The relationship between fish assemblages and the helminth communities of a prey fish, in a group of small shallow lakes

Galaxias maculatus (small puyen) is an abundant native fish distributed in lakes and rivers of the Patagonia, and it is the frequent prey of other fishes, fish-eating birds, and mammals. Previous studies have shown that it is parasitized by 33 metazoan species and that the richness and composition of the parasite communities vary between lakes. The aim of the present work was to analyze the relationship between the composition of fish assemblages and the helminth component community structure of G. maculatus . Ten environmentally similar, small, shallow lakes, belonging to the Nahuel Huapi Lake basin, were chosen because of the differences in the native fish assemblages. Parasite community structure in G. maculatus varied according to the fish assemblage of each lake. The presence of the piscivorous fish Percichthys trucha regularly produced variations in the composition and richness at the component and infracommunity levels, as well as the percentage of autogenic parasite species in G. maculatus .     

Classification, assessment and trophic reconstruction of Danish lakes using chironomids

1. Surface-sediment assemblages of subfossil chironomid head capsules from fifty-four primarily shallow and nutrient-rich Danish lakes were analysed using multivariate numerical techniques. The species data, comprising forty-one chironomid taxa, were compared to environmental monitoring data in order to establish a relationship between chironomid faunal composition and lake trophic state.
2. The subfossil assemblages were compared to the chironomid bathymetric distributions along transects from four lakes. Correspondence analysis and similarity coefficients showed that the subfossil assemblages, sampled in the lake centre, reflect the chironomid communities in the littoral at a depth of 2–7 m.
3. Two-way indicator species analysis (TWINSPAN) was used to classify the Danish lakes into five groups defined by trophic state, lake depth and pH. Eighteen chironomid taxa showed significant differences in abundance among the five groups. Canonical correspondence analysis (CCA) showed the chlorophyll a concentration ([Chl a ]) and Secchi depth to be the variables best correlated to the faunal data, and fourteen taxa were significantly correlated to [Chl a ].
4. The strong correlation between chironomid data and the ln-transformed ([Chl a ]) was used to create a weighted averaging (WA) model to infer lake trophic state. Several models were tested by cross validation (leave-one-out jack-knifing), and a simple WA model using inverse de-shrinking had a RMSEP_jack of 0.65 (ln units) and a r ²_jack of 0.67.
5. The results can be used in the assessment and reconstruction of lake trophic state for long-term monitoring and palaeoecological investigations of shallow, temperate lakes in the mesotrophic to hypertrophic nutrient range.     

Fish predation,lake acidity and the composition of aquatic insect assemblages

Aquatic insect assemblages were sampled in 2 sets of 18 small lakes in 2 regions of northeastern Ontario. Both sets included lakes with and without fish. In the set near Sudbury, fishless lakes were acidic. Using a standardized sweep net procedure, fishless lakes in both areas were found to have a greater abundance and richness of insects than lakes with fish. Irrespective of pH, fishless lakes supported a similar aquatic insect assemblage which was characterized by an abundance of nekton, especially Notonectidae, Corixidae, Graphoderus liberus (Dytiscidae) and Chaoborus americanus (Chaoboridae). Those taxa were typically absent from lakes with fish, which often had a marked abundance of Gerridae. It is concluded that fish predation is the most immediate factor structuring such aquatic insect assemblages, and is responsible for their change coincident with lake acidification.     

Lake depth and geographical position modify lake fish assemblages of the European 'Central Plains' ecoregion

1. Classification of European lake fish assemblages can be based on fish‐assemblage structure or morphological, geographical, physical and chemical lake attributes. However, substantial gaps in knowledge exist with respect to the correspondence between both classification approaches. 2. Here, we compiled fish assemblage data from 165 lakes situated in the European ‘Central Plains’ ecoregion. Cluster analysis of fish abundances was performed to compare fish assemblage types of the entire ecoregion with those from previous country‐specific studies. Nonparametric group comparisons, classification trees and partial canonical ordinations were used to infer the correspondence between fish assemblage types and morphology, geographical position and nutrient concentration of the lakes. 3. Three distinct fish assemblages were revealed: vendace (Coregonus albula), ruffe (Gymnocephalus cernuus) and roach (Rutilus rutilus) lake types. Both latitude and lake depth were the best determinants of lake type, but total phosphorus (TP) concentrations were also important. Vendace lakes were deep and had low TP concentrations, whereas the shallower ruffe and roach lakes had higher TP values. Roach lakes were more frequent in the north‐west area of the ecoregion, whereas ruffe lakes were more often found south of the Baltic Sea. 4. Controlling for the influence of nutrient concentration showed that lake morphology and geographical position were important determinants of fish assemblages. However, the variance explained was low (<20%), implying that biological interactions may also be important in forming the lake‐specific fish assemblages. 5. The results suggest that fish assemblages differ between deep and shallow lakes, and between the north‐west and south‐east locations within the Central Plains ecoregion. Accordingly, establishment of depth‐related lake morphotypes is needed, and the European ecoregions recommended to be used in evaluation systems according to the Water Framework Directive seem to be too coarse to reflect the subtle differences of fish species richness along geographical gradients.     

