| 1. |
- Almqvist, Gustaf, et al.
(author)
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Has the invasive round goby caused new links in Baltic food webs?
- 2010
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In: Environmental Biology of Fishes. - : Springer Science and Business Media LLC. - 0378-1909 .- 1573-5133. ; 89:1, s. 79-93
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Journal article (peer-reviewed)abstract
- The Ponto-Caspian round goby (Neogobius melanostomus, Pallas 1814) most probably was established in the Gulf of GdaA""sk, Baltic Sea, in the late 1980's and has since become one of the dominant species in the region. In this study we assess the role of round gobies as prey for two important fish species in the Gulf of GdaA""sk, cod (Gadus morhua) and perch (Perca fluviatilis). We compared their present diet with stomach analyses from the area prior the round goby establishment, as well as with diet analysis from Baltic regions where round gobies are absent. There were large differences in the diet between cods from the Gulf of GdaA""sk 2003-2006 compared to cods in earlier studies (1977-1981) from the Southern Baltic Sea. There were also large differences in cod and perch diets from areas with and without round goby. Presently, round goby constitutes the most important prey for medium sized cods in Gulf of GdaA""sk, and perch from the same area almost exclusively feed on gobiids. Stomach analysis, trophic level estimates, and stable isotope analyses all indicated that cod and perch in Gulf of GdaA""sk after the round goby establishment belonged to a similar trophic level. Beside round goby, no mussel feeding fish contributed much to the diet of cod or at all to the diet of perch. Thus, it is likely that round gobies constitute a new energetic pathway from mussels to top predators. However, due to the short time elapsed after round goby establishment, we can only speculate on the species future impacts on Baltic food webs.
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| 2. |
- Amcoff, Mirjam, et al.
(author)
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A test of sensory exploitation in the swordtail characin (Corynopoma riisei) based on colour matchingbetween female prey and a male ornament
- 2014
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In: Environmental Biology of Fishes. - : Springer Science and Business Media LLC. - 0378-1909 .- 1573-5133. ; 97:3, s. 247-254
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Journal article (peer-reviewed)abstract
- The sensory exploitation hypothesis states that pre-existing biases in female sensory systems may generate strong selection on male signals to match such biases. As environmental conditions differ between populations, sexual preferences resulting from natural selection are expected to vary as well. The swordtail characin (Corynopoma riisei) is a species in which males carry a flag-like ornament growing from the operculum that has been proposed to function as a prey mimic to attract females. Here, we investigated if female plasticity in feeding preferences is associated with plasticity in preference for an artificial male ornament in this species. Females were trained for 10 days by offering them differently coloured food items and were then tested for changes in preferences for differently coloured artificial male ornaments according to foraging experience. We found a rapid and pronounced change in female preference for the colouration of the artificial ornament according to food training. Thus our results support the possibility that sensory exploitation may act as a driving force for female preferences for male ornaments in this species.
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| 3. |
- Amcoff, Mirjam, et al.
(author)
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Multiple male sexual signals and female responsiveness in the swordtail characin, Corynopoma riisei
- 2015
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In: Environmental Biology of Fishes. - : Springer Science and Business Media LLC. - 0378-1909 .- 1573-5133. ; 98:7, s. 1731-1740
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Journal article (peer-reviewed)abstract
- In the courtship process, multiple signals are often used between the signaller and the receiver. Here we describe female response to multiple male visual morphological and behavioural signals in the swordtail characin, Corynopoma riisei. The swordtail characin is a species in which males display several morphological ornaments as well as a rich courtship repertoire. Our results show that high courtship intensity was associated with an increased female response towards the male ornament, increased number of mating attempts and a reduction in female aggression. The morphological aspects investigated here did not seem to correlate with female response. This may indicate that, when both behaviour and morphology are considered simultaneously, courtship behaviour may have priority over morphological cues in this species.
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| 4. |
- Backström, Tobias, et al.
