Longterm P erformance Consequences of Predator Presence in Young-of-the-Year Arctic char.
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Longterm Performance Consequences of Predator
Presence in Young-of-the-Year Arctic char.
FJÄLLMistra
Jens AnderssonDept. of Ecology and Environmetal ScienceUmeå University
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Resource polymorphism is common trait in Arctic char
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• Different diets gave rise to 2 morphotypes, henceforth benthivores and planktivores.
Results from a previous experiment
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• 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
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• 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
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• 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
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• 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:
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• 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
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The aim of the new experiment
• To investigate if the presence of a predator have an effect on morphology, behavior and performance.
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• 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
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Methods (treatment)
• 400 YOY individuals were placed in four 500 L aquarium. (100 ind. in each aquaria).
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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).
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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.
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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.
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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.
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Methods (measurement)
• Attack rate and swimming speed when foraging on each prey type in absence of predator and competitors.
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Methods (measurement)
• Attack rate and swimming speed when foraging on each prey type in absence of predator and competitors.
• Morphology by using geometric morhometrics.
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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
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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
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Average capture rates on Chironomids
0
0.1
0.2
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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
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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).
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Conclusions
• The presence of predators can induce long term effects on the YOY char performance and behaviour.
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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.
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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.
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SpeculationsIn char, predation risk may be a driving force for resource polymorphism.
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The End