- Climate Change Adaptation, Climate Change In Aquatic Systems, Freshwater Ecology, Aquatic Ecology, Climatic Changes, Biology, and 25 moreEcology, Evolutionary Biology, Climate Change, Fish Biology, Evolutionary ecology (Ecology), Ecosystems Ecology, Biodiversity and Ecosystem Function, Ecosystem Modeling, Ecosystem Services, Ecosystem ecology, Limnology, Ecosystems Services, Fish Ecology, Fish management and conservation, Fish Physiology, Freshwater Biology, Fish and zooplankton interaction, Geometric Morphometrics on fish, Arctic Lakes, Climate modeling, Ecophysiology, Animal Ecology, Animal Physiology, Animal Behavior, and Environmental Sustainabilityedit
Thermal preference and performance provide the physiological frame within which fish species seek strategies to cope with the challenges raised by the low temperatures and low levels of oxygen and food that characterize winter. There are... more
Thermal preference and performance provide the physiological frame within which fish species seek strategies to cope with the challenges raised by the low temperatures and low levels of oxygen and food that characterize winter. There are two common coping strategies: active utilization of winter conditions or simple
toleration of winter conditions. The former is typical of winter specialist species with low preferred temperatures, and the latter is typical of species with higher preferred temperatures. Reproductive strategies are embodied in the phenology of spawning: the approach of winter conditions cues reproductive activity in many coldwater fish species, while the departure of winter conditions cues reproduction in many cool and warmwater fish species. This cuing system promotes temporal partitioning of the food resources available to young-of-year fish and thus supports high diversity in freshwater fish communities. If the
zoogeographic distribution of a species covers a broad range of winter conditions, local populations may exhibit differences in their winter survival strategies that reflect adaptation to local conditions. Extreme winter specialists are found in shallow eutrophic lakes where long periods of ice cover cause winter oxygen levels to drop to levels that are lethal to many fish. The fish communities of these lakes are simple and composed of species that exhibit specialized adaptations for extended tolerance of very low temperatures and oxygen levels. Zoogeographic boundaries for some species may be positioned at points on the landscape where the severity of winter overwhelms the species’ repertoire of winter survival strategies. Freshwater fish communities are vulnerable to many of the shifts in environmental conditions expected with climate change. Temperate and northern communities are particularly vulnerable since the repertoires of physiological and behavioural strategies that characterize many of their members have been shaped by the adverse environmental conditions (e.g. cool short summers, long cold winters) that climate change is expected to mitigate. The responses of these strategies to the rapid relaxation of the adversities that shaped them will play a significant role in the overall responses of these fish populations and their communities
to climate change.
toleration of winter conditions. The former is typical of winter specialist species with low preferred temperatures, and the latter is typical of species with higher preferred temperatures. Reproductive strategies are embodied in the phenology of spawning: the approach of winter conditions cues reproductive activity in many coldwater fish species, while the departure of winter conditions cues reproduction in many cool and warmwater fish species. This cuing system promotes temporal partitioning of the food resources available to young-of-year fish and thus supports high diversity in freshwater fish communities. If the
zoogeographic distribution of a species covers a broad range of winter conditions, local populations may exhibit differences in their winter survival strategies that reflect adaptation to local conditions. Extreme winter specialists are found in shallow eutrophic lakes where long periods of ice cover cause winter oxygen levels to drop to levels that are lethal to many fish. The fish communities of these lakes are simple and composed of species that exhibit specialized adaptations for extended tolerance of very low temperatures and oxygen levels. Zoogeographic boundaries for some species may be positioned at points on the landscape where the severity of winter overwhelms the species’ repertoire of winter survival strategies. Freshwater fish communities are vulnerable to many of the shifts in environmental conditions expected with climate change. Temperate and northern communities are particularly vulnerable since the repertoires of physiological and behavioural strategies that characterize many of their members have been shaped by the adverse environmental conditions (e.g. cool short summers, long cold winters) that climate change is expected to mitigate. The responses of these strategies to the rapid relaxation of the adversities that shaped them will play a significant role in the overall responses of these fish populations and their communities
to climate change.
