Hydraulic forces impact larval fish drift in the free flowing section of a large European river

Abstract

Dispersal of fluvial freshwater fish larvae occurs commonly in heavily regulated rivers. Studies increasingly indicate that drifting young fish have an active component to their movement and so are capable of coping with the dynamic hydraulic forces typical of rivers. We investigated hydraulic–drift relationships of the young stages of fish over one breeding season along a gravel shore of the Austrian Danube using stationary drift nets from the first occurrence until the end of the seasonal peak (April–June 2008). Observed densities of families and developmental stages were related to the hydraulic parameters flow velocity (in three spatial directions), turbulent kinetic energy and water depth, derived from a three‐dimensional hydrodynamic model of the sampling site. We detected distinct responses of drifting young fish to several hydro‐physical factors under conditions (low light level, over‐critical currents), which were considered to cause washouts and passive drift. In general, drift densities decreased with water depth and flow velocity. Weak swimmers (e.g. bull head Cottus gobio and early‐stage cyprinid larvae) avoided turbulent flows, as their abilities to orientate and hold position may be limited. Early larval as well as early juvenile stages of cyprinids used lateral currents directing to the bank, potentially to drop out of the flow and reach inshore areas. Our study indicates that there are family‐specific and stage‐specific responses to hydraulic variables and that fish actively disperse, probably to minimize mortality and maximize successful dispersal. Copyright © 2013 John Wiley & Sons, Ltd.

Movement patterns and rheoreaction of larvae of a fluvial specialist (nase, Chondrostoma nasus): the role of active versus passive components of behaviour in dispersal

“…They were significantly larger than larvae of the same release event that were captured in drift nets. Lechner et al (2014) released marked L2 and L4 larvae simultaneously in the Danube River. On the fifth day after release, only L4 larvae were detected up to 150 m upstream of the release point, while L2 larvae were exclusively recaptured downstream.…”

Patterns and processes in the drift of early developmental stages of fish in rivers: a review

“…The Murray cod (Maccullochella peelii, Percichthyidae) in the Murray River, Australia (Humphries 2005), and pumpkinseeds (Lepomis gibbosus, Centrarchidae) in the River Rhone, France (Copp and Cellot 1988), predominantly drift as free embryos. Cyprinids, on the other hand, mostly disperse during their early larval development (larval stages L1-L4; Copp et al 2002;Zitek et al 2004a;Sonny et al 2006) or at the transition between the larval and the juvenile period (stages Rev Fish Biol Fisheries (2016) 26:471-489 473 L6/J1; Reichard and Jurajda 2007;Lechner et al 2014b). But the former generality, that downstream dispersal is most intensive during early embryogenesis and sharply decreases upon the achieving of the juvenile period (Pavlov 1994), does not always apply: e.g., the drift in two Czech rivers, Morava and Kyjovka, and in a bypass section of the River Rhone was dominated by juvenile cyprinids, percids and cobitids (Peňáz et al 1992;Reichard et al 2001).…”

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

“…In this study, the three Neogobius species alone were responsible that the Gobiidae were the second most abundant family in the drift. Moreover, gobiids are also known as the dominant family in other drift studies (Zitek et al, 2004b;Lechner et al, 2010). The general dominance of the Neogobius species over the genus Proterorhinus is likely a result of their high invasive potential and possibly reflects the effects of direct competition (Wolfram & Mikschi, 2007;Wiesner et al, 2010).…”

“…However, only the Cyprinidae, Gobiidae, and Percidae are regularly caught in larger numbers, indicating that drifting plays a significant role in their life histories (Zitek et al, 2004b;Lechner et al, 2010Lechner et al, , 2014. Drift patterns in cyprinids have been extensively described and discussed (Reichard et al, 2002a(Reichard et al, , 2004Sonny et al, 2006;Reichard & Jurajda, 2007), including the effect of shore morphology on cyprinid drift (Schludermann et al, 2012;Lechner et al, 2013).…”