Aquatic products
1 The biodiversity of China¡¯s
marine aquatic products and stresses upon it
2 The diversity of China¡¯s
freshwater aquatic resources and threats to it
3 Proteciton of aquatic resources
in China
China is
one of the most abundant aquatic resource countries in the world. The aquatic
yield in China was 25.17 million t in 1995, ranking it first in the world.
The reason
for Chinese fisheries to occupy the front rank is because of its vast expanse
of sea area and numerous rivers, lakes and reservoirs. China borders the
Pacific Ocean to the east and includes the Bohai Sea, the Yellow Sea, the East
China Sea and the South China Sea with a total area of 4.75 million km2,
which covers temperate, warm-temperate, subtropical and tropical zones. Small
and large islands are spread all over the national sea territory and number
more than 7,100. The length of coastline is over 18,000 km, and the island
coastline is more than 14,000 km long. The meandering coastline forms various
bays where there are good habitats and nursery grounds for many living marine
resources.
The inland
waters of China cover 17.47 million ha, of which lakes cover 7.52 million and
reservoirs 2.3 million. There are more than 5,000 rivers each with a drainage
area of over 100 km2. The large and diverse inland waters provide
the necessary conditions for various freshwater living resources.
1 The
biodiversity of China¡¯s marine aquatic products and stresses
upon it
Over 20,278
marine species have been recorded from China¡¯s seas (including Hong Kong, Macao
and Taiwan) and of which aquatic products consist of : fish (3,032), crabs
(734), shrimp (546) and various molluscs (2,557) (including 2,456 shellfish and
101cephalopods) species. In addition, there are 790 species of large commercial
seaweed and 29 mammals. Such a large number of living resources demonstrate the
abundance and diversity of China¡¯s marine aquatic products.
According
to records, there are 1,805 species of fish in China¡¯s seas, belonging to 738
genera, 212 families and 37 orders. Based on distribution patterns, the coastal
marine fish off China comprise 916 Indo-western Pacific species (50.76% of the
total species), 734 north Pacific species (40.66% of the total), and 75 other
species shared by the Atlantic, Indian and Pacific Oceans (4.16% of the total).
Endemic species only distributed along the Chinese coast comprise 80 species
(4.43% of the total). Based on their temperature-adapted attributes, there are
63(3.4%) cold-temperate (4~12¡æ) species, 368 (20.39%) warm-temperate
(12~25¡æ)
species, 1,374(76.1%) warm water (20~25¡æ) species, and 3 boreal
species (0.17%). It is, thus, clear that the marine fish are mainly tropical
and subtropical Indo-western Pacific species. They are widely distributed in
the South and East China Seas, while cold-temperate species, originating from
the north Pacific, dominate the Yellow and Bohai Seas, particularly the central
and northern parts of the former. The Bohai Sea is a semi-enclosed sea which is
a spawning and nursing ground for many commercially important fishes and
shrimps. The Yellow Sea is affected by the interactions of high temperature and
high salinity of the Kuroshio Current and coastal cold-water masses and form the
spawning and feeding grounds of a few boreal species, such as the Pacific
herring (Clupea pallasi), Cod (Gadus macrocephalus) and flatfishes
(Pyeuronectidae). The East China Sea is a more open nearshore ecosystem and the
formation of the well-known Zhoushan fishing ground is due to mixing of the
warm Kuroshio Current and inputting rivers (Yangtze River, Qiantangjiang and
Minjiang). Because the continental shelf is wide in the northern part of the
South China Sea, and where the Pearl and Han Rivers discharge directly into the
area, the northern South China Sea is also a good coastal fishing ground.
There are
numerous endemic species of marine living resources in China. Of these, fish
species make up more than 100. Some species are of high economic value, such as
the fleshy prawn (Penaeus chinensis).
Some species have scientific importance, such as the Lancelet (Branchiostoma belcheri). They are of
critical importance in studying animal evolution.
In spite of
the abundant species and high yield (marine production was 14,391,297 tonnes in
1995), China¡¯s coastal waters are, at present, subjected to serious threats
from various aspects.
a. Overfishing
Since
the 1960s, the number of fishing boats and their horsepower have been
increasing continuously as has the use of modern fishing gear and improved
fishing methods. Coastal and inshore fishery resources have, as a consequence,
been heavily fished and caused the depletion of many stocks. The yield of
traditional fishing targets, such as the Large yellow croaker (Pseudosciaena crocea), Small Yellow
croaker (P. polyactis), Cuttlefish (Pagrosomus
major) and jellyfish (Rhopilema
esculenta), have been sharply declining. Some of these species no longer
have a fishing season. Meanwhile, their numbers and distributions have been
reducing year after year. The decrease in high-valued species has been
accompanied by an increase in low-value species, for example, the main
commercial fish such as Large and Small yellow croaker, Chinese herring (Ilisha elongata), Pomfret (Pampus argenteus) and Jack mackerel (Trachurus japonicus) have already
deteriorated severely and some of them no longer have a fishing value.
