthalmichthys molitrix, Mylopharyngodon piceus and Hypophthalmichthys nobilis) have declined after damming in the largest Chinese rivers (Zhang et al., 2012). Thus, water conservancy projects are a primary threat to fish in the Qiantang River.

 

Table I. The list of freshwater fishes in the Qiantang River. a mean non-native freshwater fish species in the Qiantang River; b mean freshwater fish species endemic to China; c mean migratory fish species. IUCN: CR mean Critically Endangered; DD mean Data Deficient; EN mean Endangered; LC mean Least Concern; NE mean Not Evaluated; NT mean Near Threatened; VU mean Vulnerable.

Order/ Family	Scientific name of species	IUCN
Acipenseriformes
Acipenseridae	Acipenser sinensis Gray 1835c	CR
Polyodontidae	Psephurus gladius Martens 1861c	CR
Anguilliformes
Anguillidae	Anguilla japonica Temminck and Schlegel 1846c	EN
	Anguilla marmorata Quoy and Gaimard 1824c	EN
Beloniformes
Hemiramphidae	Hyporhamphus intermedius Cantor 1842c	LC
Clupeidae	Tenualosa reevesii Richardson 1846c	CR
Engraulidae	Coilia nasus Temminck and Schlegel 1846c	LC
	Coilia mystus Linnaeus 1758c	LC
Characiformes
Serrasalmidae	Piaractus brachypomus (Cuvier, 1818)a	NE
Cypriniformes
Balitoridae	Formosania stigmata Nichols 1926b	DD
	Vanmanenia stenosoma Boulenger 1901	DD
Cobitidae	Cobitis rarus Chen 1981	LC
	Cobitis sinensis Sauvage and Dabry de Thiersant 1874	LC
	Niwaella laterimaculata Yan and Zheng 1984b	DD
	Leptobotia pellegrini Fang 1936	LC
	Leptobotia tchangi Fang 1936	DD
	Misgurnus anguillicaudatus Cantor 1842	LC
	Parabotia banarescui Nalbant 1965	LC
	Parabotia fasciatus Dabry de Thiersant 1872	LC
	Parabotia maculosa (Wu, 1939)	LC
	Paramisgurnus dabryanus Dabry de Thiersant 1872	LC
Cyprinidae	Abbottina rivularis Basilewsky 1855	LC
	Acheilognathus barbatulus Günther 1873	LC
	Acheilognathus chankaensis Dybowski 1872	LC
	Acheilognathus hypselonotus Bleeker 1871	LC
	Acheilognathus imberbis Günther 1868b	LC
	Acheilognathus macropterus Bleeker 1871	LC
	Acheilognathus meridianus Wu 1939	LC
	Acheilognathus polylepis Wu 1964	LC
	Acheilognathus taenianalis Günther 1873	LC
	Acheilognathus tonkinensis Vaillant 1892	LC
	Table continued on next column..............
Order/ Family	Scientific name	IUCN
	Acrossocheilus fasciatus Steindachner 1892	LC
	Acrossocheilus kreyenbergii Regan 1908b	LC
	Acrossocheilus parallens Nichols 1931b	LC
	Acrossocheilus wenchowensis Wang 1935	LC
	Aphyocypris chinensis Günther 1868	LC
	Atrilinea roulei Wu 1931	VU
	Belligobio nummifer Boulenger 1901	LC
	Carassius auratus Linnaeus 1758	LC
	Chanodichthys dabryi Bleeker 1871	LC
	Chanodichthys erythropterus Basilewsky 1855	LC
	Chanodichthys mongolicus mongolicus Basilewsky 1855	LC
	Coreius heterodon Bleeker 1864	LC
	Ctenopharyngodon idella Valenciennes 1844c	LC
	Culter alburnus Basilewsky 1855	LC
	Cyprinus carpio Linnaeus 1758c	LC
	Cirrhinus molitorella (Valenciennes, 1844)ac	NT
	Cirrhinus mrigala (Hamilton, 1822)a	LC
	Distoechodon tumirostris Peters 1881	LC
	Elopichthys bambusa Richardson 1845c	LC
	Gnathopogon taeniellus Nichols 1925	LC
	Gobiobotia longibarba Fang and Wang 1931b	DD
	Gobiobotia paucirastella Zheng and Yan 1986	DD
