The movement pattern and density distribution of perch, Perca fluviatilis L., in a channelized lowland river

Abstract

Abstract. The movement pattern and the abundance of perch, Perca fluviatilis L., were studied in the Kleine Nete, a eutrophic, canalized lowland river in north Belgium. Since the behaviour of perch is strongly affected by habitat type, two kinds of river section were chosen, based on physical characteristics: homogeneous sections with regard to depth, bottom type and current speed; and heterogeneous sections with a riffle and pool pattern. The fish were caught by electrofishing and all perch larger than 10 cm were marked individually. The population densities were much higher in the heterogeneous parts. In these sections about 30% of marked perch stayed within a home range, while in the homogeneous sections all were mobile. The older individuals showed a stronger tendency to accept a home range than the 1‐ or 2‐year‐old perch. This difference may be explained by different behaviour: young perch live in small schools, while older perch are often solitary. The low densities and the high mobility of perch in the homogeneous river sections indicate that these parts of the river are not a suitable habitat for perch. Habitat improvement of the homogeneous sections wilt probably result in higher overall population densities.

Environmental drivers of fish spatial distribution and activity in a reservoir with water level fluctuations

“…However, some individuals showed greater mobility (n = 6, perch and pikeperch) and lesser use of the littoral zone at low water levels, when littoral habitat was more homogeneous (dominance of fine substrates without vegetation). These results are similar to those of Bruylants et al (1986), who showed higher mobility for perch in homogeneous areas (similar depth, substrate and current) than in heterogeneous areas (succession of pool/riffle) of rivers. Dispersal of favourable patches when habitat is homogeneous (low water level) might explain these observations (Baras, 1992), since individuals must then cover greater distances to reach favourable habitats for accomplishing their vital functions (reproduction, rest/ protection and food seeking).…”

Behavioural pattern in cyprinid fish below a weir as detected by radio telemetry

“…As argued by many authors, fish behaviour can be affected by various factors such as turbulence and changes in river flow induced by power stations (e.g. Bouck, 1980; Weitkamp and Katz, 1980) or by riverbed channelization (Bruylants et al., 1986). Eurytopic species have no specific preferences for running waters (Schiemer and Waidbacher, 1992).…”

Impact of habitat diversity on the sampling effort required for the assessment of river fish communities and IBI

“…Therefore, even besides spawning migration, fishes can be very mobile in search for food or shelter or migration could even be related to energy conservation of fishes (Heermann & Borcherding, 2006), meaning that the suggestion of Seegert (2000) is not sufficient to cope with natural fluctuations in fish communities. Bruylants et al (1986) mentioned that fishes in homogeneous river stretches are more mobile than in heterogeneous reaches. Therefore, it is possible that certain species are not always sampled during consecutive fishing periods, even when they are present in the water system or even within the watercourse itself.…”

“…In addition, factors, such as sample length (Karr et al, 1986;Didier & Kestemont, 1996), fish movement (Stott et al, 1962;Bruylants et al, 1986; fish migration as well as daily activity patterns) and microhabitat distribution (Lyons, 1992;Angermeier & Smogor, 1995;Didier & Kestemont, 1996) can have a major impact on the catch, and thus on subsequent river quality evaluation. Therefore, observed patterns or changes in fish communities could be biased by inaccurate sampling methodology, being an artefact of the sampling area rather than changes in fish communities per se.…”