Conversely, other, low trophic level, species have replaced them, such as the
Round scad (Decapterus maruadsi),
Scaled sardine (Sardinella zunasi),
Japanese anchovy (Engraulis japonicus),
Half-fin anchovy (Setipinna taty) and
Red gurnard (Lepidotrigla microptera).
The biological characteristics of fish have also changed, for example, the
average age of the spawning populations of Large and Small yellow croaker,
Hairtail (Trichiurus haumela), Red
seabream (Pagrosomus major), Spotted
maigre (Nibea albiflora) and Pomfret
have been reduced from 4~5 years in the 1950s to 1~2 years in the 1980s, with
smaller-sized individuals and earlier maturation. Overfishing affects not only
fish resources, but also the yield of other valuable marine animals, such as
the Fleshy prawn, Sea cucumber (Apostichopus
japonicus), Abalone (Haliotis discus
hannai) and Scallop (Chlamys farreri).
Seaweeds are also subjected to the same adversity. Examples include the
reduction in Gelidium amansii in the
Yellow and Bohai Seas, Enteromorpha
prolifera in the East China Sea, and Gracilaria
verrucosa, Eucheuma sp. and Caloglossa leprieurii in the South China
Sea.
b. Pollution
The
depletion of China¡¯s marine resources started in the mid-1960s when oil
drilling was just beginning, and the drainage of industrial wastewater and
domestic sewage was not so large. Since the 1970s, coastal fishery waters have
been increasingly polluted and water quality has been deteriorating
continuously because of the development of the petroleum industry and the
increasing drainage of industrial wastes and domestic sewage. These threats
have seriously influenced the existence of China¡¯s marine living resource.
Pollution has also caused the eutrophication of the sea. Red tides have
occurred often in the last ten years. The recorded number of red tide species
has reached 127 in China. The occurrence of red tides often leads to a high
mortality of fish, shrimp and shellfish, especially benthic species. This has
seriously threatened biodiversity. For example, there were three production
areas for the clam Scapharca subcrenata in the Bohai Sea, but now there
is only one and this with a decreasing annual yield from 400,000 t to 10,000 t,
due to excessive harvesting and industrial pollution.
c.
Destruction of habitats
The
reclamation of land the sea during the 1960s was extremely harmful to the
biodiversity of coastal waters. As an example, in Fujian Province, the area of
coastal mudflat was 280,000 ha. Of this, 74,600 ha have been reclaimed for
agriculture and an other 17,000 ha for salt pans, accounting for one third of
the total former mudflat area. Many habitats and spawning areas have been lost
as a consequence. The Lancelet which is listed as a Class ¢ònational protected species,
has declined in biomass. The large-scale reclamation of land from the sea has
resulted in a reduction and deterioration in benthic habitats.
d. Side effects of mariculture
Before the
1960s, the marine fishery was mainly dependent on fishing natural stocks. Since
then, mariculture has gradually risen, with production accounting for 14%~15%
of the marine total until the early 1980s, and 28.6% in 1995. The development
of mariculture has given large economic benefits on the one hand, but also
resulted in adverse side effects on the other, one of which is the pollution of
some areas were biodiversity was high but is now low.
Many fishery
species in China have been endangered due, mainly, to overfishing, such as the
Chinese bahaba (Bahaba flavolabiata),
Dugong (Dugong dugon), Red coral (Corallium japonicum), Chambered red
nautilus (Nautilus pompilius), Acorn
worm (Glossobalanus polybronchioporus)
and Saccoglossus hwangtauensis. At present, more than 40 marine species
have become First and Second Class national protected species.
2 The
diversity of China¡¯s freshwater aquatic resources and threats to
it
The total
area of inland water in China is 270,000km2, accounting for 2.8% of
the total territory. According to fishery sector data, there are 795 species
and subspecies of fish in China¡¯s inland waters, excluding brackish water
species in estuaries. They belong to 228 genera, 43 families and 15 orders.
There are more species in the waters of the eastern area, e. g., 381 species of
fish in the Pearl River, 370 species in the Yangtze River (294 freshwater
species and 9 migratory species), 191 species in the Yellow River, and 175
species in the Heilongjiang River systems in northeast China. The number of
species of fish is less in the western part of China, e. g., only about 50
species in Xinjiang and 44 species in Tibet. Other species, including molluscs
and crustaceans also show relatively high richness. These include a large
number of economically important and widely utilized species. In addition,
there are many rare species, such as the Baiji (Lipotes vexillifer), Chinese sturgeon (Acipenser sinensis), Chinese paddlefish (Psephurus gladius), Chinese sucker (Myxocyprinus asiaticus), Reds kate (Dasyatis akajei), Sichuan taimen (Hucho bleekeri), Dali schizothoracin (Schizothorax taliensis), and Chinese mitten crab (Eriocheir sinensis).
