Diversity Of Fish Assemblages Research Articles

Structure‐from‐motion photogrammetry demonstrates that fine‐scale seascape heterogeneity is essential in shaping mesophotic fish assemblages

AbstractBenthic components of tropical mesophotic coral ecosystems (MCEs) are home to diverse fish assemblages, but the effect of multiscale spatial benthic characteristics on MCE fish is not well understood. To investigate the influence of fine‐scale benthic seascape structure and broad‐scale environmental characteristics on MCE fish, we surveyed fish assemblages in Seychelles at 30, 60 and 120 m depth using submersible video transects. Spatial pattern metrics from seascape ecology were applied to quantify fine‐scale benthic seascape composition, configuration and terrain morphology from structure‐from‐motion photogrammetry and multibeam echosounder bathymetry and to explore seascape–fish associations. Hierarchical clustering using fish abundance and biomass data identified four distinct assemblages separated by the depth and geographic location, but also significantly influenced by variations in fine‐scale seascape structure. Results further revealed variable responses of assemblage characteristics (fish biomass, abundance, trophic group richness, Shannon diversity) to seascape heterogeneity at different depths. Sites with steep slopes and high terrain complexity hosted higher fish abundance and biomass, with shallower fish assemblages (30–60 m) positively associated with aggregated patch mixtures of coral, rubble, sediment and macroalgae with variable patch shapes. Deeper fish assemblages (120 m) were positively associated with relief and structural complexity and local variability in the substratum and benthic cover. Our study demonstrates the potential of spatial pattern metrics quantifying benthic composition, configuration and terrain structure to delineate mesophotic fish–habitat associations. Furthermore, incorporating a finer‐scale perspective proved valuable to explain the compositional patterns of MCE fish assemblages. As developments in marine surveying and monitoring of MCEs continue, we suggest that future studies incorporating spatial pattern metrics with multiscale remotely sensed data can provide insights will that are both ecologically meaningful to fish and operationally relevant to conservation strategies.

Seascape context matters more than habitat condition for fish assemblages in coastal ecosystems

Ecosystems are increasingly degraded, fragmented and lost because of human activities globally. These impacts cause changes in the distribution of biodiversity and key ecological functions, modifications to food webs and reductions in ecosystem condition and seascape connectivity. Understanding whether, and how, the spatial context (i.e. extent, position) and condition (i.e. structure and condition of patches, including habitat forming species) of ecosystems coalesce to support their function as animal habitats is critical for effective and cost efficient coastal management. These potential combined, or interactive, effects of spatial context and habitat condition on fish assemblages are, however, rarely quantified. We sampled fish assemblages from six different ecosystems (mangrove, seagrass, saltmarsh, log snag, rocky outcrop and unvegetated sediment) across 13 estuaries in eastern Australia and quantified the relative importance of spatial context and habitat condition variables for fish assemblage composition. Spatial context variables were consistently more important than habitat condition in structuring fish abundance and diversity. Sites that were closer to smaller vegetated habitats (i.e. mangrove and seagrass) and key seascape features (i.e. estuary mouth and intertidal flats) typically supported diverse fish assemblages in high abundance. While the composition of fish assemblages was primarily linked to spatial context variables, habitat condition variables that index food availability were also important for fish in mangroves, seagrass and rocky outcrops. Our results show that fish abundance and diversity are intimately linked to seascape connectivity and heterogeneity, and have important implications for conservation planning and fisheries management decisions in coastal ecosystems. We highlight the importance of quantifying the influence of the combined effects of habitat condition and spatial context for biodiversity across multiple ecosystems, and expect the outcomes to lead to more efficient and effective management planning.

Temporal Changes in Taxonomic and Functional Diversity of Fish Assemblages in the Upper Yangtze River After Impoundment of the Three Gorges Reservoir, China

Anthropogenic disturbances are one of the primary factors that drive biodiversity loss. Temporal changes in biodiversity respond to such disturbances. In the present study, we investigated the temporal changes in taxonomic and functional diversity of fish assemblages in different habitats (Three Gorges Reservoir, TGR; running water above the TGR, UTGR; and tributary Chishui River, CSR) in the upper Yangtze basin after impoundment of the TGR from 2008 to 2015. During the survey, the taxonomic and functional composition of fish assemblages varied among the habitats. Although taxonomic diversity increased and functional diversity decreased significantly in the entire upper Yangtze basin, no significant changes in the diversities were observed in each habitat. The habitats showed directional changes in the composition of fish species. The slope of the directional changes in the TGR was more than that in the UTGR and CSR. These results indicated that the distribution of fish species was associated with the habitat after the impoundment. The assembly of the fish assemblage was driven primarily by the neutral process in the entire survey area but was promoted by a combination of species sorting and neutral process in each habitat. The impoundment caused more effects on the TGR than on the UTGR, but it slightly affected the CSR. Regarding fishing closure, conservation measures for fish diversity should be established according to the different habitats. The study findings suggest the removal of small dams in tributaries and ecological regulation in the mainstream and continuous monitoring of fish biodiversity.

