Stream Fish Research Articles

Range Extension of Blackfin Darter and Tennessee Dace, and First Collection of Western Blacknose Dace from Locust Fork of the Black Warrior River in 80 Years

Novel records of stream fishes continue to shape our understanding of species distributions and are often representative of geological and evolutionary histories. We report the discovery of Chrosomus tennesseensis (Tennessee Dace) and confirm previous collections of Etheostoma nigripinne (Blackfin Darter) in the Mobile River Basin. Additionally, we report the rediscovery of Rhinichthys obtusus (Western Blacknose Dace) from the Locust Fork watershed of the Black Warrior River system. The latter species was last collected from the Locust Fork watershed in 1939 and considered extirpated. The discovery of the Tennessee Dace represents the first collection in the Mobile River Basin. These recent collections from the Locust Fork watershed may indicate that a stream-capture event is responsible for the isolation of these populations from the Tennessee River Basin. Subsequent studies should incorporate population-level genetic analyses coupled with historical geological information to understand how these populations became isolated and how recent stream-capture events could inform our understanding of allopatric speciation in aquatic populations.

Can bait improve the efficiency of underwater video monitoring of fish in headwater streams? A case study from the Rondegat River, South Africa

The use of action cameras for underwater video sampling provides a non-harmful alternative for monitoring endangered and threatened fish populations in clear headwater streams. Here, we examine the use of baited remote underwater video systems (BRUVS) for the monitoring of vulnerable species in the clear headwater streams of the Cederberg Wilderness Area, South Africa. We tested whether baits (bread and Marmite™) increased the number of individuals recorded in comparison to un-baited BRUVS. Overall, baiting cameras increased the number of individuals recorded, with bread outperforming Marmite™. Numbers recorded varied notably among species and sites. We conclude that BRUVS are a useful monitoring tool, but caution that monitoring programmes should first determine the effectiveness of a range of baits to attract each species expected at the study sites.

Riverscape nesting dynamics of Neosho Smallmouth Bass: To cluster or not to cluster?

AbstractAimHierarchical stream habitat conditions influence patterns of fish abundance and population dynamics. The spawning period is important for stream fishes but coincides with unpredictable environmental conditions and stressors. Thus, identifying habitats that confer suitable spawning is crucial to managing vulnerable fish populations, including narrow‐range endemics. Here, we evaluate reach‐ and catchment‐scale habitat features related to Neosho Smallmouth Bass (Micropterus dolomieu velox) nest presence, abundance and aggregations (clusters) and quantify nest microhabitat.LocationOzark Highlands ecoregion, USA.MethodsWe conducted snorkel and habitat surveys from 2016 to 2018 to quantify nest abundance, describe nest cluster characteristics and quantify nest microhabitat. We used field‐collected and geospatial variables and developed generalized mixed models to evaluate the influence of multi‐scale habitat features on nest cluster presence and nest abundance.ResultsNest clusters, scarcely known for other Smallmouth Bass populations, contained 25% of all documented nests. Presence of nests was more likely in warmer stream reaches with wide, shallow channels and more pool habitat. Nest cluster presence was more likely with greater nest densities and earlier in the spawning season. The abundance of Smallmouth Bass nests was related to several reach‐scale habitat conditions, with greater nest counts in warmer reaches and reaches with deeper pool habitat. Regardless of cluster behaviour, nesting Smallmouth Bass used similar microhabitats, including a range of depths (0.26–1.85 m), low velocities (<0.1 m/s) and typically gravel substrates.Main conclusionsOur results indicate plasticity in nesting ecology within Neosho Smallmouth Bass populations and highlight the need to consider multiple aspects of stream habitat when developing conservation and management plans. The importance of reach‐scale habitat features suggests it may be important to limit landscape and channel alterations. Nest clustering behaviour suggests these populations may be vulnerable to human influence during the nesting season, but also provides management opportunities for protection during critical time periods.

Historic fish samples from the Southeast USA lack microplastics

Most of earth's systems and the organisms that inhabit them are known to contain microplastics, which are well documented to have lethal and sublethal effects on living things. Due to their generally short timeframe and recent focus, contemporary studies of microplastics in fish are unable to inform past patterns of microplastic ingestion, and as such there is a knowledge gap regarding when microplastics began showing up in fishes. We examined n = 185 historical (museum) fish samples representing seven species from five freshwater systems across 51 years in order to look for microplastic samples over time. We found only three microplastic particles, two of which were in the more recent years of collection (1996 and 2006). Although our results are not conclusive toward understanding the true nature of microplastic occurrence over time in fishes, our findings present strong evidence that southeast U.S. stream fish likely did not ingest large numbers of microplastics during the 20th century.