Is the island biogeography model a poor predictor of biodiversity patterns in shallow lakes?

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Effects of catchment perturbations by logging and wildfires on zooplankton species richness and composition in Boreal Shield lakes

SUMMARY 1. Forest logging and wildfires are important perturbations of the boreal forest, but their effects on lake biota remain largely unknown. Here, we test whether zooplankton species richness and species assemblages differed among three groups of lakes in Eastern Canada characterised by different catchment conditions: logged in 1995 ( n =9); burnt in 1995 ( n =9); unperturbed ( n =20). Lakes were sampled in June, July and September 1 year after catchment perturbations.
2. Cumulative species richness in reference lakes averaged 46 (33–60) of which 63% were rotifers. Mean cumulative species richness and mean diversity in logged and burnt lakes did not differ from those in reference lakes.
3. Lake species assemblages were described by the density of 62 species (41 rotifers and 21 crustaceans). Among-group differences in species assemblages were not significant. Eighteen per cent of the total variability in species assemblages could be explained by 13 environmental factors, among which dissolved oxygen concentration and cyanobacteria biovolume were the most important. About 5% of species assemblage variability was attributed to covariation between environmental factors and time of sampling, while 4.1% was attributed to temporal variation.
4. Variations in zooplankton species richness and assemblages in Boreal Shield lakes are important, both among lakes and among sampling dates. They seem to depend on environmental factors unrelated to catchment-based perturbations, at least on the short-term of 1 year.     

Influence of fish assemblage and shallow lake productivity on waterfowl communities in the Boreal Transition Zone of western Canada

1. Shallow lakes in the Boreal Transition Zone (BTZ) in Alberta, Canada are naturally productive systems that provide important breeding and moulting habitat for many waterfowl (Anseriformes). To examine the relative importance of biotic and abiotic factors on waterfowl population densities, species richness and community composition, we surveyed 30 shallow lakes and evaluated the relationships among fish communities, lake characteristics and waterfowl in both breeding and moulting habitat. Shallow lakes were either fishless (n = 15), contained only small‐bodied fishes (n = 10) or contained large‐bodied, mostly predatory, fish in addition to small‐bodied fish (n = 5). 2. Environmental factors, including water colour, submerged aquatic vegetation, lake area and potassium, explained 24.3% of the variation in breeding waterfowl communities. Fish assemblage contributed independently to a small but significant proportion (13.4%) of the variation, while 13.8% of the explained variation was shared between environmental factors and fish assemblage. In total, 51.5% of the variation in breeding waterfowl communities was explained. 3. Overall, 55.5% of the total variation in moulting waterfowl communities was explained. Environment alone [especially total phosphorus, lake area, maximum depth and dissolved organic carbon (DOC)] and variation shared by fish and environment similarly accounted for most of the explained variation in moulting waterfowl communities (21.7% and 25.7% respectively), while fish assemblage was only one‐third as important (8.1%). 4. Both breeding and moulting waterfowl densities increased with lake productivity, even in eutrophic and hypereutrophic lakes. Breeding waterfowl density was also twice as great in fishless lakes than in lakes with fish, after accounting for lake area. 5. Certain waterfowl taxa were linked to fishless lakes, especially in the moulting season. Canvasback and moulting ring‐necked ducks were linked to small‐bodied fish lakes, whereas moulting common goldeneye were indicators of large‐bodied fish lakes. Knowledge of fish presence and species composition can therefore help guide conservation and management of waterfowl habitat in western Canada. Our results suggest that management efforts to maintain the most productive waterfowl habitat in the BTZ should focus on smaller, shallow, fishless lakes, particularly given that larger fish‐bearing systems have greater regulatory protection.     

