| Chondrichthyans are composed of sharks, rays, skates and chimaeras. Because of the unique status in biological system evolution and the vital role in the ecosystem, chondrichthyan has received more and more takes. The researchers have done a lot of works and obtained many important research results. Especially elasmobranch is in the top nutrition level in the sea food chain, the change of its amount has very tremendous influence on other marine animal's survival, the population quantity change as well as the entire sea ecosystem. During the past 30 years, elasmobranch stock's serious decline and the serious threat on species survival caused by humanity's excessive fishing therefore aroused the global interest. The research on elasmobranch was started comparatively late in China, some research achievements on reproductive biology, reproductive physiology, molecular biology, biochemistry and so on have been gotten, but urgently awaited to strengthen in aspects of ecology research, population biology research and so on.This research attempts to study the species of chondrichthyan and geographic distribution situation as well as the chondrichthyan stock condition of China's sea area, through the domestic chondrichthyan research and the fishery situation summary and the investigation, and by unifying to the domestic and foreign material analysis. Besides, strategy of the maintaining and management of chondrichthyan stock in China is discussed based on the present situation and the international organization developed situation of the shark's maintaining and management. It has provided the scientific basic data and the policy-making basis for reasonable use and the protection of chondrichthyans, the protection of the marine ecosystem and the protection of the marine biological diversity.The research indicated that chondrichthyans widely distribute in the Indian Ocean, the Pacific Ocean and the Atlantic Ocean, the Southern Hemisphere from the equator to latitude 55 S, the Northern Hemisphere from the equator to above latitude 80 N. The majority species concentrate in the equator and its both sides. Along with the latitude increase, it assumes the tendency degression. Chondrichthyes in China is made up of 146 species, 21 genera and 8 families of sharks; 84 species, 17 genera and 3 families of skates; and 6 species, 2 genera and 1 family of chimaeras. The composition of the shark is most by Carcharhinidae, Squalidae is next best; Scyliorhinidae is next again. The ray is most by Dasyatidae and Rajidae, and there is 6 species belonging to 5 genera of the chimaeras. Chondrichthyans spread widely in China's sea area, but there are marked differences among species distribution of all sea area. In China there are 8 species of chondrichthyans that could be found in every sea area. At present only 5 species of sharks and 6 species of skates have been recorded in Bohai Sea. In the Yellow Sea 24 families and 49 species of chondrichthyans have been recorded. In the East China Sea, there is a record of 30 families and 125 species of chondrichthyan, 13 species among them are only recorded in the East China Sea . 25 families and 75 species of chondrichthyans are recorded in Taiwan Strait. In the waters surrounding Taiwan 38 families and 163 species of chondrichthyans have been recorded, 44 species of which have caught record just in Taiwan. The records of chondrichthyans in South China Sea include 156 species of 35 families, 29 species of which have been found only in the South China Sea.According to the nature of optimum temperature, Chondrichthyans in China can be divided into three types of warm-water species, warm- temperature species and cold- temperature species. The geographic distribution of chondrichthyan extremely affected by water temperature, depth and other environmental factors. View from the chondrichthyans distribution of all China's sea area, the higher the latitude of sea area is, the smaller the number of chondrichthyans is, the lower the proportion of warm-water species is, and the warm-temperature species gradually become the dominant species, cold-temperature species increase in the number. According to the horizontal distribution, chondrichthyans can be divided into widespread style, southerly style, northerly style and offshore style. At present a record of the deep-sea chondrichthyan in China is about 70 species, including 31 species in South China Sea, 37 species in the waters surrounding Taiwan, 27 species in East Sea. The deep-sea chondrichthyans can be found occasionally in Taiwan Strait and the Yellow Sea. Sea there are no recorded in the Bohai sea. At present, there is a capture record of 146 species of sharks in China, 15% of which are important economic species with their high yield, 22 species of which are common species. Because of the low output of chondrichthyan, the Chinese government has not included it in the scope of fishery statistics. It is estimated that Chinese annual output of sharks in general is about 10,000-15,000 tons. The world shark catches are generally one-tenth of the total sharks resources. The shark resources should be between 10-15 million tons in China. Viewing from shark output of years, most varieties of shark resources have little change in China, and there is no phenomenon of