Traits Of Fish Species Research Articles

Intra-habitat structural complexity drives the distribution of fish trait groups on coral reefs

Three-dimensional (3D) habitat complexity is a primary driver of organism distribution and community structure across ecosystems. Identifying the specific metrics and spatial scales at which complexity is functionally important for communities is therefore a critical component in forecasting ecosystem function. Here we pair fish species traits with multiple metrics from habitat photogrammetry to evaluate the most important measures and scales of 3D complexity driving ecological functions within one of the most structurally diverse ecosystems on the planet: coral reefs. From May to July 2019, we collected high-resolution (1 cm) large- and small-scale intra-habitat (25 m2) structural complexity data across eight reefscapes (∼2500 m2) and conducted co-located fish functional group surveys in the Florida Keys, FL, USA. We used a hierarchical clustering analysis to group 80 observed fish species by four traits related to habitat use (social level, body size, crypsis, activity period) and feeding guild to generate mechanistic predictions about fish-habitat relationships. Evaluating relationships between the resulting trait-based functional groups (k = 9) and four metrics of intra-habitat complexity (large-scale vertical relief, and small-scale vector ruggedness [VRM], VRM deviation, and profile curvature) revealed that trait groups respond independently to the various measures and scales of reef complexity. While large-scale complexity (relief) is strongly related to the presence of solitary, cryptic, nocturnal carnivores, likely due to prey availability as well as day-time refuge opportunities, herbivore abundance is unaffected by increasing vertical relief, potentially due to predator avoidance. Instead, gregarious (i.e., schooling) herbivores increase with small-scale complexity measured by VRM and VRM deviation across reefscapes, while less gregarious herbivores only respond to small-scale complexity when these same measures occur in low-relief habitat, possibly due to a tradeoff between grazing resource availability and predator visibility. Our results reveal how unique elements of complexity provided by both biotic benthic communities as well as large-scale habitat features like vertical relief are differentially important to fish functional groups. The general relationships we identified using traits provide a framework for predicting fish community responses to changes in specific measures of structural complexity on coral reefs globally. Our work illustrates how preserving 3D habitat complexity by protecting or augmenting (e.g., via restoration) structure-forming organisms can support diverse organismal communities and overall ecosystem productivity.

Predicting successful reproduction and establishment of non-native freshwater fish in peninsular Florida using life history traits

Identification of factors that facilitate successful completion of invasion process stages by nonnative species is a major priority among invasion biologists. Stage-based analyses of non-native fish species traits have been conducted for several regions, but not for a subtropical non-native species hotspot like peninsular Florida. Typically, establishment is the first stage of analysis but Florida is home to many nonnative fish species that have successfully reproduced, yet failed to establish. Therefore, we used life history traits and three model types (categorical and regression trees, logistic regression, and discriminant analysis) to predict successful reproduction and establishment by non-native fishes in peninsular Florida. Statistical models for predicting both successful reproduction and establishment suggested parental care was the most important variable, but other traits included in the best models differ between the two stages. The high level of parental care in successful non-native fishes of Florida is unique among non-native freshwater fish faunas across the United States. Other studies also found that suites of traits used to predict various stages of the invasion process differ, suggesting that stage-based analyses provide a good foundation for better understanding invasion processes. Our results may be applied to stage-based risk screening tools for nonnative fishes in Florida.

Microplastics and the functional traits of fishes: A global meta-analysis.

Over the years, concern about the effects of microplastics has grown. Here, we answered the main question "What are the impacts of microplastics on the functional traits of fish species?" through a meta-analysis. The general impact of microplastic exposure on the functional traits of fishes and specifically on eight variables, namely, behaviour, development, fecundity, feeding, growth, health, hatching and survival was explored. Subgroup analyses were performed to detect correlations between the impact of microplastics and the following factors: species, life stage, habitat, water column habitat, day of exposure to microplastics and microplastic size, type and shape. A meta-regression analysis allowed understanding the correlation between the impact of microplastics and the size of organisms. Generally, microplastics have a negative effect on the functional traits of fishes. Feeding and behaviour, followed by growth showed the greatest impact. Among the subgroup analysis, four of the eight variables considered showed a significant difference between groups: species, life stage, microplastic shape and days of exposure to microplastics. Depending on their life stage, organisms may be more sensitive to microplastic pollution. Changes in growth rates, development of early life stage and behavioural patterns in fishes may have a negative effect on the structure and functions of aquatic ecosystem in the long term and consequently affect the ability of aquatic ecosystems to provide ecosystem services and sustain human communities.

