Fish Richness Research Articles

Parasite Species Richness of Fish from Fish Ponds and Fingerling Sources in Central Ethiopia: It’s Implication on Aquaculture Development

Parasite Species Richness of Fish from Fish Ponds and Fingerling Sources in Central Ethiopia: It’s Implication on Aquaculture Development

The Value of Habitat Complexity and Diversity of Reef Fish Species in Sangiang Island, Bima Regency, West Nusa Tenggra

Coral reef ecosystems in the marine environment have a vital role, especially in providing habitat for the diversity of commercial and non-commercial fish species. This study aims to assess the species richness of coral reef fish based on the complexity of the habitat of Sangiang Island, Bima Regency. The data collection method used Underwater Visual Census on the belt transect, and the habitat complexity value is determined by the chain intercept transect method. Data analysis used Shannon-Wiener Index Diversity (H '), Abundance (Ki), and Habitat complexity (C). Next is a simple regression analysis between habitat complexity as the independent variable and fish abundance as the dependent variable. In this study, 106 species were found and covering 24 families. The three fish families, Pomacentridae, Labridae, and Lutjanidae, are the most dominant of the other families. Meanwhile, the diversity index ranged from 1.874-2.753 with an average value of ± SD 2.35 ± 0.317, and the abundance value ranged from 0.774-2.528 individuals/m2 with an average value of ± SD 1.505 individuals / m2 ± 0.745. Furthermore, the analysis showed that hábitate complexity had a significant effect on fish abundance. The coefficient of determination (R2) of 80% can explain the relationship of habitat complexity to fish abundance in the study location. This study concludes that coral reef habitat complexity is a determining factor for the level of fish diversity and abundance in the study area. Therefore, the protection of coral habitat is a strategy for the protection of coral reef fish resources.

Restoration of rapids habitat in a Great Lakes connecting channel, the St. Marys River, Michigan

Aquatic habitat has been extensively altered throughout the Laurentian Great Lakes to increase navigation connectivity. In particular, the St. Marys River, a Great Lakes connecting channel, lost >50% of its historic rapids habitat over the past century. In 2016, the natural flow was restored to the Little Rapids area of the St. Marys River. The goal of our study was to evaluate physical and ecological responses to the restoration of the Little Rapids area. Extensive habitat and biological data were collected prior to restoration (2013 and 2014), and after restoration (2017 and 2018). Measured parameters included total suspended solids, current velocity, benthic macroinvertebrates, and larval, juvenile, and adult fishes. Total suspended solids stayed low (<4 mg/L) following restoration, with the exception of a single construction‐related event. Pre‐restoration data indicated that all measured velocities were below the target flow rate of 0.24 m/s, whereas 70% of the measured habitat was above the target flow post‐restoration. Abundance and richness of benthic macroinvertebrates were reduced following restoration (>90% reduction). We observed a 45% increase in richness of larval fish 2 years after restoration and a 131% increase in catch per unit effort. For adult fishes, the proportion of individuals with a preference for fast‐moving waters increased from 1.5 to 45% in the restored area, and from 7 to 15% upstream of the restored area; a similar response was observed for lithophilic spawners. The physical and biological conditions of the Little Rapids improved and resembled conditions typical of rapids habitat extent in other areas of the river and other systems.

Ecological engineering across organismal scales: trophic-mediated positive effects of microhabitat enhancement on fishes

Retrofitting microhabitat features is a common ecological engineering technique for enhancing biodiversity and abundance of small, epilithic organisms on artificial shorelines by providing refuge spaces and/or ameliorating abiotic conditions. These features are typically too small to be utilised as refugia by larger, highly motile consumers such as fish, but they may affect these organisms through other mechanisms. This study sought to determine whether microhabitat enhancement units alter the fish abundance, richness and assemblage composition on tropical seawalls and explores possible underlying trophic mechanisms. We created 12 experimental plots consisting of 6 enhanced plots, each with 20 microhabitat enhancement tiles, and 6 control plots without tiles on intertidal seawalls at Pulau Hantu, an offshore island south of mainland Singapore. Benthic cover and fish assemblage were surveyed within each plot using photoquadrats and underwater video cameras, respectively, from April 2018 to February 2019. We found greater abundance and species richness and distinct assemblages of fish in the enhanced plots compared to the control plots. These differences were driven largely by an increase in both abundance and richness of fish species with epibenthic-feeding strategies and were significantly associated with higher biotic cover in the enhanced plots, especially epilithic algal matrix (EAM). Our results indicate that, in addition to facilitating epilithic organisms, microhabitat enhancement can provide food resources for epibenthic-feeding fishes, increase fish biodiversity, and alter fish assemblages in tropical urbanised shorelines.

