Fish Barrier Prioritisation (Landscape Scale Coastal, with economic analysis)

The objective of this method is to identify and assess anthropogenic physical barriers (biophysical, such as weed chokes, are not considered) that prevent, delay or obstruct fish migration in coastal catchments. Fish barriers identified through this process are ranked in order of priority, accounting for the cumulative impacts’ barriers have on the environment, fisheries resources and the economy. Social, economic and fisheries productivity benefits of barrier remediation are also considered.

This method systematically identifies all potential physical barriers to fish passage in a study area. The top ranked barriers in the study areas have remediation options costed to facilitate adoption of fish barrier remediation by local governments and natural resource management (NRM) groups. A holistic prioritisation process is used to objectively choose barriers to remediate to obtain the greatest benefits. This holistic process assists decision makers in determining where to best allocate funding opportunities to ensure the greatest environmental and socioeconomic outcomes for the study area. The assessment incorporates the impact on fish movement, location in the catchment (stream order) and surrounding land use in the first stage. The second stage incorporates an assessment of habitat condition and the third stage incorporates an assessment of social, economic and fisheries productivity.

Future assessments involve updating the progress of installing fish passage at barriers, to provide refined guidance for future remediation works, and barriers are scored again. The list of barriers were refined from the priority barriers form the previous biological assessment. Structures remediated were removed from the list, which affected original scores as ‘number of barriers downstream’ were less due to remediated barriers.

Barriers to fish passage such as dams, weirs, causeways, culverts, earthen bunds and floodgates can impact the health of river systems by altering natural flow regimes, and causing impassable barriers to aquatic fauna, especially fish. High value fish species, both ecologically and economically, are in decline due to barriers impeding strict migratory life cycle strategies (i.e. feeding, recruitment) which requires unimpeded access between habitats (i.e. between inland freshwater habitats and estuary/marine habitats). 

This method’s objective is to identify and assess physical anthropogenic barriers that prevent, delay or obstruct fish migration in coastal catchments. Fish barriers identified through this process are ranked in order of priority, accounting for the cumulative impacts barriers have on the environment, fisheries resources, economy and local community. The ultimate aim is to remediate barriers preventing connectivity, and this method assists decision makers in choosing which barriers to focus on, as in many coastal catchments there are large numbers of barriers which outweigh the resources available to remediate.

This method identifies and prioritises barriers through 3 major stages.

Stage 1 – Catchment Scale: GIS Analysis – Spatial & Temporal Habitat Characteristics

The first stage systematically identifies all potential barriers to fish passage in the study area. This is done through catchment-scale GIS analysis of biological, geographic and environmental characteristics associated with each potential barrier to produce a prioritised list for ground-truthing.

Stage 2 – Fine Scale: Site Specific Ecological Assessment (includes field validation)

The second stage performs a fine-scale, site specific barrier assessment to validate, score and rank priority barriers based on passability, configuration, in-stream habitat availability and flow conditions.

Stage 3 – Social, Economic and Fisheries Productivity Prioritisation

The third stage further refines and prioritises barriers based on economic, social and fisheries productivity criteria.

The top ranked fish barriers, depending on the area (can vary from 20 to 50) are listed with remediation options and indicative costs. This list is then available for adoption by local governments and NRM groups. Importantly, this stage considers the net benefits of improving connectivity versus the economic cost of remediation. Barriers that can be remediated with low cost fishways while increasing fisheries productivity or restoring vulnerable fish species score high, whereas barriers requiring technical and expensive fishways score lower. Holistic prioritisation process to make this selection effective and applicable straightaway.