Functional Traits of Fish Species: Adjusting Resolution to Accurately Express Resource Partitioning

Trait-based community descriptors have been widely used to make inferences about community assembly processes. The level of traits discrimination (measurement resolution) can have consequences for how good diversity patterns correlate with predictor variables. Here, we develop a novel framework to evaluate: i) how much information is lost when the measurement resolution of functional traits is lowered, and; ii) to what extent morphological traits and phylogeny can be used as surrogates of feeding strategy. We also tested whether measurement resolution of traits affects the ability of community functional diversity metrics to discriminate different habitats. We used empirical data from marine fish communities and correlated pairwise dissimilarities based on the most detailed measurement resolution of diet with pairwise dissimilarities based on different resolutions of diet, ecomorphology, and phylogeny. We then compared functional diversity between three marine regions using the different feeding trait resolutions, phylogeny and ecomorphology to detect environment filtering. Phylogeny and ecomorphological traits were not correlated with fish diet. There was a strong correlation between the highest and second highest measurement resolution, with the association decaying for lower resolution data. Significantly, high-resolution data are better able to discriminate different habitats than functional diversity. These results do not support the use of surrogates for trophic traits and highlight the importance of measurement resolution in studies of functional diversity in tropical marine ecosystems

A novel approach to an ecofunctional fish index for Mediterranean countries

The implementation of the European Water Framework Directive, especially regarding the establishment of fish indexes for riverine habitats, has taken different paths in different countries. For example, in Italy previous efforts have been directed towards a taxonomy-based index, contrarily to most other European countries where an ecofunctional approach took place. Taxonomical indexes are particularly hard to apply to Mediterranean countries, where fish taxonomy is often revised causing problems in practical implementation. Alternatively, ecofunctional characteristics of fish communities could be exploited to inform on river habitat quality and to detect anthropogenic impacts, thus reducing the index sensitivity to the taxonomical variability of the fish fauna. We therefore proposed a new, multimetric index based on ecofunctional traits of fish species (EFFI, EcoFunctional Fish Index) and tested it on 208 river sampling stations of the Emilia-Romagna region, northern Italy. Using theoretical reference communities, ecological quality ratios were estimated for the whole area expressing the ecological distance of each site from reference conditions. Perhaps unsurprisingly, this work underlined how fish communities were more degraded at lower altitudes than at higher ones. EFFI scores were remarkably close to two already-established indexes for chemical (LIM) and macrozoobenthos communities (IBE) alteration. Further work should explore the validity of this approach over a wider geographical range as well as investigate the definition of environmental class boundaries and its potential intercalibration with other indexes.

Responses of Herbivorous Fishes on Coral Reef Cover in Outer Island Indonesia (Study Case: Natuna Island)

Coral reefs are one of the most highly productive marine ecosystems, with the largest transfer of energy attributed to the trophic interaction between herbivores and algae. Rapid demographic growth, leading to transmigration to small islands such as Natuna Island where located on outer Island Indonesia.The aim of the present study is to test for significant associations between herbivore fish species traits and Habitat complexity was derived from coral reef cover. Method to record each observed herbivore fish species with UVC (Underwater Visual Census) using SCUBA diving equipment along modification line transects. A total of 39 different fish species belonging to 3 families‟ herbivore fish were identified. Total biomass of herbivorous fish correlated with Dead Coral Algae (DCA). Biplot of the first two axes for the nonmetric multidimensional a scaling (NMDS) analysis for family and grazer showed the dominance of herbivore fish grazer.

Linking fish species traits to environmental conditions in the Jakarta Bay-Pulau Seribu coral reef system

Coral reefs around the globe have been subjected to a wide range of stressors. In the present study, fish species were recorded across a pronounced in-to-offshore gradient in the Jakarta Bay-Pulau Seribu reef system. In addition to this, fish species traits were obtained from FishBase. RLQ analysis revealed a significant association between fish species traits and environmental variables. Fish species associated with perturbed, inshore waters were resilient to disturbance, had higher mortality rates, higher growth rates and mainly consumed animals. In contrast, fish species associated with less perturbed, mid- and offshore waters had greater life expectancy, higher age at maturity, greater life span, greater generation time and mainly fed on plants or plants and animals. Eutrophication, pollution and physical destruction of coral substrate in inshore waters has thus selected for a low biomass and depauperate fish community characterised by fast growing and short lived species.