Two centuries for an almost complete community turnover from native to non-native species in a riverine ecosystem.

Non-native species introductions affect freshwater communities by changing community compositions, functional roles, trait occurrences and ecological niche spaces. Reconstructing such changes over long periods is difficult due to limited data availability. We collected information spanning 215years on fish and selected macroinvertebrate groups (Mollusca and Crustacea) in the inner-Florentine stretch of the Arno River (Italy) and associated water grid, to investigate temporal changes. We identified an almost complete turnover from native to non-native fish (1800: 92% native; 2015: 94% non-native species) and macroinvertebrate species (1800: 100% native; 2015: 70% non-native species). Non-native fish species were observed ~50years earlier compared to macroinvertebrate species, indicating phased invasion processes. In contrast, α-diversity of both communities increased significantly following a linear pattern. Separate analyses of changes in α-diversities for native and non-native species of both fish and macroinvertebrates were nonlinear. Functional richness and divergence of fish and macroinvertebrate communities decreased non-significantly, as the loss of native species was compensated by non-native species. Introductions of non-native fish and macroinvertebrate species occurred outside the niche space of native species. Native and non-native fish species exhibited greater overlap in niche space over time (62%-68%) and non-native species eventually replaced native species. Native and non-native macroinvertebrate niches overlapped to a lesser extent (15%-30%), with non-natives occupying mostly unoccupied niche space. These temporal changes in niche spaces of both biotic groups are a direct response to the observed changes in α-diversity and species turnover. These changes are potentially driven by deteriorations in hydromorphology as indicated by alterations in trait modalities. Additionally, we identified that angling played a considerable role for fish introductions. Our results support previous findings that the community turnover from native to non-native species can be facilitated by, for example, deteriorating environmental conditions and that variations in communities are multifaceted requiring more indicators than single metrics.

A network of grassroots reserves protects tropical river fish diversity.

Intensive fisheries have reduced fish biodiversity and abundance in aquatic ecosystems worldwide1-3. 'No-take' marine reserves have become a cornerstone of marine ecosystem-based fisheries management4-6, and their benefits for adjacent fisheries are maximized when reserve design fosters synergies among nearby reserves7,8. The applicability of this marine reserve network paradigm to riverine biodiversity and inland fisheries remains largely untested. Here we show that reserves created by 23 separate communities in Thailand's Salween basin have markedly increased fish richness, density, and biomass relative to adjacent areas. Moreover, key correlates of the success of protected areas in marine ecosystems-particularly reserve size and enforcement-predict differences in ecological benefits among riverine reserves. Occupying a central position in the network confers additional gains, underscoring the importance of connectivity within dendritic river systems. The emergence of network-based benefits is remarkable given that these reserves are young (less than 25 years old) and arose without formal coordination. Freshwater ecosystems are under-represented among the world's protected areas9, and our findings suggest that networks of small, community-based reserves offer a generalizable model for protecting biodiversity and augmenting fisheries as the world's rivers face unprecedented pressures10,11.

Empirical characterization factors to be used in LCA and assessing the effects of hydropower on fish richness

