Longterm Performance Consequences of Predator

Presence in Young-of-the-Year Arctic char.

FJÄLLMistra

Jens AnderssonDept. of Ecology and Environmetal ScienceUmeå University

Resource polymorphism is common trait in Arctic char

• Different diets gave rise to 2 morphotypes, henceforth benthivores and planktivores.

Results from a previous experiment

• Different diets gave rise to 2 morphotypes, henceforth benthivores and planktivores.

• Planktivores had a higher swimming speed when foraging on either prey compared to the benthivores.

Results from a previous experiment

• Different diets gave rise to 2 morphotypes, henceforth benthivores and planktivores.

• Planktivores had a higher swimmingspeed when foraging on either prey compared to the benthivores.

• Planktivores had a higher consumption rate on zooplankton compared to benthivores.

Results from a previous experiment

• Different diets gave rise to 2 morphotypes, henceforth benthivores and planktivores.

• Planktivores had a higher swimmingspeed when foraging on either prey compared to the benthivores.

• Planktivores had a higher consumption rate on zooplankton compared to benthivores.

• There were no differences between morphotypes with respect to consumption rate on chironomides.

Results from a previous experiment

• What is the price of including zooplankton in the diet since they do not loose any competitive ability on chironomids?

The previous experiment asks the question:

• What is the price of including zooplankton in the diet since they do not loose any competitive ability on chironomids?

The previous experiment asks the question:

The answer?

• Planktivory includes a higher level of activity which has been shown to increase the predation risk and hence foraging on zooplankton could increase the predation risk

The aim of the new experiment

• To investigate if the presence of a predator have an effect on morphology, behavior and performance.

• To investigate if the presence of a predator have an effect on morphology, behavior and performance.

• And if so, do this effect match the results of diet induced differences from the previous experiment.

The aim of the new experiment

Methods (treatment)

• 400 YOY individuals were placed in four 500 L aquarium. (100 ind. in each aquaria).

Methods (treatment)

• 400 YOY individuals were placed in four 500 L aquarium. (100 ind. in each aquaria).

• Plastic tubes were placed at the bottom to immitate natural substrate (shelter).

Methods (treatment)

• 400 YOY individuals were placed in four 500 L aquarium. (100 ind. in each aquaria).

• Plastic tubes were placed at the bottom to immitate natural substrate (shelter).

• A net (1 cm meshsize) were placed horizontally, 15 cm above bottom allowing YOY char to pass through.

Methods (treatment)

• 400 YOY individuals were placed in four 500 L aquarium. (100 ind. in each aquaria).

• Plastic tubes were placed at the bottom to immitate natural substrate (shelter).

• A net (1 cm meshsize) were placed horizontally, 15 cm above bottom allowing YOY char to pass through.

• A large char (25 cm) were placed into two out of four aquarias.

Methods (treatment)

• 400 YOY individuals were placed in four 500 L aquarium. (100 ind. in each aquaria).

• Plastic tubes were placed at the bottom to immitate natural substrate (shelter).

• A net (1 cm meshsize) were placed horizontally, 15 cm above bottom allowing YOY char to pass through.

• A large char (25 cm) were placed into two out of four aquarias.

• All YOY char were fed frozen copepods from above.

Methods (measurement)

• Attack rate and swimming speed when foraging on each prey type in absence of predator and competitors.

Methods (measurement)

• Attack rate and swimming speed when foraging on each prey type in absence of predator and competitors.

• Morphology by using geometric morhometrics.

Swimming speed during foraging

0

450

900

1350

1800

Chironomidae Daphnia

Food type

Sp

ee

d

Result from diet induced YOY-types

B Pl

Planktivores always swim faster independent of prey

0

450

900

1350

1800

Chironomides Daphnia

Food type

Sp

ee

d

Result from predator induced YOY-types

P NP

YOY from non-predator treatment always swim faster independent of prey

Average capture rates on zooplankton

0

0.25

0.5

0.75

1

0 5 10 15 20

Density

Cap

ture

rat

e

Planktivores () have higher capture rates on zooplankton

Result from diet induced YOY-types

0

0.2

0.4

0.6

0.8

1

0 5 10 15 20

Density

Cap

ture

rat

e

Result from predator induced YOY-types

YOY from non-predator treatments () have higher capture rates on zooplankton

Average capture rates on Chironomids

0

0.1

0.2

0.3

0 0.2 0.4 0.6 0.8 1

Density

Cap

ture

rat

e

Result from diet induced YOY-types

There is no difference in capture rates on Chironomides between treatments

Result from predator induced YOY-types

0

0.025

0.05

0.075

0.1

0 0.2 0.4 0.6 0.8 1

Density

Ca

ptu

re r

ate

There is no difference in capture rates on Chironomides between treatments

Morphology

• We could not find any morphological differences between fry reared in the presence of predators compared to fry reared in the absence of predators (POWER = 0.78).

Conclusions

• The presence of predators can induce long term effects on the YOY char performance and behaviour.

Conclusions

• The presence of predators can induce long term effects on the YOY char performance and behaviour.

• The changes of performance and behaviour due to presence of predators compared to non-presence of predators are similar to the changes due to growth on a plankton diet compared to growth on a chironomid diet.

Conclusions

• The presence of predators can induce long term effects on the YOY char performance and behaviour.

• The changes of performance and behaviour due to presence of predators compared to non-presence of predators are similar to the changes due to growth on a plankton diet compared to growth on a chironomid diet.

• Hence, a combination of diet induced phenotypic plasticity and predation risk may be the cause of different morphotypes of Arctic char often find in one lake.

SpeculationsIn char, predation risk may be a driving force for resource polymorphism.

The End