Fish assemblage monitoring in Alberta’s Ells River: Baseline fish and habitat variability prior to major development

The collection of sentinel fish species for Environmental Effects Monitoring (EEM) has provided ancillary fish assemblage surveys on several tributaries in the Athabasca Oil Sands Region (AOSR) of Alberta, Canada over the last decade. Using available, comparable data we investigated baseline fish assemblage variability along the Ells River, a tributary of the Athabasca River experiencing increasing proximity to natural bitumen deposits and proposed mining development as it approaches confluence with the mainstem Athabasca. Transect-based electrofishing data from four sites surveyed in September 2013, 2014 and 2018 showed significant spatiotemporal variability in assemblages, where spatial variability was greatest in 2013 and temporal variability was observed in assemblages both upstream (2013–2014) and downstream (2014–2018) of proposed development. Habitat assessments in 2018 revealed significant relationships among pH, algae cover and site slope with fish assemblages of the same year. Due to the complementary nature of assemblage surveys, data challenges (changing methodologies, sampling effort, and limited ancillary physiochemical data) have presented limitations to the multivariate approach applied in the study. Moving forward, employing consistent methods for fish collections and fine-scale habitat assessments will improve the ability to correlate assemblage variability with changes in the physical environment. Ultimately, this will aid in developing potential triggers of change that may be attributed to or confound adjacent, expanding Oil Sands activities. These findings will also inform monitoring programs on the use of fish assemblages as indicators of change, potentially providing an alternative to existing biomonitoring approaches in small streams with small fish populations.

Early Oligocene (Rupelian) fishes (Chondrichthyes, Osteichthyes) from the Ashley Formation (Cooper Group) of South Carolina, USA

Matrix surrounding a dermochelyid carapace and two cetacean skulls recovered from the Givhans Ferry Member of the Ashley Formation (lower Oligocene, Rupelian Stage) in South Carolina, USA yielded a surprisingly diverse assemblage of euselachian and teleost fishes. We identified 21 elasmobranch taxa, including 13 selachians and eight batoids, nearly all of which are known to occur in the overlying upper Oligocene (Chattian) Chandler Bridge Formation. Notable occurrences within the Ashley Formation paleofauna include a new shark, Scyliorhinus weemsi n. sp., and the first South Carolina Oligocene records of Squalus sp., Pristiophorus sp., and Pachyscyllium sp. Numerous teleost taxa were also documented based on isolated teeth, including species of Albulidae, Paralichthyidae, Osteoglossidae, Sparidae, Sciaenidae, Sphyraenidae, Scombridae, Trichiuridae, and possibly Labridae.

Dredging transforms the seafloor and enhances functional diversity in urban seascapes

Landscape modification alters the condition of ecosystems and the complexity of terrain, with consequences for animal assemblages and ecosystem functioning. In coastal seascapes, dredging is routine practice for extracting sediments and maintaining navigation channels worldwide. Dredging modifies processes and assemblages by favouring species with wide trophic niches, diverse habitat requirements and tolerances to dredge-related eutrophication and sedimentation. Dredging also transforms the three-dimensional features of the seafloor, but the functional consequences of these terrain changes remain unclear. We investigated the effects of terrain modification on the functional diversity of fish assemblages in natural and dredged estuaries to examine whether dredging programs could be optimised to minimise impacts on ecological functioning. Fish assemblages were surveyed with baited remote underwater video stations and variation in functional niche space was described using species traits to calculate metrics that index functional diversity. Terrain variation was quantified with nine complementary surface metrics including depth, aspect, curvature, slope and roughness extracted from sonar-derived bathymetry maps. Functional diversity was, surprisingly, higher in dredged estuaries, which supported more generalist species with wider functional niches, and from lower trophic levels, than natural estuaries. These positive effects of dredging on functional diversity were, however, spatially restricted and were linked to both the area and orientation of terrain modification. Functional diversity was highest in urban estuaries where dredged channels were small (i.e. <1% of the estuary), and where channel slopes were orientated towards the poles (i.e. 171–189°), promoting both terrain variation and light penetration in urban estuaries. Our findings highlight previously unrecognised functional consequences of terrain modification that can easily be incorporated into dredging programs. We demonstrate that restricting the spatial extent of dredging operations and the orientation of dredged channel slopes, wherever this is practical, could help to limit impacts on ecosystem functioning and productivity in urban seascapes.

