Species of Freshwater Fishes and Invertebrates
Found on Lantau Island
Freshwater Fishes
Amphibians
Invertebrates
Whitecheek Goby (Rhinogobius duospilus)
Classification: Chordata > Actinopterygii > Gobiiformes > Gobiidae
IUCN status: Least Concern (LC) (2024)
Red List of China's Vertebrates: Data Deficient (DD)
Whitecheek goby is a small benthic freshwater fish, with a maximum standard length of about 6.2 cm. It is generally greyish brown with extensively dispersed dark pigmentation. This species displays sexual dimorphism, which males have distinctive markings. Male individuals possess several parallel orange-red stripes on the branchiostegal membrane and a pair of dark brown spots on the basal region. Adult males can also be characterised by oblique, parallel dark stripes on the cheek.
This species resides in freshwater streams and mainly preys on benthic macroinvertebrates. Unlike amphidromous fishes, it produces relatively larger eggs. Its larvae can skip the planktonic stage and complete the life cycle entirely within the stream.
Whitecheek goby is recorded across the Pearl River, including Guangdong, Guangxi, and Hong Kong, and extending into the Pearl River Basin in northern Vietnam. It is a common species in Hong Kong, where it is easily encountered in freshwater streams like Tung Chung Stream, Tai Po Kau Nature Reserve, and Shing Mun Reservoir.
Due to dam construction and water pollution, the population trend of whitecheek goby is decreasing. Its visually striking colouration has also attracted the interest of aquarists, leading to active trading on an international scale.
Pterocryptis anomala
Classification: Chordata > Actinopterygii > Siluriformes > Siluridae
IUCN status: Least Concern (LC) (2011)
Red List of China's Vertebrates: Least Concern (LC)
Pterocryptis anomala, a medium-sized native freshwater catfish in Hong Kong, can grow up to 25 cm in total length. Its pale brown body is laterally compressed. The dorsal surface and head sides are uniformly brown, with irregularly distributed dark brown patches throughout the body. This species has a large mouth with three pairs of fleshy barbels. The long brown maxillary barbels extend towards the anterior third of the anal fin. It also possesses an extremely long anal fin that reaches close to the emarginate caudal fin.
It usually inhabits boulder-strewn, fast-flowing freshwater streams. This species is nocturnal, usually concealing itself among rocks and submerged plants during daytime. It may also be found in shaded pools or during overcast days. Small fishes, crustaceans, aquatic insects, and their carcasses are the potential food sources.
This species is distributed in southeast China, ranging from the Minjiang and Zhujiang (Pearl River) drainages southwards to the streams in Hong Kong. Within Hong Kong, it can be found in the New Territories and Lantau Island, although it is seldom encountered on Hong Kong Island.
P. anomala is an indicator species which is sensitive to water pollution. Agricultural and household effluents may have negative impacts on their population levels.
Predaceous Chub (Parazacco spilurus)
Classification: Chordata > Actinopterygii > Cypriniformes > Cyprinidae
IUCN status: Data Deficient (DD) (2012)
Red List of China's Vertebrates: Least Concern (LC)
China Red Data Book: Vulnerable (VU)
Predaceous chub is a small- to medium-sized freshwater fish. It can grow to a maximum length of about 40 cm, although it commonly measures around 10 cm. Its body is elongated and laterally compressed, with pale pink to pale brown colouration. A distinct black band runs along the mid-lateral of the body, coupled with a dark spot at the base of the caudal fin. With maturation, both band and spot tend to become less conspicuous. This species has a wide, terminal mouth without barbel. Its dorsal fin is small and short, while the anal fin is well-developed.
This species is normally found in unpolluted brooks with strong currents. This diurnal species is active during the daytime, engaging in foraging behaviours. It primarily feeds on insects, such as Baetidae, Culicidae and Heptageniidae larvae, along with zooplankton, small crustaceans, and fishes.
Worldwide, this species is recorded in southeastern China, Hainan Island, and Vietnam. In Hong Kong, it has a broad distribution across many unpolluted streams, including Double Dragon River and Tai Po Kau Forest Stream.
Predaceous chub plays a crucial role in mosquito control through its feeding habits. However, local activities such as destructive fishing practices and dam construction probably contributed to population declines, given its high sensitivity to water quality.
