| 1. |
- Hirsch, Philipp Emanuel, et al.
(author)
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A previously undescribed set of Saprolegnia spp. In the invasive spiny-cheek crayfish (Oronectes limosus, Rafinesque)
- 2008
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In: Fundamental and Applied Limnology. - : Schweizerbart. - 1863-9135. ; 172:2, s. 1-5
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Journal article (peer-reviewed)abstract
- Coinciding with a population decline in the invasive spiny-cheek crayfish Orconectes limosus in Lake Constance. SW Germany, we found crayfish specimens with a fungus-like Aufwuchs which after DNA-isolation and sequencing was identified as consisting of a set of previously undescribed Saprolegnia species. This finding may have implications for the farming and conservation of native crayfish as well as for the lake's ecosystem. We propose that spiny-cheek crayfish might function as a disease vector for these potential pathogens.
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| 2. |
- Hirsch, Philipp Emanuel, et al.
(author)
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Interactions between native juvenile burbot (Loto loto L.) and the invasive spiny-cheek crayfish (Oronectes limosus, Rafinesque) in a large European lake
- 2008
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In: Canadian Journal of Fisheries and Aquatic Sciences. - 0706-652X .- 1205-7533. ; 65:12, s. 2636-2643
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Journal article (peer-reviewed)abstract
- Freshwater crayfish are successful invaders in many ecosystems and as cryptic nocturnal species display a potential niche overlap with benthic nocturnal fish. In this study, we tested the effects of the invasive spinycheek crayfish (Orconectes limosus) on native young-of-the-year (YOY) and adult burbot (Lota lota) in Lake Constance. Using mesocosm experiments, we tested if shelter preferences of YOY and adult burbot and crayfish changed between single and mixed species treatments. To further study the role of crayfish as a stressor for burbot, we monitored the nocturnal behaviour of the species in mesocosms using passive integrated transponder ( PIT) tag technology and subsequently determined the plasma cortisol levels in burbot after single and mixed species treatments. Spinycheek crayfish successfully repelled YOY burbot from their preferred daytime shelters into alternative, previously unselected shelters. Crayfish also affected the nocturnal behaviour of YOY burbot by eliciting avoidance behaviour and caused an increase in the plasma cortisol levels. While adult burbot did not display any changes between single and mixed species treatments, our results indicate negative effects of spinycheek crayfish on YOY burbot. We conclude that the frequently dense, invasive crayfish populations in lakes may negatively influence local benthic fish populations via their YOY cohorts.
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| 3. |
- Bartels, Pia, et al.
(author)
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Dissolved Organic Carbon Reduces Habitat Coupling by Top Predators in Lake Ecosystems
- 2016
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In: Ecosystems (New York. Print). - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 19, s. 955-967
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Journal article (peer-reviewed)abstract
- Increasing input of terrestrial dissolved organic carbon (DOC) has been identified as a widespread environmental phenomenon in many aquatic ecosystems. Terrestrial DOC influences basal trophic levels: it can subsidize pelagic bacterial production and impede benthic primary production via light attenuation. However, little is known about the impacts of elevated DOC concentrations on higher trophic levels, especially on top consumers. Here, we used Eurasian perch (Perca fluviatilis) to investigate the effects of increasing DOC concentrations on top predator populations. We applied stable isotope analysis and geometric morphometrics to estimate long-term resource and habitat utilization of perch. Habitat coupling, the ability to exploit littoral and pelagic resources, strongly decreased with increasing DOC concentrations due to a shift toward feeding predominantly on pelagic resources. Simultaneously, resource use and body morphology became increasingly alike for littoral and pelagic perch populations with increasing DOC, suggesting more intense competition in lakes with high DOC. Eye size of perch increased with increasing DOC concentrations, likely as a result of deteriorating visual conditions, suggesting a sensory response to environmental change. Increasing input of DOC to aquatic ecosystems is a common result of environmental change and might affect top predator populations in multiple and complex ways.
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| 4. |
- Behrens, Jane W., et al.
(author)
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Personality- and size-related metabolic performance in invasive round goby (Neogobius melanostomus)
- 2020
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In: Physiology and Behavior. - : Elsevier. - 0031-9384 .- 1873-507X. ; 215, s. 1-6
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Journal article (peer-reviewed)abstract
- Differences between individuals in behavioral type (i.e. animal personality) are ecologically and evolutionarily important because they can have significant effects on fitness components such as growth and predation risk. In the present study we are used the invasive round goby (Neogobius melanostomus) from an established population in controlled experiments to examine the relationships among personality, metabolic performance, and growth rate (inferred as size-at-age). Boldness was measured as the time to return to normal behavior after a simulated predator attack, where fish with shorter freezing times were categorized as "bold" and fish with longer times were categorized as "shy." We show that bold fish have significantly higher standard metabolic rate (SMR) than their shy conspecifics, whereas there was no difference between personality types in their maximum metabolic rate (MMR) or aerobic scope (AS). Bold fish furthermore had a smaller size-at-age as compared to shy fish. Together this provides evidence of a metabolic underpinning of personality where the high-SMR bold fish require more resources to sustain basic life functions than their low-SMR shy conspecifics, indicating that bold round goby from established populations with high densities (and high competition for food) pay a price of reduced growth rate.