Drivers of temporal variations in fish assemblages from mangrove creeks in Beihai, southern China.

Mangroves are regarded as important settlement grounds and nurseries for fishes due to the sheltered nature of these ecosystems. To identify the drivers of temporal variations in fish assemblages, seasonal variations of fish assemblages and environmental variables were investigated in Nanliu River Estuary, China, from July 2019 to May 2020. In total, 17,680 individuals weighing 24,724.73 g belonging to 23 families and 45 species were collected. The dominant species were Ambassis urotaenia, Mugil cephalus, Coptodon zillii, Gambusia affinis, and Bostrychus sinensis. Fish assemblages were significantly different in seasonal periodicity according to the results of nonmetric multidimensional scaling (NMDS) and permutational multivariate analysis of variance (PERMANOVA). Kruskal-Wallis test results revealed that species richness, fish abundance, and biomass were significantly different, seasonally. The highest number of fish specimens captured was recorded in winter and summer, while the highest biomass was observed in autumn. Different ecological types of fish utilized mangroves in different ways. Hence, the findings in this study are instrumental in understanding and the conservation of mangroves even coastal wetland and fish resources in the process of mangrove restorations.

Spatial and Temporal Variations in Fish Assemblage in Feitsui Reservoir, in Northern Taiwan, from 2006–2020

Reservoirs are artificial ecosystems that modify the hydrological and environmental components nearby. The long-term monitoring of fish assemblages in reservoirs may provide key information to understand how these artificial ecosystems allow fish population fluctuations and identify proper conservation strategies. A sentinel-site approach method assessed changes in fish assemblages in the Feitsui Reservoir (1024 ha) over 14 years, including the periods 2006–2008, 2010–2011, 2016, 2018, and 2020. Fish assemblages, sampled using gill nets, were composed of 38 species (12 families and 8 orders) with Cyprinidae as the dominant family; the fish fauna were dominated by species of the family Cyprinidae (71%) and Cichlidae (20.3%). Principal component analysis and nonmetric multidimensional scaling categorized the assemblages into two groups (cold and warm seasons), and we identified three parameters that were significantly correlated with the season (p &lt; 0.05): SD (R = −0.04), Chl-a (R = 0.01), and algal count (R = 0.19); the algal count was higher in the warm season than in the cold season. The fish assemblage in the cold and warm seasons contained no exclusive taxa, contributing to the dissimilarity between the groups. The fish assemblage for the years before and after 2010 indicated partial overlap between the two groups; S. macrops contributed greatly to the separation of the two periods (&gt;10% each; SIMPER) and O. mossambicus was dominant in assemblage structures after 2010. Our findings show the importance of long-term fish monitoring for the investigation of the effects of nonnative fish species on native fish species composition.

Long-term changes in the functional trait composition and diversity of fish assemblages in eastern plain lakes under the regime of river-lake connectivity loss