	Gobiobotia tungi Fang 1933	DD
	Hemibarbus labeo Pallas 1776c	LC
	Hemibarbus longirostris Regan 1908	LC
	Hemibarbus maculatus Bleeker 1871	LC
	Hemibarbus qianjiangensis Yu 1990	LC
	Hemiculter leucisculus Basilewsky 1855	LC
	Hemiculter lucidus Dybowski 1872	LC
	Hemiculterella sauvagei Warpachowski 1888b	LC
	Hemiculterella wui Wang 1935	LC
	Hypophthalmichthys molitrix Valenciennes 1844c	LC
	Hypophthalmichthys nobilis Richardson 1845c	LC
	Labeo rohita (Hamilton, 1822)ac	LC
	Megalobrama mantschuricus Basilewsky 1855	LC
	Microphysogobio chenhsienensis Fang 1938	LC
	Microphysogobio fukiensis Nichols 1926	DD
	Table continued on next column..............
Order/ Family	Scientific name	IUCN
	Microphysogobio kiatingensis Wu 1930	DD
	Microphysogobio tafangensis Wang 1935	DD
	Mylopharyngodon piceus Richardson 1846c	LC
	Nipponocypris temminckii Temminck and Schlegel 1846	DD
	Ochetobius elongatus Kner 1867	CR
	Onychostoma barbatulum Pellegrin 1908	NT
	Opsariichthys bidens Günther 1873	LC
	Parabramis pekinensis Basilewsky 1855c	LC
	Plagiognathops microlepis Bleeker 1871	LC
	Pseudobrama simoni Bleeker 1864	LC
	Pseudogobio vaillanti Sauvage 1878	LC
	Pseudohemiculter dispar Peters 1881	LC
	Pseudohemiculter hainanensis Boulenger 1900	LC
	Pseudolaubuca engraulis Nichols 1925	LC
	Pseudolaubuca sinensis Bleeker 1864	LC
	Pseudorasbora elongata Wu 1939b	VU
	Pseudorasbora parva Temminck and Schlegel 1846	LC
	Rhodeus lighti Wu 1931	LC
	Rhodeus ocellatus ocellatus Kner 1866	LC
	Rhodeus sinensis Günther 1868	LC
	Rhynchocypris oxycephalus Sauvage and Dabry de Thiersant 1874	LC
	Sarcocheilichthys kiangsiensis Nichols 1930	LC
	Sarcocheilichthys nigripinnis nigripinnis Günther 1873	LC
	Sarcocheilichthys parvus Nichols 1930	LC
	Sarcocheilichthys sinensis sinensis Bleeker 1871	LC
	Saurogobio dabryi dabryi Bleeker 1871	LC
	Saurogobio dumerili Bleeker 1871b	LC
	Saurogobio lissilabris Bănărescu and Nalbant 1973	LC
	Sinibrama macrops Günther 1868b	LC
	Spinibarbus denticulatus Oshima 1926	LC
	Spinibarbus hollandi Oshima 1919	LC
	Squalidus argentatus Sauvage and Dabry de Thiersant 1874	LC
	Squalidus nitens Günther 1873	LC
	Squalidus wolterstorffi Regan 1908	LC
	Squaliobarbus curriculus Richardson 1846	LC
	Tinca tinca (Linnaeus, 1758)ac	LC
	Toxabramis swinhonis Günther 1873	LC
	Table continued on next column..............
Order/ Family	Scientific name	IUCN
	Xenocypris davidi Bleeker 1871	LC
	Xenocypris macrolepis Bleeker 1871	LC
	Zacco platypus Temminck and Schlegel 1846	LC
Cyprinodontiformes
Adrianichthyidae	Oryzias latipes Temminck and Schlegel 1846	LC
Poeciliidae	Gambusia affinis (Baird and Girard, 1853)a	LC
Lepisosteiformes
Lepisosteidae	Lepisosteus osseus (Linnaeus, 1758)a	LC
Mugiliformes
Mugilidae	Planiliza haematocheila (Temminck and Schlegel, 1845)c	NE
	Mugil cephalus Linnaeus 1758c	LC
Polynemidae	Eleutheronema tetradactylum Shaw 1804c	NE
Osmeriformes
Salangidae	Neosalanx tangkahkeii Wu 1931	LC
	Protosalanx chinensis Basilewsky 1855c	DD
	Salanx ariakensis Kishinouye 1902c	DD
	Salanx longianalis Regan 1908bc	DD
Perciformes
Centrarchidae	Lepomis macrochirus Rafinesque, 1819a	LC
	Micropterus salmoides (Lacepède, 1802)a	LC