Sucker-belly Loach
(Pseudogastromyzon myersi)
Classification: Chordata > Actinopterygii > Cypriniformes > Balitoridae
IUCN status: Least Concern (LC) (2011)
Red List of China's Vertebrates: Data Deficient (DD)
Sucker-belly loach is a small pool-dwelling balitoroid loach, growing to a maximum standard length of about 6 cm. Its depressed body is brownish-yellow, with coarse, blackish-brown horizontal bands and irregular blotches dispersed along the back and sides of the body. It has a depressed head with a ventral mouth. Pectoral and pelvic fins are laterally expanded, which form a ventral sucker-like adhesive disc. This specialised feature facilitates tight adherence to solid surfaces in the fast-flowing streams.
It is usually found in the unpolluted, rapidly flowing stony streams. Its diet is dominated by the unicellular algae, diatoms, and filamentous cyanobacteria that cling to rocky surfaces. It is a fast-growing species with a brief lifespan of around 25 months, suggesting high population turnover rates.
This species is recorded in Southern China, including Guangdong Province and Hong Kong. It is abundant and widespread in Hong Kong, frequently encountered in the streams of Lantau Island, New Territories, and Kowloon, and particularly prevalent in the reservoir catchments and upland streams.
Due to its high abundance and sedentary nature, sucker-belly loach may impact the local stream habitat, typically affecting algal biomass and assemblage composition within the ecosystem.
Striped Stone Loach
(Schistura fasciolata)
Classification: Chordata > Actinopterygii > Cypriniformes > Nemacheilidae
IUCN status: Data Deficient (DD) (2012)
Red List of China's Vertebrates: Data Deficient (DD)
Striped stone loach is a small benthic nemacheilid loach. It can reach total lengths of up to 12 cm, commonly averaging around 6 cm. Its elongated body has a greyish-yellow colouration, characterised by 8 to 19 vertical black bars across the body. It has a flattened head that is slightly wider than it is tall. Ventral mouth bears three pairs of barbels. Pelvic fins are located directly below the origin of the dorsal fin. This species has a less specialised body form and fin structure as compared to balitorid loaches.
This loach generally inhabits freshwater streams with rapid current but also shows tolerance to slightly brackish water. It exhibits a high level of resilience to water pollution, making it adaptable to streams affected by dam construction and pollution.
Striped stone loach can be found in southern China and northern Vietnam. Within Hong Kong, it is frequently observed in upland streams and reservoir catchments, including Tai Tam Upper Reservoir, Pok Fu Lam Reservoir, and Shing Mun Reservoir.
Short-legged Horned Toad
(Megophrys brachykolos)
Classification: Chordata > Amphibia > Anura > Megophryidae
IUCN status: Endangered (EN) (2020)
Megophrys brachykolos is a small-sized toad, reaching up to 5 cm in snout-vent length. Its robust body has a greyish-brown colouration, with a distinct hollow dark triangular marking between eyes. Dorsal surface appears smooth with a few scattered granules and usually exhibits a dark Y-shaped marking at the centre. Upper eyelid has a small horn-like protuberance. Hindlimbs are short, often marked with several horizontal brown lines. Its tadpole is characterised by a funnel-shaped mouth that is as wide as the body when expanded. It is generally brown to dark brown in colour, with a slightly depressed head and body.
This species is nocturnal and typically inhabits the upper reaches of forest streams. Adult individuals generally conceal themselves among crevices, leaf litter, or beneath rocks. They primarily prey on earthworms, ants and other insects. Larvae, on the other hand, reside in aquatic zones, where they filter-feed on surface microparticles.
Short-legged horned toad is recorded in southern China. In Hong Kong, it is abundant on Lantau Island and Hong Kong Island, with occurrence records in various regions such as Tai Ho, Pak Mong, Tai Tam Reservoir and Pofulam Reservoir.
Despite its abundance in Hong Kong, the population of short-legged horned toads faces various threats. Urban development and mosquito control programmes, for instance, pose potential risks to its populations by potentially diminishing the extent and quality of its habitat.
Lesser Spiny Frog
(Quasipaa exilispinosa)
Classification: Chordata > Amphibia > Anura > Dicroglossidae
IUCN status: Least Concern (LC) (2019)
Quasipaa exilispinosa is a medium-sized frog, with a maximum snout-vent length of around 10 cm. Its colouration varies from greyish-brown to reddish-brown, with yellow specks scattered across the dorsal surface. Its stout body is covered with numerous tubercles and granules. Eyes exhibit a prominent dark cross-shaped marking with a black pupil at the centre. Dark bands are present on both front and hind limbs. During the breeding season, males develop short horny spines on the chest and fingers, allowing them to cling tightly onto the female’s body. Its tadpole is brownish-yellow in colour, with three to five black horizontal bands and dark spots at the base of the tail.
