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opencc-zeroMay 2020View details →

Trophic structure and mercury transfer in the subarctic fish community of Great Slave Lake, Northwest Territories, Canada

In recent decades, mercury concentrations have increased in fish of Great Slave Lake (GSL), a subarctic great lake in northern Canada with important recreational, subsistence, and commercial fisheries. This study characterized habitat use and trophic position of common fish species in GSL near the City of Yellowknife (Northwest Territories, Canada), measured mercury concentrations in water and in taxa from lower trophic levels of the food web, and examined trophic and biological influences on mercury concentrations within and among fish species. Northern pike (Exos lucius) and lake whitefish (Coregonus clupeformis) fed predominantly nearshore, cisco (Coregonus artedi) and longnose sucker (Catostomus catostomus) fed predominantly offshore, and burbot (Lota lota) fed roughly equally in both habitats. Habitat-specific feeding did not influence mercury bioaccumulation in fish, in contrast with published studies of smaller lakes. Water concentrations of total mercury and methylmercury were low and showed little spatial variation among sites or depths. Zooplankton (>200 µm) had similarly low methylmercury concentrations to littoral and profundal amphipods, suggesting little habitat-variation of mercury exposure near the base of the food web. Age, size, and trophic position were significant explanatory variables for muscle total mercury concentrations within populations of fish species. Among fish species, size and trophic position explained 80% of the variation in muscle total mercury concentrations. This study generated the most comprehensive dataset to date on mercury bioaccumulation in the food web of GSL, which will serve as a baseline for future studies of this great lake.

opencc-zeroJan 2020View details →

Data from: Disturbance-mediated consumer assemblages determine fish community structure and moderate top-down influences through bottom-up constraints

<ol> <li>Disturbance is a strong structuring force that can influence the strength of species interactions at all trophic levels, but controls on the contributions to community structure of top-down and bottom-up processes across such gradients remain poorly understood. Changes in the composition of predator and consumer assemblages, and their associated traits, across gradients of environmental harshness (e.g., flooding) are likely to be a particularly important influence on the strength of top-down control and may drive bottom-up constraints.</li> <li>We examined how consumers with particular traits, and the predators that consumed them, varied across a gradient of stream flooding disturbance and used experiments to assess the predation impact on those contrasting consumer communities (ultimately quantifying how flood disturbance altered the strength of top-down control).</li> <li>Consumer community composition and mobility were strongly related to flood disturbance; the biomass and drift of protected primary consumers (i.e., those with morphological defences) decreased with increasing flood disturbance. Predatory fish species had different disturbance niches, and path analysis identified that both direct flood-disturbance effects and indirect bottom-up constraints of flood-disturbance on consumers influenced predatory fish composition and biomass. Fishes generally fed most effectively on consumer types associated with their particular niche, but all fishes were strongly size-selective when feeding on protected consumers. Although protected consumers did not grow large enough to escape predation, an in situ experiment showed protected consumers were at a reduced risk of predation as disturbance increased compared to unprotected consumers.</li> <li>Overall, top-down control declined with flood disturbance, but the effect depended on consumer traits. Predatory fishes were only capable of exerting top-down control on protected consumers in benign habitats but impacted unprotected consumers across a larger range of the disturbance gradient. Collectively our findings suggest that a shift towards a more disturbed state will probably result in reduced predator impacts and a weakening of top-down control. Moreover, predicted increases in the frequency and intensity of climatic events causing disturbance, such as flooding, are likely to result in a community shift that disproportionately impacts protected consumers and the predators that utilise them as prey through the subsequent bottom-up constraints.</li> </ol>

opencc-zeroJan 2020View details →

Common barriers, but temporal dissonance: genomic tests suggest ecological and paleo-landscape sieves structure a coastal riverine fish community

