Distribution of migratory fish in the stream (depth, velocity, body size, predators)

Abstract

In order to supplement the available information for the eco-hydraulic approach to designing fish passages, taking into account the taxonomic, dimensional structure, as well as taking into account the presence of predatory fish in the stream, the distribution of migratory fish of the boreal plain faunistic complex (Russian Federation) was studied. Three depth-velocity sections from the shore to the midstream were investigated: 5 m and 27.8 cm/s, 8 m and 44.4 cm/s, 11 m and 55.6 cm/s. Analysis of the migration distribution of fish showed that in the direction from the shore to the midstream, the proportion of representatives of Cyprinidae decreases from 41.8–24.3% and that of Percidae decreases from 25.0–18.4%. For individuals of two groups: the Acipenseridae and Lotidae, Coregonidae and Esocidae, patterns of distribution in the structure of migratory fish are opposite – their share increases with increasing speed and depth characteristics: 23.0–40.2% and 10.2–17.1%, respectively. An assessment of the dimensional structure revealed a feature of increase in the size range of fish from the shore to the midstream: the dominance of small individuals (<10 cm) in the shore area is replaced by the dominance of large fish (> 30 cm) in the area of higher speeds and depths. A significant difference in the distribution for all studied taxonomic fish groups between the shore and the midstream was shown. Thus, it has been established that for Cyprinidae during the migration period, the choice shifts in favour of minimizing energy costs, and the choice to avoid the risk of predation from individuals of the groups: Coregonidae and Esocidae, and also Percidae, shifts in favour of the former. The distribution of perch is influenced by the reduction of energy costs and the simultaneous avoidance of predation and cannibalism. For the fish group Acipenseridae and Lotidae, their predominance in the deeper area is due to their less developed visual orientation mechanism in the stream because they are bottom-living fish species.

Insights into Daily Dynamics of Fish Migration during Spring in the Konda River

“…In order to analyze fish migration in the Lower Irtysh basin of the Konda River, hydroacoustic monitoring is carried out regularly. Previous publications have considered the distribution [45,46] and the effects of water temperature [47]. In contrast, here, we aim to provide a holistic view of fish migration in the Konda River in spring, with a focus on daily and monthly dynamics.…”