| 131. |
- Stålhammar, Martin, et al.
(författare)
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The impact of catch-and-release on the foraging behaviour of pike (Esox lucius) when released alone or into groups
- 2012
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Ingår i: Fisheries Research. - : Elsevier BV. - 0165-7836 .- 1872-6763. ; 125, s. 51-56
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Tidskriftsartikel (refereegranskat)abstract
- A commonly practiced method intended to reduce mortality from recreational fisheries is mandatory (e.g., small fish protected by minimum-size limits) or voluntary catch-and-release (C&R), where fish are caught with hook and line and released alive on the assumption that fish survive unharmed. C&R can, however, have both lethal and sub-lethal consequences for fish, with altered behaviour serving as a useful indicator of sub-lethal effects. We here present a mesocosm study on the short-term effects on foraging-behaviour in response to C&R in pike (Esox lucius). when being released alone or into conspecific groups. Due to the potential of cannibalistic attacks or agonistic interactions post-release, we expected that foraging behaviour would be affected by social environment at release. We found that the time to first interest in and attack on prey was significantly delayed in caught and released pike individuals, but these delays were less pronounced in pike released into groups of conspecifics. We also found that the caught and released pike expressed agonistic behaviours in comparable frequencies to unfished group conspecifics. We conclude that the short-term effects of C&R involve altered foraging behaviours, partly depending on the social context at release. Altered feeding, even if only in the short-term, may reduce body growth post-release, which may affect individual fitness and also have effects at the fish community level as a result of changes in pike predation pressure. (C) 2012 Elsevier B.V. All rights reserved.
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| 132. |
- Svanbäck, Richard, et al.
(författare)
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The interaction between predation risk and food ration on behavior and morphology of Eurasian perch
- 2017
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 7:20, s. 8567-8577
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Tidskriftsartikel (refereegranskat)abstract
- The risk of both predation and food level has been shown to affect phenotypic development of organisms. However, these two factors also influence animal behavior that in turn may influence phenotypic development. Hence, it might be difficult to disentangle the behavioral effect from the predator or resource-level effects. This is because the presence of predators and high resource levels usually results in a lower activity, which in turn affects energy expenditure that is used for development and growth. It is therefore necessary to study how behavior interacts with changes in body shape with regard to resource density and predators. Here, we use the classic predator-induced morphological defense in fish to study the interaction between predator cues, resource availability, and behavioral activity with the aim to determine their relative contribution to changes in body shape. We show that all three variables, the presence of a predator, food level, and activity, both additively and interactively, affected the body shape of perch. In general, the presence of predators, lower swimming activity, and higher food levels induced a deep body shape, with predation and behavior having similar effect and food treatment the smallest effect. The shape changes seemed to be mediated by changes in growth rate as body condition showed a similar effect as shape with regard to food-level and predator treatments. Our results suggests that shape changes in animals to one environmental factor, for example, predation risk, can be context dependent, and depend on food levels or behavioral responses. Theoretical and empirical studies should further explore how this context dependence affects fitness components such as resource gain and mortality and their implications for population dynamics.
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| 133. |
- Turesson, Håkan, et al.
(författare)
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Foraging behaviour and capture success in perch, pikeperch and pike and the effects of prey density
- 2004
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Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 65:2, s. 363-375
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Tidskriftsartikel (refereegranskat)abstract
- The effect of school size on capture success in three different piscivores, perch Perca fluviatilis, pikeperch Stizostedion lucioperca and pike Esox lucius, was investigated. Roach Rutilus rutilus were used as prey in a pool experiment where individual predators were presented prey at densities of one, two, four, eight and 16 prey, respectively. Treatments were replicated seven times for each predator species. Perch was at first virtually unable to capture a prey from a school and suffered a significant confusion effect with increasing prey density. The effect, however, was limited in the long run, as the perch was a very effective predator in its hunting strategy where it singled out and repeatedly attacked single prey irrespective of prey density or school size. Pikeperch and pike were able to attack and capture prey at any prey density equally successfully and thus did not suffer from a confusion effect. Neither did these predators receive any apparent advantages from increasing prey density. (C) 2004 The Fisheries Society of the British Isles.
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| 134. |
- Turesson, Håkan, et al.
(författare)
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Predator-prey encounter rates in freshwater piscivores: effects of prey density and water transparency
- 2007
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 1432-1939 .- 0029-8549. ; 153:2, s. 281-290
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Tidskriftsartikel (refereegranskat)abstract
- One of the most fundamental components of predator-prey models is encounter rate, modelled as the product of prey density and search efficiency. Encounter rates have, however, rarely been measured in empirical studies. In this study, we used a video system approach to estimate how encounter rates between piscivorous fish that use a sit-and-wait foraging strategy and their prey depend on prey density and environmental factors such as turbidity. We first manipulated prey density in a controlled pool and field enclosure experiments where environmental factors were held constant. In a correlative study of 15 freshwater lakes we then estimated encounter rates in natural habitats and related the results to both prey fish density and environmental factors. We found the expected positive dependence of individual encounter rates on prey density in our pool and enclosure experiments, whereas the relation between school encounter rate and prey density was less clear. In the field survey, encounter rates did not correlate with prey density but instead correlated positively with water transparency. Water transparency decreases with increasing prey density along the productivity gradient and will reduce prey detection distance and thus predator search efficiency. Therefore, visual predator-prey encounter rates do not increase, and may even decrease, with increasing productivity despite increasing prey densities.