Assessments of spatial and temporal congruency across taxa from genetic data provide insights into the extent to which similar processes structure communities. However, for coastal regions that are affected continuously by cyclical sea-level changes over the Pleistocene, congruent interspecific response will not only depend upon co-distributions, but also on similar dispersal histories among taxa. Here, we use SNPs to test for concordant genetic structure among four co-distributed taxa of freshwater fishes (Teleostei: Characidae) along the Brazilian Atlantic coastal drainages. Based on population relationships and hierarchical genetic structure analyses, we identify all taxa share the same geographic structure suggesting the fish utilized common passages in the past to move between river basins. In contrast to this strong spatial concordance, model-based estimates of divergence times indicate that despite common routes for dispersal, these passages were traversed by each of the taxa at different times resulting in varying degrees of genetic differentiation across barriers with most divergences dating to the Upper Pleistocene, even when accounting for divergence with gene flow. Interestingly, when this temporal dissonance is viewed through the lens of the species-specific ecologies, it suggests that an ecological sieve influenced whether species dispersed readily, with an ecological generalist showing the highest propensity for historical dispersal among the isolated rivers of the Brazilian coast (i.e., the most recent divergence times and frequent gene flow estimated for barriers). We discuss how our findings, and in particular what the temporal dissonance, despite common geographic passages, suggest about past dispersal structuring coastal communities as a function of ecological and paleo-landscape sieves.

opencc-zeroOct 2022View details →

Data from: Variations of trophic structure and niche space in fish community along a highly regulated subtropical large river

The trophic interactions between consumers and resources play a vital role in the stability of communities. In river systems, fragmentation of natural habitats and environmental changes alters the energy basis and community composition, consequently leading to variations in the community's trophic structure and niche space. However, our understanding of how the trophic structure responds to environmental changes is still very limited. Here, based on stable isotope data, we explored and compared trophic positions (TPs), community-wide trophic metrics, and isotope niche space of fish communities in three reaches with different hydrogeomorphic conditions along a highly regulated subtropical river over three seasons. The community trophic structure and niche space showed notable spatiotemporal variations. Overall, the downstream reach had lower TPs and trophic diversity but higher trophic redundancy. The middle reach occupied a wider isotope niche space than other reaches, with the largest niche size during autumn. Furthermore, the niche overlap was relatively high in winter between reaches and in the downstream between seasons. The results implied a homogenization of feeding functional groups and energy flow pathways of species in the downstream community associated with the change of energy source and stability of hydrological conditions. The relationship between trophic structure and environmental factors suggested that the dam-induced alteration in hydrological-related aspects may drive the changes in the functional group composition, together with changes in energy basis, resulting in differences in the trophic structure of the community. The results of the present study deepen our understanding of how ecosystem functions respond to disturbance, thus contributing to an improved ability to conserve river ecosystems.

Fig. 4 in Zooplankton Community Structure Of The Fish Farm Nagļi (Latvia)

Fig. 4. Mean physico-chemical parameters in the ponds, July.

Fig. 2 in Zooplankton Community Structure Of The Fish Farm Nagļi (Latvia)

Fig. 2. Mean water temperature in the ponds.

Fig. 1 in Zooplankton Community Structure Of The Fish Farm Nagļi (Latvia)

Fig. 1. The study area and sampling sites in the Fish farm Nagļi, 2018.

Fig. 3 in Zooplankton Community Structure Of The Fish Farm Nagļi (Latvia)

Fig. 3. Mean physico-chemical parameters in the ponds, May.

opencc-by-4.0Mar 2007View details →

Fig. 1 in Environmental factors predicting fish community structure in two neotropical rivers in Brazil

Fig. 1. The Iguatemi River basin, showing the sampling sites in the Jogui and Iguatemi rivers.

opencc-zeroJan 2023View details →

Nonnative fish facilitate nonnative snails and alter food web structure in experimental pond communities

