The European Fish Hazard Index – An assessment tool for screening hazard of hydropower plants for fish

Hydroelectricity is critical for decarbonizing global energy production, but hydropower plants affect rivers, disrupt their continuity, and threaten migrating fishes. This puts hydroelectricity production in conflict with efforts to protect threatened species and re-connect fragmented ecosystems. Assessing the impact of hydropower on fishes will support informed decision-making during planning, commissioning, and operation of hydropower facilities. Few methods estimate mortalities of single species passing through hydropower turbines, but no commonly agreed tool assesses hazards of hydropower plants for fish populations. The European Fish Hazard Index bridges this gap. This assessment tool for screening ecological risk considers constellation specific effects of plant design and operation, the sensitivity and mortality of fish species and overarching conservation and environmental development targets for a river. Further, it facilitates impact mitigation of new and existing hydropower plants of various types across Europe

Session B5: Efficiency of a Nature-Like Bypass Channel at Rodley Weir, River Aire

Abstract: Man-made physical barriers (weirs) have disrupted longitudinal connectivity in many river systems around the world for centuries. Impacts of weirs on fish communities centers on the reduced ability of fish to perform upstream migrations. To counter the potential effects these structures are having on fish communities, a number of fish pass designs have been developed to ease passage around potential barriers. To monitor the effectiveness of a recently constructed nature like bypass on the River Aire, Passive Integrated Transponder (PIT) systems were installed to observe movements of brown trout (Salmo trutta). The array consists of four swim through antennas, two at either end of the pass so that swimming direction could be determined. A total of 111 wild brown trout were caught, PIT tagged and released 380 m downstream of the fish pass entrance. In total 57 brown trout (51%) were detected on the most downstream loop, and of these 49 successfully entered the pass (86%). Thirtyeight of these successfully exited the pass in an upstream direction (78%). Further analysis found that a select number of fish used the pass as an area of refuge during high flows. The possible reasons for these findings are discussed in relation to flow, temperature, time of day, season and fish size. This information is important to improve our understanding of fish pass performance, thus informing future best practice guidance of fish passage designs

Session B8: Changes in Fish Passage Metrics Following the Co-Location of a Low-Head Hydropower Turbine with an Existing Fish Pass; Revealed by an Acoustic Tracking Study of Migratory Salmonids

Abstract: Co-location of hydropower turbine outfalls with fish pass entrances has been suggested as current best practice to optimise the attraction flows for the fish pass and to mitigate the perceived negative impacts of small run-of-river hydropower schemes. To test this a five year acoustic tracking study was instigated to monitor the installation of a low-head Archimedes screw turbine alongside an existing pool-traverse fish pass on Ruswarp Weir, at the tidal limit of the River Esk (England). The study tracked the behaviour of salmon and sea trout as they approached the weir and fish pass and determined the overall passage rate (% of tagged fish ascending the weir by any route), the attraction efficiency (% of tagged fish entering the pool below the fish pass) and the fish pass efficiency (% of tagged fish detected in the pool below the fish pass that ascended the weir via the pass). Over the five years (3 years pre and 2 years post) 138 sea trout and 18 salmon were tracked using acoustic tags with arrays of fixed and mobile hydrophones to determine large-scale behaviour in the tideway and in the approach to the fish pass (a pool-traverse pass, replaced by a Larinier pass during construction of the turbine). The study showed that following the co-location of the turbine and the construction of the Larinier pass there was a significant increase in the attraction efficiency (35% to 69%) and the overall passage rate (35% to 53%) but a significant reduction in fish pass efficiency (100% to 69%) for sea trout. These results support the concept of colocating outfalls to increase attraction efficiency whilst at the same time raise concerns that this also reduced the fish pass efficiency; perhaps causing a distraction and delay to migrants, with an associated increased risk of predation

Catchment-wide interactive effects of anthropogenic structures and river levels on fish spawning migrations

Worldwide, rivers are extensively fragmented by anthropogenic structures, reducing longitudinal connectivity, inhibiting migration and leading to severe declines in many fish populations, especially for diadromous species. However, few studies have determined the effects of annual differences in hydrology on catchment penetration past barriers to spawning habitats. We investigated the upstream spawning migration of 120 (n = 61 & 59) acoustic tagged river lamprey (Lampetra fluviatilis) across two contrasting (dry and wet) years in the River Yorkshire Ouse, England. Overall, significantly more lamprey reached spawning habitat (76% vs 39%) and penetrated significantly further upstream (median [km] from release, 53.9 vs 16.8) in the wet year than the dry year. Passage at weirs was almost exclusively during elevated river levels, which directly and collectively influenced catchment-wide distribution, especially in the dry year. Indeed, higher proportions entered two upper tributaries in the wet year (9.8% vs 27.1% and 9.8% vs 30.5%), due to increased passage efficiencies at the two main river weirs (60.5–87.5% and 54.5–83.8%), and reached assumed spawning locations 66.5% and 10.9% quicker. By contrast, there was no difference in numbers of lamprey entering, or time taken to arrive at assumed spawning location, in the two lower river tributaries between years. Our study supports the landscape-scale paradigm for ecosystem restoration because of the observed catchment-level effects of hydrology and barrier distribution on fish migration. Connectivity restoration for migratory fish should be implemented at a catchment scale, with planning incorporating spatial information regarding accessibility to key habitats to reap the largest gains

