Aquaculture of neotropical catfish hybrids: Genetic strategies for conservation and management
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In general, aquaculture and fish farming cause negative impacts on the environment and wild fish populations. One of the major problems is the escape of farmed fish, especially exotic species, which can alter the population dynamics and ecology of wild stocks. Therefore, the reduction or even extinction of natural stocks may occur through predation and/or competition for resources. Furthermore, through gene introgression, interspecific hybrids of Neotropical catfish species have caused genetic contamination and threatened the genetic integrity of natural populations. These fish are produced and cultivated in aquaculture for several reasons, including the peculiarities of induced breeding of certain species, acceptance on the consumer market, and, mainly, the characteristics generated by hybrid vigor, such as better performance rates, resistance to pathogens and management, and color patterns, among other factors. Several species of Neotropical catfish have been used for interspecific hybridization programs, such as the species of Pimelodidae Pseudoplatystoma corruscans, Pseudoplatystoma reticulatum, Leiarius marmoratus and Phractocephalus hemioliopterus. However, these animals have been traded and handled erroneously by the aquaculture industry because their morphological identification is unreliable and impractical. Consequently, catfish hybrids can be introduced into the natural environment. The major risk is the fertility of these hybrids, particularly the hybrid cachapinta (female P. reticulatum x male P. corruscans), which may cause atypical crosses with wild fish and generate genetic contamination. In order to monitor the production and provide standards for the correct handling of catfish hybrids, the use of molecular/genetic markers has become an excellent tool to resolve the problem of morphological identification. In this chapter, we will discuss the applications of genetic approaches as strategies for conservation and proper management of interspecific catfish hybrids in aquaculture. Genetic methods should be applied in the context of a specific monitoring program for brood stock, trade of juvenile hybrids and for wild stocks in the natural environment. The expected result is the implementation of the concept of sustainable development, i.e., to increase the production of fish for human consumption while concurrent conservation measures reduce the risks generated by the aquaculture industry.