Channidae	Channa argus Cantor 1842	LC
Cichlidae	Oreochromis niloticus (Linnaeus, 1758)ac	LC
	Oreochromis aureus (Steindachner, 1864)ac	NE
	Oreochromis mossambicus (Peters, 1852)ac	NT
Eleotridae	Eleotris oxycephala Temminck and Schlegel 1845c	LC
Gobiidae	Acanthogobius hasta Temminck and Schlegel 1845c	NE
	Ctenogobius clarki Evermann and Shaw 1927	NE
	Ctenogobius shennongensis Yang and Xie, 1983	NE
	Glossogobius olivaceus Temminck and Schlegel 1845c	LC
	Mugilogobius abei Jordan and Snyder 1901	LC
	Odontamblyopus lacepedii (Temminck and Schlegel 1845)	NE
	Rhinogobius brunneus (Temminck and Schlegel, 1845)c	DD
	Rhinogobius cliffordpopei Nichols 1925b	LC
	Rhinogobius giurinus Rutter 1897c	LC
	Rhinogobius lentiginis Wu and Zheng 1985	LC
	Taenioides cirratus (Blyth 1860)c	NE
	Tridentiger trigonocephalus Gill 1859	DD
	Table continued on next column..............
Order/ Family	Scientific name	IUCN
Lateolabracidae	Lateolabrax japonicus Cuvier 1828c	NE
Odontobutidae	Micropercops swinhonis Günther 1873	DD
	Odontobutis obscura Temminck and Schlegel 1845	NE
	Odontobutis potamophila Günther 1861	LC
Osphronemidae	Macropodus chinensis Bloch 1790	LC
	Macropodus opercularis Linnaeus 1758	LC
Percichthyidae	Coreoperca whiteheadi Boulenger 1900	NT
	Coreoperca liui Cao and Liang 2013	DD
	Siniperca chuatsi Basilewsky 1855	LC
	Siniperca knerii Garman 1912b	LC
	Siniperca obscura Nichols 1930b	NT
	Siniperca roulei Wu 1930b	VU
	Siniperca scherzeri Steindachner 1892	LC
	Siniperca undulata Fang and Chong 1932b	NT
Pleuronectiformes
Cynoglossidae	Cynoglossus trigrammus Günther 1862	LC
	Cynoglossus semilaevis Günther 1873	LC
Scorpaeniformes
Cottidae	Trachidermus fasciatus Heckel 1839c	EN
Siluriformes
Amblycipitidae	Liobagrus anguillicauda Nichols 1926	DD
	Liobagrus styani Regan 1908	CR
Bagridae	Leiocassis longirostris Günther 1864	DD
	Hemibagrus guttatus Lacepède 1803	LC
	Hemibagrus macropterus Bleeker 1870b	LC
	Tachysurus eupogon Boulenger 1892b	LC
	Tachysurus fulvidraco Richardson 1846	LC
	Tachysurus nitidus Sauvage and Dabry de Thiersant 1874	NE
	Tachysurus vachellii Richardson 1846	DD
	Tachysurus truncatus Regan 1913	DD
	Pseudobagrus albomarginatus (Rendahl, 1928)b	LC
	Pseudobagrus brevicaudatus (Wu, 1930)	DD
	Pseudobagrus crassilabris (Günther, 1864)	LC
	Pseudobagrus ondon Shaw, 1930b	LC
	Pseudobagrus tenuifurcatus (Nichols, 1931)b	NE
	Pseudobagrus tenuis (Günther, 1873)	DD
Clariidae	Clarias batrachus (Linnaeus, 1758)ac	LC
	Clarias fuscus Lacepède 1803	LC
	Clarias gariepinus (Burchell, 1822)ac	LC
Ictaluridae	Ictalurus punctatus (Rafinesque, 1818)a	LC
	Table continued on next column..............
Order/ Family	Scientific name	IUCN
	Ameiurus nebulosus (Lesueur, 1819)a	LC
Loricariidae	Hypostomus plecostomus (Linnaeus, 1758)a	NE
Sisoridae	Glyptothorax fokiensis Rendahl 1925	LC
Siluridae	Silurus asotus Linnaeus 1758	LC
	Silurus meridionalis Chen 1977b	LC
Synbranchiformes
Mastacembelidae	Macrognathus aculeatu Bloch 1786c	LC
	Sinobdella sinensis Bleeker 1870	DD
Synbranchidae	Monopterus albus Zuiew 1793c	LC
Tetraonontiformes
Tetraodontidae	Takifugu ocellatus Linnaeus 1758c	LC
	Takifugu obscurus Abe 1949c	LC