"Systematic comparisons of the ecology between functionally similar fish species from freshwater and marine aquatic systems are surprisingly rare. Here, we discuss commonalities and differences in evolutionary history, population... more
"Systematic comparisons of the ecology between functionally similar fish species from freshwater and marine aquatic systems are surprisingly rare. Here, we discuss commonalities and differences in evolutionary history, population genetics, reproduction and life history, ecological interactions, behavioural ecology and physiological ecology of temperate and Arctic freshwater coregonids (vendace and ciscoes, Coregonus spp.) and marine clupeids (herring, Clupea harengus, and sprat, Sprattus sprattus). We further elucidate potential effects of climate warming on these groups of fish based on the ecological
features of coregonids and clupeids documented in the previous parts of the review. These freshwater and marine fishes share a surprisingly high number of similarities. Both groups are relatively short-lived, pelagic planktivorous fishes. The genetic differentiation of local populations is weak and seems to be in part correlated to an astonishing variability of spawning times. The discrete thermal window of each species influences habitat use, diel vertical migrations and supposedly also life history variations. Complex life cycles and preference for cool or cold water make all species vulnerable to the effects of global warming. It is suggested that future research on the functional interdependence between spawning time, life history characteristics, thermal windows and genetic differentiation may
profit from a systematic comparison of the patterns found in either coregonids or clupeids. "
features of coregonids and clupeids documented in the previous parts of the review. These freshwater and marine fishes share a surprisingly high number of similarities. Both groups are relatively short-lived, pelagic planktivorous fishes. The genetic differentiation of local populations is weak and seems to be in part correlated to an astonishing variability of spawning times. The discrete thermal window of each species influences habitat use, diel vertical migrations and supposedly also life history variations. Complex life cycles and preference for cool or cold water make all species vulnerable to the effects of global warming. It is suggested that future research on the functional interdependence between spawning time, life history characteristics, thermal windows and genetic differentiation may
profit from a systematic comparison of the patterns found in either coregonids or clupeids. "
"1. Variations in the strength of ecological interactions between seasons have received little attention, despite an increased focus on climate alterations on ecosystems. Particularly, the winter situation is often neglected when studying... more
"1. Variations in the strength of ecological interactions between seasons have received little attention, despite an increased focus on climate alterations on ecosystems. Particularly, the winter situation is often neglected when studying competitive interactions. In northern temperate freshwaters, winter implies low temperatures and reduced food availability, but also strong reduction in ambient light because of ice and snow cover. Here, we study how brown trout [Salmo trutta (L.)] respond to variations in ice-cover duration and competition with Arctic charr [Salvelinus alpinus (L.)], by linking laboratory-derived physiological performance and field data on variation in abundance among and within natural brown trout populations.
2. Both Arctic charr and brown trout reduced resting metabolic rate under simulated ice-cover (darkness) in the laboratory, compared to no ice (6-h daylight). However, in contrast to brown
trout, Arctic charr was able to obtain positive growth rate in darkness and had higher food intake in tank experiments than brown trout. Arctic charr also performed better (lower energy loss) under simulated ice-cover in a semi-natural environment with natural food supply.
3. When comparing brown trout biomass across 190 Norwegian lakes along a climate gradient, longer ice-covered duration decreased the biomass only in lakes where brown trout lived together with Arctic charr. We were not able to detect any effect of ice-cover on brown trout biomass in lakes where brown trout was the only fish species.
4. Similarly, a 25-year time series from a lake with both brown trout and Arctic charr showed that brown trout population growth rate depended on the interaction between ice breakup date and
Arctic charr abundance. High charr abundance was correlated with low trout population growth rate only in combination with long winters.