Cost-effective environmental mitigation measures i hydropower rivers

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Using acoustic tracking of an anadromous lamprey in a heavily fragmented river to assess current and historic passage opportunities and prioritise remediation

Anthropogenic structures extensively fragment riverine systems, reducing longitudinal connectivity, inhibiting migration and leading to severe declines in many fish populations, especially for diadromous species. This study investigated the upstream spawning migration of anadromous river lamprey (Lampetra fluviatilis) in a heavily fragmented tributary of the Humber Estuary, the location of one of the largest UK river lamprey populations. Overall, this study quantified river lamprey migration, spawning habitat distribution and historic river levels to develop a novel empirical index to understand the impact of man-made barriers and prioritise their remediation. Passage at all weirs only occurred during episodic high river levels, often after prolonged delays with no lamprey passing below average levels for the time of year or utilising the fish pass at the first weir (T1) at the tidal limit. Barrier passage opportunities at the first four weirs were only possible for 30.3%, 38.7%, 52.1% and 6.7% of the migration period, but were lower and severely limited in 15 of the last 21 years. In addition, more lamprey (60%, n = 18) were last detected in reaches with no spawning habitat than in spawning habitat (40%, n = 12). Given the impassibility of, and lack of retreat from, T1 to other Humber tributaries, the River Trent is currently considered an ecological trap for a large proportion of lamprey that enter from the Humber Estuary. This passage should be urgently remediated, per the prioritisation index presented here, to aid river lamprey conservation, especially given their status as a designated feature of the Humber SAC

Extinction risks and threats facing the freshwater fishes of Britain

1.Extinctions occur naturally in all environments, but rates have accelerated rapidly during the Anthropocene, especially in fresh water. Despite supporting many fish species of conservation importance, there has never been a formal assessment of their extinction risks in Britain, which has impeded their inclusion in relevant legislation and policy. This study therefore used the International Union for the Conservation of Nature (IUCN) Red List of Threatened SpeciesTM Categories and Criteria to conduct the first systematic assessment of the extinction risks and threats facing the native freshwater and diadromous fishes of Britain. Additionally, national assessments were produced for England, Scotland and Wales, reflecting the level at which environmental policy decisions are taken in Britain.2.Seven species were categorised as being threatened with extinction at regional level, with European eel Anguilla anguilla and allis shad Alosa alosa classified as Critically Endangered, Atlantic salmon Salmo salar, vendace Coregonus albula and European whitefish Coregonus lavaretus classified as Endangered, and Arctic charr Salvelinus alpinus and twaite shad Alosa fallax classified as Vulnerable. In addition, burbot Lota lota was classified as Regionally Extinct, ferox trout Salmo ferox was categorised as Data Deficient, and 25 species were categorised as Least Concern. European sturgeon Acipenser sturio and houting Coregonus oxyrinchus, although probably native, qualified as only “vagrants” in fresh water, so were categorised as Not Applicable.3.The assessments provide objective baselines against which future changes can be determined, and a key evidence base to support policy and management decisions for the conservation of freshwater and diadromous fish species and their habitats in Britain. It is recommended that the assessments are repeated every 10 years, which would enable changes in conservation status, the effectiveness of policies and where targeted interventions may be required to be examined using the Red List Index

The Virtual Ventricular Wall: A Tool for Exploring Cardiac Propagation and Arrhythmogenesis

Methods for the experimental and clinical investigation of cardiac arrhythmias are limited to inferring propagation within the myocardium, from surface measurements, or from electrodes at a few sites within the cardiac wall. Biophysically and anatomically detailed computational models of cardiac tissues offer a powerful way for studying the electrical propagation processes and arrhythmias within the virtual heart. We use virtual tissues to study and visualise the effects of patho- and physiological conditions, and pharmacological interventions on transmural propagation in the virtual ventricular walls. Class III drug actions are quantitatively explained by changes induced in the transmural dispersion of action potential duration. We illustrate the automated construction of a virtual anisotropic ventricle from Diffusion Tensor MRI for individual hearts, and use it to explore mechanisms leading to ventricular fibrillation. The virtual ventricular wall provides an effective tool for exploring, evaluating and visualising processes during the initiation and maintenance of ventricular arrhythmias