Fish drift in a Danube sidearm‐system: II. Seasonal and diurnal patterns

Abstract

Seasonal and diurnal patterns of larval and juvenile fish drift were investigated in the Marchfeldkanal, a man-made side branch of the Danube River near Vienna, Austria. A clear seasonal pattern with peak densities in mid-June was found. Species composition varied over time, showed a site specific pattern and was dominated by tubenose goby Proterorhinus marmoratus. Water temperature was the main factor responsible for the increase of drift densities until the median drift date and repeated occurrence of early larval stages in drift indicated repeated spawning for many species. Significant differences in drift densities between different time periods of the day (day, dusk, night and dawn) were found for common bream Abramis brama, barbel Barbus barbus, chub Leuciscus cephalus, tubenose goby and roach Rutilus rutilus. The highest drift rates occurred at night (2200-0400 hours), with 86% of all larvae drifting during the hours of darkness. Fish larvae of different lengths drifting at different phases of the day were found for common bream, bleak Alburnus alburnus and chub, with largest larvae drifting during dusk (chub) and day (bleak and common bream). For bleak, all gudgeon species Gobio spp., tubenose goby, roach and for all cyprinid species combined, one 2 h night sample was found to be sufficient to predict the total 24 h drift. # 2004 The Fisheries Society of the British Isles

Modelling the dispersal of riverine fish larvae: from a raster-based analysis of movement patterns within a racetrack flume to a rheoreaction-based correlated random walk (RCRW) model approach

“…Result of the sensitivity analysis for selected parameters of the RCRW model regarding the transformed longitudinal and lateral coordinates and , in combination with the error measures over-reorientation (oRe) and error in the desired movement direction (EM). dent on diel patterns characterized by a nocturnal increase in drift, could neither be sufficiently proved nor disproved in our study, whereas other studies support the concept of a diel impact on larval downstream movement (e.g., Copp et al 2002;Zitek et al 2004;Pavlov et al 2008). In light of these proven impacts on movement patterns, a stagespecific and RCRW model, using flow velocity-dependent fractions of movement patterns f U,M , has been developed in combination with a relatively smooth transition of the fitted lognormal distributions concerning durations of movement sequences ⌬t j,M,U between flow velocity classes.…”

The drift of early life stages of Percidae and Gobiidae (Pisces: Teleostei) in a free-flowing section of the Austrian Danube

“…The seasonality of drift intensity found in Proterorhinus matches only partially with other studies. In a study in an artificial sidearm of the Austrian Danube, Proterorhinus was the dominant genus and exhibited a slightly bimodal seasonal pattern, with high DD throughout June and very low values in late May and early August (Zitek et al, 2004a). In contrast, Janáč et al (2013) found maximum DD in May and almost no specimens of Proterorhinus after mid-June in the Dyje.…”

“…During the day, the former were virtually absent in the drift, while the latter were already drifting at the beginning of sampling. Illumination level is a key factor in fish larvae drift and usually negatively correlated with DD (Reichard et al, 2002a), resulting in the highest DD between dusk and dawn (Pavlov, 1994;Reichard et al, 2002a;Zitek et al, 2004a). The ultimate reason behind this fact, however, is still not clear.…”

“…It is important for dispersal, as well as for reaching suitable nursery habitats after hatching (Pavlov et al, 1978;Brown & Armstrong, 1985;Pavlov, 1994;Fuiman & Werner, 2002). Drift entry of fish species is influenced by a number of abiotic and biotic factors, such as discharge, flow velocity, population density, predation, or foraging (Oesmann, 2003;Zitek et al, 2004a;Reichard & Jurajda, 2007). The main factors of timing and intensity of drifting, however, are linked to spawning events, which in turn are primarily influenced by temperature in temperate rivers (Brown & Armstrong, 1985;Reichard et al, 2002b).…”

“…This leads to seasonal characteristics of drift activity of relatively limited duration (weeks-months) in most species inhabiting temperate zones (Zitek et al, 2004a;Reichard & Jurajda, 2007). Furthermore, many species exhibit diurnal changes in drift activity, with fish drifting more commonly during the night (Pavlov et al, 2000;Reichard et al, 2002b;Zitek et al, 2004a;Nunn et al, 2010). Drifting itself (i.e.…”