Reynolds shear-stress and velocity: positive biological response of neotropical fishes to hydraulic parameters in a vertical slot fishway

Abstract

The barriers created by dams can cause negative impacts to aquatic communities, and migratory fish species are directly affected. Fishways have been developed to allow the upstream passage of fishes through dams. In Brazil, after the implementation of environmental laws, these structures have been built based on European and American fishway designs. Studies have shown selectivity for different neotropical fishes in some Brazilian fishways, and the main challenge has been to promote upstream passage of a large number of diverse fish species. The patterns of flow circulation within the fish ladder may explain fish selectivity although few studies detail the fish response to hydraulic characteristics of fish ladder flow. This paper presents a laboratory study, where a vertical slot fishway was built in a hydraulic flume and the behavior of two neotropical fish species (Leporinus reinhardti and Pimelodus maculatus) were analyzed. The structure of flow was expressed in terms of mean velocity, Reynolds shear-stress and velocity fluctuation fields. The individuals of Leporinus reinhardti had higher passage success than Pimelodus maculatus in the laboratory flume. Both species preferred areas of low to zero Reynolds shear-stress values. In addition, different preferences were observed for these species concerning the horizontal components of velocity fluctuation.Interrupções em rios, como as causadas por barragens, provocam impactos negativos sobre as comunidades aquáticas e as espécies migratórias de peixes são diretamente afetadas. A fim de permitir a passagem de peixes, mecanismos de transposição são construídos junto a barramentos. No Brasil, após a implantação de leis ambientais, estas estruturas passaram a ser amplamente construídas e foram baseadas em projetos desenvolvidos na Europa e na América do Norte. Análises de mecanismos já construídos têm mostrado grande seletividade para espécies neotropicais e as demandas da diversa fauna de peixes neotropical são apresentadas como principal desafio ao projeto de passagens para peixes. Os padrões de escoamento dentro de escadas para peixes podem explicar a seletividade destes mecanismos, mas poucos estudos detalham a resposta dos peixes às características hidráulicas encontradas dentro das escadas. Este estudo apresenta uma análise realizada em um laboratório onde foi construída uma escada do tipo ranhura vertical e analisados os comportamentos de duas espécies neotropicais (Leporinus reinhardti e Pimelodus maculatus). O escoamento foi estudado considerando os campos de velocidade média, tensão cisalhante de Reynolds e flutuações de velocidades. Os indivíduos da espécie Leporinus reinhardti apresentaram maior sucesso de passagem do que os da espécie Pimelodus maculatus. Ambas as espécies preferiram áreas de tensão de Reynolds igual a zero. Além disso, diferentes preferências foram observadas para cada espécie em relação às componentes horizontais da flutuação da velocidade.

Assessing hydrodynamic space use of brown trout, Salmo trutta, in a complex flow environment: a return to first principles.

“…Further, the importance of turbulence is well recognised, and a variety of different metrics (e.g. TI: Smith et al, 2005;RTI: Cotel et al, 2006;TKE: Smith et al, 2006;and τ: Hayes and Jowett, 1994;Silva et al, 2011Silva et al, , 2012aDuarte et al, 2012) have been used to define suitable habitat or migratory routes, although such statistical links remain difficult to interpret from an ecological perspective. However, attempts to quantify hydrodynamic space use by fish living in lotic environments frequently fail to consider both drag and turbulence together.…”

“…Third, laboratory studies continue to attempt to find statistical links between patterns of fish distribution/ movement and one or more of any number of turbulent flow characteristics, such as turbulence intensity (TI), relative turbulence intensity (RTI), turbulent kinetic energy (TKE), turbulent length scale (TLS) or Reynolds shear stresses (τ) (e.g. Smith et al, 2005Smith et al, , 2006Silva et al, 2011Silva et al, , 2012aDuarte et al, 2012). However, the biophysical interpretation of these statistical links remains obscure.…”

Upstream and downstream migration speed of Prochilodus costatus (Characiformes: Prochilodontidae) in upper São Francisco basin, Brazil

“…Even though data on swimming capacity derived from laboratory experiments is available for some species (Santos et al, 2009(Santos et al, , 2012Castro et al, 2010;Duarte et al, 2012;Sampaio et al, 2012;Duarte, Santos, 2014), little research has examined the swimming performance of Neotropical migratory species in natural river systems and most data are derived from mark-recapture studies that may considerably underestimate actual speeds (Godoy, 1975;Delfino, Baigun, 1985). Few studies have measured the migration speeds of Neotropical species during spawning or post-spawning migrations using field-collected biotelemetry data (Godinho et al, 2007;Andrade Neto, 2008;Fries, 2013;Pérez, 2014).…”

Conversion of Vertical Slot Fishways to Deep Slot Fishways to Maintain Operation during Low Flows: Implications for Hydrodynamics

“…Their findings suggest that high turbulent kinetic energy can confuse fish in their efforts to move through the fishway along energy efficient paths, increasing fish fatigue [24]. On the contrary, pool areas with low turbulent kinetic energy and Reynolds shear stress values can be used by fish for resting during the ascent though the fishway [25,26]. It should be noted, however, that fish response to variations of these parameters is still not well documented, and that other turbulence descriptors such as the eddy size and strength are also suspected to be important for effective fish passage [27].…”