Fish Assemblage Structure Research Articles

Fish responses to multiple scales in coastal blackwater Atlantic Forest streams in Southeast Brazil

Abstract Environmental factors act at multiple spatial scales in a hierarchical manner to shape the organization of biota. However, the relative influence of different scale-related factors is poorly known, especially in Atlantic Forest Blackwater streams. Therefore, we herein aimed to evaluate local, landscape and spatial factors that shape fish assemblages in 14 blackwater restinga coastal Atlantic Forest streams under natural conditions and verify species occurrence patterns among four sub-basins during the low-precipitation season. When we combined local, landscape and spatial factors, variance partitioning explained a high proportion of variation in species matrix. Local variables pH and Total Dissolved Solids explained most of the variability, and these were the most important factors in determining fish community structure. Significant differences in fish assemblage structure among the four sub-basins were observed, and Mimagoniates microlepis, Phalloceros harpagos, and Hollandichthys multifasciatus were the species that most contributed to this dissimilarity. The important contribution of local predictors, the high number of endemic species herein recorded, the presence of an endangered species (Spintherobolus broccae), and near pristine conditions, may be used as baseline conditions for the assessment of similar environments.

Variation in patterns of fish assemblage and their environmental correlates in a tropical river basin from the Gulf of Mexico slope

Abstract Understanding patterns of freshwater fish assemblage structure is key to protect them from ongoing human-induced threats to aquatic biodiversity. Yet, studies on associations between fish assemblages and habitat are lacking from many areas of high diversity in Middle America. We assessed fish assemblage structure and environmental associations from a portion of the Lacantún River sub-basin (Usumacinta River, Chiapas, Mexico). Based on environmental data and 17,462 individuals (56 species, 46 genera, and 22 families) captured from 13 sites sampled between 2017–2019, we found that stream order, distance to the Usumacinta, forest cover, temperature, and dissolved oxygen are key to explaining assemblage composition. Four clusters were found via multivariate regression tree analysis, with stream order and dissolved oxygen as defining variables. Our findings suggest that fish communities remain spatially structured even at small scales, in association to environmental gradients among habitats.

The influence of landscape at multiple spatial scales of the river basins at the Eastern Amazon fish assemblage

Abstract The Amazon River basins present distinct natural and anthropogenic characteristics that influence the structure of stream habitats and their associated biota. The influence of these characteristics can be evaluated through different spatial scales. We aimed to assess the influence (with and without the effect of spatial-geographical factors) of local, macroscale, and land-use variables in the structure of stream fish assemblages of Amazonian catchments with different deforestation levels. A partial redundancy analysis and a reduced metrics model were used to assess these influences. With geographic-spatial effects, we verified that the macroscale and local variables explained the variation in fish composition, and, without the effects, land use also explained the variation in this composition. In the forested catchments, the biota was associated with streams with natural characteristics (e.g., leaf banks). In the deforested catchments, it was associated with land use, sandy catchments with higher soil density (higher capacity of degradation), and less complex streams (fewer leaf banks, more sand). The associated fish have life features linked to these characteristics (e.g., Gymnorhamphichthys rondoni associated with sand). This configuration seems to be a result of both the impact of land use in the catchment (i.e., increased erosion, increased sedimentation) and the naturally sandy constitution of the catchment as well, reflecting the sandy substrate.

Length-weight relationship, sex ratio, and diet of three fish species (Actinopterygii: Teleostei) in streams of the Pomba River basin, Paraíba do Sul river drainage, Southeastern Brazil

This study aimed to estimate the parameters of length-weight relationship, sex ratio, and diet of three freshwater fish species that inhabit streams in the Pomba River basin (Rio de Janeiro, Brazil). Fishes were sampled with seine nets (2.0 × 1.20 m, 2 mm mesh size) and dip nets (0.46 × 0.33 m, 2 mm mesh size) from October to December 2018. Measurements were taken for total length (TL - 0.1 cm precision) and total weight (TW - 0.01 g precision). Growth model parameters were estimated. This study provides new length-weight relationship data for Deuterodon intermedius (Eigenmann, 1908), Australoheros paraibae Ottoni & Costa, 2008, and Hypostomus punctatus Valenciennes, 1840. All of them ingested a wide variety of food items, including plant material like algae, animal material such as terrestrial and aquatic insects, and undefined matter such as detritus or mud. The three species showed a higher number of females. Our study provides basic information for functional diversity studies, as well as for future investigations associated with the evaluation of anthropic impacts, either occasional or chronic, on the fish assemblage structure of the Pomba River basin.

