Universidade Federal de Santa Catarina - UFSC, Programa de Pós-graduação em Aquicultura, Florianópolis, SC, Brasil.
Instituto Federal de Educação Ciência e Tecnologia de Rondônia, Ariquemes, RO, Brasil.
Braz J Biol. 2024 Feb 26;84:e276197. doi: 10.1590/1519-6984.276197. eCollection 2024.
In this study, we analyzed the altitudinal distribution and body condition of the juvenile migratory fish Megaleporinus obtusidens and Salminus brasiliensis in the Uruguay River, a South American subtropical river. We used the presence/absence data and condition factor (K) of juveniles as indicators to try to characterize some recruitment patterns of migratory fish in the main channel of the Uruguay River. Gillnet sampling was conducted during two reproductive years, 2015-2016 and 2016-2017 (November and March of each reproductive year), in three Uruguay River stretches at different levels of altitude. The nets remained in the water for 10-12 hours per night or day for 10 days during each field trip (NOV-15, MAR-16, NOV-16, and MAR-17). The abundance of M. obtusidens juveniles were similar between the two reproductive years, whereas S. brasiliensis capture was higher during the 2015-2016 reproductive year. The probability of finding M. obtusidens juveniles in the Uruguay River was negatively correlated (p < 0.05) with the altitudinal gradient of the sampling points, as shown by the GLM model. For S. brasiliensis, the logit model indicated a non-significant probabilistic relationship (p > 0.05) between the presence of juveniles of this fish species and the altitude gradient. Regarding the body condition of juveniles, the water quality of the sampling points did not affect the juvenile condition factor for either species; however, a positive relationship (p < 0.05) was found with the water level for both species, even with an adjusted R2 of 0.13 for M. obtusidens and 0.48 to S. brasiliensis. Altitude gradient and water level were factors that may affect the juvenile distribution and body condition of these species, respectively, in the Uruguay River. Therefore, this information can be used in hydropower generation policies to conserve migratory fish populations in the Uruguay River Basin.
在本研究中，我们分析了南亚热带乌拉圭河洄游性幼鱼 M. obtusidens 和 S. brasiliensis 的海拔分布和身体状况。我们使用幼鱼的存在/缺失数据和条件因子 (K) 作为指标，试图描述乌拉圭河主河道中洄游性鱼类的一些补充模式。在两个繁殖年份（2015-2016 年和 2016-2017 年）的繁殖期，我们在三个不同海拔高度的乌拉圭河河段进行了刺网采样。在每个野外考察期间（2015 年 11 月、2016 年 3 月、2016 年 11 月和 2017 年 3 月），每夜或每天在水中放置刺网 10-12 小时，持续 10 天。M. obtusidens 幼鱼的丰度在两个繁殖年份之间相似，而 S. brasiliensis 的捕获量在 2015-2016 繁殖年更高。GLM 模型显示，M. obtusidens 幼鱼在乌拉圭河中的出现概率与采样点的海拔梯度呈负相关（p < 0.05）。对于 S. brasiliensis，对数模型表明，该鱼类幼鱼的存在与海拔梯度之间没有显著的概率关系（p > 0.05）。关于幼鱼的身体状况，采样点的水质对这两种鱼类的幼鱼条件因子没有影响；然而，对于这两种鱼类，都发现了与水位的正相关关系（p < 0.05），即使对于 M. obtusidens，调整后的 R2 为 0.13，对于 S. brasiliensis，调整后的 R2 为 0.48。海拔梯度和水位是可能分别影响这些物种在乌拉圭河幼鱼分布和身体状况的因素。因此，这些信息可用于水力发电政策，以保护乌拉圭河流域的洄游性鱼类种群。