Fish diversity in tidepools: assembling effects of environmental heterogeneity

Tidepools are considered ecosystems of high interchangeable fish biota. However, natural and anthropogenic actions that alter negatively marine ecosystems functioning (e.g., algal exploitation) are causing homogenization of fish biodiversity. Here, we describe the functional and taxonomic assembling of fishes in beach rocks of northeastern Brazil. Traits of fish species were retrieved from Fishbase and beta diversity was assessed by the dispersion of abundance, presence-absence and functional diversity in the multivariate space. We explained spatial-temporal variation in: alpha diversity, taxonomic and functional community composition; as well as temporal variation in functional, beta and gamma diversities. We found an annual stability in fish diversity and composition, and that fish biota was assembled mainly per tidepools’ depths. Substrate heterogeneity was correlated to depth, highlighting the role of local features as filters to organize the fish fauna vertically in tidepools, especially a cultivation of algae that influences the local assembling. We also highlight the uniqueness status of beach rocks in the Brazilian tropical region.

DNA barcoding reflects the diversity and variety of brooding traits of fish species in the family Syngnathidae along China’s coast

DNA barcoding offers a rapid and accurate assessment for species labelling and identification. Here, we investigated the performance of DNA barcodes in a sample of Syngnathidae, a unique group of fish with male pregnancy. A total of 1002 DNA barcodes using 649 base-pair fragments of the cytochrome c oxidase subunit I (COI) gene were generated. All species were associated with distinct DNA barcode and could be readily distinguished; seven of the COI barcode clusters represented the first species records submitted to the Barcode of Life Data Systems (BOLD) and GenBank databases. In the Neighbor-joining tree of COI sequences, two major clusters (Gastrophori and Urophori) were displayed, which could also be classified by their brood pouches. However, the tail-brooding Hippichthys cyanospilus and trunk-brooding Syngnathoides biaculeatus were reverse-clustered together with the Gastrophori and the Urophori, respectively. Both seahorse and pipefish sequences showed high frequencies of nucleotide substitutions. The probability of nucleotide substitutions, those in pipefish were higher than that of all seahorses. However, we identified no signal for positive selection based on the COI gene in any of the data sets. Our results supported DNA barcoding as an efficient molecular tool for achieving better monitoring, conservation, and management of fisheries.

The influence of environmental variables on the functional structure of headwater stream fish assemblages: a study of two tropical basins in Central Brazil

We investigated functional patterns of fish assemblages of two adjacent basins (Araguaia and Tocantins) to test whether their headwater stream fish assemblages are more functionally (dis)similar than expected by chance and whether these (dis)similarities are related to differences of environmental conditions between basins. We used an analysis of similarities (ANOSIM) on a functional dissimilarity matrix to test for (dis)similarities between fish assemblages of both basins. We performed RLQ and fourth-corner analyses to determine fish species trait-environment relationship. Our results revealed functional dissimilarities between fish assemblages of both basins and significant species trait-environment relationships, suggesting that environmental conditions are driving such dissimilarities. Inter-basin dissimilarities are mainly driven by altitudinal and water temperature gradients, whereas dissimilarities among streams within the basins are influenced by channel depth, turbidity and conductivity. These five environmental variables mostly affected six fish species traits (body mass, water column position, substrate preference, parental care, foraging locality and migration) in different manners. This study is an attempt to understand functional trends of fish assemblages in a tropical region that remains poorly known but severely threatened.

Study on fish life history traits and variation in the Taiwan Strait and its adjacent waters

Large portions of the world’s fishery resources are overexploited. Life history traits of fish species are important indicators to reveal different life history strategies and to indicate population responses to fishing pressures. For this study, empirical data on fishing grounds located in the coastal area between Fujian Coast and Taiwan Island were collected. These areas have experienced severe overfishing in the past 30 years, leading to changes in the structure and function of the fish communities. Fifty-one commercial fish species in this fishing ground were selected to study the life history traits. Using the life history traits, all the species were grouped into five different life history strategies by principle component analysis. More than 60% of the species were categorized in Group 5 that was similar to r-strategists. Twenty-five commercial species were selected for further analysis of changes in life history variables, and to discuss the population responses to exploitation. Results showed that most of the species appeared to become smaller size, shorter life, earlier maturation and faster growing under long-term exploitation. The exploitation rate of each species was also calculated to further discuss the impacts of fishing pressures to fish populations. Four species were found with the severest changes on life history traits indicating some of the species might be more susceptible to exploitation. This study on fish life history traits and their long-term variations under fishing pressures could provide important scientific implications for fishery management and conservation.