5. In conclusion, the two species differed in performance under ice, and the observed outcome of competition in natural populations was strongly dependent on duration of the ice-covered period. Our study shows that changes in ice phenology may alter species interactions in Northern aquatic
systems. Increased knowledge of how adaptations to winter conditions differ among coexisting species is therefore vital for our understanding of ecological impacts of climate change."
2. Both Arctic charr and brown trout reduced resting metabolic rate under simulated ice-cover (darkness) in the laboratory, compared to no ice (6-h daylight). However, in contrast to brown
trout, Arctic charr was able to obtain positive growth rate in darkness and had higher food intake in tank experiments than brown trout. Arctic charr also performed better (lower energy loss) under simulated ice-cover in a semi-natural environment with natural food supply.
3. When comparing brown trout biomass across 190 Norwegian lakes along a climate gradient, longer ice-covered duration decreased the biomass only in lakes where brown trout lived together with Arctic charr. We were not able to detect any effect of ice-cover on brown trout biomass in lakes where brown trout was the only fish species.
4. Similarly, a 25-year time series from a lake with both brown trout and Arctic charr showed that brown trout population growth rate depended on the interaction between ice breakup date and
Arctic charr abundance. High charr abundance was correlated with low trout population growth rate only in combination with long winters.
5. In conclusion, the two species differed in performance under ice, and the observed outcome of competition in natural populations was strongly dependent on duration of the ice-covered period. Our study shows that changes in ice phenology may alter species interactions in Northern aquatic
systems. Increased knowledge of how adaptations to winter conditions differ among coexisting species is therefore vital for our understanding of ecological impacts of climate change."
Reliable information on fish stocks is given crucial importance in fisheries science and ecosystem management. Among others, the European Water Framework Directive calls for consistent sampling methods that provide comparable and... more
Reliable information on fish stocks is given crucial importance in fisheries science and ecosystem management. Among others, the European Water Framework Directive calls for consistent sampling methods that provide comparable and reproducible results. However, the standardized sampling of fish in lakes by gillnets is conducted by low effort only in the pelagic areas, thus potentially not reflecting between-lake
variability in fish density. Here, we compared two additional fishing methods, hydroacoustics and midwater trawl sampling, to estimate pelagic coregonid densities in two deep lakes. Night-time trawling was conducted in four different depth layers and compared with the simultaneously obtained abundance and biomass estimates from echo recordings. Overall areal fish biomass from both methods corresponded
to each other (R2 = 0.40), with slope and intercept of major axis regression not differing from unity. However, we found differences in estimates for the deepest layers fished, and for very small and the largest coregonids, most likely to be explained by the specific technological details of either method. Our study supports that either hydroacoustics or trawl sampling should accompany gillnet fishing to monitor
pelagic fish assemblages. Because both methods result in estimates of absolute fish densities per volume or area, their application may uncover subtle responses of fish assemblages to anthropogenic disturbance in deep lakes.
variability in fish density. Here, we compared two additional fishing methods, hydroacoustics and midwater trawl sampling, to estimate pelagic coregonid densities in two deep lakes. Night-time trawling was conducted in four different depth layers and compared with the simultaneously obtained abundance and biomass estimates from echo recordings. Overall areal fish biomass from both methods corresponded
to each other (R2 = 0.40), with slope and intercept of major axis regression not differing from unity. However, we found differences in estimates for the deepest layers fished, and for very small and the largest coregonids, most likely to be explained by the specific technological details of either method. Our study supports that either hydroacoustics or trawl sampling should accompany gillnet fishing to monitor
pelagic fish assemblages. Because both methods result in estimates of absolute fish densities per volume or area, their application may uncover subtle responses of fish assemblages to anthropogenic disturbance in deep lakes.