Hydropower is often presented as a clean, reliable, and renewable energy source, but is also recognized for its potential impacts on aquatic ecosystem biodiversity. We used direct empirical data of change in fish species richness following impoundment to develop ecological indicators to be used in Life Cycle Assessment (LCA), and accounting for hydropower impacts on aquatic ecosystems. Data were collected on 89 sampling stations (63 stations located upstream, and 26 located downstream of a dam) distributed in 26 reservoirs from three biomes (boreal, temperate and tropical). Overall, the impact of hydropower on fish species richness was significant in the tropics, of smaller amplitude in temperate biome and minimal in boreal biome, stressing the need for regionalisation when developing indicators. The impact of hydropower was consistent across scales for a given biome (same directionality and statistical significance across sampling stations and reservoirs). However, the indicators were sensitive to the duration of the study (the period over which data have been collected after impoundment), which can underestimate the impacts. This result highlights the need to account for the duration of the transient dynamics to reach a steady state (rate of change in species richness = 0) before developing ecological indicators. By using the LCA approach, our suggested indicators contribute to fill a major gap in assisting decision-makers when evaluating the potential of alternative energy technologies, such as hydropower, to decarbonize the worldwide economy, while minimizing the impacts on aquatic ecosystems.

Use of artificial structures to enhance fish diversity in the Youjiang River, a dammed river of the Pearl River in China.

The fragmentation and homogenization of habitats have seriously affected the fishery resources of the Pearl River. To protect the fishery resources, a novel artificial habitat, constructed using bamboo and palm slices, was deployed in the Youjiang River, a tributary of the Pearl River in China. The results of field and laboratory experiments showed that fish abundance, species richness and Shannon–Wiener diversity index were higher in the artificial habitats than at the control sites. There was no significant impact on fish biomass, as the artificial habitats attracted more Cultrinae and Gobioninae fish that are of a smaller size. Artificial habitats can serve as spawning grounds for fish that produce sticky eggs and refuges that improve the survival rates of juvenile fishes. This study revealed that this novel artificial habitat created suitable habitats and suitable spawning substrate for fish, improved fish richness and diversity in the structureless freshwater ecosystem like the Youjiang River.

Sustainable desalination: Long-term monitoring of brine discharge in the marine environment

The environmental impact of desalination is the most important concern related to its sustainable development. We present the results of a long-term environmental plan to monitor brine discharge (BD) from a desalination plant located in a high environmental value area in Spain. Generalized additive models were used to analyze the biological parameters of biological communities. Results of 17 years of BD monitoring show how its environmental impact can be minimized through well-planned decision-making between scientists and industry. The brine dilution prior to its discharge into an artificial channel of low ecological value significantly reduced the brine influence area. P. oceanica shoot production and echinoderms abundances were relatively stable across historical series and similar values in control and impacts locations were observed. Conversely, there was a higher abundance and species richness of fishes in the BD area. The important findings reported here should be considered for future applications in similar projects.

Influence of some physico-chemical variables on wild fish richness beneath sea-cage fish farms in the Aegean Sea, Turkey

AbstractThis study aims to determine the relationship between physico-chemical variables on a seasonal basis and wild fish assemblages beneath sea-cage fish farms. Assemblages of wild fish were counted monthly on two separate days at each of six fish farms between August 2015 and July 2017, by six rapid visual counts (RVC) in 5 minutes with scuba by two divers. Seawater samples were simultaneously taken by a Nansen bottle during the RVC from the fish farm barge. SST (°C), salinity (ppm), dissolved oxygen (mg l−1) and pH were measured by YSI multiparameter, while Secchi disk was also used for light transmittance. Wild fish species richness went up with increasing temperature and salinity in the Izmir region, however, this stopped at about 26°C and about 39 ppm. Wild fish richness increased when the DO was at a level of 7 mg l−1 and the pH at about 7.9 in Izmir. Between 10 and 20 m, light transmittance showed greater wild fish species richness in Izmir region. In contrast, the wild fish species richness of the Muğla region fluctuated more. In terms of wild fish species richness, these fluctuations increased with salinity and DO, while they decreased with SST, pH and light transmittance. However, the range of variation of the recorded physico-chemical variables is rather narrow. The results of the correlation matrix indicate that the relationship between wild fish species richness and pH and SST was statistically significant in Izmir region (P < 0.05).