An Evaluation of the Relations Between Flow Regime Components, Stream Characteristics, Species Traits, and Meta‐Demographic Rates of Warm‐Water‐Stream Fishes: Implications for Aquatic Resource Management

AbstractFishery biologists are increasingly recognizing the importance of considering the dynamic nature of streams when developing streamflow policies. Such approaches require information on how flow regimes influence the physical environment and how those factors, in turn, affect species‐specific demographic rates. A more cost‐effective alternative could be the use of dynamic occupancy models to predict how species are likely to respond to changes in flow. To appraise the efficacy of this approach, we evaluated relative support for hypothesized effects of seasonal streamflow components, stream channel characteristics, and fish species traits on local extinction, colonization, and recruitment (meta‐demographic rates) of stream fishes. We used 4 years of seasonal fish collection data from 23 streams to fit multistate, multiseason occupancy models for 42 fish species in the lower Flint River Basin, Georgia. Modelling results suggested that meta‐demographic rates were influenced by streamflows, particularly short‐term (10‐day) flows. Flow effects on meta‐demographic rates also varied with stream size, channel morphology, and fish species traits. Small‐bodied species with generalized life‐history characteristics were more resilient to flow variability than large‐bodied species with specialized life‐history characteristics. Using this approach, we simplified the modelling framework, thereby facilitating the development of dynamic, spatially explicit evaluations of the ecological consequences of water resource development activities over broad geographic areas. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Global warming and potential shift in reference conditions: the case of functional fish-based metrics

The reference condition approach, advocated by the Water Framework Directive, is the basis of most currently used multimetric indices using functional traits of fish species. The ecological status of streams is assessed by measuring the deviation of the observed trait values from the theoretical values of reference conditions in the absence of anthropogenic disturbances. While reference conditions serve as baselines for ecological assessment, they vary with natural environmental conditions. Therefore, global warming appears to be a major threat to the use of current indices for diagnosing future stream conditions, as climate change is projected to modify assemblage composition, suggesting that the functional structure of fish assemblages will also be affected. The main objectives of this study are to assess the potential effect of climate change on the trait composition of fish assemblages and the consequences for the establishment of reference conditions. The results highlight the relation between environmental, especially climatic, conditions and functional traits and project the effects of climate change on trait composition. Traits based on species intolerance are expected to be most negatively affected by the projected climatic shift. The consequences for the development of multimetric indices based on fish functional traits are discussed.

Relationships between species feeding traits and environmental conditions in fish communities: a three-matrix approach

Understanding the relationships between species biological traits and the environment is crucial to predicting the effect of habitat perturbations on fish communities. It is also an essential step in the assessment of the functional diversity. Using two complementary three-matrix approaches (fourth-corner and RLQ analyses), we tested the hypothesis that feeding-oriented traits determine the spatial distributions of littoral fish species by assessing the relationship between fish spatial distributions, fish species traits, and habitat characteristics in two Laurentian Shield lakes. Significant associations between the feeding-oriented traits and the environmental characteristics suggested that fish communities in small lakes (displaying low species richness) can be spatially structured. Three groups of traits, mainly categorized by the species spatial and temporal feeding activity, were identified. The water column may be divided in two sections, each of them corresponding to a group of traits related to the vertical distribution of the prey coupled with the position of the mouth. Lake areas of low structural complexity were inhabited by functional assemblages dominated by surface feeders while structurally more complex areas were occupied by mid-water and benthic feeders. A third group referring to the time of feeding activity was observed. Our work could serve as a guideline study to evaluate species traits x environment associations at multiple spatial scales. Our results indicate that three-matrix statistical approaches are powerful tools that can be used to study such relationships. These recent statistical approaches open up new research directions such as the study of spatially based biological functions in lakes. They also provide new analytical tools for determining, for example, the potential size of freshwater protected areas.

