干旱区生态环境知识资源中心

Captive breeding and the release of captive-bred individuals into the wild are among the techniques used for the conservation of rare and endangered fish species. After a brief description of the methods of captive breeding and the establishment of breeding stocks, this paper provides examples of the application of these techniques to endemic fish species of arid regions in south-western USA and examines some current cases and the future possibilities for their use in the Mediterranean region. Special attention is given to the analysis of the strict constraints imposed on fish breeding for conservation purposes, in which the aim is to produce fish with all the morphological, behavioural and genetic characteristics of the taxa to be conserved, and which are capable of effectively adapting to the natural environment when introduced. In terms of genetic management of captive populations, the fundamental problems which are faced involve the categorization of the species-resources to be conserved (identification of cases of inter- and intra-specific introgression), the establishment of founder stocks that contain the maximum genetic diversity depending on the genetic structure of the species (strong intra- or interpopulation variability), and the retention of genetic variability during captive breeding (the need to reduce to the minimum the phenomena of genetic drift, inbreeding and unintentional selection of non-adapted genotypes). Because of these difficulties and risks in terms of genetic conservation, captive breeding should remain a temporary safeguard measure, while awaiting the implementation of measures for protecting species in their restored original habitat or translocation to strictly protected substitute habitats. With this aim in view and in conclusion, the paper suggests methods for organizing a critical plan to safeguard the most endangered species or subspecies in the Mediterranean region by captive breeding.