Barrier remediation through biopassage structures (fishways)
Aquatic fauna passage (biopassage), or fish passage, is the process where aquatic fauna move naturally around their environment. Biopassage is critical to the survival of many native species. Many fish need to move freely within waters at different times to access food, shelter, avoid predators, and to reproduce. They often require the free passage between system types, such as between freshwater and marine environments.
Biopassage over barriers (such as weirs and dams) can be remediated through structures such as fishways, fish ladders, fish friendly culverts, elver passes and turtleways[2]. However in the first instance, it should be determined whether the barrier is still required and should be removed rather than building a biopassage structure.
Potential benefits from this intervention:
Assists in restoring connections between aquatic habitats, in areas where it may have previously been lost or reduced.
Biopassage structures can provide shelter, resting areas, and areas for fish and other aquatic fauna to avoid predators.
Assists with maintaining and improving fish stocks for recreational, First Nations and commercial users by allowing fish life history stages to continue.
Biopassage structures can be engineered for larger barriers such as dams or smaller barriers, and there are several types that suit a variety of situations.
Biopassage structures can be engineered to suit different life stages of fish different swimming abilities and sizes.
Biopassage structures can be designed to suit the hydrological characteristics of the waterway (resilience to flood, etc.).
Biopassage structures can enhance aquatic fauna movement if correctly designed,constructed and maintained, without having to remove the barrier, which may not be a viable option (water supply, etc.).
Some biopassage designs use natural materials (such as rock ramps) and require little maintenance.
Potential negative implications from this intervention:
Local fish community composition that will use the biopassage structure need to be considered as there is a risk that the biopassage structure will act as an additional barrier to aquatic fauna passage. For example, many Australian fish species migrate as juveniles and do not possess the strength to use fish passage structures that may be designed for stronger adult fish. If fish cannot effectively transit through the holding chamber, they be at risk from increased predation.
Some biopassage structure options are very costly.
Biopassage structures require water to operate, and therefore, cannot facilitate fish passage during dry periods or periods of low flow. Certain flow requirements are required to attract fish to use the biopassage structure.
Biopassage structures are at risk of being damaged by strong currents, and flooding events, and so, will require regular maintenance.
Some biopassage designs require a large area to be fully functional which could become an issue if there are constraints with land availability.
All biopassage structures collect debris, and many facilitate the growth of weeds at their inlet and outlets, which can block components of the structure, alter hydraulic conditions and result in physical or behavioural barriers for fish movement.
Intervention considerations:
Seek appropriate specialist advice and check legal obligations (e.g. permits).
Many catchment areas contain several barriers to aquatic fauna passage, and barrier remediation may need to be prioritised to the barriers with the highest impact on aquatic fauna passage.
All biopassage structures require regular maintenance to preserve the functionality of the structure, and this should be integrated into an appropriate asset maintenance system.
Ideally, biopassage structures should be inspected, checked hydraulically, and dewatered to check for blockages at least annually and ideally before the flow season[1][3].
Biopassage structure operation is essential during periods of peak fish movement (typically spring and summer) and should be documented.
Prior to construction, check with electricity, water, and telecommunication providers regarding considerations for any existing infrastructure.
A comprehensive list of biopassage structures, including management considerations is available here.
Additional information
Publications:
^ O'Connor, J, Stuart, I, Jones, M & Arthur Rylah Institute for Environmental Research (2017), Guidelines for the design, approval and construction of fishways. [online] Available at: http://nla.gov.au/nla.obj-664261559 [Accessed 25 February 2021].
^ Stuart, IG & Marsden, TJ (2019), 'Evaluation of cone fishways to facilitate passage of small-bodied fish', Aquaculture and Fisheries. [online] Available at: https://doi.org/10.1016/j.aaf.2019.02.003.
^ O'Connor, J, Stuart, I, Jones, M & Arthur Rylah Institute for Environmental Research (2017), Guidelines for the design, approval and construction of fishways. [online] Available at: http://nla.gov.au/nla.obj-664261559 [Accessed 25 February 2021].
^ Stuart, IG & Marsden, TJ (2019), 'Evaluation of cone fishways to facilitate passage of small-bodied fish', Aquaculture and Fisheries. [online] Available at: https://doi.org/10.1016/j.aaf.2019.02.003.
Last updated: 3 June 2022
This page should be cited as:
Department of Environment, Science and Innovation, Queensland (2022) Barrier remediation through biopassage structures (fishways), WetlandInfo website, accessed 30 August 2024. Available at: https://wetlandinfo.des.qld.gov.au/wetlands/management/rehabilitation/rehab-process/step-4/intervention-options/fishways.html
— Department of Environment, Science and Innovation