Use of fish functional traits to associate in-stream suspended sediment transport metrics with biological impairment

Loss of ecological integrity due to excessive suspended sediment in rivers and streams is a major cause of water quality impairment in the USA. Current assessment protocols for development of sediment total maximum daily loads (TMDLs) lack a means to link temporally variable sediment transport rates with specific losses of ecological functions as loads increase. In order to accomplish this linkage assessment, a functional traits-based approach was used to correlate site occurrences of 17 fish species traits in three main groups (preferred rearing habitat, trophic feeding guild, and spawning behavior) with suspended sediment transport metrics. The sediment transport metrics included concentrations, durations, and dosages for a range of exceedance frequencies; and mean annual suspended sediment yields (SSY). In addition, this study in the Northwestern Great Plains Ecoregion examined trait relationships with three environmental gradients: channel stability, drainage area, and elevation. Potential stressor responses due to elevated suspended sediment concentration (SSC) levels were correlated with occurrences of five traits: preferred pool habitat; feeding generalists, omnivores, piscivores, and nest-building spawners; and development of ecologically based TMDL targets were demonstrated for specific SSC exceedance frequencies. In addition, reduced site occurrences for preferred pool habitat and nest-building spawners traits were associated with unstable channels and higher SSY. At an ecoregion scale, a functional traits assessment approach provided a means to quantify relations between biological impairment and episodically elevated levels of suspended sediment, supporting efforts to develop ecologically based sediment TMDLs.

Modeling the Relations Between Flow Regime Components, Species Traits, and Spawning Success of Fishes in Warmwater Streams

Modifications to stream hydrologic regimes can have a profound influence on the dynamics of their fish populations. Using hierarchical linear models, we examined the relations between flow regime and young-of-year fish density using fish sampling and discharge data from three different warmwater streams in Illinois, Alabama, and Georgia. We used an information theoretic approach to evaluate the relative support for models describing hypothesized influences of five flow regime components representing: short-term high and low flows; short-term flow stability; and long-term mean flows and flow stability on fish reproductive success during fish spawning and rearing periods. We also evaluated the influence of ten fish species traits on fish reproductive success. Species traits included spawning duration, reproductive strategy, egg incubation rate, swimming locomotion morphology, general habitat preference, and food habits. Model selection results indicated that young-of-year fish density was positively related to short-term high flows during the spawning period and negatively related to flow variability during the rearing period. However, the effect of the flow regime components varied substantially among species, but was related to species traits. The effect of short-term high flows on the reproductive success was lower for species that broadcast their eggs during spawning. Species with cruiser swimming locomotion morphologies (e.g., Micropterus) also were more vulnerable to variable flows during the rearing period. Our models provide insight into the conditions and timing of flows that influence the reproductive success of warmwater stream fishes and may guide decisions related to stream regulation and management.

Fish Traits: A Database of Ecological and Life‐history Traits of Freshwater Fishes of the United States

AbstractThe need for integrated and widely accessible sources of species traits data to facilitate studies of ecology, conservation, and management has motivated development of traits databases for various taxa. In spite of the increasing number of traits‐based analyses of freshwater fishes in the United States, no consolidated database of traits of this group exists publicly, and much useful information on these species is documented only in obscure sources. The largely inaccessible and unconsolidated traits information makes large‐scale analysis involving many fishes and/or traits particularly challenging. We have compiled a database of > 100 traits for 809 (731 native and 78 nonnative) fish species found in freshwaters of the conterminous United States, including 37 native families and 145 native genera. The database, named Fish Traits, contains information on four major categories of traits: (1) trophic ecology; (2) body size, reproductive ecology, and life history; (3) habitat preferences; and (4) salinity and temperature tolerances. Information on geographic distribution and conservation status was also compiled. The database enhances many opportunities for conducting research on fish species traits and constitutes the first step toward establishing a central repository for a continually expanding set of traits of North American fishes.