Effects of fishing on the trophic structure of carnivorous fish assemblages from shallow rocky bottoms of the Mediterranean Sea and the temperate Atlantic Ocean

Abstract Here, we assess whether fishery exploitation affects the trophic structure of carnivorous fish. We censused fish and analysed the stable isotope ratios of C and N of species targeted by fishermen in areas open to fishing and marine protected areas (MPAs) in the Mediterranean Sea and the north-eastern Atlantic Ocean. Results demonstrated a major impact of fishing on the biomass and size structure of nektobenthic carnivorous fish. However, those changes did not modify the diversity of the trophic resources used by the assemblage, the pattern of resource partitioning between species, or the degree of trophic redundancy. These results add to recent evidence suggesting that MPAs implemented in fished seascapes may fail to restore the original structure of the food webs that once existed in pre-fished ecosystems because regional decimation and extinction of highly mobile predators prevent recovering the original diversity of predators at local scales, even in no-take areas. If so, more strict local fishing regulations are unlikely to restore the original diversity of high trophic level carnivores and restoration goals should be reframed in terms of an objective that is less unrealistic than restoring the pre-fished condition while still recovering aspects of the historical trophic structure.

Effects of a nuclear power plant warmwater outflow on environmental conditions and fish assemblages in a very large river (the Danube, Hungary)

AbstractDirect or indirect effects of nuclear power plants' (NPPs) warmwater effluents on the structure of biotic assemblages are poorly known in very large rivers. We examined changes in physical habitat structure, temperature condition and their possible effects on the structure of Danubian fish assemblages due to the outflow of the Paks NPP's warmwater channel, in Hungary. Seasonal surveys conducted both upstream and downstream from the outfall showed that its hydromorphological effects were generally local and comparable to natural or other anthropogenic hydromorphological changes. The effect of the returned cooling water was more apparent in the seasonally recorded surface water temperatures and depended highly on the spatial positioning of the sampling sites. However, environmental and spatial variables accounted only for a low amount of variance in case of both shoreline and offshore fish assemblage data. Overall, we found that the outflow exerted only a local scale effect on the structure of Danubian fish assemblages. Rather, fish assemblages varied largely both inshore and offshore, which dynamics overruled any effects of the artificially elevated temperature. Our study highlights the importance of the assessment of hydrogeomorphological variability of rivers and their influence on fish assemblage variability when examining spatial effects of thermal pollution.

Changes in Fish Assemblage Structure after Pen Culture Removal in Gehu Lake, China

The removal of the net enclosure has been used as a lake management strategy in various regions of China as ecological development is given more attention. Nevertheless, little is known about the substantive impact of this measure on fish communities in inland lakes. To this end, the fish community composition and structural features after the removal of the net enclosure in Gehu Lake were explored and evaluated in this study from 2021 to 2022 and compared to the investigation before the net enclosure removal from 2017 to 2018. Belonging to 7 orders, 10 families, and 46 species, a total of 17,151 fish were collected, with pelagic, sedentary, and omnivorous species dominating. In comparison, the number of species increased by 10 after removal, and fish alpha diversity increased. The Index of Relative Importance (IRI) revealed that the composition of dominating species remained constant, including Coilia nasus, Hypophthalmichthys molitrix, and Hypophthalmichthys nobilis; Parabramis pekinensis, Megalobrama amblycephal, and Culter mongolicus were upgraded from common species to general species. Culter alburnus, Hemiculter bleekeri, and Pseudobrama simoni were downgraded from general species to common species. Elopichthys bambusa had become a common species (IRI = 109.35), which was not discovered before removal. According to the hierarchical clustering (HC) and non-metric multidimensional sequencing (NMDS), the fish community of the northern reserve was highly aggregated. As the Abundance Biomass Comparison (ABC) curve and biodiversity index indicated, the fish community structure of the whole lake was in a state of moderate anthropogenic disturbance with reduced stability, while that of the northern reserve was in a state of light anthropogenic disturbance with greater stability. The number of fish species increased in this survey compared to the period before removal, species and dominant species composition altered dramatically, and total lake stability declined. This study demonstrates that the fish diversity in Gehu Lake increased after the removal of the net enclosure. Meanwhile, the stability of the fish community structure was decreased temporarily. Lake restoration is a long-term process, and the underlying impact of the removal of the net enclosure still requires continuous monitoring and further studies.

