Movement is a basic feature of fish ecology, being related to dispersal, recolonization, and recovery of local populations after disturbance. Non-migratory species are the main component of stream fish communities, especially in the Neotropics, but there is little information on the characteristics of their movement. In this capture-recapture study, we describe the individual movement of the armored catfish Rineloricaria aequalicuspis in a stream in southern Brazil. We also assess whether this species displays heterogeneous movement, as well as its degree of mobility and the relationship between individual fish movement and body size and local habitat characteristics. Data on individual fish positions were obtained monthly from November 2018 to March 2019, in ten 20-m stream sections along a 430-m stream stretch. Individual fish were captured by kick sampling and measured, photographed (for later photo-identification), and released back to the stream. The movement frequency distribution was moderately leptokurtic (kurtosis = 3.31), indicating heterogeneous movement with two groups of individuals, stationary and mobile. The maximum movement distances were 248 m and 208 m, downstream and upstream, respectively, while the mean movement distance was 98.6 m. Density of individuals was the main factor affecting the probability of movement, suggesting a role for resource availability and intraspecific interactions. The heterogeneous movement pattern observed for R. aequalicuspis indicates that intra-populational variability in movement behavior occurs in non-migratory stream species, which have been often assumed to be either sedentary or mobile species. We highlight that sedentary behavior should not be assumed a priori for stream fishes, not even for those species usually considered to be of low mobility, as many loricariids.

运动是鱼类生态学的一个基本特征，与扰乱后当地种群的分散、重新定殖和恢复有关。非洄游物种是溪流鱼类群落的主要组成部分，尤其是在新热带地区，但关于其运动特征的信息很少。在这项捕获-重新捕获研究中，我们描述了装甲鲶鱼Rineloricaria aequalicuspis的个体运动在巴西南部的一条溪流中。我们还评估了该物种是否表现出异质运动，以及其运动程度以及个体鱼类运动与体型和当地栖息地特征之间的关系。从 2018 年 11 月到 2019 年 3 月，在 430 米长的溪流段上的 10 个 20 米长的溪流段中，每个月都获得了关于单个鱼群位置的数据。通过踢采样捕获个体鱼并进行测量、拍照（用于稍后的照片识别），然后将其放回溪流中。运动频率分布为中等瘦峰（峰态 = 3.31），表明两组个体的异质运动，静止和移动。最大移动距离分别为下游和上游 248 m 和 208 m，而平均移动距离为 98.6 m。个体密度是影响移动概率的主要因素，表明资源可用性和种内相互作用的作用。观察到的异质运动模式R. aequalicuspis表明运动行为的种群内变异发生在非洄游河流物种中，这些物种通常被认为是定居或流动物种。我们强调，不应该先验地假设河流鱼类的久坐行为，即使是那些通常被认为是低流动性的物种，如许多loricariids。