1、The status of abalone culture in ChinaThe status of abalone culture in ChinaABSTRACT Since 1990 abalone culture has spread widely from north to south on Chinas coast. Estimated total yield for the year 2001 was around 4,500 tonnes (excluding Taiwan). There are several hundreds of abalone farms along
2、 the coast. Some of the bigger farms produce more than 100 t of live abalone each year. The main cultured species are Haliotis diversicolor aquatilis Reeve in the south and H. discus hannai Ino in the north. Additionally H. discus discuss Reeve has been introduced from Japan and hybridized with H. d
3、iscuss hannai. Crossbreeding has been applied in production. Tank culture and floating raft methods are important in the south and north respectively. At present, epidemic virus diseases and Vibrio are the gravest threat. Farms have suffered heavy economic losses as a result of these.KEY WORDS: abal
4、one, culture, ChinaINTRODUCTIONSince the previous review of abalone culture in China, written for the 1989 First International Symposium on Abalone Biology, Fisheries and Culture (Nie 1992) there has been dramatic change. Abalone culture in a mass scale in China began in the mid 1980s. It developed
5、rapidly in the 1990s spreading along the coasts from north to south. Estimated abalone output was about 4,500 tonnes (excluding Taiwan) in 2001, 99% produced by cultivation. Haliotis diversicolor aquatilis (i.e., H. diversicolor supertexta) was around 65% of the total yield. The cultured species are
6、 varied. The technique of crossbreeding has been used widely (Nie et al. 1995a, Nie & Wang 2000). Triploid breeding has already started in production situations (Wang et al. 1990, Sun et al. 1993, Sun et al. 1998, Zhang et al. 1998). Because the abalone industry has developed rapidly sales prices ha
7、ve declined sharply. This has been especially so for the price of small abalone. For example H. diversicolor aquatilis sales price has been sometimes less than the cost of production. Epidemic diseases have occurred frequently since 1993 (Liu et al. 1995, Nie et al. 1995a, Ma et al. 1996). In partic
8、ular a virus disease has appeared successively during late winter in the south since 1999 (Huang et al. 1999). Farms have suffered heavy losses and the virus is a serious threat for abalone culture at present.Cultured Species and DistributionThere are eight species of abalone along Chinas coasts. Ge
9、ographically H. discus hannai Ino is the only species in Liaoning and Shandong Provinces in northern China. The other seven species are distributed in Fujian, Taiwan, Guandong, and Hainan, the southern provinces. These species are H. diversicolor diversicolor Reeve, H. diversicolor aquatilis Reeve,
10、H. varia Linnaeus, H. planata Sowerby, H. ovina Gmelin, H. clathrata Reeve, and H. asinina Linnaeus (Lu 1978, Dai & Wu 1989). Because H. diversicolor diversicolor grows slowly, H. diversicolor aquatilis becomes very important. This species was introduced from Taiwan to the southern continental coast
11、s in 1989 and is now raised widely there. Additionally H. discus discus Reeve was introduced from Japan in 1986, H. discus hannai Ino from Dalian in 1990 and their hybridized generation are raised in the mid and northern Fujian (Nie et al. 1995b). There are now several hundreds of abalone farms in C
12、hina. The largest produce more than 100 tonnes of live abalone per year.Culture MethodsThe culture methods used in China are quite varied. Because of the coastal and climatic conditions they are different in the north and south. Long line raft is an important method in the north. A length of 60-80 m
13、 of rope ties together plastic floating globes to support cages. There are two sorts of cage currently in use. A special cage for abalone culture consists of 6-12 tiers of 60-cm diameter plastic dishes. The entire assembly is covered with a net sealed with a zipper. The second type used is a scallop
14、 cage, of 8-12 tiers of 33-cm diameter. Most rafts are mixed culture with abalone and algal food, Laminaria or Undaria. Rafts are also used in some bays in the south where the wind and waves are weak. In these instances a plastic basket, the same as indoor tank culture baskets, is used instead of th
15、e other cages.Tank culture on land is the main type in the south. Because of frequent typhoons the culture had to develop on land. Concrete tanks are used of around 30-50 cubic meters. A dark PVC basket of 40 cm x 30 cm x 13 cm is in common use, usually in a stack of 8-12 tiers arranged in rows in a