The reef fish assemblage of a coral reef system in the southwestern Gulf of Mexico

Reef fish species richness of the Veracruz Reef System National Park (VRSNP) in the SW Gulf of Mexico is well known. However, the knowledge of the assemblage structure and its spatial variability in the reef ecosystem is quite limited. For that purpose, 5 field surveys (2012-2015) were performed, using the stationary visual census method, at 10 selected reefs. The most important findings were: 116 reef species were recorded. Average total reef fish density (2.31 Ind/m2) is similar to the records for the Caribbean reefs in the 20th century. The top 5 most abundant species were: Chromis multilineata, Ocyurus chrysurus, Abudefduf saxatilis, Stegastes leucostictus, and Elacatinus jarocho. We found evidence of a spatial distribution pattern with 3 well-defined groups of reefs: (1) those near the city of Veracruz, (2) those near the outlet of the Jamapa River, and (3) those farther from the city. Higher fish densities are associated to both high hermatypic coral and low crustose coralline algae bottom covers. The assemblage structure of reef fishes is different at distinct geomorphological reef zones. As expected, with some differences in the species abundance order, the assemblage structure of reef fishes is similar at all coral reefs in the Gulf of Mexico.

Continental slope fishes of the Potiguar Basin off Northeast Brazil in the Equatorial Atlantic ocean

Deep-sea fish species compose around 15% of the observed fish biodiversity, and studies concerning the ecology and distribution of these marine fish species are essential to understand the magnitude of human influence on the deep ecosystems. The western South-Atlantic deep-sea fishes are well described and began to be studied in 1873. Nevertheless, studies considering fish community structure are still scarce in this area. This present study analysed the effects of oceanographic variables on deep-sea fish assemblages structure, density and species richness. To measure diversity, interpolated and extrapolated accumulation curves were drawn using Hill numbers along the Southwest Equatorial Atlantic Ocean depth intervals. A total of 36 trawls were carried out by an otter-boarded bottom trawl net between depths of 150 and 2000 m. Fish biomass showed the highest values between 150 and 400 m, reaching the highest numbers at 400 m, with a decline in the areas of 1000 m and 2000 m. The highest species richness was seen in the shallowest areas (150 m), with a declining trend towards deeper regions. Fish assemblages and habitats' affinity, species, individual lengths, depth, coast distance, longitude and density were used to identify and quantify clusters. The caught fishes belonged to 167 species (115 demersal, 52 pelagic), distributed within 63 families and three orders. The spatial and bathymetric occurrences of some species in the present study were broadened. The most important species in 150, 400, 1000 and 2,000m depth strata were Citharichthys cornutus, Saurida caribbaea, Monomitopus americanus and Dibranchus tremendus, respectively. Assemblages were clustered in four groups; the cluster's richness values were 64, 30, 10, and 11, respectively. Clusters 1, 2 and 3 represented depth values of 150, 400 and 1000 m and overlapped in k-means, showing a more similar pattern, unlike cluster 4 (2,000m). The most profound fish assemblage varies statistically significantly by depth, density, richness and diversity. Rapoport's rule interpretations explained the negative relationship between richness, density and depth and the positive association of length and depth. Despite the highest richness in cluster 1 and the lower richness in 4, they had the lowest effective diversities (Hill numbers), cluster 3 showed the lowest richness, but it had a high evenness trend and then had the highest effective diversity.

