| 1. |
|
|
| 2. |
- Adriaenssens, Bart, 1979
(author)
-
Individual variation in behaviour: personality and performance of brown trout in the wild
- 2010
-
Doctoral thesis (other academic/artistic)abstract
- Individuals from the same population often show very different behaviour. These differences, when consistent across time, are referred to as animal personality or behavioural syndromes. Explaining the occurrence of animal personality from an evolutionary perspective has however proven a difficult issue to tackle. This thesis studies aspects of individual behavioural variation and personality in brown trout (Salmo trutta). More specifically, I investigate (1) to what extent variation in behaviour is consistent within and across contexts, (2) environmental and genetic effects on behaviour, (3) how this affects performance in the wild, and (4) whether this understanding can be used to improve rearing methods of supplementary hatcheries. I found brown trout to express a wide variation of behaviours and provide evidence that much of this behavioural variation is associated in bigger behavioural syndromes. As a result, separate behaviours of brown trout cannot be considered as isolated units, but combine into clusters that sometimes are associated with non-behavioural measures such as body size or growth rate. Variation was further influenced by both inherited and environmental effects. First, individuals from different maternal and paternal origin differed in size, aggressiveness and response to novel prey or novel food. These results suggest that maternal and/or genetic effects influence behaviour and growth in brown trout (I). Second, reduced rearing densities in a hatchery increased the response to novel prey, food search ability in a maze and predator response (II). And third, hatchery trout were more successful foragers than wild conspecifics, yet showed less repeatable explorative behaviour across time (III). Personality traits were generally poor predictors of growth and survival upon release, suggesting that several behavioural strategies can be successful in nature. Nevertheless, in paper IV, slow exploring individuals grew faster than more bold trout. Furthermore, parr reared at reduced densities were twice as likely to survive in the stream as trout reared at high densities. In conclusion, my results contradict simple associations between risk taking behaviour and growth-mortality tradeoffs under natural conditions. This challenges the recent view that individual differences in growth strategies can explain variation in behaviour and suggests more heterogeneous links between personality and life-history in nature (V). In addition, I show that reduced rearing hatchery densities facilitate the development of adaptive behaviour in brown trout, a finding that may have implications for current rearing methods in supplementary hatcheries.
|
|
| 3. |
- Adriaenssens, Bart, 1979, et al.
(author)
-
Natural selection, plasticity, and the emergence of a behavioural syndrome in the wild
- 2013
-
In: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 16:1, s. 47-55
-
Journal article (peer-reviewed)abstract
- Individuals often show consistent behavioural differences where behaviours can form integrated units across functionally different contexts. However, the factors causing and maintaining behavioural syndromes in natural populations remain poorly understood. In this study, we provide evidence for the emergence of a behavioural syndrome during the first months of life in wild brown trout (Salmo trutta). Behavioural traits of trout were scored before and after a 2-month interval covering a major survival bottleneck, whereupon the consistency and covariance of behaviours were analysed. We found that selection favoured individuals with high activity levels in an open-field context, a personality trait consistent throughout the duration of the experiment. In addition, a behavioural syndrome emerged over the 2 months in the wild, linking activity to aggressiveness and exploration tendency. These novel results suggest that behavioural syndromes can emerge rapidly in nature from interaction between natural selection and behavioural plasticity affecting single behaviours.
|
|
| 4. |
|
|
| 5. |
- Adriaenssens, Bart, 1979, et al.
(author)
-
Shy trout grow faster: exploring links between personality and fitness-related traits in the wild.
- 2011
-
In: Behavioral Ecology. - 1045-2249. ; 22:1, s. 135-143
-
Journal article (peer-reviewed)abstract
- In many animals, individual differences in behavior show remarkable consistency across situations and contexts (i.e., animal personality and behavioral syndromes). Studies on the association between personality traits and fitness-related measures in nature are, however, important to clarify the causes and consequences of this phenomenon. Here, we tested for correlations between 3 behavioral axes in brown trout (Salmo trutta) parr: exploration tendency, behavioral flexibility, and aggressiveness. Next, we tested how these individual behaviors relate to social dominance and performance under natural conditions (growth, survival, and movement). We found support for behavioral syndromes in brown trout with less explorative individuals being less aggressive and showing more flexible behavior. In addition, these low-explorative personality types grew faster than bolder conspecifics in the wild. Standardized aggression in the laboratory was a poor indicator of social dominance, and neither of these 2 traits affected performance in the wild. These results challenge the view that personality traits can be predicted by constant associations with life-history trade-offs (e.g., boldness is linked with rapid growth). Moreover, our findings suggest that fitness predictions from laboratory measures of behavior should be made with caution and ideally tested in nature.
|
|
| 6. |
- Brockmark, Sofia, 1973, et al.
