Flow in nature-like fishway and its relation to fish behaviour

Abstract

Experimental results on the nature-like fishway induced flow field and its relation to fish behaviour are presented. A rocky-ramp with 5% slope was built along a 8.9 m × 0.9 m × 0.6 m laboratory flume, and acoustic Doppler velocity measurements were taken in a grid with 186 points for low, middle, and high discharges. The flow is characterized applying spatial and point analysis techniques. Point analysis consistently shows that the boulder to boulder distance is small enough to disrupt turbulent coherent structures. At boulder wakes no predominance of sweep and ejection events occur, evidencing a good resting place for fish migration. The nature-like rocky-ramp offers a diversity of flow conditions controlled by the boulders geometry that might allow a variety of fishes to develop their preferred paths characterized by flow properties with different magnitudes depending on the particular species. Obtained results compare well with similar ones reported for other standard fishways.Résumé : Cet article présente les résultats d'expériences concernant le champ de courant induit dans une passe migratoire d'aspect naturel et sa relation avec le comportement des poissons. Une rampe rocheuse ayant une pente de 5 % a été construite le long d'un canal jaugeur de laboratoire mesurant 8,9 × 0,9 × 0,6 m; des mesures de vitesse ont été prises au débitmètre acoustique selon une grille de 186 points à des débits faibles moyens et élevés. L'écoulement est caractérisé en appliquant des techniques d'analyse spatiale et par points. L'analyse par points montre de manière uniforme que la distance de rocher à rocher est suffisamment petite pour perturber les structures cohérentes de turbulence. Il n'y a aucune prédominance de balayage et d'éjection dans les sillages des rochers, prouvant qu'il s'agit d'un bon endroit de repos pour les poissons en migration. La rampe rocheuse d'aspect naturel offre une diversité de conditions d'écoulement contrôlées par la géométrie des rochers, ce qui pourrait permettre à plusieurs espèces de poissons de développer leur chemin préféré selon les propriétés d'écoulement de différentes amplitudes propres aux espèces particulières. Les résultats obtenus se comparent bien à d'autres résultats similaires rapportés pour d'autres passes migratoires standards. [Traduit par la Rédaction] Mots-clés : débitmètre acoustique, habitat du poisson, passe migratoire, écoulement, passes migratoires d'aspect naturel, turbulence.

An Efficiency Analysis of a Nature-Like Fishway for Freshwater Fish Ascending a Large Korean River

“…The nature-like fishway has a very low slope of 1%, providing lower water velocity and turbulence compared to other fishways [22]. Water velocity is an important parameter for the attraction and passage efficiencies of a fishway because a high water velocity prevents small fish with weak swimming ability from using the fishway [18].…”

“…In this regard, the Sangju Weir fishway was verified as having an appropriate water velocity and turbulence for a nature-like fishway, facilitating its usage by small individuals. Furthermore, while technical fishways have a constant water velocity and water depth due to their homogenous structure, nature-like fishways have lower slopes and nature-mimicking irregular substrates, producing various water depths and velocities [22]. Such nature-like fishway environments allow fish of different sizes and swimming abilities to use the fishway [9].…”

Alternative mitigation measures for fish passage in standard box culverts: Physical modelling

“…The first plate was fixed with its leading edge in line with the barrel entrance. Gaps between rectangular plates were introduced to avoid fish traveling through complete darkness since fish tend to be attracted to regions of light (BRETON et al 2013). The diagonal baffle configuration consisted of 0.012 m high baffles, oriented to 60 with the streamwise flow direction, with 0.10 m longitudinal spacing between baffles.…”

“…The selection of the type of culvert fish pass and of the fish pass characteristics depends on the swimming capacities of the fish species. Currently there was no simple technical means for measuring the characteristics of turbulence in a fish pass, although it is acknowledged that the turbulence in a fish pass plays a key role in fish behaviour (LIU et al 2006, YASUDA 2011, BRETON et al 2013. Key turbulence characteristics, deemed most important to fish movement, were identified as turbulence intensity, Reynolds stresses, turbulent kinetic energy, vorticity, dissipation and eddy length scales (PAVLOV et al 2000.…”

Changes in particulate organic matters and plankton populations in nature-like fishways: role of nature-like fish ways in water treatment

“…However, in the late 1970s, nature-like bypass channels were developed in Europe and were characterized by a "soft" engineering approach (Katopodis and Rajaratnam, 1983). These nature-like fishways are built with diverse materials, such as large wood debris, boulders, and riparian vegetation, imitating natural stream geomorphologic conditions (Bretón et al, 2013). Due to their heterogeneous structure, compared with conventional fishways, nature-like fishways offer a greater variety of water velocities and depths, making them amenable to a wider range of fish species and sizes (Aarestrup et al, 2003).…”