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

Abstract

The drift of early development stages is an essential element of dispersal in many fish species. It is caused by a multitude of factors and is thus highly specific for each taxon and developmental stage. In this paper, we examined the drift of free embryos, larvae, and juveniles of percids and gobiids in a freeflowing stretch of the Austrian Danube. We assessed the drift density (DD) at different distances from the shore, described seasonal and diel patterns, and how size of drifting fish changed throughout the season. The seasonal patterns as well as the DDs were highly specific for each genus, while the diel patterns and changes in size of drifting fishes differed primarily at family level. In addition, we compared two opposed shorelines-a near-natural gravel bar and a rip-rap stabilized shore. The shores differed significantly and on both shores the DD of gobies was higher compared to percids. Among the Gobiidae, the invasive Neogobius species clearly dominated (99% of total gobiid catch) over the native tubenose goby Proterorhinus semilunaris. Percid DD was substantially higher on the near-natural shore, with Zingel and Sander as the most abundant genera.

Species‐specific fish larvae drift in anthropogenically constructed riparian zones on the Vienna impoundment of the River Danube, Austria: Species occurrence, frequencies, and seasonal patterns based on DNA barcoding

“…In addition, such structural alterations affect the hydraulics of inshore areas, which may have dramatic effects on the dispersal and viability of native fish populations (Lechner et al, ; Schiemer, Keckeis, & Kamler, ). Our results are in line with other studies (Lechner et al, ; Ramler, Ahnelt, Nemeschkal, & Keckeis, ) that report that the near natural shores provide substantially more suitable larval habitats for native fish fauna than anthropogenically stabilized shores.…”

“…Most species appeared for 3 to 4 weeks, whereas some displayed an extended drifting periods of up to 8 weeks. Other studies in this area have recorded similar seasonal patterns, even though most of them did not cover the entire drifting season and therefore missed the peaks of either the early drifters (e.g., Bullhead in April) or those last to drift (Lechner et al, , Ramler et al, , Zitek, Schmutz, & Ploner, ). In the last 2 weeks of July, only a small number of Chub, Round Goby, and Barbel were recorded, indicating the end of drifting for most species.…”

The importance of a constructed near-nature-like Danube fish by-pass as a lifecycle fish habitat for spawning, nurseries, growing and feeding: a long-term view with remarks on management

“…However, the distribution of the caught larvae in the stream section of the by-pass is comparable to that of gravel bars in the remaining free-flowing Danube and its tributaries. The distribution of larvae caught in the pool pass is more similar to that of riprap sections in the main channel (Lechner et al 2010(Lechner et al , 2014Melcher and Schmutz 2010;Ramler et al 2016;Meulenbroek et al 2018).…”

Effects of hydraulic engineering restoration measures on invasive gobies in a large river (Danube, Austria)

“…Secondly, discharge, and thus the available volume of water, has an effect on the catchability of fishes and therefore influences abundance estimates (e.g. Ramler et al 2016;Speas et al 2004). During the pre-survey sampling, the average discharge was lower than at the post-surveys.…”

“…This difference of goby abundances in side channels is probably influenced by larger-scale factors such as different types of upstream habitats. In gobies, most dispersal is probably directed downstream, especially during the drift of early life stages, which is known to be an important dispersal mechanism in gobies (Borcherding et al 2016;Janáč et al 2013;Ramler et al 2016). Accordingly, the higher abundance of gobies in the project section may be due to a higher upstream stock of gobies.…”