 

Water pollution is additionally a very serious environmental problem in China (Yu et al., 2019). Over the last forty years, vast amounts of contaminants (organochlorine pesticides, heavy metal, microplastics) have polluted water of the Qiantang River (Zhou et al., 2006; Su et al., 2013; Shi et al., 2017). The partial reach of the Qiantang River was particularly seriously polluted in 1990s-2010s (Website, 2020). Further, eutrophication and extreme weather events have induced algae blooms in the Qiantang River (Guo et al., 2018). Nonetheless, over the last ten years, the water quality of the Qiantang River improved slightly (MARA, 2018), but lethal fish events have been still recurrent in the Qiantang River every year (Jia et al., 2010).

Sand mining is an important threat to freshwater biodiversity in the region (Reid et al., 2019). Zhejiang is one of the fastest growing economic regions in China (NBS, 2020). In the past thirty years, the urban area increased by about six times (Cui, 2013). During this time, many illegal sand mining operations were initiated in the upper reach of the Qiantang River and destroyed stream habitats for small fish, such as Ctenogobius shennongensis, Microphysogobio kiatingensis and Cobitis rarus. Moreover, as many small fish (Rhodeus sp. and Acheilognathus sp.) spawn in the gills of freshwater mussels (Mills and Reynolds, 2003), sand dredgers have disrupted spawning habitats and impeded development. As a result, these small fish have been extirpated from the upper reaches of the Qiantang River.

Over-exploitation is a serious and widespread threat to global freshwater biodiversity (Reid et al., 2019). In long term, overexploitation of fisheries resources increasingly common in China (Xiong et al., 2018b; 2019a). The total catch of Qiantang River has increased from 9044 tonnes in 1978 to 159809 tonnes in 2019 (Fig. 2), and almost doubled in the last four years alone. In the Hangzhou reach of the Qiantang River, there are nearly 1000 fishing boats which have registered in the fishery administration. Further there are many illegal fishing boats which catch undocumented fish at night, and these can often employ illegal fishing gear (such as electrofishing and poison) (Xiong et al., 2018b, 2019a). In addition to population declines, the proportion of small individual fish in the catch is increasing and is up to over 70% in some regions of the Qiantang River, illustrating the demographic effects of overexploitation (Hao et al., 2017, 2019).

 

Non-native species are another important threat to freshwater biodiversity (Xiong et al., 2015, 2017; Wang et al., 2016; Reid et al., 2019) Many Chinese waterbodies have experienced very high invasion rates by non-native aquatic species (Xiong et al., 2018a; Wang et al., 2021). In recent years, numerous non-native species were introduced in the Qiantang River for aquaculture. Inevitably, some non-native species have escaped and established invasive populations in the Qiantang River. In particular, P. brachypomus and Oreochromis sp. have become very widely distributed in the Qiantang River. Furthermore, G. affinis has a very long history (over 100 years) in the Qiantang River (Cheng et al., 2018), and this species has become very widespread in adjacent freshwater habitats. The invasion by these non-native fish species has caused the significant decline of native fish species (Xiong et al., 2022). Meanwhile, some non-native aquatic plant species (such as Sagittaria platyphylla and Myriophyllum aquaticum) have formed dense monocultures, decreasing the oxygen in waterbodies and deteriorating water quality (Wang et al., 2020; Xiong et al., 2021). Ultimately, the invasion of these non-native aquatic plants has caused mortality of a great number of fish, while some invasive aquatic plants (such as Alternanthera philoxeroides) provide suitable habitats for some non-native fishes (e.g. G. affinis), thus further facilitating the invasion by non-native fish (Xiong et al., 2019b).