This species inhabits mountain streams within forests or shrublands. As a nocturnal species, it seeks refuge under rocks or leaf litter during the daytime and forages at night. It tends to prey on small insects, crustaceans and frogs. It typically breeds in the rainy season and hibernates through the winter.
Lesser spiny frog is an endemic species to South China, with recorded populations in Fujian, Guangdong, Guangxi, Hunan and Hong Kong. Within Hong Kong, this prevalent amphibian is easily encountered in hill streams, such as Sheung Tam Stream and Tai Shing Stream.
Bee shrimp (Caridina cantonensis)
Classification: Arthropoda > Malacostraca > Decapoda > Atyidae
IUCN status: Least Concern (LC) (2013)
Bee shrimp is a typical landlocked freshwater species, reaching up to 26 mm in total length when fully matured. Its small body has yellowish colouration, with a few black spots scattered across ventrolateral regions of the carapace and abdominal somites. It has a long rostrum that extends beyond the second segment of antennular peduncle. First pereiopods are short and stout, contrasting with long and slender second pereiopods. Both sets of pereiopods are equipped with dense simple setae that enable effective brushing and scraping of particulate matter and periphyton from the substratum.
This species usually inhabits mountain streams and rivulets. It mainly feeds on periphyton, fine-particulate organic matter, and leaf litter. As a fully aquatic species, it completes its entire life cycle within freshwater environment. It exhibits an abbreviated larval development that enables it to skip planktonic stages and directly hatch into juveniles.
Worldwide, this species is recorded in southern China and Vietnam. In Hong Kong, it is prevalent and widespread in various streams, such as Pak Ngau Shek, Kap Man Hang, and Pak Tam Chung.
Although bee shrimp are highly abundant in Hong Kong, anthropogenic activities pose a potential threat to their population. Recent studies showed that their genetic structures are highly differentiated among streams, with limited dispersal ability across these water bodies. The construction of dams and pollution could lead to a permanent loss of genetic diversity within their populations.
Crane river prawn
(Macrobrachium formosense)
Classification: Arthropoda > Malacostraca > Decapoda > Palaemonidae
IUCN status: Least Concern (LC) (2013)
Crane river prawn, a medium-sized freshwater shrimp, can reach a total length up to 12 cm. Their body colouration typically ranges from bluish-brown to reddish-brown and deep blue. It has a roughened carapace, which is approximately one-third of its total length. Its long rostrum extends beyond the end of the antennular peduncle. Second pereiopods are robust and extremely long, reaching half of the total length. These prominent pereiopods have 2 teeth on the cutting edge of fingers. Cephalothorax, abdomen, and telson are densely covered with microspinules.
This species predominantly inhabits brackish waters, ranging from estuaries to hill streams that are linked to the sea. It is an opportunistic feeder, preying not only on small fishes but also consuming algae and dead bodies in the environment. As an amphidromous species, its larvae requires to develop in saline waters. It has a long planktonic larval stage in brackish waters before migrating upstream to become juveniles.
It is recorded in southeastern China, Japan, and Indonesia. It is a widespread species in Hong Kong, where it can be easily observed in streams across the New Territories, Hong Kong Island, and Lantau Island.
Crane river prawn possesses a strong scaling ability, enabling it to overcome waterfalls and barriers. Man-made obstructions such as dams and canals appear to have a lesser impact on its migratory patterns.
Sinolapotamon anacoluthon
Classification: Arthropoda > Malacostraca > Decapoda > Potamidae
IUCN status: Vulnerable (VU) (2008)
Sinolapotamon anacoluthon is a medium-sized freshwater crab with colouration differences between genders. The female's body is dull olive-brown, whereas the male exhibits a blue shade of grey. Its carapace is gently convex, with a sharp epibranchial tooth and a noticeable H-shaped groove. Chelipeds are asymmetric, with one side being larger and more robust. Chela is slender and has many punctae on the outer surface.
This species resides in fast-flowing streams with minimal to no pollution. It is typically found in shaded, shallow areas with a rocky substrate. Terrestrial leaf litter that falls into streams serves as its major food source. It has specialised reproductive strategies that females hatch eggs within their abdomen and release juveniles. During the brooding period, females usually retreat into burrows or seek refuge in cavities beneath stones.