Assessing the effects of multiple land uses on the functional beta diversity of stream fishes in the Amazon region

Large-scale deforestation not only modifies the landscape, but also affects in the structure of the habitat, and threaten the functional structure of the aquatic biota. This study evaluates the partitioning of the functional beta diversity of stream fish along a gradient of environmental impact and determines which functional traits are associated with the gradient. Biological, environmental, and landscape variables were sampled in 2014 and 2015. The functional structure of the fish fauna was characterized using 12 functional traits. The functional beta diversity and functional replacement were influenced by changes in local abiotic and landscape conditions, caused by modifications in forest cover, with the functional traits varying systematically in accordance with environmental features. We found no association between environmental variables and functional traits. Our results raise concerns with regard to the transformation of the landscapes in which streams are found caused by changes in land use, and we would recommend the preservation of an adequate buffer of good quality riparian vegetation in management or restoration projects to guarantee the long-term conservation of stream ecosystems.

The effect of different logging regimes on the ecomorphological structure of stream fish assemblages in the Brazilian Amazon

AbstractWe evaluated the effects of changes in habitat structure resulting from conventional logging (CL) and reduced-impact logging (RIL) on the ecomorphological structure of stream fish assemblages in the eastern Brazilian Amazon, investigating (1) which habitat characteristics are influenced by different logging methods, (2) the differences in the ecomorphological structure of fish assemblages between two logging methods and undisturbed forest (UF), and (3) the relationships between ecomorphological traits of fish assemblages and habitat variables. We measured 13 habitat variables and characterized 11 ecomorphological traits of 55 fish species collected in 34 sampling sites (stream stretches) located in CL, RIL, and UF. In logged areas, the streams present a fine sediment increase and reduced vegetation cover, while in the UF a greater amount of natural shelter and more cover vegetation were observed. These environmental changes selected ecomorphological traits of stream fish assemblages, recording a greater relative width of the mouth in UF, higher ventral flattening index in RIL, or greater relative head length, and higher caudal peduncle compression index in CL. In this sense, we recommend that logging practices, including RIL, should be reviewed as a means of adopting better strategies to minimize human disturbances in streams.

Importance of non‐native isopods and other terrestrial prey resources to steelhead/rainbow trout Oncorhynchus mykiss in coastal streams in Big Sur, California

AbstractTerrestrial invertebrates provide important prey subsidies to many stream fishes. Non‐native invertebrates are widespread in many ecosystems, yet they have received little attention in studies of subsidies to stream food webs. We sampled coastal basins in Big Sur, California, to determine the importance of non‐native isopods and other terrestrial invertebrates in the summer diet of steelhead/rainbow trout (Oncorhynchus mykiss) and to estimate the density of isopods along streambanks. Terrestrial invertebrates contributed more than 40% of the energetic value of O. mykiss stomach contents at most sites and up to 75% at some locations. Non‐native isopods Armadillidium vulgare or Porcellio scaber occurred at all sites, reaching mean densities of up to 13 individuals/m2 on streambanks, and accounted for up to 20% of the energy in the diet. The proportion of non‐native isopods in the diet was positively correlated with their density at a site, and the frequency and energetic value of terrestrial invertebrates and non‐native isopods in O. mykiss diets increased with fish size. In terms of the broader diet, the energetic value and taxonomic composition of stomach contents varied among sites but there was no major geographic pattern or trend to the variation, and overall O. mykiss diets were generally similar across the region. Our results highlight that non‐native terrestrial invertebrates may provide a considerable but overlooked subsidy to stream fishes.

Unraveling the role of environmental factors and dispersal capacity in a metacommunity of Amazonian stream fishes

Separating species in terms of dispersal capacity can be useful to understand how local and regional factors affect the distribution of organisms in metacommunities. In this study, we sought to unravel how the characteristics of local habitats and spatial distances structure fish communities in Amazonian streams. We hypothesized that fishes classified with high dispersal capacity are mainly structured by mass effects and respond to environmental and spatial variables in the same proportion, while fishes classified with low dispersal capacity are mainly structured by species sorting, responding mainly to local environmental variables. We collected fish from 36 well-preserved streams in the Capim river basin in northern Brazil during the dry season. In general, the community composition was structured by characteristics of the local habitat. Spatial variables influenced each group at different intensities, agreeing with the models of species sorting and mass effects and corroborating our hypotheses. Thus, our findings suggest that the dispersal mode affects how metacommunities are structured. The differences in the patterns observed between the groups compared can help in the management and conservation of species, such as those with greater environmental requirements and more susceptible to habitat changes. We emphasize the need to maintain habitat integrity and connectivity in headwater streams to conserve species in their habitats.

