What we know and what we don’t know about twaite shad in ... · Claridge & Gardner (1978) Twaite...

What we know and what we don’t know about twaite shad

in the Severn Estuary in relation to predicting the impact

of tidal power schemes.Miran Aprahamian APEM / IFM

April 25 2017

Twaite shad in the Severn Estuary

Severn


Putcher ranks in the Severn Estuary, UK.


Migration

Catch of twaite shad in the Severn

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

15

-Ap

r

19

-Ap

r

23

-Ap

r

27

-Ap

r

1-M

ay

5-M

ay

9-M

ay

13

-May

17

-May

21

-May

25

-May

29

-May

2-J

un

6-J

un

10

-Jun

14

-Jun

18

-Jun

22

-Jun

Me

an

catc

h p

er

tid

e

* * * * * * * * * * *


Migration - patterns

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

Nu

mb

er o

f fi

sh m

-2

Tidal State

Catch in relation to tidal state

FLOOD

EBB

0

10

20

30

40

50

60

70

00:5

9:5

9

02:5

9:5

9

04:5

9:5

9

06:5

9:5

9

08:5

9:5

9

10:5

9:5

9

12:5

9:5

9

14:5

9:5

9

16:5

9:5

9

18:5

9:5

9

20:5

9:5

9

22:5

9:5

9

Time (hour)

Nu

mb

er

of

sh

oals

Diel Behaviour


Juvenile migration

Claridge & Gardner (1978)


The growth of juvenile shad in the Severn


Abundance of twaite shad in the

Severn 1979-1998

0

10

20

30

40

50

60

70

79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98

Year

Mea

n C

atch

per

Tid

e

Shad Life Cycle - Key biological information


Age at maturity

0

10

20

30

40

50

60

2 3 4 5 6 7 8 9

Age (year)

Pe

rce

nt

ma

turi

ng Male

Female

0.0000

0.2000

0.4000

0.6000

0.8000

1.0000

1.2000

3 4 5 6 7 8 9 10

Pro

po

rtio

n

Age (years)

Proportion repeat spawners - females

0.00

2.00

4.00

6.00

8.00

10.00

12.00

3 4 5 6 7 8 9 10

CP

UE

Age (years)

Age composition - Female

Virgin Repeat

0

5

10

15

20

25

30

35

1 2 3 4 5 6 7

Per

cen

tage

Number of spawnings

Number of spawnings

Female Male

1986

0

20

40

3 4 5 6 7 8 9 > 10

1987

0

20

40

3 4 5 6 7 8 9 > 10

1988

0

20

40

3 4 5 6 7 8 9 > 10

1989

0

20

40

3 4 5 6 7 8 9 > 10

1990

0

20

40

3 4 5 6 7 8 9 > 10

1991

0

20

40

3 4 5 6 7 8 9 > 10

1992

0

20

40

3 4 5 6 7 8 9 > 10

1993

0

20

40

3 4 5 6 7 8 9 > 10

1994

0

20

40

3 4 5 6 7 8 9 > 10

1995

0

20

40

3 4 5 6 7 8 9 > 10

1996

0

20

40

3 4 5 6 7 8 9 > 10

1997

0

20

40

3 4 5 6 7 8 9 > 10

Population structure 1986-1997Twaite shad in the Severn Estuary


0

20

40

60

80

100

120

Nu

mb

er o

f O

+ A

losa

fal

lax

Year class

Hinkley Point Power Station - Severn0+ Alosa fallax

(Data courtesy of P. Henderson, PISCES)


YCS in relation to mean June-August temperature

y = 0.851x - 13.341

R2 = 0.7708

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

16.0 17.0 18.0 19.0 20.0

Mean daily temperature (degrees celsius)

Lo

ge

Ye

ar

cla

ss

str

en

gth


Stock recruitment relationship

0

500000

1000000

1500000

2000000

2500000

3000000

0 2000000 4000000 6000000 8000000 10000000

Spawning stock (eggs)

Recru

its

at

Ag

e 6

(eg

gs)

0

200000

400000

600000

800000

1000000

0 2000000 4000000 6000000 8000000 10000000

Spawning stock (eggs)

Rec

ruit

s at

Ag

e 6

(te

mp

erat

ure

ad

just

ed)

[eg

gs]

R=0.299Sexp(-2.5895E-07S)

r2 = 0.132

Model component and structure

Eggs

5 yr 10 yr9 yr 8yr7 yr6 yr

Eggs

3 yr 4 yrs

Ricker

Model

Egg survival, juvenile & adult mortality

+ temperature component

Hindcast – mortality & maturation schedule

Forecast - mortality

y = -0.6651x + 6.3724

R² = 0.9694


Influence of temperature on S/R relationship

0

2000000

4000000

6000000

8000000

10000000

12000000

0 1000000

2000000

3000000

4000000

5000000

6000000

7000000

8000000

9000000

10000000

Stock (eggs)

Recru

its (

eg

gs)

