your fisheries. novel design, installation and assessment of coarse fish … · stocked fish - age...
TRANSCRIPT
Noveldesign,installationandassessmentofcoarsefishpassageusingtheLowCostBaffle(LCB)solutionatagaugingstation
TobyHullSouthEastRiversTrustSeniorProjectOfficer
What did the fish say when it swam into a wall?
Pollocks
Gauging Weir??
The Problem
- Impassable barrier at most/all flow conditions (coarse fish)- Active Gauging Station
- Non-standard flume construction- Steep downward slope 1:3.3
- Flat 2.4m wide crest with shallow flows- Very Urban Location
Gauging Accuracy Fish Passage
ProjectBackground
Hogsmill River Connectivity Project
Aim : Catchment scale fish passage
Started in 2012 as a CRF Project
18 barriers identified in total
Tackling the last few now
The Problem
TheProblemLow Cost Baffle Solution (LCBs)
The ProblemLow Cost Baffle Solution (LCBs)
=
- Developed for use on 1:5 slope- 200mm high baffles- 400mm centre spacing- 250mm notch- 200mm off-set- Upper baffles 1m from crest(600mm with a 120mm baffle)
Source ‘Servais, 2006’
> 0.6 drowned-out factor/ratio
1 : 5 slope120mm / 200mmDrowned out ratio = 0.6Streaming FlowPassable
1 : 3.3 slope83mm / 200mmDrowned out ratio = c.0.4Plunging FlowImpassable
32
32o
42o
Increasing Baffle Heights&
Fix all other variablesSolution =
Gauging Accuracy Fish Passage
Positioning Top Baffle
Positioning Top Baffle
Theoretical with no modelling
Baffled by Science ???
Positioning Top Baffle
Positioning Top Baffle
ModelledNo change in gauging accuracy
Positioning Top Baffle
ModelledInaccuracies at flows > 6.38 cumecs
Positioning Top Baffle
Positioning Top Baffle
ModelledInaccuracies at flows > 6.38 cumecs
Positioning Top Baffle
ModelledReduction to 120mm baffle
Velocity ≈ 2m/sec
Delivery
Delivery
Hogsmill HyrdographInfluence from STW
Low Flows High Flows
Monitoring
Aims 1). Inform if passage has been achieved at the Kingston site
2). Provide insight as to whether the principle of the modified baffle design can be applied to other weirs
Monitoring
Monitoring
- No mains power at the site
- Fish passage video surveillance software very expensive
- Without software many hours of reviewing footage
- High likelihood of missing passage (speed, user error, high turbidity, poor image quality etc)
- At best would only demonstrate if baffles passable, not the whole weir
Monitoring
Monitoring
MonitoringPIT Tagging (Passive Integrated Transponder)
Monitoring
Monitoring
A1 A2 A3
Monitoring
Monitoring
Monitoring
Stocked Fish- Age 1+- Source: EA’s Calverton Fish Farm
Mean Range Mean RangeBarbel Stocked 120 191 168 – 210 79 53 – 109Chub Stocked 119 177 160 – 209 76 53 – 129Chub Wild 194 319 178 – 525 605 71 – 2,494Dace Wild 50 187 142 – 227 100 35 – 202Roach Wild 30 221 142 – 300 224 46 - 501
Species Source No. Length (mm) Mass (g)
513 fish in study
Results
Monitoring undertaken since 21st February 2017 (c.5 months)
Headline Stat62 tagged fish have successfully passed the weir
(12% of total tagged fish)
Results
Monitoring undertaken since 21st February 2017 (c.5 months)
Headline Stats
Baffles Weir
Stockedc.40% bafflesc.30% over weir
Wildc.50% bafflesc.40% over weir
Results
Results
Results
Results AnalysisPassage is being assessed in terms of:
- Temperature - Flow- Diurnal Patterns- Depths- Velocities
Results
Conclusion
1). Inform if passage has been achieved at the Kingston site
Project/Monitoring Aims
2). Provide insight as to whether the principle of the modified baffle design can be applied to other weirs
Passage with 35% efficiency across the entire structure has be achieved.
The downslope of the weir has 45% efficiency at the 1:3.3 slope. Thisdemonstrates that weirs with a slope shallower than this can be madepassable using this novel approach.
Can weirs with even steeper gradients be made passable by adopting the principle of increasing baffle heights.
??
Lessons Learnt• Fragility of maintaining apparatus and continuous data collection over
prolonged periods
Lessons Learnt
• Fragility of maintaining apparatus and continuous data collection over prolonged periods
• Taking a science based approach
• Collaborative working & good communication between stakeholders to find a satisfactory outcome for all
• Be experimental but best done with robust monitoring. Evidence like this can then be rolled out with confidence
What’s Next- Second electrofishing survey and tagging of fish upstream
and relocation downstream (testing homing instinct)
- JBA continue spot gauging program to assess the impact of the baffles on gauge accuracy and revise weir rating accordingly
- Angus Lothian (Durham Uni.) will undertake the analysis of the findings and draw conclusions as part of his PhD
- Disseminate findings for the ‘Greater Good’
Contributions
Angus Lothian , Dr Martin Lucas, Jeroen Tummers
Toby Hull & Dr Chris Gardner
Chris Di Marco, Darryl Clifton-Dey & Dan Griffiths
Thank you.
If you have any questions, please let minnow