Incorporating Network Connectivity into Stream Classification Frameworks.

Stream classification frameworks are important tools for conserving aquatic resources. Yet despite their utility, most classification frameworks have not incorporated network connectivity. We developed and compared three biologically informed stream classification frameworks considering the effects of variables indexing local habitat and/or connectivity on stream fish communities. The first framework classified streams according to local environmental variables largely following the precedent set by previous stream classifications. The second framework classified streams according solely to network connectivity variables, while the third framework considered both local and connectivity variables. Using fish community data from 291 wadeable streams in South Carolina, USA, we used conditional inference tree analyses to identify either seven or eight discrete types of wadeable streams within each framework. Classifications were evaluated on their ability to describe community composition at a subset of sites not used in model training, and canonical correspondence analysis suggested that each framework performed similarly in describing overall community variation, with about 19% of variation explained. After accounting for the effects of biogeography and land use in our analytical approach, each classification explained a substantially higher amount of community variation with 46% of variation explained by our connectivity-informed classification and 42% explained by our locally informed classification. Classifications differed in their ability to describe elements of community structure; a classification incorporating connectivity predicted species richness better than the one that did not. This study ultimately addresses an important knowledge gap in the classification literature while providing broader implications for the conservation of aquatic organisms and their habitats.

Autumn electrofishing reduces harm to Ontario (Canada) stream fishes collected during watershed health monitoring

Electrofishing surveys provide important information on watershed health, and the status of imperiled and recreationally important stream fishes. Concerns about the harmful effects of electrofishing on the endangered redside dace Clinostomus elongatus have resulted in restrictions on its use in sampling activities in the province of Ontario, Canada. However, the effectiveness of these restrictions is unproven. We undertook a paired sampling gear study in 2018-2019 to test whether an alternate gear (seine nets) or a change in electrofishing timing (autumn rather than summer) reduced harm to stream fishes. The study took place in streams located in the Greater Toronto Area. We found large differences in the frequency and magnitude of sampling-related mortalities between sampling gear and seasons. During individual surveys, electrofishing mortality never exceeded 9% in the summer or 4% in the autumn, while seining-related mortality reached 60% at two stream sites. Overall, autumn electrofishing resulted in mortality rates that were 5.6 and 15 times lower than summer electrofishing and summer seining. These results indicate that survival of Ontario stream fishes can be improved by delaying electrofishing until early autumn.

Streams fish from Upper Araguaia and Middle Rio da Mortes basin, Brazil: generating subsidies for preservation and conservation of this critical natural resource

Abstract: The Araguaia River basin has the highest fish biodiversity within the Cerrado biome (Brazilian savannah), with many endemic and threatened species by human activities. Despite growing efforts to catalog Neotropical freshwater fish biodiversity, many regions are still undersampled. Our objective is to complement the information about stream fish in two hydrographic basins in the Cerrado. We sampled 72 streams with 50 m stretch in the Upper Araguaia (n = 32) and Middle Rio das Mortes (n = 40) basins. We collected 14,887 individuals distributed in 137 species, 81 genera, 30 families, and six orders. Characidae, Loricariidae, and Cichlidae were the families richer in species. We found a high diversity of rare fish species in the streams sampled, ca. 71.5% of the species had at least five individuals collected, and 18 species had only one collected specimen. The most frequent species were Astyanax cf. goyacensis, Knodus cf. breviceps, and Characidium cf. zebra. Both basins shared around 43% of the species. We caught 76 species in Upper Araguaia and 120 species in Middle Rio das Mortes. Seventeen exclusive fish species occurred in Upper Araguaia, whereas 61 were found in the Middle Rio das Mortes basin. Our analysis showed lower diversity of fish in Upper Araguaia than in the Middle Rio das Mortes basin. Considering the exclusive fish species of both basins, the human threats in those regions, and the few existent protected areas, we need a better look at the aquatic biodiversity conservation of this ecosystem.

First record of larvae of Spiroxys (Nematoda: Gnathostomatidae) parasitizing fishes in stream of the Caatinga domain.

