Paths to the unknown: dispersal during the early life of fishes

The special issue brings together selected contributions from the 39th Annual Larval Fish Conference hosted by the University of Vienna, Austria, and presents the latest research and understanding of dispersal patterns and processes of early life stages of fishes of various aquatic environments around the world (open ocean, coastal areas, estuaries, and rivers). An important component of this compendium is to indicate new approaches and to outline the importance of integration of information about movements and dispersal for recruitment, population dynamics, species conservation, and management issue

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

Recruitment of Chondrostoma nasus (Linnaeus 1758) and similar fish species in rivers is related to spatio-temporal linkages between larval hatching and nursery habitats. Active swimming behaviour contradicts the assumption that passive particle tracing models can serve as a proxy for larval dispersal models. A racetrack flume with an inshore area of near-natural slope was created to observe individual larval trajectories. A new three-step, raster-based analysis was developed to distinguish four types of movement patterns: active upstream, active downstream, active-passive and passive. Both larval developmental stage- and release site-specific occurrences of these movement patterns were experimentally found for nine flow velocity classes (â ¤0.225 m s-1). These current-induced movement patterns, and evaluated durations within them, were used to develop a biased and correlated random walk (BCRW) model which includes rheoreactionâ a key behavioural response of fish to flow within rivers. The study introduces the concept and application of a rheoreaction-based correlated random walk (RCRW) model which, coupled with a 3D hydrodynamic model, allows prediction of the spatio-temporal effects of various river discharges, morphologies and restoration scenarios on larval fish dispersal.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

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

Invasive gobies can have severe detrimental effects on local fish communities, however, direct methods for population control are often insufficient (i.e. fishing) or not feasible (i.e. poisoning). Indirect methods, such as habitat modifications in the course of restoration programs, appear promising but are poorly studied. In this study, we investigate the effects of different restoration measures on the abundance and occurrence of non-native gobies in the main stem of a free-flowing section of the Danube and attempt to disentangle these measures from general large-scale trends by applying a Before-After-Control-Impact design. We found three invasive goby species (racer, bighead, and round goby) in the sampling area, partly with very high abundances. Four to six years after the installation, the measures had negative (riprap removal), neutral (side arm reconnection), or positive (groyne field adaptations) effects on goby abundances. We conclude that the impact of the measures depends on the type of intervention, is species-specific, and is largely related to substrate composition. Independent from the effect of the measures, abundances of bighead and round goby dropped in the project and reference sections after the pre-survey. This general decline probably indicates a stabilization phase of the goby populations on a lower level, but may also be influenced by a major flood event. Nevertheless, our results indicate a high potential of shoreline modifications for invasive species control, calling for considering and incorporating them in river restoration programs.© The Author(s) 201