东部平原湖泊区是我国淡水湖泊最集中的地区，分布着我国的五大淡水湖等诸多湖泊.然而，江湖阻隔对该区域湖泊的生物多样性造成严重威胁.本文选取东部平原的9个湖泊，对江湖阻隔前后鱼类功能性状（3组分类性状和6个连续性状）和功能多样性指数的变化规律开展了研究.结果表明，9个湖泊的鱼类总物种数由江湖阻隔前的140种减少为江湖阻隔后的100种，平均物种数由79.6种减少到52.1种（减少34.4%）.江湖阻隔后鱼类群落的功能性状和功能多样性指数发生了显著变化，洄游性鱼类（包括河海洄游和江湖洄游）物种占比（由39.7%降至32.6%）和鱼食性物种占比（由31.1%降至25.2%）显著下降，而非洄游性物种占比（由60.3%升至67.5%）和浮游生物食性物种占比（由13.5%升至15.5%）显著上升.连续型性状中，平均营养级（由3.14降至3.10）显著下降、平均生长速率（由0.57 a^-1升至0.65 a^-1）显著上升.阻隔后的物种数（SR）、功能丰富度指数、功能离散度指数和功能分散指数显著低于阻隔前.本研究表明江湖阻隔后鱼类群落不仅物种丰富度下降，且功能性状趋向同质化（或单一化）发展，致使功能多样性下降.研究结果可为东部平原湖泊的渔业资源管理及湖区生态修复和保护提供重要的理论依据.;The eastern plain lake area is the most concentrated area of freshwater lakes in China, supporting numerous lakes, including China's five largest freshwater lakes. However, human activities such as disconnecting lakes from the mainstream are seriously threatening the aquatic biodiversity in the region. In this study, 9 lakes in the eastern plain were selected to study the temporal (before and after the river-lake disconnection) changes in functional traits (3 groups of categorical traits and 6 continuous traits) and functional diversity index of fish assemblages. The results showed that the total number of fish species across the 9 lakes decreased from 140 species to 100 species through time, and the average species richness per lake decreased from 79.6 to 52.1 (accounting for 34.4% of historical species). The functional trait composition and diversity indices of fish communities changed significantly before and after the river-lake disconnection. The percentages of migratory (from 39.7% to 32.6%) and piscivorous species (from 31.1% to 25.2%) significantly decreased, while the percentages of non-migratory (from 60.3% to 67.5%) and planktivorous species (from 13.5% to 15.5%) significantly increased. For the continuous traits, the average trophic level (from 3.14 to 3.10) significantly decreased but the average growth rate (from 0.57 a^-1 to 0.65 a^-1) significantly increased. Species richness, FRic, FDiv and FDis all significantly decreased. These results indicated that, after river-lake disconnection, fish assemblages experienced not only a decrease in species richness but also homogenization (or simplification) trend of functional trait composition and decline in functional diversity. Our study provided scientific background for the ecological protection and restoration of eastern plain lakes in China.

Environmental correlates of elasmobranch and large fish distribution in a river-dominated estuary

Coastal areas serve as vital habitat for many marine fishes and often host broad gradients of environmental conditions that result in diverse species assemblages. Understanding the influence of environmental variables on the distribution and abundance of fishes is especially important for devising appropriate management strategies. We documented large fish community structure in the Apalachicola Bay system from 2018 to 2021 using fishery-independent longline and gillnet surveys. Spatiotemporal variation in fish assemblages was evaluated with permutational multivariate ANOVA, while community- and species-level habitat relationships were described across gradients of environmental variables with non-metric multidimensional scaling and generalized additive models. We captured 5085 fishes from 17 elasmobranch and 33 bony fish species, with gafftopsail catfish Bagre marinus, blacktip shark Carcharhinus limbatus, Atlantic sharpnose shark Rhizoprionodon terraenovae, and hardhead catfish Ariopsis felis comprising 82.1% of the total catch. Fish communities varied spatially throughout the system, and changes in these communities were most strongly correlated with gradients in salinity, clarity, and depth. We documented higher species richness and density of young elasmobranchs in our surveys compared to adjacent systems, supporting past suggestions that this area serves as important juvenile shark habitat. We suggest that flow from the Apalachicola River, transporting nutrients to the system and supporting numerous environmental niches across spatiotemporal scales, plays an influential role in maintaining the elevated diversity and density of elasmobranchs observed in this study.

Novel findings of late Cenomanian-Turonian Pachyophiid snakes, fishes and plants in the SE Bosnia-Herzegovina

New fossils from the Late Cenomanian-Turonian locality in the Bileca area are reported. The fossils include a diverse assemblage of snakelike reptile remains, fishes and plants. While fossil snakes have already been found in this area, the remains of fish and plants are reported for the first time. Based on the state of fossil preservation, the following were identified: the snake Pachyophis (Simoliophiidae), the pychnodont fish Coelodus sp., and plant remains of the flowering plants groups Magnoliidae exc. Lilianae, Arecaceae (palm trees), and Cycadopsida.