+2oC

+1oC

Current

1;1


Influence of temperature on S/R relationship

0

2000000

4000000

6000000

8000000

10000000

12000000

0 1000000

2000000

3000000

4000000

5000000

6000000

7000000

8000000

9000000

10000000

Stock (eggs)

Recru

its (

eg

gs)

+2oC

+1oC

Current

1;1

Population just able to persist


Model performance

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

16.0 16.5 17.0 17.5 18.0 18.5 19.0 19.5

Mean temperature (June-August) oC

Recru

its

/ S

tock


Tidal lagoons - predicting the impact


Distribution at sea

Life cycle - impacts

SeaEstuaryRiver

Autumn

May-June Spring

Summer-Autumn

2 - 7 year

June


Model predicting impact

Eggs

5 yr 10 yr9 yr 8yr7 yr6 yr

Eggs

3 yr 4 yrs

Ricker

Model

Egg survival, juvenile & adult mortality

+ temperature component

Hindcast – mortality & maturation schedule

Forecast - mortality

Additional mortalityAdditional mortality

https://www.google.co.uk/search?q=Tidal+turbine&espv=2&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjr79muy7rTAhWSYVAKHewSA0kQ_AUIBigB&biw=1920&bih=974#imgrc=PC9BY9ADh-srpM:


Turbine mortality rates – Shad (juvenile)

Mechanism Percent mortality

Pressure 0%

Sheer 48%

Strike 5%

Total 53%


Bay of Fundy Studies

AdultAmerican shad

• 46.3 ± 34.7% (Hogans & Melvin,1985)

• 21.3 ± 15.2% (Hogans, 1987)

Juvenile (0+) (Gibson & Myers, 2002) American shad

• 23.4% (6.1-58.8)

Alewife

• 7.7% (1.5-31.4)

Blueback herring

• 8.1% (3.5-17.2)


Consequence of additional mortality

0.0

0.5

1.0

1.5

2.0

0.0 0.2 0.4 0.6 0.8 1.0

Proportional Turbine Mortality

Ab

un

dan

ce (

Pro

po

rtio

n)

0.0

0.5

1.0

1.5

2.0

0.0 0.2 0.4 0.6 0.8 1.0


Ab

un

da

nc

e (

Pro

po

rtio

n)

0.0

0.5

1.0

1.5

2.0

0.0 0.2 0.4 0.6 0.8 1.0


Ab

un

da

nc

e (

Pro

po

rtio

n)

0.0

0.5

1.0

1.5

2.0

0.0 0.2 0.4 0.6 0.8 1.0


Ab

un

da

nc

e (

Pro

po

rtio

n)

Juvenile Adult

Current

+1 oC

Information Needs


• 1) how often and what proportion of the

adult pre-and post spawned

population/s might pass through the

turbines,

• 2) how often and what proportion of the

juvenile population/s might pass through

the turbines and

• 3) the level of adult and juvenile turbine mortality.

Twaite shad in the Severn Estuary - thank you for listening

Environmental concerns are so serious that, if

not faced head on from the start, a great deal of

engineering time and effort will be wasted’

‘traditional engineering feasibility studies which

concentrate on finding the most economically

attractive scheme followed by environmental

scrutiny are no longer acceptable.

‘ENVIRONMENTAL ISSUES NEED TO BE PART

OF THE DESIGN.’ Eric Van Walsum

SEVERN BARRAGE

as first proposed by Thomas Fulljames in 1849


Shad Life Cycle - Basic Model


ttteiiie bETTELog

i

SRFXLog

it eeaFeY )()(()))((())((3

5

1111

))(

10

7

))(( 1111

i i

SRFXLogFe iiie

Where:

Et = the number of eggs deposited in year t (stock)

Xi = the number of eggs deposited by age class i where )()()()))(((

6vvvjjjttte

fpmfpmbETTELogeeeaX

Tt = temperature (oC) in year t

)()()((

)()))((())((3

5

1111 vvvjjjttteiiie

fpmfpmbETTELog

i

SRFXLog

it eeeaFeY

))(

10

7

))(( 1111

i i

SRFXLogFe iiie

))1()()((((

)())((3

5

1111 aaavvvjjjiiie fpm

i

fpmfpm

i

SRFXLog

ieReFe

))1()()(()()))((( aaavvvjjjttte fpm

i

fpmfpmbETTELogeReeea

)))1()()(()())((10

7

1111 aaavvvjjjiiie fpm

i

fpmfpm

i

SRFXLog

ieReFe

Shad Life Cycle - Predicting Impact

Where:

Et = the number of eggs deposited in year t (stock)

Xi = the number of eggs deposited by age class i where )()()()))(((

6vvvjjjttte

fpmfpmbETTELogeeeaX

Tt = temperature (oC) in year t

mj,v,a = Instantaneous rate of turbine mortality for juvenile (j), virgin (v) and adult (a) fish

pj,v,a = Number of passes through the turbine for juvenile (j), virgin (v) and adult (a) fish

fj,v,a = Fraction of the juvenile (j), virgin (v) and adult (a) population which passes through the turbines


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What we know and what we don’t know about twaite shad in ... · Claridge & Gardner (1978) Twaite...

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