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| 135. |
- Turesson, Håkan, et al.
(författare)
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Prey size selection in piscivorous pikeperch (Stizostedion lucioperca) includes active prey choice
- 2002
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Ingår i: Ecology of Freshwater Fish. - : Wiley. - 0906-6691 .- 1600-0633. ; 11:4, s. 223-233
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Tidskriftsartikel (refereegranskat)abstract
- Knowledge of the mechanisms behind prey selection in piscivorous fish is important for our understanding of the dynamics of freshwater systems. Prey selection can involve active predator choice or be a passive process. We experimentally studied size-selectivity in pikeperch, feeding on roach and rudd. When given a choice of different prey sizes, pikeperch selected small prey. Passive selection mechanisms ( encounter rate, capture success and satiation) could not fully explain the pattern of diet choice. Instead, behavioural analysis revealed that the pikeperch actively selected small-sized prey. Optimal foraging theory, predicting that predators will choose prey sizes giving highest energy return per time spent foraging, is assumed to explain active choice. We measured handling times for a range of prey sizes and found that the most profitable sizes were also the chosen ones, both in experiments and in the field. This suggests that pikeperch choose their prey to maximise energy intake per unit time.
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| 136. |
- Turesson, Håkan, et al.
(författare)
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Satiation effects in piscivore prey size selection
- 2006
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Ingår i: Ecology of Freshwater Fish. - : John Wiley & Sons. - 0906-6691 .- 1600-0633. ; 15:1, s. 78-85
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Tidskriftsartikel (refereegranskat)abstract
- We present a functional response model that primarily evaluates effects of satiation in piscivore prey-size selection. The model also includes other passive processes, such as prey-size-dependent encounter rate and prey-size-dependent capture success, where capture success decreases and encounter rate increases with prey size. The model generates a wide variety of outcomes, where small, intermediate or large prey is positively selected for. These very different selectivity patterns are generated without any active prey choice included in the model. The results stress the importance of controlling for satiation and other passive processes in empirical studies on prey-size selection, especially if the aim is to test active prey choice in piscivores. © 2005 The Authors Journal compilation 2005 Blackwell Munksgaard.
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| 137. |
- Vinterstare, Jerker, et al.
(författare)
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Antipredator phenotype in crucian carp altered by a psychoactive drug
- 2021
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Ingår i: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 11:14, s. 9435-9446
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Tidskriftsartikel (refereegranskat)abstract
- Predator-inducible defenses constitute a widespread form of adaptive phenotypic plasticity, and such defenses have recently been suggested linked with the neuroendocrine system. The neuroendocrine system is a target of endocrine disruptors, such as psychoactive pharmaceuticals, which are common aquatic contaminants. We hypothesized that exposure to an antidepressant pollutant, fluoxetine, influences the physiological stress response in our model species, crucian carp, affecting its behavioral and morphological responses to predation threat. We examined short- and long-term effects of fluoxetine and predator exposure on behavior and morphology in crucian carp. Seventeen days of exposure to a high dose of fluoxetine (100 µg/L) resulted in a shyer phenotype, regardless of the presence/absence of a pike predator, but this effect disappeared after long-term exposure. Fluoxetine effects on morphological plasticity were context-dependent as a low dose (1 µg/L) only influenced crucian carp body shape in pike presence. A high dose of fluoxetine strongly influenced body shape regardless of predator treatment. Our results highlight that environmental pollution by pharmaceuticals could disrupt physiological regulation of ecologically important inducible defenses.
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| 138. |
- Vinterstare, Jerker, et al.
(författare)
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Defence versus defence : Are crucian carp trading off immune function against predator-induced morphology?