Freshwater
aquatic resources in China are also subject to threat from overfishing so that
many commercially important species have become either rare or endangered, such
as the Hilsa herring (Macrura reevesii).
Because of fishing in the estuary and lower reaches of the Yangtze River when
the adult fish migrate into their spawning ground in the upper reaches,
spawning opportunities have been lost so that the biomass declines day by day .
Many stocks have been depleted due to the destruction of their spawning grounds
by reclamation of land from lakes. The following three factors are most harmful
to freshwater fishery resources.
a. Hydraulic structures
The impact
of hydraulic structures on aquatic resources is large. Water conservancy works
have developed vigorously since the foundation of modern China. However,
because of a lack of passing facilities in the construction of reservoirs and
dams, the migratory routes of some fishes, shrimps and crabs have been blocked,
prohibiting their routine migration for spawning and breeding. Their biomasses,
particularly of semi-migratory species such as Black carp (Mylopharyngodon piceus), Grass carp (Ctenopharyngodon idellu), Silver carp (Hypophthalmichthys molitrix), Bighead carp (Aristichthys nobilis), Sheltostshek (Elopichthys bambusa), and White bream (Parabramis pekinensis) has largely decreased, as a consequnece. An
example is Jiangsu Province where river crabs used to teem. Their yield has,
however, declined from about 6,000 t in the early 1950s to 4,650 t in 1959 and
1,700t in 1963. It disappeared from rivers and lakes in this province by the
1970s, owing to the large-scale construction of hydraulic structures.
b. Water pollution
Polluted
rivers and lakes account for 82.3% of the countries total according to
investigations of 532 water systems. Some sections of rivers are seriously
polluted. The northern part of China, with less rainfall, is more serious than
the southern, with more. The discharge of organic polluted waste water consumes
large amounts of oxygen causing fish unconsciousness and death. Heavy metal
pollution is even more harmful to aquatic organisms, for example, the second
Songhuajiang River used to abound in fish, but many commercially important
species have now become rare, and some have even disappeared because a chemical
plant discharged wastewater containing mercury. As a consequence, Grass carp,
Silver carp, Bighead carp, Common carp (Cyprinus
capio), Prussian carp (Carassius
auratus) and the Amur catfish (Silurus
asotus) have become rare, and the Black carp, Black bream (Megalobrama terminalis), Northern pike (Esox lucius) and Ussuri cisco (Coregonus ussuriensis) have disappeared
from the river.
c. Introduction of exotic species
The
successive introduction of fish species from the Yangtze River Pearl River, and
Erqis Rivers to the Tarim River in Xinjiang has increased the number of species
from 15 to 41 since the 1950s. However, the competition for space and food
threatens the existence of the original inhabitants. For example, the number
and distribution of Aspiorhynhus laticeps
and Tarim schizothoracin (Schizothorax
biddulphi) have been reduced and they are now endangered.
3 Protection
of aquatic resources in China
Many
protection measures which could be adopted for other biotic resources, such as
the establishment of reserves, the formulation and enforcement of regulations,
will be discussed in Section 1.3 of Chapter 4. The following measures are aimed
at freshwater aquatic resources.
a. Protection of populations
Some
valuable and rare living resources for fishery aquaculture have declined
rapidly in biomass. For example, the yield of four species of carp (Black carp,
Grass carp, Silver carp and Bighead carp, ¡°China¡¯s so called four domestic
fishes¡±) has now declined from 50% in the mid-1960s to 20%~30% of the total
production of freshwater fish today. It has been demonstrated by research that
protecting natural spawning grounds and the random copulation of spawning stock
are the most effective way to protect fish germplasm resources. An ecological
pool was, therefore, established by China during the ¡°Eighth Five-Year Plan¡± in
the old course of the Yangtze River, but was then partitioned from the river.
It is suggested the old course be half-closed in order to protect the germplasm
resources of the ¡°four domestic fishes¡± and other valuable and rare species.
b. In-vitro storage of germplasm resources
The
techniques of frozen semen and fish embryos be adopted for long-term storage
and sustainable utilization of some rare fish germplasm resources in China. The
storage technique of fish semen in China has already achieved progress and the
frozen semen of the ¡°four domestic fishes¡± has been applied to production
practices, and achieved satisfactory results.