Background] For having very strong adaptability to the natural environment, tilapia has become a common species in the southern waters of China. However, the species and distribution of tilapia in Jiulong River has not been reported. [Method] By using drift nets at 6 stations in Hua′an reaches of Jiulong River in November 2013 and April 2014, we examined species composi-tion, quantity, and distribution of tilapia. [Result] The results showed that there were 3 species of tilapia, Tilapia zillii, Oreochro-mis nilotica and O.galilaea. Of the total catches, 35.96% in quantity and 30.63% in weight were tilapia. The ratio of tilapia in cat-ches was the highest at Tankou, accounting for 72.97% in quantity and 61.55% in weight. Among the samples of tilapia, T.zillii was the most abundant accounting for 62.50% in quantity and 54.53% in weight of all tilapia. Individual size of all tilapia was small, the average body length of O.nilotica, S.galilaea and T.zillii was 13.4 cm, 12.9 cm, and 12.0 cm and their average body weights, 107.3 g, 96.9 g, and 74.1 g, respectively. [Conclusion and significance] From upstream ( North) to downstream ( South) , the quantity and number of species of tilapia greatly varied. Tilapia has become one of the main fish groups in some areas of Jiulong River. As an alien species, tilapia has obvious competitive advantage over native fish, its invasion may cause a decline of biodiversity and fishery re-sources in Jiulong River.%【背景】罗非鱼类对自然环境具有很强的适应能力，在我国南方水域已经成为常见种，但至今九龙江罗非鱼类的种类与分布情况尚未见报导。【方法】2013年11月和2014年4月，在九龙江华安段设置6个站位，采用流刺网对罗非鱼类的种类组成、数量和分布进行2次调查。【结果】调查水域罗非鱼种类有齐氏罗非鱼、尼罗罗非鱼和加利亚罗非鱼3种。罗非鱼类分别占本次调查渔获总数量和总重量的35.96%和30.63%，以潭口河段罗非鱼类所占比例最高，分别占该站位渔获总数量和总重量的72.97%和61.55%。调查采集的罗非鱼类样品中以齐氏罗非鱼占比最高，占罗非鱼类数量和重量的62.50%和54.53%。罗非鱼类均为小型个体，以尼罗罗非鱼个体为最大，平均体长和体重分别为13.4 cm和107.3 g；其次为加利亚罗非鱼，分别为12.9 cm和96.9 g；最小为齐氏罗非鱼，分别为12.0 cm和74.1 g。【结论与意义】罗非鱼类个体数量和种类数量从九龙江上游(北)到下游(南)呈现从无到有、从少到多的趋势，在部分水域罗非鱼类已经成为主要类群。外来物种罗非鱼类对本土鱼类具有竞争优势，其对九龙江水域的入侵可能导致生物多样性的下降和渔业资源的衰退。
展开▼
