stress-resilience differences related to emergence …orgprints.org/30381/1/mgesto 8isfe...

1 DTU Aqua, Technical University of Denmark

Stress-resilience differences related to emergence time in farmed rainbow trout

Manuel Gesto, Alfred Jokumsen

Section for Aquaculture, DTU Aqua

Technical University of Denmark


Swim-up behavior and Emergence time

Individual variation in time from emergence in salmonid fishes.

Has emergence time any effect on fish robustness?? Any effect on stress resilience?

By E. Peter Steenstra By E. Peter Steenstra


Previous data

Wild fish with different emergence time seem to have different SCS and competitive ability. Fish emerging early have been shown to be more aggressive, prone to be dominant, proactive.

Farmed fish??


Does farmed fish sorted by emergence time differ in how they respond and resist against punctual and repeated stressors?

Hypothesis


Three swim-up fractions:

Stress resilience

Vaz-Serrano et al., 2011

Early 20%

Medium 20%

Late 20%

Selecting fish by emergence time: Sorting device


Mortality after sorting

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Cumulative mortality (%)

early

medium

late


A

B

C

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early medium late

dead

fis

h

Cumulative mortality (/tank) at day 20

Mortality after sorting


300 300 300 300 300 3003 x 3 x 3 x

EARLY MEDIUM LATE

Daily stress (air exposure)Acute stress

14 days

stressed

control

Sampling points: 0, 1, 2, 4, 8 h.

Brains and blood

5 g fish

StressControl

Stress resilience test – Exp. Design

StressControl StressControl


Stress markers analyzed:

• Fish length/weight – condition factor

• Plasma cortisol

• Plasma glucose and lactate

• Brain serotonergic activity

Data provided information about:

- Normal acute stress response in each fraction

- Effects of repeated stress on the normal acute

stress response - Resilience

Stress resilience test – samples


Data – Fish size

Fish size and condition factor – Among Fractions n= 150


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Time after exposure (min)

Early

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0 60 120 240 480


medium

Stress resilience data - Cortisol

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Late

Response to acute stress in control fish


Stress resilience data - Cortisol

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0 60 120 240 480pla

sm

a c

orti

sol

(n

g/

mL)


early control

early stress rep

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pla

sm

a c

orti

sol

(n

g/

mL)


medium control

medium stress rep

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late control

late stress rep

Response to acute stress in repeatedly stressed fish

Early Medium

Late


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Sero

ton

erg

ic a

cti

vit

y (

%

5H

IA

A/

5H

T)

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0,00

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Early Medium Late

control repeated stress

Stress resilience data – Brain serotonergic activity


Restrictive feeding – competition tests

Fish (~60 g) from the three different fractions were PIT-tagged and held together in the same tanks.

3 tanks containing 15 fish of every fraction (45 fish /tank) each.

Growth of the fish was then evaluated under different feeding regimes.

Has emergence time any effect on juvenile growth or on juvenile competitive ability for food?


Restrictive feeding – competition exp.Competition and growth

After 15 days under normal feeding (~2% body mass/day):

After 10 days of fasting:



After 7 days at low density with restrictive feeding (0.5% body mass/day):

Next step:

Stocking density reduced: 15 fish per tank (5 fish of each fraction, size-paired)


Conclusions

Acute stress response and stress resilience are different in fish from different emerging fractions.

Early fraction apparently has a higher capacity to habituate to mild stressors, i.e. more resilient.

No relationship has been found between emergence time and fish growth or fish competitive ability.

Performance of farmed trout related to emergence time seem to be highly influenced by fish origin/genetic background


Acknowledgements

RobustFish is part of the Organic RDD 2 programme, which is coordinated by International Centre for Research in Organic Food Systems (ICROFS).

It has received grants from the Green Growth and Development programme (GUDP) under the Danish Ministry of Food, Agriculture and Fisheries.

Jonas Müller – Christian Albrechts Universität zu Kiel

Present and former members of RobustFish project: Peter V Skov, Ivar Lund, Lars-Flemming Pedersen, Erik Höglund.

Our technicians: Ole Madvig Larsen, Rasmus Frydenlund Jensen


Stress resilience data - Glucose

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Pla

sm

a g

luco

se (

mM

)

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0,00

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0 60 120 240 480

Early Medium Late


control repeated stresscontrol repeated stress


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Pla

sm

a l

acta

te (

mM

)

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Early Medium Late

control repeated stress

Stress resilience data - Lactate



Data – Fish size

Fish size and condition factor – Control vs Repeated stress n=225

*P=0.006

*P=0.005



At low density and with restrictive feeding, fish truly compete for food.

Any relationship between dominance and emergence fraction?

Apparently not

stress-resilience differences related to emergence …orgprints.org/30381/1/mgesto 8isfe...

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