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- Brodersen, Jakob, et al.
(author)
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Condition-dependent individual decision-making determines cyprinid partial migration
- 2008
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In: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 89:5, s. 1195-1200
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Journal article (peer-reviewed)abstract
- Partial migration is a common phenomenon among many animals and occurs in many types of ecosystems. Understanding the mechanisms behind partial migration is of major importance for the understanding of population dynamics and, eventually, ecosystem processes. We studied the effects of food availability on the seasonal partial migration of cyprinid fish from a lake to connected streams during winter by the use of passive telemetry. Fish with increased access to food were found to migrate in higher proportion, earlier in the season, and to reside in the streams for a longer period compared to fish with decreased access to food. Furthermore, fewer unfed migrants returned to the lake, indicating higher overwinter mortality. Our results suggest that individual fish trade off safety from predation and access to food differently depending on their body condition, which results in a condition-dependent partial migration. Hence, our main conclusion is that individual decision-making is based on assessment of own condition which offers a mechanistic explanation to partial migration. Moreover, this may be of high importance for understanding population responses to environmental variation as well as ecosystem dynamics and stability. Read More: http://www.esajournals.org/doi/abs/10.1890/07-1318.1
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| 4. |
- Brodersen, Jakob, et al.
(author)
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Variable individual consistency in timing and destination of winter migrating fish
- 2012
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In: Biology Letters. - : The Royal Society. - 1744-9561 .- 1744-957X. ; 8, s. 21-23
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Journal article (peer-reviewed)abstract
- Migration is an important event in the life history of many animals, but there is considerable variation within populations in the timing and final destination. Such differential migration at the population level can be strongly determined by individuals showing different consistencies in migratory traits. By tagging individual cyprinid fish with uniquely coded electronic tags, and recording their winter migrations from lakes to streams for 6 consecutive years, we obtained highly detailed long-term information on the differential migration patterns of individuals. We found that individual migrants showed consistent site fidelities for over-wintering streams over multiple migratory seasons and that they were also consistent in their seasonal timing of migration. Our data also suggest that consistency itself can be considered as an individual trait, with migrants that exhibit consistent site fidelity also showing consistency in migratory timing. The finding of a mixture of both consistent and inconsistent individuals within a population furthers our understanding of intrapopulation variability in migration strategies, and we hypothesize that environmental variation can maintain such different strategies.
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| 5. |
- Brönmark, Christer, et al.
(author)
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Regime shifts in shallow lakes: the importance of seasonal fish migration
- 2010
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In: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 646:1, s. 91-100
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Conference paper (peer-reviewed)abstract
- Shallow eutrophic lakes commonly exist in two alternative stable states: a clear-water state and a turbid water state. A number of mechanisms, including both abiotic and biotic processes, buffer the respective states against changes, whereas other mechanisms likely drive transitions between states. Our earlier research shows that a large proportion of zooplanktivorous fish populations in shallow lakes undertake seasonal migrations where they leave the lake during winter and migrate back to the lake in spring. Based on our past research, we propose a number of scenarios of how feedback processes between the individual and ecosystem levels may affect stability of alternative stable states in shallow lakes when mediated by fish migration. Migration effects on shallow lakes result from processes at different scales, from the individual to the ecosystem. Our earlier research has shown that ecosystem properties, including piscivore abundance and zooplankton productivity, affect the individual state of zooplanktivorous fish, such as growth rate or condition. Individual state, in turn, affects the relative proportion and timing of migrating zooplanktivorous fish. This change, in turn, may stabilize states or cause runaway processes that eventually lead to state shifts. Consequently, such knowledge of processes coupled to seasonal migration of planktivorous fish should increase our understanding of shallow lake dynamics.
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| 6. |
- Chapman, Ben, et al.
(author)
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A foraging cost of migration for a partially migratory cyprinid fish
- 2013
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In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:5
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Journal article (peer-reviewed)abstract
- Migration has evolved as a strategy to maximise individual fitness in response to seasonally changing ecological and environmental conditions. However, migration can also incur costs, and quantifying these costs can provide important clues to the ultimate ecological forces that underpin migratory behaviour. A key emerging model to explain migration in many systems posits that migration is driven by seasonal changes to a predation/growth potential (p/g) trade-off that a wide range of animals face. In this study we assess a key assumption of this model for a common cyprinid partial migrant, the roach Rutilus rutilus, which migrates from shallow lakes to streams during winter. By sampling fish from stream and lake habitats in the autumn and spring and measuring their stomach fullness and diet composition, we tested if migrating roach pay a cost of reduced foraging when migrating. Resident fish had fuller stomachs containing more high quality prey items than migrant fish. Hence, we document a feeding cost to migration in roach, which adds additional support for the validity of the p/g model of migration in freshwater systems.
