Fish-Friendly Obstructions to Fish Migration: Understanding fish response to velocity and turbulence conditions

Supervisors: Prof. Jo Cable, Dr. Catherine Wilson & Dr Jun Zhang (University of Bath)

In the UK, 43% of river habitats are classified as severely modified and there is continued pressure for further development (abstractions, flood protection etc). Typically, the hydrodynamic environment of a river is enriched by longitudinal and lateral variations in bathymetry, water depth and bed armour material, which promotes the generation of secondary currents, turbulence, and variation in local flow velocity and flow depth. However, hydraulic and hydro-ecological models (e.g. PHABSIM, MesoHABSIM) that define changes in physical habitat availability for target fish give only crude velocity and water level predictions in rivers of complex bathymetry and in high turbulence regions associated with fish passes, hydrometric and hydropower obstructions. In adapting existing riverine environments to meet the Water Framework Directive, it is essential to maintain the natural character, stability and discharge capacity whilst enhancing recolonisation processes (Hey, 1997), but in practice the optimal conditions for fish are poorly classified.

Existing protocols for evaluating fish swimming performance (Tierney, 2011) give no consideration to the magnitude of the turbulence (e.g. the temporal variation of the velocity) so fish swimming performance and stamina could be currently drastically over-estimated for demersal (bottom dwelling) fish and under-estimated for pelagic (water column) fish. Furthermore, the turbulence signature (magnitude of turbulence in relation to the time-averaged velocity) produced in a natural river (with variable bathymetry; rough bed and banks, bedforms, vegetation, islands and man-made structures) will be distinctly different to that produced in an idealised swimming chamber. Manmade and natural features can produce turbulent structures, which are a highly three-dimensional nature.

Key questions to be answered in this project include:

Is fish swimming performance impacted by the turbulence signature of the flow and those generated by obstructions to migration?

Does fish health impact on swimming performance and passage/transit time?

Which hydrodynamic metrics govern passage/transit time in a fish pass or manmade obstruction? How will climate change affect these?
At Cardiff, the student will collect detailed measurements under different flow conditions with various manmade obstructions to assess the velocity and turbulence characteristics when a fish’s swimming behaviour becomes unstable. In collaboration with Bath, the student will develop a linked habitat and flow modelling approach whereby a generic open source 3-D Computational Fluids Dynamic code (e.g. FLUENT, Pheonics, OpenFOAM, TELEMAC) is linked to a programming and post-processing software environment, such as MATLAB, in which new habitat suitability rules are implemented based on the empirical data and existing ecological models.

Start date: October 2016. Please note that mandatory activities will take place during September 2016.

Academic criteria: 2:1 degree in any Biological Sciences subject/ equivalent.

To apply, please email your CV and a covering letter to the primary supervisor of the project(s) you are applying for, including two named referees. Additionally, applicants should submit an application for postgraduate study via the Cardiff University Online Application Service, including an upload of your CV. Applicants should select Doctor of Philosophy (Biosciences), with a start date of October 2016. In the research proposal section, please specify the project title and supervisors of this project and copy the project description in the text box provided. In the funding section, please select "I will be applying for a scholarship / grant" and specify that you are applying for funding from NERC GW4+ DTP.