Assembly of non‐native fishes in North Patagonian streams: Species occurrence and abundance respond to different spatial scales

AbstractEcological communities are structured by combinations of biotic and abiotic factors acting at different spatial scales. However, the relative influence of the different scale‐related variables on assemblage composition is poorly understood, despite being key to the effective and efficient management of fluvial ecosystems. We took advantage of the relatively recent and well‐studied history of salmonid introductions in Patagonia to evaluate if non‐native species show different patterns of association with abiotic factors depending on the spatial scale of the environmental filter. We used a hierarchical approach to characterised environmental variables at the basin and reach scales to assess their influence on the presence, abundance and structure of the salmonid assemblages in breeding streams. We saw no evidence that presence/absence patterns of salmonid distribution were driven by landscape variables, except for those basins with physical environmental barriers to colonisation. However, we did find evidence for relative abundances being influenced by climatic and geomorphological variables (e.g., precipitation and relief). Our results do not support a scenario in which any of the salmonid species modulates the distribution of the other species, suggesting that interference has played only a minor role in determining current fish distribution in fluvial systems of the region. Instead, current patterns of presence and abundance of salmonids are best explained as the product of environmental filters. Our findings contribute to our understanding of the ecology of individual species and provide insight into the mechanisms structuring fish assemblages in Southern Hemisphere's lotic systems.

Co-occurrence of seagrass vegetation and coral colonies supports unique fish assemblages: a microhabitat-scale perspective.

Numerous studies have suggested that seagrass beds provide nursery habitats for juvenile fish in both tropical and subtropical regions. Most of these previous studies applied a landscape-scale perspective, in which seagrass beds and coral reefs are treated as independent, homogenous habitats. However, this perspective might overlook the microhabitat-scale perspective within the habitats, for example, the possibility that small-sized hard substrates (e.g., coral colonies) within seagrass beds might serve as fish nurseries. The present study aimed to examine the effects of the presence of microhabitats (small-sized coral colonies) within seagrass beds on the structure of fish assemblages. Fieldwork was conducted at Urasoko Bay, Ishigaki Island, Okinawa, Japan. Four habitat zones were selected: (1) seagrass bed with presence of massive coral colonies (SGCO), (2) seagrass bed without coral colonies (SG), (3) sandy bottom (without seagrass vegetation) with massive coral colonies (CO), and (4) sandy bottom without seagrass vegetation or coral colonies (SA). Six 20 m × 2 m line transects were established and monthly underwater observations were conducted between June and October in 2018 and 2019. A cluster analysis, analysis of similarity, and principal component analysis revealed that the fish assemblage at SGCO was significantly different from the other three habitat zones. This was because some fish species (e.g., Ostorhinchusishigakiensis and Lutjanus gibbus) were almost exclusively present at SGCO and rarely seen at CO, SG, and SA. Most individual fish belonging to these species were found on coral colonies at SGCO, suggesting that the co-occurrence of seagrass vegetation and coral colonies is essential for the habitats of these fish species. Although other fish species present at SGCO were also found at SG, three species, Parupeneus barberinus, Stethojulis strigiventer, and Lethrinus atkinsoni, were more abundant at SGCO with some found on coral colonies in this habitat zone. Several fish species that occurred at both SGCO and CO (e.g., Ostorhinchus properuptus, Cheilodispterus quinquelineatus, Chrysiptera cyanea, and Pomacentrus chrysurus) were more abundant or showed a greater size range at SGCO, suggesting greater survival rates in this habitat zone because of the co-occurrence of seagrass vegetation and coral colonies. This study demonstrated the existence of a unique fish assemblage structure at SGCO. Although the adoption of a landscape-scale perspective (three-dimensional structure of the vegetation) is necessary, a microhabitat-scale perspective that includes the presence of small hard substrates should also be considered to accurately evaluate the nursery function of seagrass beds.