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| 7. |
- Hansen, Joan H., et al.
(author)
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Ecological consequences of animal migration : Prey partial migration affects predator ecology and prey communities
- 2019
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In: Ecosystems (New York. Print). - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; , s. 1-15
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Journal article (peer-reviewed)abstract
- Patterns of animal migration and the ecological forces that shape them have been studied for centuries. Yet ecological impacts caused by the migration, such as altered predator–prey interactions and effects on community structure, remain poorly understood. This is to a large extent due to the scarcity of naturally replicated migration systems with negative controls, that is, ecosystems without migration. In this study, we tested whether partial migration of certain species within the overall prey community affects foraging ecology of top predators and thereby alters energy pathways in food webs. We carried out the study in independent replicated freshwater lake systems, four with and four without opportunity for prey migration. Specifically, we compared predator foraging mode in lakes where cyprinid prey fish perform seasonal partial migrations into connected streams with lakes lacking migratory opportunities for prey fish. We found clear seasonal bottom-up effects of prey migration on predators, including changes in size structure and total biomass of ingested prey, size-specific changes in littoral versus pelagic origin of diet, and a higher degree of feast-and-famine for predators in systems with migratory prey. Our analyses further showed that partially migratory prey species constitute a larger part of the prey community in systems that allow migration. Hence, prey migrations have important implications for predator foraging ecology and may cause seasonal shifts in the importance of their supporting energy pathways. We suggest that such bottom-up effects of partial migration may be a widespread phenomenon both in aquatic and in terrestrial ecosystems. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.
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| 8. |
- Hansson, Lars-Anders, et al.
(author)
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A lake as a microcosm : Reflections on developments in aquatic ecology
- 2013
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In: Aquatic Ecology. - : Springer Science and Business Media LLC. - 1386-2588 .- 1573-5125. ; 47, s. 125-135
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Journal article (peer-reviewed)abstract
- In the present study, we aim at relating Forbes' remarkable paper on "The lake as a microcosm", published 125 years ago, to the present status of knowledge in our own research group. Hence, we relate the observations Forbes made to our own microcosm, Lake Krankesjon in southern Sweden, that has been intensively studied by several research groups for more than three decades. Specifically, we focus on the question: Have we made any significant progress or did Forbes and colleagues blaze the trail through the unknown wilderness and we are mainly paving that intellectual road? We conclude that lakes are more isolated than many other biomes, but have, indeed, many extensions, for example, input from the catchment, fishing and fish migration. We also conclude that irrespective of whether lakes should be viewed as microcosms or not, the paper by Forbes has been exceptionally influential and still is, especially since it touches upon almost all aspects of the lake ecosystem, from individual behaviour to food web interactions and environmental issues. Therefore, there is no doubt that even if 125 years have passed, Forbes' paper still is a source of inspiration and deserves to be read. Hence, although aquatic ecology has made considerable progress over the latest century, Forbes might be viewed as one of the major pioneers and visionary scientists of limnology.
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| 9. |
- Hulthén, Kaj, et al.
(author)
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A predation cost to bold fish in the wild
- 2017
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In: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 7
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Journal article (peer-reviewed)abstract
- Studies of predator-mediated selection on behaviour are critical for our understanding of the evolution and maintenance of behavioural diversity in natural populations. Consistent individual differences in prey behaviour, especially in the propensity to take risks (“boldness”), are widespread in the animal kingdom. Theory predicts that individual behavioural types differ in a cost-benefit trade-off where bolder individuals benefit from greater access to resources while paying higher predation-risk costs. However, explicitly linking predation events to individual behaviour under natural conditions is challenging and there is currently little data from the wild. We assayed individual behaviour and electronically tagged hundreds of fish (roach, Rutilus rutilus) before releasing them into their lake of origin, thereby exposing them to predation risk from avian apex predators (cormorants, Phalacrocorax carbo). Scanning for regurgitated tags at the cormorant roosting site provided data on individual predation events. We found that fish with higher boldness have a greater susceptibility to cormorant predation compared to relatively shy, risk-averse individuals. Our findings hereby provide unique and direct evidence of behavioural type-dependent predation vulnerability in the wild, i.e. that there is a predation cost to boldness, which is critical for our understanding of the evolution and maintenance of behavioural diversity in natural populations.
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