Stage 1 Catchment Scale: GIS Analysis Spatial & Temporal Habitat Characteristicss

• Stream hierarchy
• Catchment condition
• Number of potential barriers downstream
• Distance to next barrier upstream
• Percentage of catchment (stream length) cut off by barrier
• Barrier’s geographical position within the sub-catchment

Stage 2 Fine Scale: Site Specific Ecological Assessment

• Barrier passability (Barrier type)
• Stream or riparian condition
• In-stream habitat condition
• Proximity to estuary
• Water supply
• Habitat for migratory fish upstream

Stage 3 Social, Economic and Fisheries Productivity Prioritisation

• Estimated cost
• Community and in-kind support
• Conservation significance
• Fisheries productivity and economic benefits
• Technical viability, how difficult to build
• Remediation effectiveness (which species can migrate, all or some)

• Locational and spatial data for barriers (i.e. bridges, culverts, road crossings, infrastructure)
• High quality imagery (satellite/drone)
• Stream ordered drainage network (eg. Strahler stream order and gradient) and/or Queensland waterways for waterway barrier works (layer by Fisheries QLD)
• Land use (Queensland Land Use Mapping Program (QLUMP))
• Barrier types
• Riparian condition
• Instream habitat condition
• Conservation significance
• Habitat suitability
• Economic significance
• Cultural significance
• Streamflow classification
• Barrier flow characteristics (height, passability)

Expert knowledge of riverine fauna ecology including life cycle and habitat requirements. Field assessment skills, and GIS data analysis skills. Knowledge of fisheries in the study area, including any listing under environmental legislation. Research skills to get baseline information about fish species in the study area.

• Geographic Information System for barrier identification and prioritisation.
• High quality imagery (satellite/drone)
• Species lists
• Spatial data

Stage 1 Desktop Analysis: All potential physical barriers in the study area are identified and a dataset is produced with a unique geo-referenced identification number. A prioritised list for ground-truthing (field assessment) is produced.

Stage 2 Field Assessment: A second list of physical barriers is produced, from refining the list in Stage 1. This list scores physical barriers according ecological criteria and contains site specific information about the barrier.

Stage 3 Socio Economic Assessment: A third list of physical barriers is produced from refining the list in Stage 2. This list scores physical barriers based on economic, social and fisheries productivity criteria. A final list of the top ranked fish barriers in the study area is produced, which also show remediation options (fishway options) and indicative costs.

• Input to investment strategies for fish barrier remediation works
• Threat and risk identification
• Decision support
• Inform priorities of management interventions required to reduce risks to ecosystems from different threats and improve ecosystem condition

Designed for federal, state or local government agencies, water utilities, and natural resource management groups.

• Assesses one of the key threats to aquatic ecosystem – loss of connectivity, from headwaters to estuary
• Accounts for ecological, social, and economic considerations
• Risk based approach allows for targeted prioritisation of barriers
• Informs management interventions at site scale despite being catchment scale assessment
• Repeated assessments can take into account changes in the catchment area and refine rankings
• Adaptive monitoring and management
• Considers the net benefits of improving connectivity versus the economic cost of remediation – which provides workable and costed solutions for remediation

• Method covers streams only, wetlands/offstream barriers not included
• Method applies to fish species only
• Instream habitat condition assessment plays a minor role in rankings and finer scale pressures may not be considered
• Focuses on migration and not all fish movement
• Conservation significance ranks common or abundant species low, common species may still be impacted by barriers to fish passage
• Economic scoring can penalise larger barriers, which may be the most important to remediate. See Fish Barrier Prioritisation (Landscape Scale/Coastal, no economic analysis) and case study for a similar methodology that does not incorporate this analysis in the scoring.

Fitzroy Basin Fish Barrier Prioritisation Project

Greater Brisbane Fish Barrier Prioritisation

Mackay Whitsunday Fish Barrier Prioritisation, Final Report for Reef Catchments NRM&Mackay Regional Council

Southern Gulf Catchments Barrier Prioritisation Report

Sunshine Coast Council Fish Barrier Prioritisation

This page should be cited as:

Department of Environment, Science and Innovation, Queensland (2020) Fish Barrier Prioritisation (Landscape Scale Coastal, with economic analysis), WetlandInfo website, accessed 18 March 2024. Available at: https://wetlandinfo.des.qld.gov.au/wetlands/resources/tools/assessment-search-tool/fish-barrier-prioritisation-landscape-scale-coastal-with-economic-analysis/