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Marine shrimp culture

Marine shrimp culture began in Asia, where for many centuries farmers gathered harvests from tide-supplied tanks. Modern culture as we know it first appeared in the 1930's, when Japanese scientists initiated larvaculture works with the Marsupenaeus japonicus, obtaining the first postlarvae produced in a laboratory.

Nowadays, more than 50 countries explore this activity. Thailand is the largest cultured shrimp producer in the world, and Ecuador the largest in South America. USA, Western Europe and Japan are the main consumers, and despite having intensive production and high technology, present a relatively low production.

In Brazil, the activity of marine shrimp culturing first appeared in the 1970's with the creation of the Empresa de Pesquisa Agropecuária do Rio Grande do Norte (EMPARN - Agriculture and Cattle Breeding Research Company of Rio Grande do Norte). It was initially maintained by the rearing of Farfantepenaeus brasiliensis and Marsupenaeus japonicus. In the first half of the 1980's, an incitement program for the culture of marine shrimp made possible the development of many shrimping companies. Government-funded pioneer projects invested around 22 million dollars in the activity. However, political and economical problems, technology shortage and fragility of the cultured species hampered, at that time, the growth of the sector. By the end of the 1980's, the activity began to acquire a technical-industrial character, and the improvisations practiced up to that moment began to give space to professionalism and strategical planning, based on new technologies adopted as main tools of the new commercial enterprises.

Today, despite the fact that the species responsible for the great development of Brazilian shrimp farming is exotic, Litopenaeus vannamei, native of the Pacific coast of Mexico, Central America and South America, a complete dominion of its biological cycle is possessed by Brazil. During more than ten years, Brazil imported L. vannamei postlarvae and breeders from countries located in the Pacific coast, such as Ecuador, Panama, Venezuela, Mexico and USA (southern Florida and Hawaii). The domain of the reproductive cycle and of the postlarvae production resulted in self-sufficiency and offer regularization, making the consolidation of the technology for captive stock formation possible. This situation lead to the end of the matrixes and breeders importation that contributed with the introduction of diseases and were constantly used as solutions for offer continuity of postlarvae, with negative reflexes on the performance of the acvity in the country. The rise of postlarvae production laboratories and the implementation of new balanced food items ignited the success of the new cultured species. Currently, records reveal the existence of 18 larvaculture laboratories in Brazil, the majority located in the northeastern region of the country. This is mainly due to the favorable climatic and topographic conditions for the rearing of this species.

Marine shrimp farming basically comprises two phases: the larvaculture, responsible for the larvae production, and the growout, responsible for the growth of the shrimp to the commercial age. Larvaculture is performed in specialized laboratories, generally subdivided into two different sectors: maturation and nursery. Maturation is the sector responsible for breeding and spawning. Normally, males and females are kept together in appropriate tanks until breeding takes place. After breeding, the fertilized females are tranferred to the spawning tanks, later returning to the maturation tanks. One female may produce up to 300.000 eggs per spawn and maturate up to four times a month.

The newly-hatched nauplii go to the nursery, staying there until they reach the postlarva stage. Generally, it is during this phase that the shrimp are transferred to the growout farms and released in land tanks, staying there for approximately three months until the optimum commercial weight, about 12 g, is reached.

Depending on the density of the growout tank and on the diet type, shrimp farming may be classifed into three main systems: extensive (1 to 4 shrimp/m2, natural diet), semi-intensive (5 to 30 shrimp/ m2, natural diet plus supplements) and intensive (30 to 120 shrimp/ m2, diet consisiting exclusively of balanced rations), with the extensive and semi-intensive being the most widely used among the third world countries.

Despite disposing of favorable conditions for the practice of shrimp farming throughout its entire coast, the development of this activity is concentrated in the Northeast, with modest initiatives being recorded in the northern, southeastern and southern regions, especially due to the low temperatures registered during the winter. The technical-economical practicality of marine shrimp farming in these regions is obtained in one or two culture cycles/year, differently from the Northeast region where culture is virtually continuous through the whole year, permitting the generation of 2.5 to 3 cycles per year. The possibility of obtaining a higher number of cycles in the Northeast is due to the more elevated and more stable temperatures in this region.

Data from 2001 showed the existence of 507 marine shrimp farms in Brazil, amounting to a total of 8.500 ha of flooded area, 97% located in the Northeast region, responsible for nearly 95% of the country's production. In average, the productivity of cultured shrimps passes 4t/ha/year, totaling to around 40.000 tons in 2001, an extremely high number when compared to the natural area that a species needs to reproduce (ABCC, 2002).


 

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