(author)
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Anaesthesia and handling stress effects on pigmentation and monoamines in Arctic charr
- 2017
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In: Environmental Biology of Fishes. - : Springer. - 0378-1909 .- 1573-5133. ; 100:5, s. 471-480
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Journal article (peer-reviewed)abstract
- Stress responsiveness differs between individuals and is often categorized into different stress coping styles. Using these stress coping styles for selection in fish farming could be beneficial, since stress is one main factor affecting welfare. In Arctic charr (Salvelinus alpinus) carotenoid pigmentation is associated with stress responsiveness and stress coping styles. Thus this could be an important tool to use for selection of stress resilient charr. However, anaesthetics seem to affect carotenoid pigmentation, and it would be better if the method for selection could be implemented during normal maintenance, which usually includes anaesthetics. Therefore, this study investigated how the use of anaesthetics affected carotenoid pigmentation, i.e. number of spots, over time compared to no-anaesthetic treatment. Additionally, the stress indicators monoamines and glucocorticoids were investigated. The results indicate that the anaesthetic MS-222 affects number of spots on the right side. This anaesthetic also increased dopaminergic activity in the telencephalon. Both brain dopaminergic and serotonergic activity was associated with spottiness. Further, behaviour during anaesthetization was associated with spots on the left side, but not the right side. Repetition of the same treatment seemed to affect spot numbers on the right side. In conclusion, this study shows that inducing stress in charr affects the carotenoid spots. Thus, it is possible to use anaesthetics when evaluating spottiness although careful planning is needed.
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| 5. |
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| 6. |
- Blom, Eva-Lotta, 1973, et al.
(author)
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Acoustic and visual courtship traits in two sympatric marine Gobiidae species – Pomatoschistus microps and Pomatoschistus minutus
- 2016
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In: Environmental Biology of Fishes. - : Springer Science and Business Media LLC. - 0378-1909 .- 1573-5133. ; 99, s. 999-1007
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Journal article (peer-reviewed)abstract
- Divergence in courtship traits across species can evolve as adaptations to different environments, and also through avoidance of reproductive interference and character displacement. Differences may also be explained by phylogenetic relationships. We compared different courtship traits, including male courtship sounds, in two sympatric Pomatoschistus species. Both species are characterised by having male and female courtship, and paternal care of eggs in nests under mussel shells and rocks. In addition to presenting novel observations, we reviewed the literature on courtship traits for both species and complemented it with new observations. We found that courting males of the common goby P. microps sing louder and produce sounds of shorter duration than males of the sand goby P. minutus. Furthermore, males of P. microps swim faster towards females during courtship than males of P. minutus. The eyes of P. minutus females turn black during courtship attempts, whereas this is not the case for females of P. microps. Species-specific differences in courtship sounds and behavior may lead to different susceptibility of the two species to environmental change such as noise pollution and turbidity.
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| 7. |
- Brodersen, Jakob, et al.
(author)
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Short-and long term niche segregation and individual specialization of brown trout (Salmo trutta) in species poor Faroese lakes
- 2012
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In: Environmental Biology of Fishes. - : Springer Science and Business Media LLC. - 0378-1909 .- 1573-5133. ; 93:3, s. 305-318
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Journal article (peer-reviewed)abstract
- Trophic niche divergence is considered to be a major process by which species coexistence is facilitated. When studying niche segregation in lake ecosystems, we tend to view the niche on a one-dimensional pelagic-littoral axis. In reality, however, the niche use may be more complex and individual fidelity to a niche may be variable both between and within populations. In order to study this complexity, relative simple systems with few species are needed. In this paper, we study how competitor presence affects the resource use of brown trout (Salmo trutta) in 11 species-poor Faroese lakes by comparing relative abundance, stable isotope ratios and diet in multiple habitats. In the presence of three-spined sticklebacks (Gasterosteus aculeatus), a higher proportion of the trout population was found in the pelagic habitat, and trout in general relied on a more pelagic diet base as compared to trout living in allopatry or in sympatry with Arctic charr (Salvelinus alpinus). Diet analyses revealed, however, that niche-segregation may be more complex than described on a one-dimensional pelagic-littoral axis. Trout from both littoral and offshore benthic habitats had in the presence of sticklebacks a less benthic diet as compared to trout living in allopatry or in sympatry with charr. Furthermore, we found individual habitat specialization between littoral/benthic and pelagic trout in deep lakes. Hence, our findings indicate that for trout populations interspecific competition can drive shifts in both habitat and niche use, but at the same time they illustrate the complexity of the ecological niche in freshwater ecosystems.
