Ecological and behavioural influences on juvenile fish migrations in regulated rivers: a review of experimental and field studies

Abstract

This paper reviews results of experimental and field studies of downstream migration of young fish carried out in the Institute of Ecology and Evolution (Russian Academy of Sciences) as a part of the research programme on fish behaviour and ecology. Studies of fish migrations have been dominated by descriptions of migratory routes and proximate control of orientation. Behaviour and ecological factors influencing variability of downstream migrations of fish larvae and fry are still poorly understood. Life cycles of most of freshwater fishes can be roughly considered as a sequence of ''residential'' and ''migratory'' phases. Migrating, or just moving between microhabitats, fish are especially vulnerable to various threats including impacts of water abstraction systems. Abiotic (water flow velocity, rheogradients, turbulence, visual habitat heterogeneity) and biotic (foraging conditions, predators, competitors and parasites) factors can cause changes in fish spatial distribution as well as shift from residential to migratory behaviour. From the viewpoint of fish protection, these changes are important not only in the vicinity of water abstraction sites, but also in more distant parts of the aquatic system that should be taken into account in long-term assessments of impacts of abstraction on fish populations in regulated rivers. Besides macro-and mesoscale impacts that affect fish migrations and spatial distribution, micro-scale habitat heterogeneity (hydrodynamic and visual) are important as factors triggering and controlling various aspects of young fish behaviour. Interactions of water abstraction zones with fish populations have to be analysed at ecological (meso-scale spatial overlapping and longterm dynamics) and behavioural (effects of microscale structures and events) levels.

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.…”

“…In accordance with Zens et al (2017), we found that for higher flow conditions -corresponding to higher velocity classes in our study and higher flow scenarios in Zens et al (2017) -Au movement was lower and Ap movement was dominant. Also, in accordance with other studies (Lechner et al 2014b;Schludermann et al 2012;Pavlov et al 2008), we found highly significant larval stage-specific differences (L2, L4) in the fractions of movement patterns for Au and P movements. Thus hypothesis (b), that movement patterns are dependent on larval developmental stage and concomitant changes in swimming ability, is confirmed.…”

“…Dispersal modes of fish during the crucial larval phase of their life cycle is an important factor in recruitment and is governed by abiotic triggers (e.g., hydrology and hydraulics: Pavlov (1994); and discharge: Lechner et al 2017;Korman et al (2004); Reichard and Jurajda (2004)), in combination with biotic triggers (e.g., physiology and behaviour: Gaudin and Sempeski (2001); Heggenes and Dokk (2001);Pavlov (1994)). In a study on juvenile fish movement, Pavlov et al (2008) concluded that micro-scale habitat heterogeneity, interacting with individual behavioural variability within fish populations, could affect the proportion of resident to migratory fish in a river. Hence, "rheoreaction", defined as active fish behaviour induced by the current (Pavlov et al 2010), refutes the implementation of passive particles as a proxy for fish larvae (Lechner et al 2014a;Schludermann et al 2012;Stoll and Beeck 2012).…”

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

“…For each event of downstream movement, the proper movement rate (relative to water flow; V f ) was calculated according to Pavlov et al (2008) as…”

“…Our work is based on the fundamental concept of Pavlov et al (2008), who proposed three different types of downstream dispersal of riverine fish larvae based on swimming activity and orientation of larvae: passive drift (P), active downstream (Ad) movement, and an intermediate type, active-passive (Ap) downstream movement. Beyond these, active upstream (Au) and lateral movements are also assessed in the present study, and the effects on displacement distances are evaluated.…”