A toolkit for optimizing fish passage barrier mitigation actions

1. The presence of dams, stream–road crossings and other infrastructure often compromises the connectivity of rivers, leading to reduced fish abundance and diversity. The assessment and mitigation of river barriers is critical to the success of restoration efforts aimed at restoring river integrity. 2. In this study, we present a combined modelling approach involving statistical regression methods and mixed integer linear programming to maximize resident fish species richness within a catchment through targeted barrier mitigation. Compared to existing approaches, our proposed method provides enhanced biological realism while avoiding the use of complex and computationally intensive population/ecosystem models. 3. To estimate barrier passability quickly and at low cost, we further outline a rapid barrier assessment methodology. The methodology is used to characterize potential passage barriers for various fish species common to the UK but can be readily adapted to different planning areas and other species of interest. 4. We demonstrate the applicability of our barrier assessment and prioritization approach based on a case study of the River Wey, located in south-east England. We find that significant increases in species richness can be achieved for modest investment in barrier mitigation. In particular, dams and weirs with low passability located on mid- to high-order streams are identified as top priorities for mitigation. 5. Synthesis and applications. Our study shows the benefits of combining a coarse resolution barrier assessment methodology with state-of-the-art optimization modelling to cost-effectively plan fish passage barrier mitigation actions. The modelling approach can help inform on-the-ground river restoration decision-making by providing a recommended course of action that best allocates limited resources in order to restore longitudinal connectivity and maximize ecological gains

Swimming performance and behaviour of bighead carp (Hypophthalmichthys nobilis): application to fish passage and exclusion criteria

The bighead carp (Hypophthalmichthys nobilis) is one of the most commercially important freshwater fish species in China, but their abundance has declined considerably in recent decades, partly due to river regulation. In other countries it is invasive, posing an ecological and economic threat. To improve fish pass effectiveness at impediments to migration in its native range, and create velocity barriers to reduce range expansion where it is invasive, an improved understanding of swimming ability and behaviour is needed. The burst, prolonged, and sustained swimming performance of juvenile bighead carp were quantified experimentally through constant acceleration trials (Umax), fixed velocity tests, and volitional passage efficiency trials through three consecutive constrictions. The effects of fork length (FL), temperature, swimming speed and method (swim chamber/open channel flume section) on endurance in fixed velocity trials were evaluated. The utilisation of low velocity areas close to the flume edge and floor at different mid-channel velocities was also explored. The mean sustained swimming speed in endurance tests was 3.84 FL s?1 (range equivalent to 0.37–0.78 m s?1), and burst speeds reached 12.78 FL s?1 (up to 1.22 m s?1 for larger fish). The meanUmax was 6.81 FL s ?1 (0.51 m s?1). In fixed velocity trials, method did not influence endurance and fish rarely utilised low velocity areas in the corners of the flume when water velocity exceeded sustained swimming ability. Passage efficiency decreased at successive flume constrictions, possibly indicating a poor repeat burst swimming performance. Field validation is required to verify wild bighead carp behaviour and passage in the hydraulic conditions created by fish passes

Data from: A toolkit for optimizing fish passage barrier mitigation actions

The presence of dams, stream&ndash;road crossings and other infrastructure often compromises the connectivity of rivers, leading to reduced fish abundance and diversity. The assessment and mitigation of river barriers is critical to the success of restoration efforts aimed at restoring river integrity. In this study, we present a combined modelling approach involving statistical regression methods and mixed integer linear programming to maximize resident fish species richness within a catchment through targeted barrier mitigation. Compared to existing approaches, our proposed method provides enhanced biological realism while avoiding the use of complex and computationally intensive population/ecosystem models. To estimate barrier passability quickly and at low cost, we further outline a rapid barrier assessment methodology. The methodology is used to characterize potential passage barriers for various fish species common to the UK but can be readily adapted to different planning areas and other species of interest. We demonstrate the applicability of our barrier assessment and prioritization approach based on a case study of the River Wey, located in south-east England. We find that significant increases in species richness can be achieved for modest investment in barrier mitigation. In particular, dams and weirs with low passability located on mid- to high-order streams are identified as top priorities for mitigation. Synthesis and applications. Our study shows the benefits of combining a coarse resolution barrier assessment methodology with state-of-the-art optimization modelling to cost-effectively plan fish passage barrier mitigation actions. The modelling approach can help inform on-the-ground river restoration decision-making by providing a recommended course of action that best allocates limited resources in order to restore longitudinal connectivity and maximize ecological gains.,River Wey Fish Sampling DataRiver Wey fish sampling dataset used in species richness regression analysis (King et al. 2016).River Wey Barrier DataRiver Wey barrier dataset used in barrier optimization analysis (King et al. 2016).OPL modelCPLEX Studio OPL project, including (.mod), data (.dat), settings (.ops) files, and Excel (.xlsx) files, used in performing optimization analysis (King et al. 2016).,</span

River Wey Fish Sampling Data

River Wey fish sampling dataset used in species richness regression analysis (King et al. 2016)

OPL model

CPLEX Studio OPL project, including (.mod), data (.dat), settings (.ops) files, and Excel (.xlsx) files, used in performing optimization analysis (King et al. 2016)

River Wey Barrier Data

River Wey barrier dataset used in barrier optimization analysis (King et al. 2016)