Genetic variation in native and farmed populations of Tambaqui (Colossoma macropomum) in the Brazilian Amazon: regional discrepancies in farming systems

The tambaqui, Colossoma macropomum, is the most popular fish species used for aquaculture in Brazil but there is no study comparing genetic variation among native and farmed populations of this species. In the present study, we analyzed DNA sequences of the mitochondrial DNA to evaluate the genetic diversity among two wild populations, a fry-producing breeding stock, and a sample of fish farm stocks, all from the region of Santarém, in the west of the Brazilian state of Pará. Similar levels of genetic diversity were found in all the samples and surprisingly the breeding stock showed expressive representation of the genetic diversity registered on wild populations. These results contrast considerably with those of the previous study of farmed stocks in the states of Amapá, Pará, Piauí, and Rondônia, which recorded only two haplotypes, indicating a long history of endogamy in the breeding stocks used to produce fry. The results of the two studies show two distinct scenarios of tambaqui farming in the Amazon basin, which must be better evaluated in order to guarantee the successful expansion of this activity in the region, and the rest of Brazil, given that the tambaqui and its hybrids are now farmed throughout the country.

坦巴基鱼（tambaqui，学名Colossoma macropomum）是巴西水产养殖中最受欢迎的鱼类品种，但目前尚无研究对该物种的野生种群与养殖种群的遗传变异开展比较分析。本研究通过分析线粒体DNA（mitochondrial DNA）序列，对来自巴西帕拉州西部圣塔伦地区的2个野生种群、1个苗种繁育亲鱼种群以及1个养殖种群样本的遗传多样性进行评估。结果显示，所有样本的遗传多样性水平均无显著差异；尤为意外的是，该繁育亲鱼种群竟能充分代表野生种群所记录的遗传多样性。上述结果与此前在阿马帕州、帕拉州、皮奥伊州及朗多尼亚州开展的养殖种群研究结果差异显著：后者仅检测到2种单倍型（haplotype），表明其苗种繁育所用的亲鱼种群长期存在近交现象。两项研究的结果共同揭示了亚马孙流域坦巴基鱼养殖的两种截然不同的发展模式。鉴于坦巴基鱼及其杂交品种目前已在巴西全国范围内推广养殖，因此亟需对这两种模式开展更系统的评估，以确保该养殖产业在亚马孙流域及巴西其他地区均可实现健康可持续的扩张。