flow, cumecs - FreshwaterLife

Fish and Flows in the Suffolk
Stour
Graeme Peirson, Roy Sedgwick,
Robin Burrough & RosWright

Relationships between coarse fish
populations and flows…..
• Why do we need to know ?
– More pressure on water resources, increasing
demand
– Catchment Abstraction Management Systems
(CAMS)
– Low flows – Resource Assessment Methodology
(RAM)
– How much water can we take, when and where,
to have minimal impact on aquatic ecosystems ?
– Climate change – drier summers, warmer winters
- how will it affect fisheries ?

Relationships between coarse fish
populations and flows…..
• High flows may also be important
– Compensation releases, water transfer schemes
– Climate change – some scenarios predict more
summer flood events and most predict wetter
winters.

Suffolk Stour
• Long dataset with regular sampling
• Consistent approach
• Already intensively collated and
analysed

Population Dynamics Model
• Fish Population Dynamics Model
– powerful statistical model - Bayesian inference
– draws information from raw data and combines
this to improve estimates of parameters about
which we have little direct information
• inaccurate ageing (older fish)
• low catchability of younger age-groups
– interpolation

PDM
• Estimates of uncertainty
• Better quality and quantity of raw data -
more accurate and precise the output, hence
PDM is no substitute for good data

0+ density (/100m2)
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
Chub recruitment, Lower Stour
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
Long-term average
1984
1985
1986
1987
1988
1989
Year
1990
1991
1992
1993
Significantly better than average
Significantly worse than average
No significant difference
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004

Fish recruitment and flow….
• Can we detect any “signal” of flow
impacts on coarse fish population
dynamics?

Ely Ouse transfer water in
- Kirtling Green
Upper Stour
Abstraction
- Wixoe
Lower Stour
Abstraction - Stratford
Stratford-Flatford
Abstraction - Cattawade

Stour investigations
• Lower Stour: Sudbury-Stratford St. Mary
– Flow Data from Lamarsh
– Temperature data estimated for Wixoe
– Good numbers of fish of three main spp -
roach, chub,dace
– Possible impacts of Ely Ouse transfer less
marked than in Upper Stour

Flow, cumec
Flow, cumec
Flow, cumec
5
4
3
2
1
0
1972
1.0
0.5
0.0
0.3
0.2
0.1
0
River Stour, Lamarsh mean daily flow Apr-Sept 1972-2004
FLOWS…..
River Glem, Glemsford, mean daily flow 1972-2000
apr-sept
1972
1974
1974
1976
1976
1978
1978
1980
1980
1982
1982
1984
1984
1986
1986
year
1988
year
River Box, Polstead, Mean Daily flows, April-Sept,
1972-2000
1972
1974
1976
1978
1980
1982
1984
1986
Year
1988
1988
1990
1990
1990
1992
1992
1992
1994
1994
1994
1996
1996
1996
1998
1998
1998
2000
2000
2000
2002
2004

Priory Meadow

0+, no /100m2
6
4
2
0
Recruitment and mean Daily
Flow, April-September
roach
0.0 1.0 2.0 3.0 4.0 5.0
flow , cumecs
0+, no
/100m2
0.4
0.2
0
chub
0+, no /100m2
0.00 2.00 4.00 6.00
6
4
2
0
flow, cumecs
dace
0.00 1.00 2.00 3.00 4.00 5.00
flow , cumecs

0+ length, mm
60
50
40
30
20
10
0
Autumn 0+ length and Mean
Daily Flow April-September
roach
0.00 1.00 2.00 3.00 4.00 5.00
flow, cumecs
0+ length,mm
0+length, mm
70
60
50
40
30
20
10
0
chub
60
50
40
30
20
10
0
0.00 1.00 2.00 3.00 4.00 5.00
flow, cumecs
dace
0.00 1.00 2.00 3.00 4.00 5.00
flow , cumecs

0+ no/100m2
0+ no/100m2
6
5
4
3
2
1
0
6
5
4
3
2
1
0
Recruitment and flow during
critical periods -dace
April
R 2 = 0.032
0 1 2 3 4 5 6 7 8
flow, cumec
June
R 2 = 0.0188
0 1 2 3 4 5 6 7
flow, cumec
0+ no/100m2
0+ length mm
6
5
4
3
2
1
0
May R 2 = 0.0902
0 1 2 3 4 5 6 7
70
60
50
40
30
20
10
0
flow, cumec
July
R 2 0.0957 =
0 0.5 1 1.5 2 2.5 3
flow, cumec

0+ no/100m2
6
4
2
0
Intensity of flow events ? – low flows
roach recruitment
0 10 20 30 40 50
Flow-days