(author)
-
Less is more: density influences the development of behavioural life skills in trout
- 2010
-
In: Proceedings of the Royal Society B Biological Sciences. - 1471-2954. ; 277:1696, s. 3035-3043
-
Journal article (peer-reviewed)abstract
- Theory suggests that habitat structure and population density profoundly influence the phenotypic development of animals. Here, we predicted that reduced rearing density and increased structural complexity promote food search ability, anti-predator response and the ability to forage on novel prey, all behavioural skills important for surviving in the wild. Brown trout were reared at three densities (conventional hatchery density, a fourth of conventional hatchery density and natural density) in tanks with or without structure. Treatment effects on behaviour were studied on trout fry and parr, whereupon 20 trout from each of the six treatment groups were released in an enclosed natural stream and recaptured after 36 days. Fry reared at natural density were faster to find prey in a maze. Moreover, parr reared at natural density were faster to eat novel prey, and showed more efficient anti-predator behaviour than fish reared at higher densities. Furthermore, parr reared at reduced densities were twice as likely to survive in the stream as trout reared at high density. In contrast, we found no clear treatment effects of structure. These novel results suggest that reduced rearing densities can facilitate the development of behavioural life skills in captive animals, thereby increasing their contribution to natural production.
|
|
| 7. |
|
|
| 8. |
- Johnsson, Jörgen I, 1959, et al.
(author)
-
Learning and context-specific exploration behaviour in hatchery and wild brown trout.
- 2011
-
In: Applied Animal Behaviour Science. - : Elsevier BV. - 0168-1591 .- 1872-9045. ; 132:4, s. 90-99
-
Journal article (peer-reviewed)abstract
- In this study we investigate whether rearing environment (wild vs. hatchery) affects the ability of brown trout parr (Salmo trutta) to learn two foraging tasks. Hatchery- and wild-reared brown trout were trained in two different foraging tasks: locating food hidden in a maze and finding a cryptic prey, and their performance within and across tasks was compared. Fish reduced their search time for cryptic prey, but not maze search time, by learning. In contrast to most previous studies hatchery-reared trout generally tended to be more successful feeders and showed faster learning than wild trout when foraging on cryptic prey. This appeared to be due to motivational effects rather than based on cognitive skills. In addition, we examine whether exploration behaviour in brown trout is repeatable across time and context (i.e. reflecting a behavioural syndrome). Individual exploration tendency was repeatable within tasks, suggesting the occurrence of personality in brown trout. However, individuals that were fast explorers in the cryptic prey task were not necessarily fast to explore the maze. Thus, a context-specific behavioural syndrome was found to best explain exploratory behaviour for both hatchery and wild trout. However, repeatability of exploration behaviour within tasks differed between hatchery and wild trout, where wild trout were found to be more consistent in their exploration strategy. (C) 2011 Elsevier B.V. All rights reserved.
|
|
| 9. |
- Locatello, L, et al.
(author)
-
Ejaculate traits in relation to male body size in the eastern mosquitofish Gambusia holbrooki
- 2008
-
In: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 73:7, s. 1600-1611
-
Journal article (peer-reviewed)abstract
- In the present study, the correlation between sperm number, sperm quality (speed, viability, longevity and length), sperm bundles quality (size and dissolving rate) and male body size has been tested in the eastern mosquitofish Gambusia holbrooki a poecilid species characterized by coercive mating tactics where males do not possess obvious ornaments, and the body size is the key determinant of pre-copulatory male mating success. The results do not tally with theoretical predictions. Indeed, no correlation between male body size and either sperm or sperm-bundle traits has been found, evidencing the lack of the theoretically expected trade-off between the investment in characters involved in mate acquisition and the investment in ejaculate quality. An explanation for the observed pattern comes from the extremely dynamic mating system of G. holbrooki, characterized by variable size-related male mating success and strong post-copulatory selective pressure, with all males facing a similar high level of sperm competition. In this situation, a higher investment in growth and maintenance at the expense of ejaculate quality is not expected. These results underscore the necessity to comprehend detailed information on species' reproductive biology and reproductive environment to understand both the evolution of ejaculate characteristics and possible deviations from theoretical predictions.
|
|
