Proceedings of the Third World Fisheries Congress: Feeding the World with Fish in the Next Millenium—The Balance between Production and Environment
Fishery Biodiversity and Community Structure in the Yellow and Bohai Seas
Bordered by China, North Korea, and South Korea, the Yellow and Bohai seas are located at 32–41°N and 118–126°30′E. A borderline to the East China Sea is commonly drawn from the mouth of the Yangtze River to Cheju Do. The Yellow Sea large marine ecosystem (LME), as internationally defined, also includes the Bohai Sea (Sherman 1992). The shallow continental shelf extends eastward from the Chinese coast; its average depth is 39.6 m and maximum depth about 100 m. This area receives more than 1.6 billion tons of sediment annually from the rivers (Valencia 1988).
This region is one of the most intensively fished areas in the world: about 300 fish, 41 crustacean, and 20 cephalopod species are found. Warm-temperate and warmwater species are dominated among the fishery species; few cold-temperate species are observed in this region. China has increased total annual catch from about half a million tons in the 1950s and 1960s to about 1.5 million tons before the 1990s and about 5 million tons in the late 1990s. Many stocks have collapsed or are depleted, and a shift of dominant species has been observed in these seas (Jin 1996).
In this paper, I present evidence for changes in community structure, the biomass of fishery resources, and fishery diversity in the Yellow and Bohai seas.
Bottom trawl surveys of the Yellow and Bohai seas from the 1950s to the 1990s were used, and landings data from northern China were collected. A classification technique of two-way indicator analysis (TWIA) for defining fish assemblages was implemented by the program TWINSPAN (Hill 1979). The Shannon diversity index (H′) was used to compute fish diversity in the Yellow and Bohai seas (Shannon and Weaver 1949; Ludwig and Reynolds 1988). Graphical representations of species frequency distribution (i.e., dominance curves, so-called K-dominance curves) were plotted (Lambshead et al. 1983; Clarke 1990).
Most fish species spawn in spring in shallow coastal waters, mainly in the Bohai Sea and the west side of the Yellow Sea. They feed in summer and autumn after spawning, then overwinter in the deep waters of the central to southern part of the Yellow Sea.
Long-distance migrations are observed in most pelagic and some demersal species of fish; some even migrate even to the East China Sea for wintering. Flatfishes and rays usually undertake short migrations between shallow and deep waters. Therefore, fish communities vary seasonally. The co-existence of species is due to their similar responses to environmental factors, and seasonal variations in species composition reflect gradual changes in environmental conditions. As a rule, migratory fishes leave the Bohai Sea when the water temperature decreases in winter, then return for spawning and feeding when the water temperature increases in spring.
The Yellow Sea fish resources are made up of two fish assemblages (Figure 1), which are defined by TWIA. The indicator species were pomfret Pampus argenteus, anglerfish Lophius litulon and Erisphex pottii, and Japanese anchovy Engraulis japonicus, which all were in the south in May 1986. In May 1998, sandeel Ammodytes personatus and greenling Hexagrammos otakii were the indicators in the northern Yellow Sea and small yellow croaker Pseudosciaena polyactis and largehead hairtail Trichiurus haumela in the southern Yellow Sea.