No./100m2
Ely Ouse Transfer Scheme
• Did it protect fish from very low flows ?
5
4
3
2
1
0
– River Box – doesn’t receive augmentation flows
Roach recruitment river Box
0 0.1 0.2 0.3
Mean daily flow, cumec
No./100m2
6
4
2
0
No./100m2
Chub recruitment River Box
0 0.1 0.2 0.3
Mean daily flow, cumec
8
6
4
2
0
Dace recruitment River Box
R 2 0.1561 =
0 0.1 0.2 0.3
Mean daily flow, cumec

0+ no/100m2
River Brett
• Perceived to “suffer from low flows”
• Perhaps some impact on dace
• Possible interaction with water quality
12
10
8
6
4
2
0
Roach recruitment, R. Brett
0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700
summer mean daily flow, cumec
0+ no/100m2
6
5
4
3
2
1
0
Dace recruitment, R. Brett,
0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700
summer mean daily flow, cumec

0+ no. per
100m2
0+ no/100m 2
0+ no/100m 2
6
4
2
0
6
4
2
0
Intensity of flow events - high flows ?
roach vs flow -days > 1 cumec
6
4
2
0
0 200 400 600
flow -days > 1cumec, 72-04
roach vs flow-days> 2 cumec
0 100 200 300 400 500
Flow-days > 2 cumec
roach vs flow-days> 5 cumec,
0 50 100 150 200 250 300
Flow-days > 5 cumec
0+density no.
per 100m2
0+ no/100m2
0+ no/100m 2
6
4
2
6
4
2
0
dace vs flow -days > 1 cumec
0 100 200 300 400 500 600
flow-days > 1cumec, 72-04
dace vs flow-days> 2 cumec
0
0 100 200 300 400 500
6
4
2
0
Flow-days > 2 cumec
dace vs flow-days> 5cumec
0 50 100 150 200 250 300
Flow-days > 5 cumec
0+ no/100m 2
0+density no.
per 100m2
0.4
0.3
0.2
0.1
chub vs flow -days > 1 cumec
0
0 100 200 300 400 500 600
flow-days > 1cumec, 72-04
chub vs flow-days> 2 cumec
0.4
0.3
0.2
0.1
0
0 100 200 300 400 500
0+ no/100m 2
0.4
0.3
0.2
0.1
0
Flow-days > 2 cumec
chub vs flow-days> 5 cumec
0 50 100 150 200 250 300
Flow-days > 5 cumec

mdf, cumecs
5.000
4.000
3.000
2.000
1.000
0.000
Timing rather than volume ?
Dace hatch
01/04/1997
01/05/1997
Mean daily flows April 97-Mar 98
Roach
01/06/1997
01/07/1997
01/08/1997
01/09/1997
01/10/1997
date
01/11/1997
01/12/1997
01/01/1998
01/02/1998
01/03/1998

Timing rather than volume ?
Summary - dace
Good recruitment years: flow event >1.36 cumec

19
18
17
16
15
14
1972
Mean daily water temperatures Apr-Sept 1975-2004,
Wixoe (estimated)
1974
What does cause recruitment
1976
1978
1980
1982
variability ?
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004

0+ density
0+ density
0+ density
Temperature, recruitment & growth - Middle
6
4
2
0
6
4
2
0
Roach recruitment
15 15.5 16 16.5 17 17.5 18 18.5 19
Mean daily temp apr-sept
Dace recruitment
y = 0.9602x - 14.416
R 2 = 0.3262
15 15.5 16 16.5 17 17.5 18 18.5 19
0.4
0.2
0
Mean daily temp apr-sept
Chub recruitment
y = 0.0556x - 0.8235
R 2 = 0.172
15 15.5 16 16.5 17 17.5 18 18.5 19
Mean daily temp apr-sept
Stour
0+ length
0+ length
0+ length
Roach 0+length
60
50
40
30
20
10
0
15 15.5 16 16.5 17 17.5 18 18.5 19
70
60
50
40
30
50
40
30
20
10
0
Mean daily temp apr-sept
Dace 0+length
y = 4.4201x - 27.906
R 2 = 0.1966
15 15.5 16 16.5 17 17.5 18 18.5 19
Mean daily temp apr-sept
Chub 0+length
y = 9.3052x - 128.99
R 2 = 0.2367
15 15.5 16 16.5 17 17.5 18 18.5 19
Mean daily temp apr-sept

Summary
• No detectable impact of low flows upon
coarse fish populations in the Stour.
• Some evidence that high flows at critical
times can affect recruitment.
• THIS DOES NOT MEAN TO SAY THAT
CHANGING FLOW REGIMES WILL
NOT AFFECT THE FISH COMMUNITY.