Conservation of fish biodiversity

In total, there have been 1651 freshwater fish species recorded the China (He et al., 2020). Our study system, Qiantang River, while amounting for only 0.5% of the total Chinese land area, provides suitable habitats for 167 native fishes (about 10% of the total number of Chinese freshwater fishes), with 24 species endemic. Therefore, this suggests that Qiantang River is a very important biodiversity hotspot for Chinese freshwater fish.

Approximately one fourth of the total number of fishes is migratory (11 amphidromous fish, nine anadromous fish, six catadromous fish, and 16 potamodromous fish) in the Qiantang River. Thus, the development of conservation measures should give full consideration to the life history strategies of migratory fish species and their habitats transitions. Therein, A. sinensis, P. gladius, A. japonica, C. carpio, H. molitrix, O. mossambicus and T. ocellatus in particular were listed as endangered species by IUCN (Fishbase, 2020), and A. marmorat and T. fasciatus were added to the endangered species of China in 2016. The establishment of conservation areas is the primary measure to protect spawning ground and habitats for these migratory species. This has been seen in other systems with 32 nature reserves having been established for the conservation of the Chinese alligator, bird, and golden monkey, as well as forests, marine ecosystems and, geologic relics in the Zhejiang Province (MEE, 2020), but freshwater river designations are still lacking.

The artificial propagation and release of fish fry is an effective measure to restore and enhance of fishery resources (Kitada, 2018). From 1983, more than 3.5 million individuals of artificially propagated juveniles have been released in the Qiantang River every year, with the main released species including C. auratus, C. dabryi, C. carpio, H. labeo, H. molitrix, H. nobilis, P. pekinensis, H. maculatus, L. longirostris, P. microlepis and A. fasciatus. In the future, further studies should devote attention to the artificial propagation of declining migratory fish (such as Tenualosa reevesii and Trachidermus fasciatus), which are both ecologically-significant and highly valuable fish species, but almost extinct in the Qiantang River.

Fishing bans have been proven as an effective measure for conservation and restoration of fish biodiversity and fishery resources (Li et al., 2014). Fishing bans were promulgated in the Qiantang River for several months in 2019, however, the fishing ban period was very short and many fish fry were caught by fisherman just after the breeding period in July and August. In other areas, however, fishing bans have been established for longer, such as in the Yangtze River, where they have been implemented for over ten years prior to 2020. In turn, fish biodiversity and fishery resources in some regions of the Yangtze River have recovered quickly. Thus, we call on the local government to prolong the fishing bans in the Qiantang River for several years at a time.

Conclusions

Based on our study, the Qiantang River supports a very high freshwater fish biodiversity and a great number of endemic or endangered species. Without action, we anticipate that the number of endangered species will increase in the future, particularly as many fish species have not been evaluated or have been data deficient for a long time. Overall, habitat loss, pollution, sand mining, over-exploitation and non-native species are important threats to local fish biodiversity. Thus, further research and conservation actions should be considered, including establishing nature reserves, artificial propagation and release of declining native fish fry, and fishing bans.

Acknowledgements

Special thanks to editors and two anonymous reviewers whose comments greatly improved the manuscript.

Funding

This research was supported by the project (LFBC1004) of Key Lab of Freshwater Biodiversity Conservation Ministry of Agriculture and Rural Affairs of China, Yangtze River Fisheries Research Institute. RNC acknowledges funding from the Alexander von Humboldt Foundation.

Declarations

Ethical approval

This research was conducted in accordance with ethics committee procedures of animal experiments.

Sampling and field studies

All necessary permits for sampling and observational field studies have been obtained by the authors from the competent authorities and are mentioned in the acknowledgements, if applicable.

Data availability

All data generated or analyzed during this study are included in this article.

Statement of conflict of interest

The authors have declared no conflict of interest.

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