Food and feeding ecology of piscivorous fishes at Lake St Lucia, Zululand

The food and feeding ecology of piscivorous fish in Lake St Lucia was monitored for two years. Piscivorous fishes feed predominantly on the planktivorous Gilchristella aestuarius and Thryssa vitrirostris but a wide range of prey species was recorded. Numbers of the predominant piscivores, Argyrosomus hololepidotus and Elops machnata , in an area appear to be related to the densities of their major prey, T. vitrirostris and G. aestuarius . Large piscivorous fishes are restricted to the deeper portions of the lake, whereas small piscivores such as Johnius belengerii and Terapon jarbua feed predominantly on small fishes in the littoral zone. The highly significant correlation between the composition of prey fish species in the lake and prey fish species in the diet of piscivorous fishes, indicates that piscivores are feeding in a density dependent manner. However, factors such as habitat, fish size and swimming speed of prey species are shown to be important in prey selection. Juvenile fish of species such as Sarotherodon mossambicus, Liza macrolepis and Acanthopagrus berda remain in shallow marginal areas, thus avoiding large piscivorous fishes. However by frequenting shallow areas these species become vulnerable to bird predators, especially egrets and herons.     

Biomanipulation of lake ecosystems: successful applications and expanding complexity in the underlying science

SUMMARY 1. To illustrate advances made in biomanipulation research during the last decade, seven main topics that emerged after the first biomanipulation conference in 1989 are discussed in relation to the papers included in this special issue and the general literature. 2. The substantially higher success rates of biomanipulations in shallow as opposed to stratified lakes can be attributed to several positive feedback mechanisms relating mainly to the recovery of submerged macrophytes. 3. The role of both nutrient loading and in‐lake concentrations in predicting the success of biomanipulations is emphasised and supported by empirically defined threshold values. Nutrient recycling by aquatic organisms (such as fish) can contribute to the bottom‐up effects on lake food webs, although the degree can vary greatly among lakes. 4. Ontogenetic niche shifts and size‐structured interactions particularly of fish populations add to the complexity of lake food webs and make scientifically sound predictions of biomanipulation success more difficult than was previously envisaged. 5. Consideration of appropriate temporal and spatial scales in biomanipulation research is crucial to understanding food web effects induced by changes in fish communities. This topic needs to be further developed. 6. An appropriate balance between piscivorous, planktivorous and benthivorous fishes is required for long‐lasting success of biomanipulations. Recommended proportions and absolute densities of piscivorous fish are currently based on data from only a few biomanipulation experiments and need to be corroborated by additional and quantitative assessments of energy flow through lake food webs. 7. Biomanipulation effects in stratified lakes can be sustained in the long term only by continued interventions. Alternate stable states of food web composition probably exist only in shallow lakes, but even here repeated interventions may be needed as long as nutrient inputs remain high. 8. Biomanipulation is increasingly used as a lake restoration technique by considering the needs of all lake users (sustainability approach). The combination of water quality management and fisheries management for piscivores with positive effects for both appears to be particularly promising. 9. Biomanipulation research has contributed substantially to progress in understanding complex lake food webs, which should in turn promote a higher success rate of future whole‐lake biomanipulations.     

Invasion of exotic piscivores causes losses of functional diversity and functionally unique species in Japanese lakes

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Homogenization of fish assemblages in different lake depth strata at local and regional scales

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Assessing lake typologies and indicator fish species for Italian natural lakes using past fish richness and assemblages