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| 8. |
- Costalago, David, et al.
(author)
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Influence of environmental variables on the larval stages of anchovy, Engraulis encrasicolus, and sardine, Sardinops sagax, in Algoa Bay, South Africa
- 2018
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In: Environmental Biology of Fishes. - : Springer Science and Business Media LLC. - 0378-1909 .- 1573-5133. ; 101:2, s. 225-236
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Journal article (peer-reviewed)abstract
- We investigated the environmental drivers of larval abundance of anchovy Engraulis encrasicolus and sardine Sardinops sagax in Algoa Bay, Eastern Cape (South Africa). This study comprised a pre-drought post-drought time period, comparing the responses of the fish larvae to different factors before and after the drought. The current study presents, for the first time, which environmental variables are affecting the anchovy and sardine larvae populations in the region. Easterly wind speed and zooplankton density were the only environmental variables that presented a significant change between the pre- and post-drought periods, increasing after the drought. Generalized additive models (GAMs) were used in order to explore the effects that environmental factors might have in the abundance of anchovy and sardine larvae in Algoa Bay. Specifically, the GAM that best explained the deviance of the anchovy larvae dynamics included the covariates rainfall, easterly wind speed, Chl a concentration, sardine larvae abundance and the interactions SST*Chla and sard*SST. The GAM best explaining sardine larvae abundance included only the easterly wind speed as a covariate. This model showed that there was a positive relationship between the higher values of wind speed and sardine larvae abundance.
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| 9. |
- Cunha, Mario, et al.
(author)
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The intrinsically dynamic nature of mating patterns and sexual selection
- 2015
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In: Environmental Biology of Fishes. - : Springer Science and Business Media LLC. - 0378-1909 .- 1573-5133. ; 98:4, s. 1047-1058
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Journal article (peer-reviewed)abstract
- Selection processes are influenced by both biotic and abiotic variables, most of which seasonally fluctuate. Therefore, selection may also vary temporally. Specifically, sexual selection, an integral component of natural selection, will inevitably exhibit temporal variation but the scale at which these changes occur are still not well understood. In this study, performed on a wild population of the sex-role reversed black striped pipefish Syngnathus abaster (Risso, 1827), we contrast variables such as male reproductive success, mating success, female investment, mate choice and operational sex ratio between two periods, either near the onset or end of the breeding season. Sexual selection is stronger early in the breeding season. Male reproductive and mating success are significantly affected by male size during the onset of the breeding season but not during the end. Moreover, we found that larger females reproduce mainly during the onset while smaller females had increased chances of reproducing towards the end. As our sampling was performed in two consecutive years, it could be argued that our results stem primarily from between-year variation. Nevertheless, variation in demographic parameters from the onset to the end of the breeding season is similar to that observed in past sampling events. Hence, we suggest that the change in mating patterns within the breeding season derives from seasonal fluctuations in several abiotic (e.g., temperature) and biotic variables (e.g., operational sex ratio), rendering the expression of selective forces, such as sexual selection, inherently dynamic.
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| 10. |
- Degerman, E, et al.
(author)
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Are fish populations in temperate streams affected by crayfish? - A field survey and prospects
- 2007
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In: Environmental Biology of Fishes. - : Springer Science and Business Media LLC. - 0378-1909 .- 1573-5133. ; 78:3, s. 231-239
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Journal article (peer-reviewed)abstract
- Fish populations may be affected by predation and competition from various types of organisms, among which crayfish have been suggested as important actors. We here present results from stream surveys, suggesting that neither native noble, Astacus astacus, nor introduced signal crayfish, Pacifastacus leniusculus, necessarily affect fish population densities in temperate stream communities. Comparisons of fish densities within stream sites between years with absence and presence of crayfish showed no effect of either crayfish species. A further analysis of changes in fish densities between periods without and with crayfish in low, intermediate and high densities revealed that crayfish density did neither have an effect on fish densities. Our study is one of exceptionally few that consider the above aspects in long-term perspectives in natural systems, and we discuss that previously reported divergent results of cray. sh effects on. sh may be highly dependent on specific species and methods used, and that the effects of cray. sh on. sh populations deserve further attention to enable reliable predictions of community processes in streams.
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