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

Abstract

Recruitment of Chondrostoma nasus and similar fish species in rivers is related to spatiotemporal 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-specific and release site-specific occurrences of these movement patterns were experimentally found for nine flow velocity classes (≤0.225 m·s −1 ). These currentinduced movement patterns, and evaluated durations within them, were used to develop a biased and correlated random walk model that includes rheoreaction -a key behavioural response of fish to flow within rivers. The study introduces the concept and application of a rheoreaction-based correlated random walk model, which coupled with a 3D hydrodynamic model, allows prediction of the spatiotemporal effects of various river discharges, morphologies, and restoration scenarios on larval fish dispersal.Résumé : Le recrutement de Chondrostoma nasus et d'espèces de poissons semblables dans les rivières est relié à des liens spatiotemporels entre l'éclosion des larves et les habitats d'alevinage. Le comportement de nage active contredit l'hypothèse voulant que les modèles de suivi de particules passives puissent se substituer aux modèles de dispersion des larves. Un canal de nage ovale avec une zone côtière de pente quasi naturelle a été créé pour observer les trajectoires de larves individuelles. Une nouvelle analyse de mappage en trois étapes a été mise au point pour distinguer quatre types de déplacements, à savoir : actif vers l'amont, actif vers l'aval, actif-passif et passif. Des cas de ces types de déplacements tant à l'étape du développement des larves que pour des sites de lâcher précis ont été observés expérimentalement pour neuf catégories de vitesses d'écoulement (≤0,225 m·s -1 ). Ces motifs de déplacement induits par le courant et leurs durées évaluées ont été utilisés pour développer un modèle de parcours aléatoire biaisé et corrélé qui comprend la rhéoréaction, une réaction comportementale clé des poissons à l'écoulement dans les rivières. L'étude introduit le concept et l'application d'un modèle de parcours aléatoire corrélé basé sur la rhéoréaction qui, jumelé à un modèle hydrodynamique en 3D, permet de prédire les effets spatiotemporels de différents débits, morphologies et scénarios de restauration de rivière sur la dispersion des larves de poisson. [Traduit par la Rédaction]

The influence of discharge, current speed, and development on the downstream dispersal of larval nase (Chondrostoma nasus) in the River Danube

“…Such characteristics are revealed in the unequal distribution of L2 and L4 nase over the sampling area (i.e., in particular drift nets), potentially originating from differences in behaviour, orientation, and swimming. Studies on the upstream and downstream trajectories of young nase in a racetrack flume, for instance, found correlations between developmental stage (L2, L4) and the frequency of occurrence of predefined movement patterns (i.e., active upstream, active downstream, active-passive, passive) in a velocity gradient (Glas et al 2017).…”

“…This experiment is the first attempt to directly compare larval dispersal with passive diffusion in their natural environment. The results are expected to influence the design of the first individual-based larval dispersal model in rivers (see Glas et al 2017), as well as future river management measures.…”

Evaluating flow management as a strategy to recover an endangered sturgeon species in the Upper Missouri River, USA

“…These questions are not unique to pallid sturgeon; whereas early descriptions of larval dispersal in fishes characterized the process as primarily passive (Pavlov, ), a more nuanced understanding has emerged that describes the process within an active–passive framework (Lechner et al, ; Zens, Glas, Tritthart, Habersack, & Keckeis, ). Movement patterns are influenced by both developmental stage and physical factors such as flow velocity relative to swimming ability (Glas et al, ).…”

“…In this article, we use the word “drift” to indicate the process during early larval development wherein dispersal (the more general movement of young fish away from a spawning site) by hydraulic processes occurs. Improved understanding of drift, a complex, three‐dimensional process, has been achieved with multidimensional models and high‐resolution data that capture complex interactions between hydraulics and rapidly developing fish morphology and behaviour (Glas et al, ; Schludermann, Tritthart, Humphries, Keckeis, & Bradford, ). Although sophisticated numerical models that couple hydrodynamics and behavioural aspects of dispersal are at times feasible, they are not needed for many decisions, and the required high‐resolution inputs, data‐intensive parameterization, and computationally expensive attributes of more robust models can preclude their use.…”

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

“…An experimental study by Zens et al (2018) that analyzed individual movement trajectories of a fluvial fish species showed that swimming activity, direction of movement, and orientation towards a current vector led to larval dispersal paths and distances that deviated from those of passive particles, even at overcritical current situations. The movement patterns observed in this study (Glas et al 2017), which, when coupled with a 3D hydrodynamic model, enable prediction of the effects of discharge, bed morphology, as well as restoration measures on the distribution patterns of the early stages of fish in rivers. Lechner et al (2018) show in their field experiment that the drift mode and spatial drift patterns of marked and recaptured larvae differ substantially from simultaneously released, passively drifting plastic particles.…”