Microhabitat use of larval fish in a South Carolina Piedmont stream

Understanding habitat use and nursery areas of larval fish is a key component to managing and conserving riverine fishes. Yet, freshwater researchers often focus only on adult fishes, resulting in a limited understanding of the habitat requirements for the early life stages of freshwater fishes. The goal of this study was to quantify the larval fish microhabitat use of three fish families in Twelvemile Creek, a fifth-order tributary of Lake Hartwell (Savannah River basin) in the Piedmont ecoregion of South Carolina, USA. We used handheld dipnets to sample larval fishes along 20 equidistant transects spaced 10 m apart weekly from May to July 2021 along a 200 m stream reach. We also collected microhabitat data at each larval fish capture location. Most captured individuals were in the metalarval stage and were identified to the family level. A partial distance-based redundancy analysis indicated that water velocity contributed to changes in larval fish assemblage structure. Larval fishes occupied a subset of the available habitat that was characterized by low water velocity, non-Podostemum substrate, and shallow habitats close to the shore or bed rock structure. We also detected temporal patterns in larval fish counts, with peak Percidae and Leuciscidae counts in late July and the highest Catostomidae counts in late May–early June. Our results suggest that larval fishes select habitats with low water velocity and shallow habitats close to shore microhabitat characteristics, and that riffle-pool sequences may serve as a nursery habitat for Percidae, Catostomidae and Leuciscidae metalarvae.

The uselessness of cytochrome oxydase gene analysis for genetic identification of selected Gobiidae species from some European countries

The family Gobiidae is the largest teleost family, consisting of more than 2,000 species in more than 200 genera. They have adapted to a wide range of habitats, inhabiting mostly marine and brackish waters. Recently invasive Ponto-Caspian gobies have caused significant changes to the structure of fish assemblage throughout the European waters. The aim of the study was to verify the possibility of identifying three species of the genus Gobiidae based on the analysis of the mitochondrial region of the cytochrome oxidase subunit 1 (COI) gene. 339 samples originated from seven countries and 17 different sites were investigated. Qualitative and quantitative assessment of the extracted DNA was conducted by measuring light absorbance and electrophoretic separation. Approximately 650-bp (base pairs) fragments were amplified from the 5' region of the mitochondrial COI with the PCR (polymerase chain reaction) reaction. Sequences of 652 bp were obtained and compared with reference sequences in the National Center for Biotechnology Information (NCBI). Based on the sequence analysis, we determined that in the analysed geographical regions, the goby preliminary identified morphologically as the round goby was represented by three species: round goby ( Neogobius melanostomus), tubenose goby ( Proterorhinus marmoratus), and monkey goby ( Neogobius fluviatilis). The latter two are newly reported for their new habitats. Genetic characterisation of such populations offers the opportunity to assess their genetic stability, which provides agencies managing the aquatic environment in EU countries with a tool for revising the legislation, including regulations relevant for updating the status of native and invasive species in European waters.

Seasonal and Spatial Variations in Fish Assemblage in the Yangtze Estuary and Adjacent Waters and Their Relationship with Environmental Factors

In this work, we identified the seasonal and spatial variations in fish assemblages and their relation to environmental variables in the Yangtze Estuary and adjacent waters. A total of 61 fish species in 32 families were identified over four seasons; of these, 12 species were dominant and Harpadon nehereus was the most dominant species. Fish varied in abundance, biomass, and species composition in different seasons; both biomass and abundance were highest in autumn and lowest in spring. Fish can be spatially divided into high-salinity assemblages and low-salinity assemblages. The spatial variation in fish assemblages was caused by the selectivity and adaptability of species for the environmental conditions of the estuary and the seasonal variation in fish assemblage structure likely resulted from migrations of dominant taxa associated with fish spawning and foraging behavior as well as the environment. The results of CCA analysis showed that temperature, depth, salinity, dissolved oxygen, and chlorophyll were the major factors affecting the fish assemblage differences throughout the seasons. Of these, temperature drove the seasonal variation in assemblage structure, while salinity significantly affected the spatial distribution of assemblages. This paper revealed the relationship between the seasonal and spatial distribution patterns of the fish assemblage and environmental factors and the results could provide a scientific basis for the management and sustainable utilization of fishery resources in the Yangtze Estuary and adjacent waters.