16、 tank. The baskets occupy 40-70% of the tank capacity (Nie & Wang 2000).In the western Guangdong and Hainan Province, in recent years, small abalone are cultured in the intertidal zone. A type of cylindrical concrete case, 110 cm x 80-120 cm (h) with an iron rack and net inside, is set on a low inte
17、rtidal zone (Cai & Huang 2000).Rocky intertidal zones in the north are also used. Here growers build frames and cover with net as well as other types of cages (Zhang et al. 1994).Breeding Techniques and Present ProblemsThere are some differences in breeding techniques. The methods in the north are s
18、imilar to Japanese methods in many ways, and in the south the methods approximate those of Taiwan.All hatcheries in the north maintain parent stock with elevated temperature (20degreesC) in winter and induce spawning in spring. This allows sufficient warm weather for growing larger seed (to 15 mm) b
19、efore the coming winter. In contrast the small abalone can induce spawning naturally from May to December (main season is September to November) in the south. Nonetheless some farms in the south also maintain parent animals with elevated temperature in winter and induce spawning from April to June.T
20、he substrate for larval settlement in the north is a corrugated plastic plate (40 cm x 31 cm) held in racks. Variations appear in the southern farms. Most farms prefer a transparent plastic sleet (60 cm x 40 cm) frequently set up so that many plastic sheets are hung under a wooden bar. Other types o
21、f membrane (rather than racked) corrugated plates are also used (Nie & Wang 2000).A method of spawning induction with UV light and water temperature alteration (3degreesC to 5degreesC) is current. In the north, the fertilized eggs are maintained to the post veliger stage and then put into a tank for
22、 settlement. In the south it is more common to place fertilized eggs directly in a settling tank, with no water exchange until larval settlement. From the viewpoint of mass production the latter is quite feasible because it saves a lot of labor, time, and facilities.The young juveniles are removed f
23、rom the transparent plate/ membrane at 2-4 mm, a much smaller size than during the early years of abalone culture in China. Commonly, in the north, the juveniles are then transferred in a box net with a dark plate on the net bottom. In the south they are raised directly on the bottom of another sett
24、ling tank, on a substrate of square bricks with short legs that are arranged across the bottom of the settling tanks. The density of rearing is around 3,000-5,000 juveniles per square meter. A survival rate of about 40% to 60% is obtained and measured from the removal phase (2-4 mm) up to the end of
25、 nursery rearing (20 mm), in the south. A full cycle of nursery rearing takes about 6-8 mo with a mean production rate in all settling tanks of 2,000-3,000 seed.m.sup.-2.Present ProblemsIn recent years the nursery rearing has not been as easy as in the earlier years of abalone culture in China. On o
26、ne hand large quantities of postlarvae after settlement (15 mm) per tier at the start of the grow out cycle. These animals are then scattered into other cages to reduce stocking density four times in the 2-3 y of the culture cycle. When they reach size classes of 55 mm and 75 mm they are sold to dom
27、estic and overseas markets respectively. For this phase the rafts used hang 25-30 stacks and a stack of 12 tiers crops 25-30 kg of market size abalone (Wang Q., pers. 2001).In the south, a plastic basket is used in tank culture for 30-35 individual animals of 20-mm shell length. They are then grown
28、in this basket to market size. Some farms raise 50 individuals in this basket at the start and then scatter them to give 30 individuals when they reach 30-mm shell length. A cycle from 20 mm to 50 mm takes about 6-8 mo. At present the small abalone are consumed at 90 individuals per kg (about 47 mm
29、shell length) in the southern markets. A basket crops 400 g in this 6-8 mo. Per cubic meter of water capacity there are 24-30 baskets, cropping 9-12 kg. Mean survival is about 75% (Nie & Wang 2000, Nie & Wang 2001).The concrete cases used in the south for intertidal culture raise 500-700 juveniles a
30、t 10-20 mm shell length and harvest 6-7.5 kg in around 9-12 mo. The survival rate is about 50% to 60% (Qiu C.W., pers. comm. 2001).FoodChina is a country in which abundant culture, of algae such as Laminaria japonica and Undaria pinnatifida occurs. Natural resources of Gracilaria tenuistipitata abound in the south. The brown and red algae are favorites of H. discus hannai and H. diversicolour aquatilis respectively. The feeding ha
