Fish response to turbulence

 

Turbulence within the aquatic environment can affect a fish’s stability, increase the cost of locomotion and hinder migration. It can also disorient prey organisms, increase prey encounter rates and is commonly associated with physical structures that provide flow refuging opportunities. In addition, in certain conditions fish can capture the energy contained in predictable turbulent flows and hold position with very little energy expenditure (Kármán gait). Hence, there are both positive and negative aspects of turbulence in the aquatic environment.

Fish preference for differing levels of turbulence varies both intraspecifically and interspecifically and temporally, depending on conditions such as hunger or time of day. Turbulence is complex, three dimensional and can vary in intensity, orientation, scale and periodicity. Measuring turbulence accurately has only recently been possible with the invention of technologies such as Acoustic Doppler Velocimetry (ADV) and Particle Image Velocimetry (PIV).

Most fish passes facilitate the passage of fish by providing an alternative route of passage with sufficiently reduced water velocity. This is usually achieved by the rapid dissipation of energy through the generation of turbulence using baffles. Hence, turbulence is inherent within fish passes. High levels of turbulence within fish passes are thought to be responsible for the reduced effectiveness of many fish passes. However, it has also been postulated that fish position within rivers could be controlled through the judicial use of turbulence.

Research undertaken at ICER investigated the habitat use of brown trout in a complex energetically taxing environment created in a large internal flume. High resolution measurements of the hydraulic conditions were collected using ADV and fish behaviour and habitat were analysed in relation to hydraulic conditions.

 

Media:

Hydraulic contour plot illustrating turbulent created in the wake of different sized solid cylinders (red circles) in an indoor flume

Publications:

Kerr, J.R., Manes, C. & Kemp, P.S. (2016). Assessing hydrodynamic space use of brown trout, Salmo trutta, in a complex flow environment: a return to first principles. Journal of Experimental Biology 219, 3480-3491 (doi:10.1242/jeb.134775)

 

People:

Dr. Jim Kerr

Dr. Constantino Manes

Prof. Paul Kemp