Marine fish diversity in Tropical America associated with both past and present environmental conditions

AbstractAimTropical America, including the Tropical Eastern Pacific and the Caribbean Sea, presents a high level of marine biodiversity, but its fish fauna has been poorly documented. In early studies marine species distributions were interpreted based on tectonic activity during the late Cenozoic, while more recent studies have highlighted a link with the present‐day environment. Here, we described the assemblage richness and composition of fishes in Tropical America and related these properties to both the past evolution of marine environmental conditions and current environmental gradients.LocationTropical America.TaxonDemersal and benthic fishes.MethodsWe mapped the distribution of 2,216 demersal and benthic fish species of Tropical America using existing occurrence data. We computed three assemblage indicators: species richness, composition and nestedness, which we explained by environmental gradients. We linked compositional distance to environmental differences using distance‐based redundancy analysis, species richness and nestedness using a generalized linear model. We ran simulations of a mechanistic model in which three processes determine the spatial dynamics of biodiversity: speciation, dispersal and extinction. This model yielded estimates for species assemblage properties following palaeogeographic changes in the region that shaped the current coastal habitat configuration.ResultsFish species richness in Tropical America peaks around the Florida Peninsula, Bahamas and Greater Antilles. Fish composition varies along a depth gradient, between the Tropical Eastern Pacific and the Caribbean Sea, and forms distinct domains within the Caribbean region. The nestedness component of β‐diversity is lower in shallower assemblages, especially those along the outer section of the Greater Caribbean. Species richness and nestedness are partly explained by current environmental conditions, but model simulations illustrate how this may be further explained by the tectonic history of the region.Main conclusionsSpecies richness peaks in the Greater Caribbean, coinciding with generally favourable current environmental conditions for demersal and benthic fishes. The high species richness and the low nestedness of fish assemblages in the Cuba region are compatible with the results of palaeo‐environmental changes that have occurred in that area. Effects of the plate tectonic history might still be present in the organization of fish fauna in this region.

The macroecology of fish migration

AbstractAimWe still lack a consensus on the main variables driving changes in migratory strategies. Different hypotheses have been proposed: productivity, energy, environmental heterogeneity, and genetic predisposition. This work takes an integrative view and analyses migrations from a macroecological perspective estimating the extent to which different environmental variables and historic factors influence migratory life histories.LocationGlobal.Time periodCurrent.Major taxa studiedActinopterygian fishes.MethodsUsing public domain museum records, global repositories, and global measures of temperature, productivity, precipitation and heterogeneity, we spatially analysed the distribution of anadromous, catadromous, amphidromous, potamodromous and oceanodromous migratory fish using 1,676 species and compared it to 1,616 non‐migratory fishes. After analysing the individual roles of productivity and temperature in shaping biodiversity, we conducted path analyses including several environmental variables and principal coordinates of phylogenetic structure (PCPS).ResultsThe different migratory strategies are not evenly distributed around the globe and phylogeny is a relevant variable in shaping current patterns. Productivity is positively related to species richness, except for anadromy and potamodromy, for which we observed a unimodal curve. Temperature significantly drives migratory species richness (except for anadromy). The role of environmental heterogeneity, measured as temperature seasonality and annual range, is strongest for anadromous species, which helps explain their skewed distribution towards higher latitudes and why the kinetic energy hypothesis fails in explaining their richness patterns.Main conclusionsOverall, migratory fish richness can be explained by the interaction of multiple variables, such as productivity, temperature, environmental heterogeneity, and the role of phylogeny, but these variables interact differentially in each strategy, diverging most for the anomalous anadromous fishes. Integrating these results into a global framework to better understand the evolutionary and ecological dynamics of migration will help with predicting responses to anthropogenic climate change.

Isolation promotes abundance and species richness of fishes recruiting to coral reef patches

Habitat area and fragmentation are recognised as important factors that influence population size, community structure and extinction risk. Abundance and species richness universally increase with habitat area. However, the effects of different aspects of habitat fragmentation, including variation in patch size, number and isolation are often not distinguished from each other or the overall effects of habitat amount. Here we experimentally tested predictions concerning the effects of isolation on abundance, species richness and community structure of coral reef fishes colonising patch reefs by constructing clusters of patches of the same number and size, but manipulating reef spacing. Hexagonal clusters of 7 experimental patch reefs (6 edge and 1 central) with 3 levels of isolation (1 m, 5 m, and 15 m spacing) were established at Kavieng, Papua New Guinea and colonisation was recorded after 6 weeks in 2014. We also deployed video cameras to test whether isolation affected the activity of transient predatory fishes. As predicted, isolation had a positive effect on both mean abundance and species richness at both the cluster and patch scale. The cumulative abundance and species richness exhibited linear increases in relation to habitat area within clusters (from 1 to 7 patch reefs), but the slope increased with the degree of isolation. There was some evidence that transient predators remained longer and were more successful when patches were close together, which may explain the lower abundance and richness of juvenile fish assemblages on more aggregated patch reefs. This study demonstrates that while habitat amount is fundamentally important, isolation has significant effects that will need to be distinguished from other aspects of fragmentation when examining the processes structuring reef fish communities.

