Proceedings of the Third World Fisheries Congress: Feeding the World with Fish in the Next Millenium—The Balance between Production and Environment
Viewpoints on the Conservation of Genetic Diversity of Farmed Fishes in China
China is the first country to have practiced aquaculture. The history of the culture of common carp Cyprinus carpio dates back more than 2,000 years. Even the culture of the “four major domesticated fishes” (silver carp Hypophthalmichthys molitrix, bighead carp Aristichthys nobilis, grass carp Ctenopharyngodon idella, and black carp Mylopharyngodon piceus) dates back 1,500 years.
China also is the largest producer of freshwater fish in the world. According to government statistics, the production of freshwater aquaculture was 14.22 million tons in 1999. The most important species include silver carp and bighead carp, which make up 45–50% of the total; grass carp, 20%; and common carp and crucian carp Carassius auratus, 20%. Chinese fisheries biologists have long been concerned with maintaining high levels of genetic variation in natural and cultured populations of these major cultured species.
The four major domesticated fishes are still wild or semiwild; there are no artificial strains of these species. Fish farmers obtain stock seeds of these species from rivers. Artificial fry propagation of these species is now common, but the traditional selective breeding of these species has been obstructed by the long life cycles of these fishes. So, genetic variation is the basic resource of a successful breeding program, and a selective breeding program should start from a base population that contains a large amount of genetic variability.
Common carp and crucian carp are traditionally cultivated species, but more than a dozen common carp varieties originate in Chinese native populations. Estimates of genetic divergence between these species are important for preventing the mixing of different varieties in a selection program.
The Chinese sturgeon Acipenser sinensis is an endangered species whose migratory passage to the natural spawning ground was blocked by construction of the Three Gorges Dam. In an effort to rescue this species, a project to produce fish fingerling for release into the Yangtze River was undertaken. In this project, levels of genetic variation of the original wild population should be maintained.
In this paper, I review the main results of studies conducted to reveal the genetic diversity of farmed carps in China. Based on these results, I present some suggestions for biodiversity conservation.
There are four subspecies of common carp in China (Wu 1977): southern Chinese carp Cyprinus carpio rubrofuscus in the Pearl and Yuanjiang rivers, European carp Cyprinus carpio carpio north of Xinjiang, chilu carp Cyprinus carpio chilia in lakes of Yunnan Province, and Amur carp (common carp) Cyprinus carpio haemapterus widely distributed in China, from the Heilongjiang River in north to south mountain range, including the Heilongjiang River basin, the Yellow River basin, and the Yangtze River basin.
Although more than a dozen varieties of common carp exist in China, their exact origin is unknown. However, clues can be found in records and morphological traits. Big-belly (tuanli), meat carp, and long-fin carp may have originated from southern Chinese carp; Xingguo red carp and red purse carp may have evolved from Amur carp. Future studies on molecular genetic markers will shed new light on this problem.
Although crucian carp traditionally has been cultured in China, it has become even more extensively cultured since the discovery of the phenomenon of allogynogenesis (Jiang et al. 1983). The silver crucian carp Carassius auratus gibelio is native to the Heilongjiang River and is the major cultured species throughout China.