In order to establish a fish-based typology of Italian lakes and identify possible reference and indicator fish species for each lake type, we analysed historical data on fish assemblages of all Italian natural lakes >0.5 km² from the period prior to the major decline in water quality in the 1950s. General linear regression models showed the ecoregion and lake altitude being the best predictors of fish species richness. The number of species was significantly higher in the Alpine than in the Mediterranean ecoregion. Among Alpine lakes, the number of fish species increased significantly with lake volume whilst decreased with altitude. In the Mediterranean lakes, none of the selected parameters was significant. Cluster analysis of fish assemblages (presence/absence) divided the lakes of the Alpine and Mediterranean ecoregions into four and two types, respectively. Pike (Esox lucius), rudd (Scardinius erythrophthalmus) and tench (Tinca tinca) were the main indicator species for the small and mostly shallow lakes in both the Alpine (Type 1) and Mediterranean (Type 6) ecoregions, minnow (Phoxinus phoxinus) for the alpine high altitude lakes (Type 2) and landlocked shad (Alosa fallax lacustris), European whitefish (Coregonus lavaretus) and burbot (Lota lota) for the large and very deep alpine lakes (Type 4). The European whitefish was the only indicator species for the deep Mediterranean lakes (Type 5). These species and associated fish assemblages may be useful indicators in future assessments of the ecological status of Italian lakes according to the European Directives (2000/60/EC and 2008/105/EC).     

Relationships between fish assemblages, macrophytes and environmental gradients in the Amazon River floodplain

During the flood season of 1992–1993, 139 species of fishes were collected from a floodplain lake system in the central Amazon Basin. Fish species distribution was examined relative to abiotic variables in seven vegetation strata on Marchantaria Island, Solimões River. Both environmental variables and species distributions were influenced by a river channel to floodplain-interior gradient. Species diversity was significantly higher in vegetated areas than in unvegetated areas, with deeper water Paspalum repens stands harbouring the highest diversity. As a result, species richness and catches were positively related to habitat complexity, while catch was also negatively related to dissolved oxygen (DO) and water depth. Low DO and shallow waters appeared to act as a refuge from predation. Fish assemblages were related to water chemistry, but species richness was not. Canonical correspondence analysis provided evidence that floodplain fish assemblages formed by the 76 most common species were influenced by physical variables, macrophyte coverage and habitat complexity, which jointly accounted for 67% of the variance of fish species assemblages. Omnivores showed no pattern relative to the river channel to floodplain-interior gradient while detritivores were more likely to be found at interior floodplain sites and piscivores closer to the river. Piscivores could be further separated into three groups, one with seven species associated with free-floating macrophytes in deep water, a second with five species found in shallow waters with rooted grasses and a third with six open water orientated species. The results suggest that fish assemblages in the Amazon floodplain are not random associations of species.     

Comparison of losses of planktivorous fish by predation and seine-fishing in a lake undergoing long-term biomanipulation

SUMMARY 1. Piscivore stocking at artificially high densities and fishing are the two common approaches to reduce the amount of planktivorous and benthivorous fish in lake biomanipulation programmes. Both measures have advantages and disadvantages, but their relative efficacy has not previously been directly compared.
2. We calculated the average annual catch of roach and bream in a lake undergoing long-term biomanipulation (Feldberger Haussee, Germany) by seining each year between 1992 and 1998. We compared this value with a bioenergetics estimate of annual consumption rates of the dominant cohorts of piscivores, pikeperch and pike, in 1997 and 1998. We also determined species composition and length distribution of prey fish in stomachs of the piscivores.
3. Roach was the dominant prey species of both pikeperch and pike, whereas bream was rarely taken by either piscivorous species. Seining removed on average larger specimens of roach than were found in the stomachs of the piscivores.
4. Based on stocking densities of the piscivores, published mortality rates, and individual consumption rates, feeding of pikeperch and pike on roach exceeded the manual removal of roach by seining by a factor of 4–15 (biomass) in 1997 and 1998.
5. Based on these results, a combination of fishing and piscivore enhancement is recommended. Whereas the stocks of adult roach and bream have to be reduced mainly by fishing, the predation of piscivores should be directed predominantly towards the juvenile zooplanktivorous fish. Therefore, small size-classes of piscivorous fish should be promoted by fisheries management, including stocking and harvest regulations.     

Similarity between contemporary vegetation and plant remains in the surface sediment in Mediterranean lakes

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Fish species and trophic diversity of haplochromine cichlids in the Kyoga satellite lakes (Uganda)