Strong impacts of signal crayfish invasion on upland stream fish and invertebrate communities

Abstract Impacts of invasive signal crayfish Pacifastacus leniusculus on native species and ecosystems are widely recognised, but mostly through small‐scale studies and laboratory experiments that may not always reflect impacts in nature. Recorded effects of signal crayfish on fish populations are equivocal. In this study, using the before–after/control–impact and control–impact approaches, the effects of signal crayfish invasion on native fishes, particularly benthic fishes and young‐of‐year (YoY) salmonids, and macroinvertebrate communities, were determined on several spatial and temporal scales through three correlated study elements (S1–S3), in upland streams of the River Tees, England. In S1, we sampled fish and benthic macroinvertebrates of 18 streams identically in 2011 and 2018. These streams were categorised into two groups: (1) uninvaded (without signal crayfish in both sampling years; n = 7); and (2) invaded (with signal crayfish) streams, comprising pre‐invaded (invaded before 2011; n = 8) and newly invaded (invaded between 2011 and 2018, n = 3). Despite similar habitat conditions in both years (all variables p > 0.05) fish and macroinvertebrate communities changed over time in pre‐invaded streams and by comparison to uninvaded streams. A decline in the abundance of benthic fish and YoY salmonids was observed in pre‐invaded and newly invaded streams. Complete disappearance of bullhead Cottus perifretum following signal crayfish invasion was recorded in two pre‐invaded streams. In the second study, S2, we assessed within‐stream differences in fishes and macroinvertebrates in two Tees streams by comparing sections with (invaded) and without (uninvaded) signal crayfish. Compared to uninvaded sections, taxonomic richness and abundance of fish and macroinvertebrates were significantly lower in invaded sections, and the overall communities also differed significantly. In S3, long‐term data series (since 1990) of water quality and macroinvertebrates of six Tees streams comprising those invaded by signal crayfish (n = 3) and uninvaded (n = 3) were analysed. Water quality showed little change, or an improvement, over time but significant changes in the macroinvertebrate taxonomic richness and community structure occurred following signal crayfish invasion. Long‐term changes in macroinvertebrate communities in invaded streams tended to be due to declines in more sedentary taxa such as molluscs and cased trichopterans. Widespread and long‐term ecological disruption is occurring because of signal crayfish invasion in upland streams of the Tees catchment that may lead to a complete disappearance of some benthic fish species, as well as reduced densities of YoY salmonids and a shift towards less diverse macroinvertebrate communities, dominated by more mobile, crayfish‐resistant taxa.

The condition of economical important coral reef fishes in eastern and western small outer island Indonesia