shark recession in most areas. But there are indications that some species such as Cetorhinus maximus, Rhincodon typus, and other relatively high economic value sharks have been received a certain degree of destruction. Investigation of shark resources and to determine the protection level have already been embarked on and made a certain progress in China. In 2004, China Red List of species listed 111 species of chondrichthyan in all as endangered and vulnerable, accounted for 47.1% of recorded chondrichthyan in China. The factors impacting the resources changes of chondrichthyan are: (1) Overfishing has destroyed the resources; (2) The habitat and feeding environment of chondrichthyan has been destroyed; (3) The bionomic strategies of the majority of chondrichthyan belong to K-strategies, which is difficult to recover rapidly from damage.All the world has paid more and more attentions to the development of shark fishing industry and the potential negative impact of shark population, and has agreed on the need to bring the special fishing industry of shark and other fishing activities whose major by-catch is shark under control.There is not the main producing area of shark in China, but prefers to consume shark, consumption of shark in China has already impacted on the global shark fishing industry.The general goal of chondrichthyan resources conservation and management strategy in China is to ensure the species resources conservation and management of chondrichthyan and its long-term sustainable use. Including: (1) to strengthen the protection of specific species;(2) to maintain marine biodiversity; (3) to balance the marine ecosystem; (4) to promote the protection of habitats; (5) to manage the sustainable use. The plans to protect chondrichthyans in China sea area should be with precautionary methods in domination sea areas. The shark conservation and management strategy principles in China are adhering to integrated and sustained development; adhering to resource conservation and changing the mode of fishery growth.The key actions of chondrichthyan resources conservation and management in China include:(1) Strengthening the legal protection of chondrichthyan conservation and management, and strengthening the fisheries administrative management. Enacting operational protection plans to protect the chondrichthyan resources, in order to strengthen the law enforcement and the implementation of the protection methods. Strengthening the fishery administration management, establishing a multipronged coordination mechanism on chondrichthyan resources protection.(2) Establishing the international or regional cooperation mechanisms of chondrichthyan resources protection, it is necessary to establish a regional protection action framework involved with China, Japan, South Korea, North Korea, Philippines, Malaysia, Vietnam and Chinese Taiwan region. Meanwhile, strengthening exchanges and cooperation with foreign counterparts to enhance the domestic level of protection.(3) Establishing the relative database of chondrichthyan resources conservation and management, including the registrations of catching, investigators/observer records, resource users'reports and the independent fishery investigation. Species identification, populations identification and population structure, catches, landings and discards, the amount of fishing and fishing gear, fishing methods, resource index, the composition of catch are important research data.(4) Strengthening the scientific research on chondrichthyan resources conservation and management, obtaining the outcomes of biology, ecology, technology, environmental science and economics, developing standards of the shark conservation action, evaluating the impacts on shark populations by human activities, and promoting the use of these research results as determined management objectives and the basis for management decisions. (5) Strengthening fishery catch management, including the control of catch or fishing, fishing gear restrictions, reducing by-catches, and to encourage the full use of the catch and specific species fishing ban, injury, interference, and so on.(6) Promoting the protection of shark by strengthening the controlling of the trade circulation links. Establishing trade tracing, verification and validation procedures, the implementation of statistics document scheme and catch document scheme is the primary component of marine fishery conservation and management measures. The effective operation of trade verification procedures may ensure that the trades with catch are up to the mustard of marine fishery conservation and management measures.(7) Exploring the mode of cooperate management with fishery stakeholders, strengthening the drumbeating and public education to promote public participation. Making public participation become the social impetus and guiding force of chondrichthyan resources conservation and management.(8) Establishing the financial mechanisms of sustainable chondrichthyan resources conservation and management strategies, financing by multi-channel, offering sustainable financial guarantee to chondrichthyan resources conservation and management in China.(9) Carrying out the training on chondrichthyan resources conservation and management.
|
PDF Full Text Request