Relationships between fishery catch rates and land cover along a longitudinal gradient in floodplains of the Amazon River

Land cover is an important driver of patterns of fish diversity and assemblage structure in Amazonian floodplains. In the floodplain of the Amazon River, remarkable changes in the land cover composition across a longitudinal gradient, from the middle Amazon to the lower Amazon, likely affects fishery catch rates at local scales. Here, we investigated potential relationships between fishery catch rates and extent of land cover types in lakes of these two regions, the middle and lower floodplains of the Amazon River. Areas of flooded shrubs, herbaceous vegetation, and open water, within buffers of 1000 and 2000 m, were quantified around the areas of 23 lakes and modeled as predictors of fishing catch rate in the two subregions of the River i.e., the lower and middle Amazon, while these regions were also included as fixed effects of our models. Comparisons of the spatial extent of the land cover types between the two regions showed a predominance of flooded herbaceous vegetation in the downstream-lower portion, and a predominance of flooded shrubs and forests upstream-middle portion. In the models, the region was consistently the variable of greatest relative importance (Σwi > 0.9), and indicates higher fishing catch rate in the middle Amazon region when compared to the lower Amazon. Flooded shrub quantified on the smallest scale was the land cover type of strongest influence driving higher fishing catch rates, regardless of the region. In particular, our results support the idea that loss of flooded shrubs in adjacent areas of floodplain lakes can lead to reduced fishing catch rates at local and regional scales.

Macroalgal physical structure predicts variation in some attributes of temperate fish assemblages better than macroalgal species composition

The importance of vegetative habitat in influencing distribution patterns, species interactions, and biodiversity is well documented in marine ecosystems, yet most previous studies on macroalgal–fish relationships have focused on influences of density and identity of macroalgae, often ignoring how the unique physical structure provided by each alga contributes to patterns. We tested whether the distribution, abundance, and biomass of rocky reef fishes could be predicted as well or better by measures of physical structure of macroalgae than by species identity and abundance. Divers visually sampled fishes and macroalgae at seven sites spread over several km at Santa Catalina Island, California, over a 1-year period, to examine how the distribution patterns of fishes related to spatiotemporal differences in the macroalgal assemblage. We found that variation in the composition, density, and diversity of the fish assemblage was equally or better explained by macroalgal structure (total surface area and height) than by macroalgal species density. In contrast, biomass and vertical distribution of fishes were better predicted by macroalgal species identity and density than by macroalgal physical structure. Of the macroalgal attributes, surface area was the best predictor of fish abundance and multivariate assemblage structure (species and their densities). However, much of the spatiotemporal variation in the fish assemblage was not explained by macroalgae, indicating that even in habitats visually dominated by macroalgae, macrophytes are only one of many factors that drive spatiotemporal variation in community structure. Our results suggest that quantifying the physical structure provided by marine macroalgae can be more useful than macroalgal species identity in predicting some aspects of fish assemblage structure.

Regional patterns in demersal fish assemblages among subsea pipelines and natural habitats across north-west Australia

