304 The Environment
crustaceans, molluscs and other marine life, of which at least 150 species are of fisheries significance.
Situated on the eastern bank of the Pearl River Estuary, Hong Kong receives fresh water from the river, especially in its western waters. The waters on the eastern side, on the other hand, are little influenced by the Pearl River outflow and are predominantly oceanic in nature. This unusual hydrography helps to contribute to the diversity of marine life.
Despite being close to the northern geographic limit for the growth of hard corals, Hong Kong supports 84 species of these. This diversity is quite rich by international standards. A variety of marine fish also breeds in Hong Kong waters. Typical of the eastern waters is the red pargo, one of several sea bream varieties whose fry are abundant along the shore of Mirs Bay in early spring.
Two marine mammal species can be found throughout the year. The Indo-Pacific humpback dolphin, also known as the Chinese white dolphin, is the best known. The other is the Indo-Pacific finless porpoise. The humpback dolphin prefers an estuarine environment and inhabits the western waters of Hong Kong while the finless porpoise lives in the eastern and southern part, where the waters are predominantly oceanic.
To enhance inshore marine resources, the AFCD has installed artificial reefs to improve fishery resources and biodiversity. The Marine Parks programme continues. to be important in protecting and conserving sites of special ecological and conservation value.
Geology and Landforms
Despite its small size, Hong Kong has a unique geology and a great variety of landforms including sea cliffs, sea caves, sea arches, geos, tombolos, wave-built terraces, sea stacks, notches and blowholes.
While most of the hexagonal volcanic rock columns in other regions of the world are composed of basic basaltic lava, those in Sai Kung are made up of acidic silica-rich rhyolitic volcanic rock. Apart from its extraordinary composition, the columns are considered to be unique for their large area (over 100 square kilometres) and size (average diameter of 1.2 metres).
The Northeast New Territories represents the most comprehensive stratigraphy of sedimentary rocks in Hong Kong, ranging from Devonian sandstone and conglomerate aged about 400 million years to Paleogene siltstone formed 55 million years ago. Fossils including ammonite, brachiopod, crinoids and insects have been found in these sedimentary rocks.
Legislation and Nature Conservation
The Director of Agriculture, Fisheries and Conservation, who is also the Country and Marine Parks Authority, is responsible for the conservation of terrestrial and