Taiwan Strait
Journal
Seas at the millennium - an environmental evaluation
Pages
499-512
Date Issued
2000
Author(s)
Abstract
Taiwan Strait is a passage between the East China Sea to the north and the South China sea to the south. The strait is a shallow shelf with an average depth of about 40 m, but the southern quarter is steep. The Penghu Islands are located in the middle of the strait, the Taiwan Shoal in the southwest, and Kaoping (submarine) Canyon in the southeast. Seventeen rivers in Taiwan flow into the strait. Steady currents in the offshore area and tidal currents along the western coast of Taiwan are two major physical features. In winter, the NE monsoon drives the water in the north strait southward to encounter the northward current from a branch of the Kuroshio, and the merging current flows to the South China Sea. In summer, when the SW monsoon prevails, South China Sea water flows northward and passes all the way through the strait. Along the western coast of Taiwan, the tidal currents flow northward in the southern section and southward in the northern section during flood tides. The current direction reverses during ebb tides. The semi-diurnal tides dominate the currents along the coast. Five types of habitat, including estuaries, sandy beaches, mud flats, lagoons, and coral reefs, exist in the coastal areas of western Taiwan. Estuaries and lagoons are important nursery grounds for many commercial species of fishes, shrimps, and prawns. The wetlands have been exploited for aquaculture; oysters, hard clams and purple clams are the main cultured organisms. Coral reefs in the Penghu Islands and Hsiaoliuchiu are dominated by reef-building corals. The reef areas in the strait are the major fishing grounds of anchovy larval fishery, demersal fish and shrimps. The offshore areas are important fishing grounds for coastal fisheries; major target fishes are mackerel, jacks, grey mullet and clupeoid larvae. The grey mullet fishery is an important seasonal fishery in the strait, generally in December every year. On the other hand, clupeoid larvae are the most abundant fishes in the coastal waters; the peak fishing season of larval anchovies in March and April. Two popular methods for artisanal fishing are beach seine and spear fishing. Major wave directions in the strait induce longshore currents to flow southward in the north strait and northward in the south strait. Generally, Taiwan's coasts have been eroded in the north and south sections of the western coast, while in the middle section, sand is deposited reducing water depth, or even forming new land. In recent years, the impact of groundwater extraction for mariculture has caused serious land subsidence along the littoral zone. There are seven districts on the western coast which suffer from serious land subsidence problems. Most of the population on Taiwan resides on the western side bordering the strait; the western coast with dense population is therefore seriously affected by human activities. Over the last two to three decades, rapid industrialization and population concentration in cities have led to runoff of domestic, industrial and agricultural wastewater, thermal effluents from power plants, pesticides and garbage via rivers to the sea. This has seriously polluted the coastal environment of Taiwan, especially the western coast. In addition, increasing fishing intensity and improved fishing methods have over-exploited the coastal fishery resources, leading to resource degradation. The coastal zone is severely abused by both the private and public sectors, causing serious damage to existing land and water resources, environmental pollution, adverse geographical changes in coastal areas, etc. Currently a wide spectrum of measures, including preventive environmental impact assessment and environmental monitoring programs, have been employed. Coastal resources are protected under a special plan, and seven coastal conservation zones (CCZ) have been established. In addition, three societies are dedicated to promoting public awareness, environmental education, research and conservation activities in Taiwan.
Other Subjects
coastal zone management; environmental assessment; human activity; China; East China Sea; South China Sea
Type
book