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| 5. |
- Ericsson, Philip, et al.
(author)
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Personality-dependent inter- and intraspecific foraging competition in the invasive round goby, Neogobius melanostomus
- 2021
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In: Journal of Fish Biology. - : Wiley-Blackwell. - 0022-1112 .- 1095-8649. ; 98:5, s. 1234-1241
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Journal article (peer-reviewed)abstract
- This study examines the impact of boldness on foraging competition of the highly invasive round goby Neogobius melanostomus Pallas 1815. Individual risk tolerance, or boldness, was measured as the time to resume movement after a simulated predation strike. Fish that resumed movement faster were categorized as "bold," fish that took more time to resume movement were categorized as "shy" and those that fell in between these two categories were determined to have "intermediate" boldness. Competitive impacts of boldness in N. melanostomus were determined in a laboratory foraging experiment in which interspecific (juvenile Atlantic cod Gadus morhua Linnaeus 1758) and intraspecific (intermediate N. melanostomus) individuals were exposed to either bold or shy N. melanostomus competitors. G. morhua consumed fewer prey when competing with bold N. melanostomus than when competing with shy N. melanostomus, whereas intermediately bold N. melanostomus foraging was not affected by competitor boldness. Bold and shy N. melanostomus consumed similar amounts of prey, and the number of interactions between paired fish did not vary depending on the personality of N. melanostomus individuals. Therefore, intraspecific foraging competition was not found to be personality dependent. This study provides evidence that individual differences in boldness can mediate competitive interactions in N. melanostomus; nonetheless, results also show that competition is also governed by other mechanisms that require further study.
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| 6. |
- Hirsch, Philipp Emanuel, et al.
(author)
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An approach to incorporate individual personality in modeling fish dispersal across in-stream barriers
- 2017
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In: Ecology and Evolution. - : Wiley. - 2045-7758. ; 7:2, s. 720-732
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Journal article (peer-reviewed)abstract
- Animal personalities are an important factor that affects the dispersal of animals. In the context of aquatic species, dispersal modeling needs to consider that most freshwater ecosystems are highly fragmented by barriers reducing longitudinal connectivity. Previous research has incorporated such barriers into dispersal models under the neutral assumption that all migrating animals attempt to ascend at all times. Modeling dispersal of animals that do not perform trophic or reproductive migrations will be more realistic if it includes assumptions of which individuals attempt to overcome a barrier. We aimed to introduce personality into predictive modeling of whether a nonmigratory invasive freshwater fish (the round goby, Neogobius melanostomus) will disperse across an in-stream barrier. To that end, we experimentally assayed the personalities of 259 individuals from invasion fronts and established round goby populations. Based on the population differences in boldness, asociability, and activity, we defined a priori thresholds with bolder, more asocial, and more active individuals having a higher likelihood of ascent. We then combined the personality thresholds with swimming speed data from the literature and in situ measurements of flow velocities in the barrier. The resulting binary logistic regression model revealed probabilities of crossing a barrier which depended not only on water flow and fish swimming speed but also on animal personalities. We conclude that risk assessment through predictive dispersal modeling across fragmented landscapes can be advanced by including personality traits as parameters. The inclusion of behavior into modeling the spread of invasive species can help to improve the accuracy of risk assessments.
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| 7. |
- Hirsch, Philipp Emanuel
(author)
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Freshwater crayfish invasions : former crayfish invader Galician crayfish hands title "invasive" over to new invader spiny-cheek crayfish
- 2009
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In: Biological Invasions. - : Springer Science and Business Media LLC. - 1387-3547 .- 1573-1464. ; 11:3, s. 515-521
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Journal article (peer-reviewed)abstract
- Biological invasions are a major threat to global biodiversity. Invasive freshwater crayfish in that context are especially prominent for their negative effects on both ecosystem integrity and native crayfish. However, some systems may have supported a crayfish species not originally native to the system without perceivable negative consequences for the ecosystem while other invasive crayfish species may constitute a major threat to ecosystem stability. Here I present an example how two crayfish, the spiny-cheek and the Galician crayfish both by researchers and governmental agencies considered non-native differ in their threats to the native ecosystem. Whereas the spiny-cheek crayfish is a recent potentially disease-transmitting and still spreading invader with high local densities the Galician crayfish might be part of the lake's fauna since several hundred years, appears in lower densities and is unlikely to be a vector of disease. Therefore, regardless of the Galician crayfish's actual date of introduction it is thus a rather "old and integrated" invader, which is now being faced and itself potentially threatened by the emergence of a "new and dangerous" invader: the spiny-cheek crayfish. This also exemplifies that in the face of often insufficient scientific information about dates of species introductions care should be taken in postulating species as invasive and dangerous without any form of risk assessment for their impact on the ecosystem.
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