Abstract – Habitat choice of fish may be influenced by many different ecological factors, e.g., predation risk, feeding opportunity, or temperature and oxygen availability. However, because most of the fish prey and their predators rely... more
Abstract – Habitat choice of fish may be influenced by many different ecological factors, e.g., predation risk, feeding opportunity, or temperature and oxygen availability. However, because most of the fish prey and their predators rely on vision for feeding, the predator avoidance and feeding
opportunity hypotheses may fail to predict distribution of fish at complete darkness. Here, we accumulated patterns of nocturnal vertical distribution of two coexisting coregonid populations in Lake Stechlin from 13 samplings over 4 years, conducted by hydroacoustics and simultaneous midwater trawling. We calculated population depths, dispersion, illumination strengths and vertical temperature gradients for all sampling dates. Illumination strengths at fish population depths were far below the critical levels for feeding by vision, suggesting that predator avoidance or feeding opportunity did not trigger the depth distribution at night. In contrast, nocturnal population depths and dispersion of vendace Coregonus albula were significantly associated with the seasonally changing vertical temperature gradient in Lake Stechlin, whereas night-time distribution of the coexisting Fontane cisco Coregonus fontanae was almost unaffected by
temperature. Vendace occurred just below the thermocline in isothermal water layers of about 6.5–9 C during stratification of Lake Stechlin, whereas Fontane cisco preferred 4–6 C cold layers. These experienced temperatures roughly correspond to species-specific optimum metabolic temperatures determined in earlier experiments. We assume, therefore, that the temperature-related vertical segregation during non-feeding hours at darkness is linked with metabolic benefits, thus suggesting that bioenergetics efficiency contributes to ultimate causes of diel vertical migrations at least in vendace.
opportunity hypotheses may fail to predict distribution of fish at complete darkness. Here, we accumulated patterns of nocturnal vertical distribution of two coexisting coregonid populations in Lake Stechlin from 13 samplings over 4 years, conducted by hydroacoustics and simultaneous midwater trawling. We calculated population depths, dispersion, illumination strengths and vertical temperature gradients for all sampling dates. Illumination strengths at fish population depths were far below the critical levels for feeding by vision, suggesting that predator avoidance or feeding opportunity did not trigger the depth distribution at night. In contrast, nocturnal population depths and dispersion of vendace Coregonus albula were significantly associated with the seasonally changing vertical temperature gradient in Lake Stechlin, whereas night-time distribution of the coexisting Fontane cisco Coregonus fontanae was almost unaffected by
temperature. Vendace occurred just below the thermocline in isothermal water layers of about 6.5–9 C during stratification of Lake Stechlin, whereas Fontane cisco preferred 4–6 C cold layers. These experienced temperatures roughly correspond to species-specific optimum metabolic temperatures determined in earlier experiments. We assume, therefore, that the temperature-related vertical segregation during non-feeding hours at darkness is linked with metabolic benefits, thus suggesting that bioenergetics efficiency contributes to ultimate causes of diel vertical migrations at least in vendace.
Recent studies have indicated that temporal mismatches between interacting populations may be caused by consequences of global warming, for example rising spring temperatures. However, little is known about the impact of spatial... more
Recent studies have indicated that temporal mismatches between interacting populations may be caused by consequences of global warming, for example rising spring temperatures. However, little is known about the impact of spatial temperature gradients, their vulnerability to global warming, and their importance for interacting populations. Here, we studied the vertical distribution of two planktivorous
fish species (Coregonus spp.) and their zooplankton prey in the deep, oligotrophic Lake Stechlin (Germany). The night-time vertical centre of gravity both of the fish populations and of two of their prey groups, daphnids and copepods, were significantly correlated to the seasonally varying water temperature between March and December 2005. During the warmer months, fish and zooplankton occurred closer to the surface of the lake and experienced higher temperatures. The Coregonus populations differed significantly in their centre of gravity; hence, also, the
temperature experienced by the populations was different. Likewise, daphnids and copepods occurred in different water depths and hence experienced different temperatures at least during the summer months. We conclude that any changes in the vertical temperature gradient of the lake as a result of potential future global warming may impact the two fish populations differently, and may shape interaction strength and timing between fish and their zooplankton prey.