Regional patterns of fish diversity, abundance, distribution, and assemblage composition are driven by a combination of biotic and abiotic conditions in the marine environment, but these conditions can be altered through anthropogenic activities, such as those associated with oil and gas extraction. The present study utilises data on fish relative abundance and diversity obtained from 1546 baited remote underwater video deployments conducted between 2004 – 2019 in depths of 9 – 170 m across 2000 km of coastline in north-west Australia on natural habitats and subsea pipelines to understand the influence of oil and gas infrastructure on fish assemblages. A total of 450 fish taxa from 56 families was observed, with populations dominated by generalist and invertebrate carnivore taxa. At the regional scale, subsea pipelines had lower diversity (lower taxonomic richness) than natural environments, but possessed a higher abundance of piscivorous and herbivorous fish taxa. Clear patterns in fish assemblage composition were observed in multivariate analyses, reflecting the proximity of oceanic shoals and banks, depth, and to a lesser extent, oil and gas infrastructure. Shallow-water and close to shoals assemblages were characterised by a diversity of site-attached (e.g., wrasses, tuskfish), reef-associated taxa (e.g., emperors). Mesophotic fish assemblages were characterised by commercially important (e.g., goldband snapper), wide-ranging (e.g., sharks) and sand-affiliated (e.g., toadfish, threadfin bream) taxa. Proximity to pipelines and platforms ranked low as predictors in the multivariate analyses suggesting a negligible regional influence of these structures on fish communities in comparison to depth and shoal habitats. Local-scale influences of subsea infrastructure, however, may be important for some fish species (infrastructure vs. immediate surrounds). Our study highlights the influence of abiotic factors on regional-scale patterns in fish assemblage structure across north-west Australia.

Prolonged drought influences the taxonomic and functional structure of fish assemblages in estuaries along the Brazilian semiarid coast

Prolonged drought influences the taxonomic and functional structure of fish assemblages in estuaries along the Brazilian semiarid coast

Coral reef fish assemblages exhibit signs of depletion in two protected areas from the eastern of Los Canarreos archipelago (Cuba, Caribbean Sea).

Understanding the impact of marine protected areas on the distribution and composition of fishes is key to the protection and management of coral reef ecosystems, and especially for fish-based activities such as SCUBA diving and recreational fishing. The aim of this research is to compare the ichthyofauna structure in three areas in the eastern part of Los Canarreos archipelago in Cuba with different management schemes: Cayo Campos-Cayo Rosario Fauna Refuge (CCCR), Cayo Largo Ecological Reserve (CL) and non-protected area (nMPA), and considering habitat differences and depth variation. A total of 131 video transects were conducted using diver operated stereo-video (stereo-DOV) in November, 2015 in backreef and forereef along the CCCR, CL and the adjacent nMPA. We recorded 84 species and 27 functional groups suggesting high complementarity of functions. Several multispecies schools were observed along surveys, which explain the biomass peaks in some sites, mainly for Lutjanidae, Haemulidae and Carangidae. A concerning issue was the bare representation of critical functional groups and threatened species. The effect of sites nested within habitats was significant and the most important driver structuring fish assemblages, while MPA condition was not evident. Favorable habitat features (habitat heterogeneity and surrounding coastal ecosystems) are likely enhancing fish assemblages and counteracting the effects of pouching derived from insufficient management. We recommend immediate actions within a strategy of precautionary management including, but not limited to, the appointment of staff for the administration of CL, frequent monitoring and effective enforcement.

Fish assemblage shifts in an Ozark river over 80 years amidst a mosaic of forest regeneration and persistent pasture

AbstractFish assemblages are useful in evaluating the health of aquatic ecosystems. Over time, fish assemblages will respond to anthropogenic disturbances but may also simultaneously respond to conservation efforts in a watershed, shifting the taxonomic and functional structure of the assemblage. We quantified temporal changes in taxonomic and functional structure of fish assemblages in the Current River, Missouri, over an 80‐year time span and related these changes to forest regeneration and persistent pasture land use within the watershed. We found shifts in taxonomic and functional assemblage structure in two time‐steps from the 1940s to 2020 related to land use within the watershed. Reforested reaches exhibited increases in benthic species, rheophilic species and invertivorous feeding guilds. Higher pasture reaches exhibited decreases in benthic species and native centrarchid species while generalist centrarchid species increased. Ultimately, fish assemblage structure in the Current River appears to be shifting to an alternative state (i.e. increased presence/abundance of benthic species) in response to forest regeneration and persistent pasture land use.