- 2019
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Ingår i: Journal of Animal Ecology. - : John Wiley & Sons. - 0021-8790 .- 1365-2656. ; 88:10, s. 1510-1521
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Tidskriftsartikel (refereegranskat)abstract
- Numerous species adopt inducible defence strategies; that is, they have phenotypically plastic traits that decrease the risk of capture and consumption by potential predators. The benefits of expressing alternative phenotypes in high- vs. low-risk environments are well documented. However, inducible anti-predator traits are also expected to incur costs, as they are not expressed when predators are absent, yet empirical evidence of such costs remains scarce. Virtually, all animals in nature are simultaneously under strong selection to evade both capture by predators and infection by parasites or pathogens and, hence, display a diverse arsenal of defences to combat these threats, raising the possibility of trade-offs between defences. A classic example of a predator-induced morphological defence is the deep-bodied shape of crucian carp that reduces risk of predation from gape-size-limited predators. The goal of this study was to examine whether predator exposure affects also immune function in crucian carp, and whether the degree of expressed morphological defence is traded off against immune function in individuals. Following exposure to manipulations of perceived risk (predator presence/absence) in a long-term experiment (8 months), key aspects of innate immune function and individual differences in the expression of inducible morphological defence were quantified. Predator-exposed individuals showed lower haptoglobin levels and complement activity, but higher natural antibody titres than fish from predator-free conditions. When experimentally challenged with a mimicked bacterial infection (LPS injection), fish reared in the presence of a natural predator showed a weaker immune response. Moreover, among predator-exposed individuals, the magnitude of morphological defence expression correlated with both baseline immune function and the ability to mount an immune response. However, these relationships were not consistently supportive of a general trade-off among defences. Our results suggest that fish exposed to predators on average reduce investment in immune function, and, further, the observed relationships among defences in predator-exposed individuals can best be explained from individual fitness and pace-of-life perspectives.
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| 139. |
- Vinterstare, Jerker, et al.
(författare)
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Experimental manipulation of perceived predation risk and cortisol generates contrasting trait trajectories in plastic crucian carp
- 2020
-
Ingår i: Journal of Experimental Biology. - : COMPANY BIOLOGISTS LTD. - 0022-0949 .- 1477-9145. ; 223:4
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Tidskriftsartikel (refereegranskat)abstract
- Most animals constitute potential prey and must respond appropriately to predator-mediated stress in order to survive. Numerous prey also adaptively tailor their response to the prevailing level of risk and stress imposed by their natural enemies, i.e. they adopt an inducible defence strategy. Predator exposure may activate the stress axis, and drive the expression of anti-predator traits that facilitate survival in a high-risk environment (the predation-stress hypothesis). Here, we quantified two key morphological anti-predator traits, body morphology and coloration, in crucian carp reared in the presence or absence of a predator ( pike) in addition to experimental manipulation of physiological stress via implants containing either cortisol or a cortisol inhibitor. We found that predator-exposed fish expressed a deeper-bodied phenotype and darker body coloration as compared with non-exposed individuals. Skin analyses revealed that an increase in the amount of melanophores caused the dramatic colour change in predator-exposed fish. Increased melanization is costly, and the darker body coloration may act as an inducible defence against predation, via a conspicuous signal of the morphological defence or by crypsis towards dark environments and a nocturnal lifestyle. By contrast, the phenotype of individuals carrying cortisol implants did not mirror the phenotype of predatorexposed fish but instead exhibited opposite trajectories of trait change: a shallow-bodied morphology with a lighter body coloration as compared with sham-treated fish. The cortisol inhibitor did not influence the phenotype of fish i.e. neither body depth nor body coloration differed between this group and predator-exposed fish with a sham implant. However, our results illuminate a potential link between stress physiology and morphological defence expression.
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| 140. |
- Vinterstare, Jerker, et al.
(författare)
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More than meets the eye : Predator-induced pupil size plasticity in a teleost fish
- 2020
-
Ingår i: Journal of Animal Ecology. - : Wiley-Blackwell. - 0021-8790 .- 1365-2656. ; 89:10, s. 2258-2267
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Tidskriftsartikel (refereegranskat)abstract
- Most animals are visually oriented, and their eyes provide their ‘window to the world’. Eye size correlates positively with visual performance, because larger eyes can house larger pupils that increase photon catch and contrast discrimination, particularly under dim light, which have positive effects on behaviours that enhance fitness, including predator avoidance and foraging. Recent studies have linked predation risk to selection for larger eyes and pupils, and such changes should be of importance for the majority of teleost fishes as they have a pupil that is fixed in size (eyes lack a pupillary sphincter muscle) and, hence, do not respond to changes in light conditions. Here, we quantify eye and pupil size of individual crucian carp, a common freshwater fish, following controlled manipulations of perceived predation risk (presence/absence). We also tested if crucian carp responded to increased predation risk by shifts in diel activity patterns. We found that crucian carp show phenotypic plasticity with regards to pupil size, but not eye size, as pupil size increased when exposed to predators (pike). Predator-exposed crucian carp also shifted from diurnal to nocturnal activity. Using a modelling exercise, we moreover show that the plastically enlarged pupils significantly increase visual range, especially for small objects under dim light conditions. Overall, our results provide compelling evidence for predator-induced pupil enlargement resulting in enhanced visual capabilities in a teleost fish. Pupil size plasticity in combination with the observed shift towards nocturnal activity may allow for efficient foraging also under dark conditions when predation risk from diurnal and visually oriented predators is reduced. The data highlight the powerful role of predation risk for eye development and evolution.
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