Prior to the 1980s, lakes Kyoga and Victoria previously supported an exceptionally diverse haplochromine fish fauna comprising at least 11 trophic groups. The species and trophic diversity in these lakes decreased when the introduced Nile perch depleted haplochromine stocks. From December 1996 to October 1998, we studied species and trophic diversity of haplochromine fishes in six satellite lakes without Nile perch in the Kyoga basin and compared them with the Kyoga main lake against historical data from Lake Victoria where Nile perch were introduced. Forty‐one species were found in the study area, of which, the Kyoga satellite lakes contributed 37 species in comparison to only 14 from the Kyoga main lake. Analysis of trophic diversity based on 24 species that contained food material revealed seven haplochromine trophic groups (insectivores, peadophages, piscivores, algal eaters, higher plant eaters, molluscivores and detritivores) in the Kyoga satellite lakes in comparison to two trophic groups (insectivores and molluscivores) in the Kyoga main lake. Many of the species and trophic groups of haplochromines depleted by the introduced Nile perch in lakes Kyoga and Victoria still survive in the Kyoga satellite lakes. This is attributed to the absence of Nile perch in those lakes. Nile perch has been prevented from spreading into the satellite lakes by swamp vegetation that separate them from the main lakes. If these swamps prevent Nile perch from spreading into the lakes, it is possible to conserve fish species, especially haplochromines, which are threatened by introduction of Nile perch in the main lakes.     

Field and experimental evidence of the effect of Jenynsia multidentata, a small omnivorous–planktivorous fish, on the size distribution of zooplankton in subtropical lakes

1. Small cladocerans, copepod nauplii and rotifers often dominate the zooplankton community in tropical and subtropical lakes. This is probably because of high predation pressure by small omnivorous–planktivorous fish, but experimental evidence is scarce.
2. This study used two approaches to test the effect of the small omnivorous–planktivorous fish species Jenynsia multidentata , which is frequently abundant in (sub)tropical eutrophic lakes in South America, on the size distribution of zooplankton. In Lake Blanca (Uruguay), which lacks any piscivores, we sampled seasonally for both fish and zooplankton. We also conducted an outdoor mesocosm experiment with treatments containing or lacking J. multidentata .
3. Together, the empirical and experimental data suggest that J. multidentata predation plays an important role in modulating the size structure of the zooplankton community in subtropical lakes. In the absence of J. multidentata , stocked large-sized zooplankters like Daphnia obtusa were abundant in the experiments, while small-sized zooplankton dominated in the presence of fish, as they did in the lake itself from spring to the end of the season.     

Effects of drought and pluvial periods on fish and zooplankton communities in prairie lakes: systematic and asystematic responses

The anticipated impacts of climate change on aquatic biota are difficult to evaluate because of potentially contrasting effects of temperature and hydrology on lake ecosystems, particularly those closed‐basin lakes within semiarid regions. To address this shortfall, we quantified decade‐scale changes in chemical and biological properties of 20 endorheic lakes in central North America in response to a pronounced transition from a drought to a pluvial period during the early 21st century. Lakes exhibited marked temporal changes in chemical characteristics and formed two discrete clusters corresponding to periods of substantially different effective moisture (as Palmer Drought Severity Index, PDSI). Discriminant function analysis (DFA) explained 90% of variability in fish assemblage composition and showed that fish communities were predicted best by environmental conditions during the arid interval (PDSI 相似文献   

Representation of aquatic invertebrate communities in subfossil death assemblages sampled along a salinity gradient of western Uganda crater lakes

We analysed subfossil death assemblages of aquatic invertebrate communities in a salinity series of 35 western Uganda maar-crater lakes to evaluate their potential as biological indicators of past habitat conditions in paleo-environmental research. The study region encompasses the climatological and hydrological gradient between the dry floor and moist shoulders of the Edward-George branch of the East African Rift Valley, and includes mesotrophic to hyper-eutrophic, and shallow unstratified to deep meromictic lakes with a surface-water salinity range between 101 and 135 400 μS/cm. Focusing on non-chironomid aquatic invertebrates with good fossil preservation, we found that fossil larval remains of the Dipteran families Culicidae, Ephydridae, and Stratiomyidae are good indicators of saline environments. Our data further suggest that the abundances of Bryozoan statoblasts and Chaoboridae are indicative of, respectively, the fraction of the littoral zone covered by aquatic macrophytes and of lake trophic state, but a lake reference data set more specifically designed to cover variation in these environmental factors will be needed to determine the strength of these relationships. In these small, simple lake basins, recent death assemblages recovered from a single mid-lake surface-sediment sample provides a more complete inventory of local aquatic invertebrate communities and the distribution of species among lakes than exploratory live sampling of those taxa in a selection of littoral, benthic and pelagic habitats.