The present study is the first report of Spiroxys larvae parasitizing stomach and intestine of three fish species in stream of Caatinga domain, Northeast, Brazil. A total of 120 fish specimens, 40 of Astyanax bimaculatus, 40 of Hoplias malabaricus, and 40 of Hoplosternum littorale were examined for nematodes. A total of 633 specimens of Spiroxys larvae were recovered for the three fish species: 227 in A. bimaculatus (prevalence (%) = 48; mean abundance = 5.78 ± 1.78 (range = 0-70); and mean intensity = 11.95 ± 2.7 (range = 2-70)), 176 in H. malabaricus (prevalence (%) = 42.5; mean abundance = 4.40 ± 1.55 (range = 0-53); and mean intensity = 10.35 ± 2.38 (range = 2-53)) and 230 in H. littorale (prevalence (%) = 42.5; mean abundance = 5.75 ± 1.98 (range = 0-52); and mean intensity = 13.53 ± 3.04 (range = 1-52)). This study expands the range of the geographic distribution of nematodes of the genus Spiroxys and increase the list of hosts, as well as contributing to the knowledge of fish parasites biodiversity in Caatinga domain.

Body size responses to land use in stream fish: the importance of different metrics and functional groups

Abstract Body size influences the effect of individuals and assemblages on ecosystem functioning and defines how they respond to ecosystem changes. We evaluated how body size structure of fish assemblages and functional groups respond to human modifications at catchment, riparian and local scales in 40 streams of the Pampa grasslands, southern Brazil. To describe body size structure, we calculated the mean, coefficient of variation, skewness, and kurtosis, using individual biomass data for the entire fish assemblages and separately by functional group. The results suggested that body size response depends on body size metrics, functional group, and the spatial scale of land use. From 11 functional groups, only five showed a clear response to land use. In general, most functional groups had a higher concentration of small sizes (left-skewed) in response to increased land use measured at distinct spatial scales (local, riparian, and catchment), and a greater concentration of sizes in a narrow and central distribution (higher kurtosis). However, the responses were complex and varied between the functional groups. We conclude that considering ecomorphological and trophic features separately by functional group and assessing multiple body size metrics contributed greatly to detecting the influence of land use on fish body size.

Generalist populations formed by generalist individuals: a case of study on the feeding habits of a Neotropical stream fish

Abstract: Aim We described the diet of the generalist stream fish Knodus chapadae and we tested if the environmental conditions are associated with population’s diet and individual specialization. Methods We analyzed the stomach contents of 287 individuals from 29 streams from the Brazilian savanna (Cerrado). Results The instream physical habitat structure, physiochemical conditions, and adjacent land use explained partially the variation in the diet of populations, but not the variation in the individual specialization. Thus, the diet changes observed at populational level were driven by changes in the average composition of the diet of individuals that, in turn, remained generalists along the environmental gradient. Conclusions Our results show that the trophic opportunism described for small characids was also observed in K. chapadae, whose diet shifts according to changes in environmental conditions. Furthermore, the opportunism expressed at the individual level can explain the trophic plasticity observed on the studied species.

Length-weight relationship and diet of the catfish Cambeva guareiensis (Siluriformes; Trichomycteridae)

Abstract: The length-weight relationship (LWR) and diet of a small trichomycterid catfish, Cambeva guareiensis, was studied based on 58 specimens captured in Corrente stream, Guareí River basin, São Paulo, Brazil. LWR analyses showed values of a ranged from 0.0097 to 0.0149 and b from 2.858 to 3.250. The analysis of the diet showed that high amounts of aquatic insects (93.75% of total items) were consumed by the species. In addition, we found no statistically significant differences when comparing the diet between the dry and rainy periods. Our study contributes to the knowledge on populational biology and feeding ecology of trichomycterid fishes in Brazilian streams.

Considerations of variability and power for long-term monitoring of stream fish assemblages

Little attention has been given to optimizing statistical power for monitoring stream fish assemblages. We explored the relationship between temporal variability and statistical power using 34 metrics from fish community data collected annually at six sites over 10 years via electrofishing. Metric variability differed by the life stage and group of species considered, use of abundance or mass data, and data standardization technique. Lower variability was associated with community data, abundance data, and time-based standardizations, while greater variability was associated with young-of-the-year data, mass data, and area-based standardizations. Simulation-based power analysis indicated metric choice, and to a lesser degree, monitoring design (annual, biennial, endpoints, or haphazard sampling) influenced power to detect change. Across a fixed number of surveys (N = 60), endpoints sampling performed best. The N needed to detect change was heavily dependent upon metric choice for all monitoring designs, with the most biologically specific metrics requiring greater N. Large savings in effort and resource expenditure can be obtained utilizing biologically relevant metrics that are robust to temporal noise within an appropriate sampling design.