More than three months of cumulative comprehensive studied we conducted to evaluate coral reef fishes composition in Eastern Indonesia Region (Liki Island) and Western Indonesia Region (Natuna Island) of small outer Island (SOI) Indonesia. There is a fundamental problem in the ecological function of the coral reef ecosystem and the potential of economically important reef fishes in small outer Island Indonesia. Several obstructions become an essential problem, including the location of SOI, which is far from the mainland with a lack of surveillance and monitoring; consequently, the coral ecosystem and its coral reef fishes are threatened. Overfishing and destructive fishing are the major problems reported in several locations on the outermost island. Both anthropogenic stressors cause degraded coral ecosystems and give the loss specific species of marine species, especially in economically important coral reef fishes that primary target for fisheries. The latest and continuous time series data is essential as necessary information to arrange the appropriate and sustainable policies in Small outer islands, especially in protected the ecosystem from ecological extinction. The main goal of our study is to evaluate the potential of economic coral reef fishes with analysis of two families of fundamental economic and targeted fisheries: groupers (Serranidae) and snapper (Lutjanidae) in eastern and western small outer island Indonesia. The data were collected in each six site location in both eastern and western region SOI using Underwater Visual Census (UVC) technique. Four parameters, including species richness, abundance, biomass, and indices of economic coral reef fishes (Shannon, Evenness, Simpson, and ENS), were compared between the eastern region (Liki) to the Western region (Natuna) with Kruskal-Wallis non-parametric statistical analysis and internal Pairwise Wilcoxon analysis. The eastern region (Liki) recorded higher fish richness, abundance, and biomass than the western region (Natuna) (p< 0.05). Comparisons with ecological indices shown in the eastern region SOI (Liki) had a more diverse economic important coral reef fishes than western region SOI (Natuna). Understanding the composition of economically important coral reef fish in SOI will reveal more about the condition of the ecological function of the coral ecosystem and their vulnerability to future changes.

Community isolation drives lower fish biomass and species richness, but higher functional evenness, in a river metacommunity

Abstract The flow of individuals among communities and their interactions with local environmental filters are increasingly recognised as determinants of biodiversity patterns in riverine ecosystems. Both incoming dispersers and local conditions are expected to systematically change along connectivity gradients from headwaters to downstream communities. However, the interplay between isolation‐centrality gradients and environmental conditions as determinants of biodiversity structure and function has seldom been considered. Here, we represented the dendritic structure of the Negro River basin riverscape (Uruguay) in a directed graph quantifying the isolation‐centrality of each river section and evaluated the direct and indirect pathways by which riverscape structure and environmental local drivers determine fish community assembly. Fish communities (n = 58) were sampled following a stratified sampling design that properly represents this isolation‐centrality connectivity gradient through the riverscape. In each community, fish abundance, biomass, richness, and functional diversity were estimated, and the direct and indirect hypothesised connections among them were evaluated with structural equation models. We showed that the range of isolation among river sections determines a 2‐fold, 5‐fold, and 25‐fold variation in total fish richness, abundance, and biomass, respectively. Additionally, isolation‐centrality was positively associated with local temperature and conductivity, while negatively related to local depth. These variables and taxonomic richness accounted for most of the variation in total fish biomass (81%) herein used as measurement of ecosystem function. Local fish abundance was negatively and positively associated with functional evenness and taxonomic richness, respectively. Furthermore, once the effect of isolation on biomass and richness was accounted for, an effect of diversity on biomass became evident. Our results provide empirical evidence for the role of riverscape structure on taxonomic and functional diversity, biomass, and the relationship between biodiversity and ecosystem function. We emphasise that in the understanding of river biodiversity and its management, local determinants should not be considered without attention to metacommunity processes.

Demersal Fish Assemblages in NE Atlantic Seagrass and Kelp

Global fisheries are in decline, calling for urgent evidence-based action. One such action is the identification and protection of fishery-associated habitats such as seagrass meadows and kelp forests, both of which have suffered long-term loss and degradation in the North Atlantic region. Direct comparisons of the value of seagrass and kelp in supporting demersal fish assemblages are largely absent from the literature. Here, we address this knowledge gap. Demersal fish were sampled using a baited camera to test for differences between habitats in (1) the species composition of the fish assemblages, (2) the total abundance and species richness of fishes, and (3) the abundances of major commercial species. Seagrass and kelp-associated fish assemblages formed two significantly distinct groupings, which were driven by increased whiting (Merlangius merlangus) and dogfish (Scyliorhinus canicula) presence in seagrass and higher abundances of pollock (Pollachius pollachius) and goby (Gobiusculus flavescens) in kelp. The abundance, diversity, and species richness did not change significantly between the two habitats. We conclude that seagrass and kelp do support unique demersal fish assemblages, providing evidence that they have different ecological value through their differing support of commercial fish species. Thus, this study improves the foundation for evidence-based policy changes.