1. Contemporary ecosystems commonly support multiple nonnative species, which can alter community structure and interact with one another directly and indirectly. Novel interactions between invasive species can result in the facilitation or suppression of one or both invaders, making it important to understand the underlying mechanisms that affect invasion outcomes. 2. Goldfish (Carassius auratus) and Chinese mystery snails (Cipangopaludina chinensis) are freshwater species that have been introduced widely through the aquarium trade and co-occur in their nonnative ranges. We used an outdoor mesocosm experiment to assess separate and combined effects of goldfish and mystery snails on pond community structure and to investigate whether goldfish and mystery snails affected one another positively, neutrally, or negatively. We predicted that the distinct trophic levels of each species and the anti-predator traits of mystery snails would lead to positive interactions between invaders and synergistic effects on the aquatic community. 3. Goldfish directly increased turbidity and decreased floating filamentous algae, zooplankton, juvenile native snails, and survival of amphibians via consumptive effects. Goldfish indirectly increased attached periphyton, phytoplankton, and body size of surviving native green frogs (Lithobates clamitans) through trophic cascades and/or release from competition. Mystery snails had more subtle effects, including reducing growth rates of native gray tree frogs (Hyla versicolor), likely through competitive interactions. 4. With goldfish present, mystery snails showed increased reproductive success (higher total biomass of juveniles), likely due to indirect competitive release from other herbivores. In contrast to their effects on native snails, goldfish did not consume juvenile mystery snails, likely due to their unique traits (e.g., large size and shell thickness). Mystery snails slightly reduced goldfish growth but did not affect their survival. 5. These results suggest unidirectional facilitation between invaders via indirect changes in the food web. Overall, our study found strong direct and indirect effects of invasive aquarium species, particularly goldfish, and provides experimental support for the invasional meltdown hypothesis within urban waterbodies, which are especially prone to invasions.

opencc-zeroFeb 2023View details →

Using standardized fish-specific autonomous reef monitoring structures (FARMS) to quantify cryptobenthic fish communities

1. Biodiversity inventories and monitoring techniques for marine fishes often overlook small (<5cm), bottom-associated ('cryptobenthic') fishes, and few standardized, comparative assessments of cryptobenthic fish communities exist. We sought to develop a standardized, quantitative survey method for cryptobenthic fishes that permits their sampling across a variety of habitats and conditions. 2. Fish-specific autonomous reef monitoring structures (FARMS) are designed to sample cryptobenthic fishes using a suite of accessible and affordable materials. To generate a variety of microhabitats, FARMS consist of three layers of stacked PVC pipes in three different sizes, as well as a bottom and top level of loose PVC-pipe fragments in a mesh basket. We deployed FARMS across a variety of habitats, including coral reefs, seagrass beds, oyster reefs, mangroves, and soft-bottom habitats across six locations (Hawai'i, Texas, Panama, Saudi Arabia, Brazil, and Curaçao). 3. From shallow estuaries to coral reefs beyond 100 m depth, FARMS attracted distinct communities of native cryptobenthic fishes with strong site or habitat specificity. Comparing the FARMS to communities sampled with alternative methods (enclosed clove-oil stations on coral reefs in Panama and oyster sampling units on oyster reefs in Texas) suggests that FARMS yield a subset of cryptobenthic species representative of those present on local coral and oyster reefs. While FARMS yield fewer individuals per sample and are restricted to cryptobenthic species, they are efficient sampling devices relative to the sampled area. 4. We demonstrate that FARMS represent a useful tool for standardized collections of cryptobenthic fishes. While natural substrata are bound to yield more mature communities with a larger number of individuals and wider range of specialist species, the potential to deploy and retrieve FARMS in turbid environments, beyond regular SCUBA depth, and where fish collections using anesthetics or ichthyocides are forbidden suggests that they are a valuable complementary technique to survey fishes in aquatic ecosystems. Deploying FARMS in locations and habitats where cryptobenthic fish communities have not been studied in detail may yield many valuable specimens of unknown or poorly known species.

publicOct 2022View details →

Data from: Variations of trophic structure and niche space in fish community along a highly regulated subtropical large river

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publicMay 2020View details →

Trophic structure and mercury transfer in the subarctic fish community of Great Slave Lake, Northwest Territories, Canada

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publicJan 2020View details →

Data from: Disturbance-mediated consumer assemblages determine fish community structure and moderate top-down influences through bottom-up constraints

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publicFeb 2023View details →

Using standardized fish-specific autonomous reef monitoring structures (FARMS) to quantify cryptobenthic fish communities

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publicJan 2023View details →

Nonnative fish facilitate nonnative snails and alter food web structure in experimental pond communities

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publicMay 2025View details →

Data from: Intraspecific body size determines isotopic trophic structure of a large river fish community

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publicOct 2025View details →

Data from: Seasonal differences in fish community structure in the upper Yangtze river based on eDNA metabarcoding: A multi-dimensional analysis

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