Linking ecology with parasite diversity in Neotropical fishes

A comparative analysis was performed to seek large‐scale patterns in the relationships between a set of fish species traits (body size, type of environment, trophic level, schooling behaviour, depth range, mean habitat temperature, geographical range, ability to enter brackish waters and capability of migration) and the diversity of their metazoan parasite assemblages among 651 Neotropical fish species. Two measurements of parasite diversity are used: the species richness and the taxonomic distinctness of a fish’s parasite assemblage, including all metazoan parasites, ectoparasites only, or endoparasites only. The results showed that, on this scale, the average taxonomic distinctness of parasite assemblages was clearly more sensitive to the influence of host traits than parasite species richness. Differences in the taxonomic diversification of the parasite assemblages of different fish species were mainly related to the fish’s environment (higher values in benthic–demersal species), trophic level (positive correlation with increasing level), temperature (positive correlation with temperature in marine ectoparasites, negative in endoparasites; positive for all groups of parasites in freshwater fishes) and oceanic distribution (higher values in fish species from the Pacific Ocean than those of the Atlantic). The results suggest that, among Neotropical fish species, only certain key host traits have influenced the processes causing the taxonomic diversification of parasite assemblages.

Multilevel Assessment of Fish Species Traits to Evaluate Habitat Degradation in Streams of the Upper Midwest

AbstractWe used species traits to examine the variation in fish assemblages for 21 streams in the Northern Lakes and Forests Ecoregion along a gradient of habitat disturbance. Fish species were classified based on five species trait‐classes (trophic ecology, substrate preference, geomorphic preference, locomotion morphology, and reproductive strategy) and 29 categories within those classes. We used a habitat quality index to define a reference stream and then calculated Euclidean distances between the reference and each of the other sites for the five traits. Three levels of species trait analyses were conducted: (1) a composite measure (the sum of Euclidean distances across all five species traits), (2) Euclidean distances for the five individual species trait‐classes, and (3) frequencies of occurrence of individual trait categories. The composite Euclidean distance was significantly correlated to the habitat index (r = −0.81; P = 0.001), as were the Euclidean distances for four of the five individual species traits (substrate preference: r = −0.70, P = 0.001; geomorphic preference: r = −0.69, P = 0.001; trophic ecology: r = −0.73, P = 0.001; and reproductive strategy: r = −0.64, P = 0.002). Although Euclidean distances for locomotion morphology were not significantly correlated to habitat index scores (r = −0.21; P = 0.368), analysis of variance and principal components analysis indicated that Euclidean distances for locomotion morphology contributed to significant variation in the fish assemblages among sites. Examination of trait categories indicated that low habitat index scores (degraded streams) were associated with changes in frequency of occurrence within the categories of all five of the species traits. Though the objectives and spatial scale of a study will dictate the level of species trait information required, our results suggest that species traits can provide critical information at multiple levels of data analysis.

A comparison of fish communities of subtidal seagrass beds and sandy seabeds in 13 marine embayments of a Caribbean island, based on species, families, size distribution and functional groups

Differences in fish community structure between different estuaries, lagoons and bays can be very large, and generalisations are complicated by the use of a wide variety of sampling methods. In the present study, fish communities of subtidal seagrass beds and sandy seabeds in 13 marine embayments of a single Caribbean island were therefore sampled using a uniform method. The objective of the study was to determine whether the seagrass and sandy seabed habitats of various embayments are characterised by typical fish assemblages which differ in terms of taxa (species, families), size classes (life stages) and functional groups (ecological species groups, feeding time and diet). This was linked to the hypothesis that differences in fish assemblages between habitats in different embayments are larger at taxonomic levels than at the level of functional groups. A second objective was to determine the most useful discriminating features between the two habitat types. The above hypothesis was rejected, since differences in fish assemblages from different seagrass and sandy seabed sites did not increase from functional to taxonomic level, but from size class to diet/species to family/feeding time to ecological species group. However, the seagrass and sandy seabed habitats could each be characterised by typical fish assemblages which differed in taxonomical and functional group composition, irrespective of differences in environmental and biotic variables between the embayments in which these habitats were situated. The two habitat types could be best characterised on the basis of fish family, ecological species group, feeding time and size distribution. Seagrass beds mainly harboured nocturnally active nursery species (Haemulidae, Lutjanidae, etc.), whose relative abundance was related to vegetation (mainly seagrass) cover. Sandy seabeds mainly harboured diurnally active bay species (Gerreidae, etc.) whose relative abundance was related to cover of bare sand. Similarities in taxonomical and functional traits of fish species predicted whether they occurred more abundantly in seagrass beds or in sandy seabeds.