Indicators of hydro-ecological alteration for the rivers of the United States

Recent decades have produced a river of field data linking hydrologic alteration to fish populations in hundreds of U.S. river systems. Adverse impact thresholds and relationships between flow alteration and fish populations are key for advancing environmental flow conservation and environmental flow regulations in U.S. waterways. Prior work has established relationships in individual rivers and fine scale basins, but not for large basins or at national scale. As a first step toward establishing consistent fish-flow relationships and adverse impact thresholds in every US waterway, we analyze a nation-wide aggregated dataset from McManamay et al., 2017 containing co-located estimates of altered hydrologic metrics (HMs) for flow and native fish richness. In each medium sized river system (HUC4) we (1) identify the hydrologic metrics that most powerfully explain observed impacts on native fish richness, (2) estimate an adverse resource impact threshold defining excessive flow alteration, and (3) attribute the main causes of observed flow alteration. Strong empirical relationships between hydrologic metrics and native fish richness are thus established for most HUC4 basins in the continental U.S., and can be used as guidelines for science-based management. However, the findings underline a major aquatic ecology data gap in the western U.S. where a lack of statistically adequate field observations currently prevent clear results, and this gap will hinder science-based management of those river basins until it is filled.

Application of a New Species‐Richness Based Flow Ecology Framework for Assessing Flow Reduction Effects on Aquatic Communities

AbstractWater‐resources managers are challenged with maintaining a balance among beneficial uses throughout river networks and need robust means of assessing potential risks to aquatic life resulting from flow alterations. This study generated ecological limit functions from species‐streamflow relations to quantify potential fish richness response to flow alteration and compared results to currently accepted streamflow management guidelines. Modeled responses of absolute richness change were watershed specific and varied among sample sets derived from hydrologic unit classifications of different sizes (large HUC 6 basins to regional scale HUC 8). With a 20% flow reduction, 10% of HUC 8 predicted a richness decrease in one or more taxa. While absolute richness change was consistent across streams within a HUC, percent richness change was stream size dependent. Comparisons with Instream Flow Incremental Methodology habitat models predicted habitat loss greater than percent richness change; however, predictions for habitat and richness decreased similarly as stream size decreased. Watershed‐specific responses from flow reductions could allow water‐resources management decisions to be made locally based on the predicted richness change for certain sized streams. Quantitative results highlight the utility of a richness‐based framework for generating watershed‐specific risk assessments that validate and inform currently employed water‐resources management practices.

Fish and benthic invertebrate relationship and their association to environmental variables in tropical sandy beaches

Fish and benthic invertebrates are important groups that inhabit shallow coastal areas. Many studies use these two groups separately to answer questions related to environmental relationships, but few assess the correlation between these two groups. This study aimed to assess correlation between richness and composition of fish and benthic invertebrate assemblages and to evaluate their responses to environmental variables in sandy beaches in a tropical coastal area in south-eastern Brazil. We tested for a correlation between fish and benthic invertebrates and evaluated which environmental variables influenced each group. Fish and invertebrate taxonomic richness were not correlated across sites. In addition, the two groups were not significantly correlated, even after controlling the effects of the environmental variables. The taxonomic richness of the two groups were influenced by different set of environmental drivers: fish were influenced mainly by the physicochemical variables, being positively correlated with salinity and dissolved oxygen, and negatively with temperature, whereas invertebrates richness were related mainly to granulometric variables, decreasing in fine and very fine sediment. Fish and invertebrate showed similar patterns with more influence of environmental variables than biotic variables that had comparatively more effects on the invertebrate than on the fish assemblage. Spatial segregation in species distribution along the beaches were found with the Gerreid fish predominating in semi-exposed beaches whereas the sparid Diplodus argenteus, the haemulid Orthopristis ruber and the clupeids Harengula clupeola and Sardinella brasiliensis predominated in the exposed beaches. The Polychaetae families Syllidae and Dorvilleidae, and isopod of the family Cirolanidae predominated in semi-protect beaches, whereas polychaetas of the families Glyceridae and Saccocirridae predominated in the exposed beaches. In this study, we showed that fish and benthic invertebrates are influenced by different environmental variables in tropical sandy beaches and no significant correlation was found between these two taxonomic groups. Our findings are a step to a better understanding of the fish-benthic invertebrate relationship and a contribution to management policies aiming the conservation of tropical coastal areas.