Diel changeover of fish assemblages in shallow sandy habitats of lowland rivers of different sizes

Abstract

Diel dynamics of species richness and fish abundance were studied in three lowland rivers that differed significantly in size (discharge) in to the upper Vistula River drainage system (Poland). Shallow sandy habitats at point bars were repeatedly sampled with beach seining over 24-h periods. Species richness peaked at dusk and then decreased throughout the 24-h period in all the rivers. Overall fish abundance changed similarly in the smallest and the largest river, whereas in the mid-sized river it increased in the late afternoon hours. Some species (three gudgeon species, golden loach, and chub) were persistently nocturnal, whereas others (dace, bleak, and roach) shifted to diurnal activity in the mid-sized and large rivers. These differences in diel changes in the abundance of certain species might be explained in the context of variation in availability (i.e., proximity) of other, more heterogeneous habitats.

Understanding the Temporal Dynamics of a Lowland River Fish Community at a Hazardous Intake and Floodgate to Inform Safe Operation

“…Indeed, Nunn et al (2010) demonstrated that diel movement patterns of lowland fish between a small tributary and the main River Avon was species specific. In Nowak et al (2019), dace (Leuciscus leuciscus), bleak (Alburnus alburnus) and roach (Rutilus rutilus) showed shifts from nocturnal to diurnal behaviour associated with seasonal movements between a small stream and a main-river. Accordingly, the temporal results presented in this study possibly include an undetected diel changeover in fish assemblage.…”