THE ENVIRONMENT
special interest are the Hong Kong newt and Romer's tree frog, which have not been recorded elsewhere in the South-East Asian region.
There are more than 200 recorded species and forms of colourful butterflies, several of which, as caterpillars, cause considerable damage to farmers' crops. These include the two commonly found species of cabbage whites, the swallowtails, and the beautiful but less common small blue. Among the many local moths are the giant silkworm moths, including the cynthia, fawn, atlas and moon. The atlas has an average wing span of 23 centimetres and the moon, 18 centimetres.
Of the local plant bugs, two are especially noted for their colour and shape. They are the rare and beautiful spotted tea bug, which has been recorded only on hilltops, and the lantern fly, which has delicately coloured wings and a remarkably long forehead. Dragon and damsel flies are common, as are wasps and metallic-coloured beetles. Of particular interest is the giant red-spotted longhorn beetle which feeds on mountain tallow and wood-oil trees. Many other species of longhorn beetles infest living or weakened trees.
Since its introduction into Hong Kong in 1938, the African giant snail has become a major pest in vegetable crops and gardens. Farmers are also troubled by several types of slug. One of these, veronicella, is a large, black slug sufficiently different from the other slugs to be placed in a separate family.
Aquatic Fauna
Hong Kong lies some 320 kilometres south of the Tropic of Cancer on the southern coast of China. Being at the junction of the vast temperate Palaearctic Japonic zoogeographical regions and the huge Indo-Pacific Province, Hong Kong possesses very diverse varieties of aquatic animals and plants. There are over 150 commercially important species of fish, crustaceans and molluscs.
The waters of Hong Kong can be divided into three sectors. Under the influence of the Zhu Jiang (Pearl River), the biggest river in southern China, the western sector is predominantly brackish. The area to the east is more oceanic while the central sector is transitional between brackish and oceanic. In some localities, notably the Tolo Harbour region, pollution associated with recent rapid urban development has decimated the abundance and diversity of aquatic life. Pollution-sensitive organisms such as coral are now found only in a few clean yet remote oceanic areas in the north east. Nevertheless, various locations still serve as spawning and nursery grounds for many aquatic species, and these in turn attract transient predators such as Spanish mackerel, little tuna, dolphinfish, sailfish and sharks.
Shark sightings have been recorded in Hong Kong waters. Most are small to medium in size and pose little danger to humans. Bigger sharks have occasionally been sighted in Mirs Bay in the north-eastern New Territories.
Four species of whale and eight species of dolphin have hitherto been recorded in Hong Kong waters and strandings occur quite frequently. The black finless porpoise and the Chinese white dolphin are the most common in terms of occurrence. In 1992, seven strandings were reported, three involving black finless porpoise and one pygmy sperm whale. Other sightings included one case each of Chinese white dolphin, striped dolphin and an unidentified whale.
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