Impact of the non-native locariid fish Pterygoplichthys pardalis in native fish community on a seasonal tropical floodplain in Mexico

The present study reports the seasonal dynamics of the fish community structure in the presence of a non-native fish (Pterygoplichthys pardalis) in tropical waterbodies of southern Mexico. The studied floodplain existed in both connected pools and disconnected pools “to the Palizada river”. Local fish fauna showed consistent assemblages across seasons, but among the 17 local fish species recorded, the non-native species P. pardalis showed the highest percentage of contribution to the fish community (ca. 20%). Conversely, the frequency of occurrence and density of the non-native species showed variation in relation to the type of waterbody and seasonality; its density was approximately four times higher in disconnected pools than in connected pools in the rainy season and its predominant size class in both pool types was 21-30 cm in standard length. Interestingly, the diversity of the native species was negatively related to the density of the non-native species, indicating that the presence of P. pardalis can be a factor involved in the decline of native fish diversity in these local communities. Currently, the possible impacts of the presence of P. pardalis on local fish diversity at the regional scale are unknown, but our results suggest that hydrological dynamics regulate the establishment of the non-native species in this region. However, future studies are needed to provide insights into the actual scenario of P. pardalis distribution in Yucatan Peninsula and the possible impacts on the native fish fauna in southern Mexico.本研究报道了墨西哥南部热带水体中，入侵鱼类下口鲶（Pterygoplichthys pardalis）存在下的鱼类群落结构季节动态。本次研究的泛滥平原包含两类池塘：连通型池塘，以及与帕利萨达河（Palizada River）不相通的非连通池塘。本地鱼类群落在不同季节间的组成相对稳定，但在记录到的17种本土鱼类中，入侵物种下口鲶对鱼类群落的贡献率最高，约占20%。与之相对的是，该入侵物种的出现频率与种群密度随水体类型及季节变化呈现显著差异：雨季时，非连通池塘内的种群密度约为连通池塘的4倍；两类池塘中，该物种的优势体长组均为标准体长21~30 cm。值得注意的是，本土鱼类多样性与该入侵物种的种群密度呈负相关关系，这表明下口鲶的存在可能是导致该区域本土鱼类群落多样性下降的潜在因素之一。目前，区域尺度下下口鲶入侵对本土鱼类多样性的潜在影响尚不明确，但本研究结果表明，水文动态调控着该区域入侵物种的定殖过程。不过，未来仍需开展相关研究，以明确尤卡坦半岛（Yucatan Peninsula）内下口鲶的实际分布状况，以及其对墨西哥南部本土鱼类群落的潜在影响。