S. anacoluthon is exclusively recorded in Hong Kong and Shenzhen, representing a potential global conservation concern. Within Hong Kong, this species is common in unpolluted local streams such as those within Kwun Yum Shan, Wu Kai Sha, and Tai Po Kau Forest Reserve.
Due to its stenotopic nature, this species is particularly vulnerable to the degradation of clean streams. While some of these streams are situated within country parks or protected areas in Hong Kong, many others are found in unprotected regions facing developmental pressures that demand immediate attention.
Mountain crab
(Nanhaipotamon hongkongense)
Classification: Arthropoda > Malacostraca > Decapoda > Potamidae
IUCN status: Least Concern (2008)
Mountain crab is a medium-sized semi-terrestrial species, reaching up to 4 cm in carapace breadth. Its reddish-orange colouration makes it striking in the freshwater environment. Carapace is convex both anteriorly and posteriorly, with a smooth surface and angular epibranchial tooth. Chelipeds are asymmetric, and the larger manus is slightly longer than the movable finger. Inner borders of fingers possess blunt teeth, fitting together when closed.
It typically inhabits woodland near flowing streams but is sometimes found in terrestrial areas far from streams. This species is largely nocturnal, staying in burrows or under rocks during the daytime. Similar to Sinolapotamon anacoluthon, another freshwater crab commonly found in Hong Kong, it suppresses the planktonic larval stages and hatches directly into juveniles. These reproductive strategies enhance their survival rate in the early stages.
Mountain crab is endemic to Hong Kong and Shenzhen, posing a potential global conservation concern. While it is prevalent in Hong Kong and can be readily found in streams across New Territories, Lamma Island, Lantau Island, and Hong Kong Island, many of those areas are under protected and not listed as conservation areas.
Giant water strider (Ptilomera tigrina)
Classification: Arthropoda > Insecta > Hemiptera > Gerridae
IUCN status: Not Evaluated (NE)
Ptilomera tigrina is a large-sized subtropic water strider that can grow up to 17.5 mm in length. It has dark-brownish body colouration with brownish-yellow marks on pronotum, mesonotum, and metanotum. The body is relatively large, with an elongated abdomen. One of its distinctive characteristics is the presence of a spine on the posterolateral region of the hind coxa. Midlegs possess special hairbrushes, which assist in its movement on the water surface.
This species inhabits a wide range of freshwater habitats, including both lotic and lentic ecosystems. It usually dwells on the water’s surface, searching for potential prey. It primarily feeds on the terrestrial insects that are trapped in the water’s surface. It has also been observed preying on live and partly dead aquatic insects by sucking their body fluids.
Giant water strider is widely distributed from subtropical to tropical regions, such as India, China, Malaysia, Cambodia, Thailand, and Vietnam. It is very common in Hong Kong and is frequently encountered in streams.
This species seems to be highly adapted to polluted environments, living in streams contaminated with plastic waste or agricultural effluents.
Enithares sinica
Classification: Arthropoda > Insecta > Hemiptera > Notonectidae
IUCN status: Not Evaluated (NE)
Enithares sinica is a small aquatic insect, with a maximum length of 9.5 mm. Its boat-shaped body is yellowish-brown, with the posterior half of the pronotum appearing black due to the scutellar colour showing through. Head is rounded with large and reniform eyes that occupy two-thirds of the head. The eye colour varies, ranging from grey to reddish-brown. In males, hind femurs possess a large, sharp tooth, and the outer claw of mid-leg is thickened.
It is commonly found in slow-flowing streams, where it dives and remains stationary in the mid-water, typically 10 to 20 cm below the surface, or anchors itself to a submerged object. This predatory bug mainly feeds on small insects. Its eggs are usually laid and glued to submerged plants.
This species is widespread in subtropical regions, including Japan, China, Taiwan, Laos, Malaysia, Philippines, and Vietnam. Within Hong Kong, it is a very common species that is frequently observed in streams.
Enithares biimpressa
Classification: Arthropoda > Insecta > Hemiptera > Notonectidae
IUCN status: Not Evaluated (NE)
Enithares biimpressa is a small-sized aquatic insect, reaching up to 10.5 mm in length. Its body is convex above, with a yellowish-brown, hyaline, and shiny colouration. Rounded head possess large reddish-brown eyes that occupy two-thirds of the head. The anterior section of the corium is greyish with yellowish-brown vermiculate markings along lateral edges, while the posterior section is black. Different from Enithares sinica, the hind femur in males is simple without a sharp tooth.
