The Response of Anguilliforms to Barriers to Migration.

Transcription

1 The Response of Anguilliforms to Barriers to Migration. Iain Russon* 1,2, Olle Calles 3 & Paul Kemp 1 IFM Annual Conference 3 rd 5 th October 2012 Contact details: 1 International Centre for Ecohydraulics Research, University of Southampton, Southampton; 2 Current address: APEM Ltd, Unit 2 Ground Floor, Gwaun Elai Business Campus, Llantrisant, South Wales, CF72 8XL; * i.russon@apemltd.co.uk; 3 Department of Biology, Karlstad University, Karlstad, Sweden.

2 General policy EU renewable energy policy Hydropower = important Clean energy Renewable EU Water Framework Directive Meet GES/GEP Must mitigate environmental impacts on migratory fish

3 Potential impacts of run-of-river hydropower Flow Reduced trigger for migration Reduced flows over natural structures Sediment transport Direct mortality Delay to migration

4 Past fish passage considerations Biased towards migrating salmonids What about other species? Atlantic salmon (Salmo salar) River lamprey (Lampetra fluviatilis) Biased to upstream migrations Downstream migration is important!

5 Anguilliforms of interest Worldwide eel and lamprey stocks in decline European river lamprey Anadromous Protected EC habitats directive Eels Catadromous IUCN critically endangered Protected CITES Eels management plans >40% escapement River lamprey (Lampetra fluviatilis) European eel (Anguilla anguilla)

6 Reasons for decline Not well understood but potentially:- Climate change Invasive parasite infestation Overfishing Habitat loss Reduced connectivity Anguillicola crassus in the swim bladder of a European eel

7 Infrastructure Reduced connectivity - highest rate in recorded history Due to infrastructure Reduced access to: Feeding Spawning Residential habitat Direct mortality Delayed migration Need to mitigate negative impacts

8 Attaining swim speeds Swim speed = main biological component used in fish pass design

9 Flume study facilities Re-circulatory flume 21.4m working length 1.4m wide Max. 0.6m depth Flat-v weir at Chilworth flume facility Overshot weir at Chilworth flume facility

10 Attaining swim speeds Aim: Attain swim speeds during voluntary movement Method: Individual eel/lamprey exposed to four discharges 0.6 m 0.2/0.3 m Thickness = 0.02 m 0.1 m 1.37 m

11 Flume width (m) Flume width (m) Results Burst speeds = higher than previously reported Eel: 1.35 m s -1 (Solomon & Beach, 2004) Lamprey: m s -1 (Laine et al., 1998) a) Low discharge U = 0.56 ± 0.03 m s -1 (min. max. = ) b) Intermediate discharge U = ± 0.03 m s -1 (min. max. = ) c) Distance downstream of bypass (m) High discharge U = 1.60 ± 0.11 m s -1 (min. max. = ) d) Distance downstream of bypass (m) Very high discharge U = 1.98 ± 0.14 m s -1 (min. max. = ) Distance downstream of bypass (m) Distance downstream of bypass (m)

12 Bar racks/screens Racks prevent trash entering and deflect fish from turbines to bypass Primarily designed for salmonids Problem: Impingement > mortality Juvenile Pacific lamprey (L. tridentata) impinged on a screen Eel mortalities on the Ätrafors power plant screen at the River Ätran, Sweden

13 Telemetry study Atrafors HEP, Sweden (Calles et al., 2010).

14 Eels released in reservoir Calles et al., 2010.

15 Eels released in intake Calles et al., 2010.

16 High mortality 40% survival intake channel group 23% survival reservoir group 30% survival All fish released upstream BUT 40% biomass escapement required! Need further information on eel behaviour

17 Flume study Aims assess behaviour to: Improve deflection efficiency towards a bypass Reduce impingement Reduce mortality Bypass approach Rack approach

18 Method Horizontal bar rack (12 mm) Individual eels used 3 angles (15 o, 30 o, 45 o ) 2 discharges (low, high)

19 Results: Approach 91.7% approaches along channel floor 95% approaches along channel walls Discharge effects lateral approach (P <0.01)

20 Results: Hydraulics

21 Results: Hydraulics

22 Results: Response to structure No avoidance until after contact with rack Don t demonstrate typical avoidance response of salmonids Thus eels highly susceptible to rack mortality Longer Weaker swimmers Will contact rack More susceptible to impingement

23 Trout at orifice weir

24 Eel orifice weir

25 Eel at channel-floor orifice

26 Conclusions Anguilliforms need protection! Require research on species specific design criteria. Poorly designed mitigation at river infrastructure can > high mortality Behavioural research needed flume studies e.g. respond after contact with structure Too late to escape? Channel floor/wall orientation

27 Thank you for you time. Questions? Iain Russon: Address APEM Ltd, Unit 2 Ground Floor, Gwaun Elai Business Campus, Llantrisant, South Wales, CF72 8XL

28 Velocities at Ätrafors racks