Natural Environment

The watershed of Lam Tsuen river is large and wide. The country parks and steep terrain along the upper course ensure protection from major damage by human activities (though the original forest cover has been cleared). Although the middle and lower courses are affected by human activities, and there are artificial channels, Lam Tsuen River still has high ecological value and biodiversity, and is especially good for fish and dragonflies.



Fish

The large, natural river basin provides fish with abundant places to live and reproduce. Compared to many rivers in Hong Kong, the upper and middle courses of Lam Tsuen River are free from serious pollution. With the food web almost complete, the diversity of fish is higher than in most other local streams.

Channel works and water pollution along the lower course have, however, affected the fish in Lam Tsuen River. Introduced exotic fish also threaten native species such as Swampy Eel (Monopterus albus) and Oriental Weatherfish (Misgurnus anguillicaudatus).



Freshwater Minnow (Zacco platypus)

Sucker-belly Loach (Psuedogastromyzon myersi)


Swampy Eel (Monopterus albus)
 

Dragonflies


There are 114 species of dragonflies in Hong Kong, at least 52 of which can be found in Lam Tsuen.

Ng Tung Chai, southwest Lam Tsuen, spans medium to high elevations above sea level. Dragonflies of Hong Kong's highlands are generally of low diversity, yet the proportion of unique and rare species is relatively high. The streams of Ng Tung Chai are clear and unpolluted, resulting in Ng Tung Chai being home to rare dragonfly species, such as Chinese Mountain Damsel (Calicnemia sinensis), Yellow-spotted Shadowdamsel (Sinosticta ogatai), Chinese Cascader (Zygonyx asahinai), South China Shadow-emerald (Idionyx claudia) and Yellow-spotted Dusk-hawker (Cephalaeschna klotsi). The latter two are even unique to Ng Tung Chai.

She Shan River, a tributary of Lam Tsuen River, also nurtures many rare dragonfly species, including Marauder Clubtail (Labrogomphus torvus), Dog-legged Clubtail (Burmagomphus vermicularis) and Black Riverdarter (Onychothemis testacea), which has only been recorded in She Shan River.

The middle course of Lam Tsuen River is polluted. Hence the dragonfly species found here are more resistant to pollution, such as Marsh Skimmer (Orthetrum luzonicum) and Crimson Darter (Crocothemis servilia).



Ng Tung Chai waterfall, along the Lam Tsuen River


Chinese Mountain Damsel (Calicnemia sinensis)

Indian Copperwing(Mnais mneme)


Marsh Skimmer (Orthetrum luzonicum)
 

Crimson Darter (Crocothemis servilia)
 

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