It is a predatory insect that utilises its fore and mid legs for hunting. Hind legs typically aid in swimming and maintaining motionless in water bodies. Potential food sources for this insect are small fishes and mosquito larvae. It usually lays eggs on submerged plants for protection.
The distribution of E. biimpressa remains understudied. Currently, it has only been recorded in Hong Kong and Shenzhen. In Hong Kong, this species is prevalent and can be found in New Territories, Lantau Island, and Hong Kong Island.
Afronurus rubromaculata
Classification: Arthropoda > Insecta > Ephemeroptera > Heptageniidae
IUCN status: Not Evaluated (NE)
Afronurus rubromaculata is an aquatic insect that can grow up to 12 mm long, making it larger than other congeners. It is generally yellow-brown in colour, with multiple pale and dark markings throughout the body. Its flattened head has 4 distinct pale-yellow spots along with a row of 4 to 5 smaller spots near its anterior margin. The upper surface of femora is densely covered with robust and pointed setae. It also exhibits a distinctive colour pattern on the abdomen, with pale yellow medially on the terga and reddish laterally.
This species is normally found in clear running water near riparian areas. It is a generalist scraper with a diet primarily composed of periphyton, particulate organic matter, and cyanobacteria.
Globally, this species has been documented in China, Thailand, Vietnam, and Far East of Russia. In Hong Kong, it can be found in New Territories and Lantau Island, such as Lam Tsuen River, Wang Shan Keuk, and Pui O.
Black-banded Gossamerwing
(Euphaea decorata)
Classification: Arthropoda > Insecta > Odonata > Euphaeidae
IUCN status: Least Concern (2011)
Euphaea decorata is the first dragonfly species documented in Hong Kong. It can reach a size up to 42 mm in its adult stage. It has colour variations exist between genders. Adult males are characterised by a broad black transverse band on their wings and a dark body, whereas younger males have dusky yellowish stripes on the body. Adult females, on the other hand, possess wings tinged with amber colouration, lacking distinct markings, and exhibit striking yellow stripes along the body. Preceding metamorphosis, the larvae has a moderately flat body with a large, pentagonal head. During the final larval stage, three conspicuous sac-like saccoid caudal gills along with a flagellum-shaped tail are readily observed.
This species resides in clear, fast-flowing streams across both lowlands and mountains. It is a carnivorous predator with ontogenetic changes in its diet. The smaller larvae mainly feed on chironomid larvae, gradually diversifying their diet to include larger aquatic insects such as chironomids and mayflies. At the adult stage, they tend to target aerial insects like mosquitoes, butterflies and bees. Additionally, it exhabits specific oviposition strategies to protect their eggs from potential threats. Females generally dive underwater, embedding their eggs into the tissues of submerged plants. Males engage in tandem linkage or hover in proximity to their mates to prevent the disruptions from other organisms.
Black-banded gossamerwing is widely distributed in southern China and northern Vietnam. In Hong Kong, it is broadly distribution across mountain streams, such as Wang Chung Stream, Tai Po Kau Forest Stream and Aberdeen Valley.
Large Stream Snail
(Sulcospira hainanensis)
Classification: Mollusca > Gastropoda > Sorbeoconcha > Pachychilidae
IUCN status: Least Concern (LC) (2012)
Sulcospira hainanensis is a large-sized snail that can grow up to 35 mm in shell height. Its shell is thick and conical in shape, with a smooth surface. The colouration of its shell undergoes changes as the snail ages. Younger individuals are pale yellow with brown stripes, whereas older snails are dark grey to black with light patches. As these snails grow, their apex often becomes incomplete, leaving only three to five whorls. Operculum is oval with around six whorls and a central nucleus.
Large stream snail is commonly found in the upper reaches of streams, dwelling on muddy to pebbly substratum among boulders. This species is known as a facultative shredder and grazer, predominantly feeding on periphyton and organic debris. As an ovoviviparous species, its larvae develop within a cephalic brood pouch and hatch directly into juveniles.
This species is recorded in southern China and Hainan Island, while the record in northern Vietnam required further confirmation. Within Hong Kong, it is the most abundant freshwater snail, which can be found in various streams, such as Shing Mun Forest Stream, Pak Ngau Shek Stream and Tai Tso Stream.
Simon F.S. Li Marine Science Laboratory
The Chinese University of Hong Kong
Hong Kong SAR, China