Maternal investment and juvenile survival in Atlantic salmon:

a field test of the ‘Big Old Fat Fecund Female Fish (BOFFFF)’ hypothesis

• Quality of maternal egg provisioning is critical

• Larger females generally produce larger eggs

• Larger embryos often have survival advantage

• Optimal egg size for maternal fitness

• Optimal egg size offspring fitness less clear

Background

• Phenotypic variation – Environmental heterogeneity

– Phenotypic plasticity

– Genetic effects

– Non genetic (parental) effects

1. How does variation in egg size affect subsequent fitness in the wild?

2. Do different environments select for different egg size?

http://www.ayrshireriverstrust.org

Breeding design

2 months 14 months 26 months

Male 1 Male 2

Time female spent in hatchery

X 6 X 6 X 6

X 12

15,000

15,000

15,000

15,000

0

1

2

3

4

Altitude

Velocity

Depth

Substrate Cover

Competition

Predation

0

1

2

3

4

Altitude

Velocity

Depth

Substrate Cover

Competition

Predation

Depth

0

1

2

3

4

Altitude

Velocity

Substrate Cover

Competition

Predation

Substrate Cover

0

1

2

3

4

Altitude

Velocity

Depth Competition

Predation

60,000

5,000 fry per female

group

Parental assignment

• DNA extraction & amplification of brookstock and all recaptured fry

• Parentage assignment to family level

• Estimates of relative survival for each female calculated

% contribution to recaptures

% contribution to stocking

Chloe Robinson

Egg size

Female rearing time ( P < 0.001) Female body size ( P < 0.001)

1 2 3 4

F

5 6

0

1

2

3

4S

urvu

val In

de

x

7 8 9 10 11 12

0

1

2

3

4

Su

rvuva

l Ind

ex

13

S1 S2 S3 S4

Sector

14

S1 S2 S3 S4

Sector

15

S1 S2 S3 S4

Sector

16

S1 S2 S3 S4

Sector

17

S1 S2 S3 S4

Sector

18

S1 S2 S3 S4

Sector

0

1

2

3

4

Su

rvuva

l Ind

ex

Female ID Su

rvival ind

ex

Site

2 m

on

ths

14

mo

nth

s 2

6 m

on

ths

Fem

ale

rear

ing

tim

e

Site Site Site Site Site

Relative survival

Egg weight (LME; P = 0.037)

Site

Su

rviv

al

ind

ex

Egg weight (mg)

Relative survival

• Egg weight was the only significant predictor of fry survival

• No genotype x environment interaction

• Survival depended on maternal identity (42% of variation)

Conclusions

• DNA parentage assignment provided method for examining effects of maternal investment

• Relative survival of hatchery-reared juvenile Atlantic salmon depends on maternal provisioning

• Likely mediated by maternal age, body size and diet

• Provides support for ‘BOFFFF’ hypothesis

With thanks to: Dr Carlos Garcia de Leaniz, Dr Sofia Consuegra, Dr John Taylor and Peter Gough. Edward Baggett, Alex Lock, Charlie Stutchbury, Chloe Robinson, Becky Phillips, Harriet Alvis & volunteers Funding: Natural Resources Wales & Welsh European Funding Office (Knowledge Economy Skills Scholarships).