fish species (Coregonus spp.) and their zooplankton prey in the deep, oligotrophic Lake Stechlin (Germany). The night-time vertical centre of gravity both of the fish populations and of two of their prey groups, daphnids and copepods, were significantly correlated to the seasonally varying water temperature between March and December 2005. During the warmer months, fish and zooplankton occurred closer to the surface of the lake and experienced higher temperatures. The Coregonus populations differed significantly in their centre of gravity; hence, also, the
temperature experienced by the populations was different. Likewise, daphnids and copepods occurred in different water depths and hence experienced different temperatures at least during the summer months. We conclude that any changes in the vertical temperature gradient of the lake as a result of potential future global warming may impact the two fish populations differently, and may shape interaction strength and timing between fish and their zooplankton prey.
Hypothesis: Ecological specialization facilitates co-existence of Coregonus spp. in Lake Stechlin. A difference in trophic ecology is the dominant means by which the species are ecologically segregated. Background: Sympatric fish... more
Hypothesis: Ecological specialization facilitates co-existence of Coregonus spp. in Lake Stechlin. A difference in trophic ecology is the dominant means by which the species are ecologically segregated.
Background: Sympatric fish species pairs in post-glacial lakes often feed on different resources, segregating available trophic resources.
Organisms: Sympatric European winter-spawning Coregonus albula and the local endemic dwarf-sized spring-spawning Coregonus fontanae.
Time and place: March–December 2005, Lake Stechlin, North Germany.
Methods: By combining stomach content analyses and stable isotope analyses we compared consumption patterns of the two species at different depths over a 10-month period.
Results: Stable isotope analyses and stomach content analyses both showed little trophic difference between the two species, but a significant effect of capture depth and body size on individual diet.
Conclusions: The sympatric species pair in Lake Stechlin does not follow the expected pattern of niche segregation. Trophic divergence is not the dominant grounds for co-existence.
Background: Sympatric fish species pairs in post-glacial lakes often feed on different resources, segregating available trophic resources.
Organisms: Sympatric European winter-spawning Coregonus albula and the local endemic dwarf-sized spring-spawning Coregonus fontanae.
Time and place: March–December 2005, Lake Stechlin, North Germany.
Methods: By combining stomach content analyses and stable isotope analyses we compared consumption patterns of the two species at different depths over a 10-month period.
Results: Stable isotope analyses and stomach content analyses both showed little trophic difference between the two species, but a significant effect of capture depth and body size on individual diet.
Conclusions: The sympatric species pair in Lake Stechlin does not follow the expected pattern of niche segregation. Trophic divergence is not the dominant grounds for co-existence.
Morphological differentiation and microhabitat segregation of two ecologically similar populations of pelagic planktivorous fishes, Coregonus albula and the smaller Coregonus fontanae, were studied in Lake Stechlin (northern Germany).... more
Morphological differentiation and microhabitat segregation of two ecologically similar populations of pelagic planktivorous fishes, Coregonus albula and the smaller Coregonus fontanae, were studied in Lake Stechlin (northern Germany). Both populations performed diel vertical migrations, although C. fontanae was always situated in deeper pelagic water than C. albula both during day and night. Landmark-based geometric morphometrics revealed that sympatric C. albula and C. fontanae differ in external morphology, with main differences found in head length and eye position, as well as in length and width of the caudal peduncle. Moreover, while C. albula has a similar morphology over all sizes, the shape of C. fontanae changes with size. Accordingly, the morphology of the two is most different at smaller size. Although the morphological differences may reflect adaptations to the slightly differing microhabitats of the two populations, there is no conclusive evidence that this correspondence between ecology and morphology is the main mechanism behind the coexistence of the closely related coregonids in Lake Stechlin.