Functional responses of stream fish communities to rural and urban land uses

Abstract We tested the effects of ruralization and urbanization on the functional diversity indices and the composition of functional traits of Neotropical stream fish communities. The study was carried out in 24 streams of the Pirapó, Piquiri, Paraná III and Iguassu river basins. Land use in the watershed was categorized as percentages of native vegetation, rural occupation and urban occupation. Statistical tests revealed negative bivariate correlations between functional dispersion and the proportion of native vegetation in the watershed. The results indicate that a higher percentage of rural or urban occupation is associated with increased functional dispersion. In the analyzes of trait composition, significant alterations were observed in response to urbanization while only the increase in herbivory responded to ruralization. As the area of native vegetation is reduced by urbanization, the trait composition changes, with reduced proportions of species with intolerance to hypoxia, migratory reproductive behavior, external fertilization, and subterminal mouth, and increased proportions of species with parental care, detritivory, internal fertilization, and an upper mouth. Therefore, fish species that have these specific characteristics are more likely to disappear from streams as urbanization progresses. In summary, urbanization was related to a greater change in the composition of functional traits than ruralization.

Seasonal consumption of terrestrial prey by a threatened stream fish is influenced by riparian vegetation

The consumption of terrestrial prey by fishes highlights the functional value of terrestrial habitats, but such consumption is not well documented for many small-bodied species. We determined the diet and consumption of terrestrial prey by a threatened fish, silver shinerNotropis photogenis, using stomach content and stable isotope analyses to better understand the functional role of riparian habitat for the species. Results indicate silver shiner is a generalist drift feeder that consumes a wide range of aquatic and terrestrial prey. Both stomach content and stable isotope analyses indicated that terrestrial prey was commonly exploited and that terrestrial prey consumption was both seasonally and spatially variable. Based on stomach contents, the contribution of terrestrial prey was (average ± SD) 41.53 ± 32.35% in fall and 20.45 ± 20.45% in summer; based on stable isotopes it was 35.24 ± 4.41% in fall and 39.88 ± 12.34% in summer. During fall, when bankside terrestrial invertebrates were more abundant, silver shiner stomachs contained significantly more terrestrial prey in reaches where riparian vegetation cover was highest, indicating that intact riparian cover may facilitate access to high-quality prey. The consumption of terrestrial prey may be particularly important in fall, as it may promote increased growth and survival leading to more successful overwintering. Our findings suggest that terrestrial subsidies are ecologically valuable for silver shiner and that the protection of reaches with intact riparian habitats would likely improve conservation and recovery efforts by helping ensure access to key prey resources.

Taxonomic and phylogenetic beta diversity in headwater stream fish communities of the Paraná and Paraguai River basins

ABSTRACT Patterns of species replacement and richness differences along environmental gradients or ecoregions shed light on different ecological and evolutionary mechanisms acting on community structure. Communities of aquatic ecosystems of different watersheds are supposed to host distinct species and lineages. Quantifying and understanding the degree to which these differences are affected by environmental and biogeographical factors remains an open question for these environments, particularly in the Neotropical region. We investigated patterns of taxonomic and phylogenetic composition of headwater streams of the Paraná and Paraguai River basins to understand how local and biogeographical factors affect the assembly of fish communities. We also quantified taxonomic and phylogenetic beta diversity by decomposing them into nestedness and turnover components. We found that local environmental factors are the main factors influencing the composition of stream fish communities. Whereas pH affected both taxonomic and phylogenetic turnover, water velocity was responsible for phylogenetic turnover and pH was the main driver of phylogenetic nestedness. Our results indicate an effect of local environmental factors in determining the structure of headwater stream fish communities through a combination of a species sorting mechanism (water velocity and pH) and phylogenetic habitat filtering (pH).

Local effects of deforestation on stream fish assemblages in the amazon-savannah transitional area

Abstract The expansion of agriculture in the southeast Amazon-Savanah transitional area has greatly decreased forest cover and influenced stream structure and functioning. We assessed the effects of forest cover loss on the integrity of streams by assessing stream physical conditions and the taxonomic and functional diversity of fish assemblages in this transitional area. We hypothesize that low forest cover, especially adjacent to streams, results in poor physical conditions (e.g., warmer temperatures, less physical structure, etc.), which in turn will decrease the taxonomic and functional diversity of fish assemblages. We detected that loss of forest cover negatively affects natural stream conditions and reduces the functional diversity of fish assemblages, but we did not find a strong effect on taxonomic diversity. Ambush and stalking predators, diurnal surface pickers (groups that exhibit opportunistic life history strategies), grazers, pickers, and browsers (groups that exhibit equilibrium life history strategies) were the functional groups with the strongest relation to altered environments. These groups can explore different niches, both with natural characteristics or altered by human activities. Our results suggest that the preservation of riparian zones can minimize the loss of specialized fish species in assemblages of Amazon-Savannah stream systems.