THE ENVIRONMENT
slug. One of these, Veronicella, is a large, black sług sufficiently different from the other slugs to be placed in a separate family.
Aquatic Life
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 region 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 types and quantities of aquatic life forms vary according to season and area.
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 northeast. 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.
A number of shark sightings have been recorded in Hong Kong waters. Most are small to medium in size and hence pose little danger to humans. Bigger sharks have occasionally been sighted in Mirs Bay in the New Territories. Nevertheless, there have been no records of sharks attacking bathers in the past 10 years.
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 and strandings. In 1989, there were 10 strandings involving five Black Finless Porpoises, three Chinese White Dolphins, one Common Dolphin and one Striped Dolphin.
In early July, two bathers were attacked by Moray eels while swimming at the gazetted swimming beach at Deep Water Bay. The victims suffered lacerations and were hospital- ised. A trapping operation was immediately mounted by the Agriculture and Fisheries and the Urban Services departments to safeguard public safety. The operation continu- ed for one week until the threat to swimmers was removed and a total of 16 Moray eels had been caught in the area. The captive eels were later released outside Hong Kong territorial waters.
Plant Life
Situated near the northern limit of the distribution of tropical Asian flora, Hong Kong has an abundant variety of plant life. It is estimated that there are about 2 600 species of vascular plants, both native and introduced.
Before the introduction of conservation measures, the hillsides were becoming in- creasingly bare of trees as a result of cutting, burning and exposure to the elements. On most, the only cover was coarse grass or scrub. Now, many slopes, especially those in the water-gathering grounds, have been planted with trees of both local and exotic species. These woodlands and other areas of countryside are protected and, in view of the growing numbers of people spending increasing amounts of their leisure time outdoors, they are
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