Interrelationships between soft corals and reef-associated fishes on inshore-reefs of the Great Barrier Reef

The composition of coral reef habitats strongly influences associated fish assemblages. As habitat formers, soft corals constitute a morphologically diverse component of coral reefs, although their importance as fish habitat is largely unquantified. Our study assessed relationships between soft and hard coral habitats and assemblages of reef-associated fishes on inshore reefs of the Whitsunday Islands, focussing on pomacentrids, chaetodontids and pomacanthids. Study sites varied in hard and soft coral cover and were assessed by the level of exposure to previous cyclone damage. The soft coral community was dominated by Sinularia spp. and constituted an average of 11.4% of benthic cover compared to 16% hard coral cover. At fine spatial scales (250 m2), significant positive relationships between soft coral cover and abundance occurred for 2 species of pomacentrids (Amblyglyphidodon curacao and A. leucogaster) as well as total Chaetodontidae and Pomacanthidae. Further, it was clear that some taxa were associated with specific soft corals. For example, A. curacao, Pomacentrus lepidogenys and Chelmon rostratus were observed associating with branching digitate Sinularia, with a more structurally complex soft coral morphology. The combination of high and medium cover of hard and soft corals supported distinct assemblages of fishes and the highest abundances of many species at the scale of sites (1000 m2). Our results indicate that soft corals provide valuable habitat, supporting diverse fish assemblages by contributing to habitat mosaics on coral reefs. These findings suggest that the ecological role of soft corals has been underestimated and therefore holds direct implications for the management of coral reefs.

Short term temporal variation of mangrove fish assemblage in Chabahar Bay (Oman Sea)

This study aimed to assess the temporal variation in fish assemblage in Chabahar Bay mangrove habitat. Baited Remote Underwater Video (BRUV) sampling method was applied to record the fish presence. Fishes were sampled monthly from June 2017 to April 2018 at daylight time (9:00 to 14:00) during high tide. Water temperature, turbidity, and salinity were recorded at the time of sampling. During the study, a total of 17 species belonging to 12 families were identified. A mbassis gymnocephalus was found as the dominant fish throughout the year except in November and December. The most abundant fish fauna in numbers was characterized by the following five species: Ambassis gymnocephalus (53.38%), Sardinella sp. (17.13%), Terapon jarbua (4.79%), Rhabdosargus sarba (3.25%) and Acanthopagrus berda (2.9%). ANOSIM showed that significant differences in the assemblage structure occurred among months (R=0.613, P < 0.001), and the CLUSTER analysis, together with the SIMPROF test showed that December is significantly different in term of fish assemblage. Canonical Correspondence Analysis (CCA) on species-environment correlations revealed that temperature and turbidity were the main parameters influencing fish occurrence in the mangrove habitat of Chabahar Bay. The overall diversity (Shannon–Wiener, Simpson’s Index of Diversity, and Pielou’s evenness), as well as functional diversity indexes (FRic and FDis), was higher in autumn and spring pointing out that the diversity is higher when the temperature had the closest value to averaged value.

Revealing the drivers of taxonomic and functional diversity of nearshore fish assemblages: Implications for conservation priorities

AbstractAimUnderstanding patterns and drivers of biodiversity are essential towards developing effective conservation strategies for shallow marine habitats broadly. However, little is known about the natural and anthropogenic factors that structure fish biodiversity of sandy beaches, one of the largest and most socio‐economically valuable nearshore habitats due to their endemic fauna, economic importance and cultural relevance. Here, we investigated how environmental variables and urbanization affect taxonomic and functional diversity of nearshore fish assemblages to provide general biodiversity patterns that can serve as baseline information for management plans when considering conservation prioritization.LocationSoutheast Brazil.MethodsWe surveyed fish communities at 77 sites along 150 km of coastline with different natural features and degrees of human influence using a combination of seine nets and surf‐BRUVS. We used generalized additive models (GAMs) to investigate the influence of environmental variables and urbanization on taxonomic and functional diversity of resident fish assemblages.Main resultsWe found that significant breaker wave height was the most important environmental variable in explaining the taxonomic and functional diversity of fish assemblages. The effects of increasing wave height were mostly negative, except for piscivorous fishes, which were most abundant at high energy sites, and for benthic and zoobenthivorous species, which were most abundant at sites with intermediate wave exposure. The latter species were also associated with higher chlorophyll‐a contributing to increased taxonomic richness and abundance. Further, anthropogenic impacts generally reduced diversity, with highest diversity only observed at the most pristine sites.Main conclusionsOur results demonstrate that both natural environmental variation and human activities structure the fish assemblages of sandy beach surf zones, affecting species that possess specific functional traits differently. These drivers should therefore be considered simultaneously in appointing protected areas in order to preserve a diversity of organisms and functional traits integral to productive beach ecosystems.

A diverse Miocene fish assemblage (Chondrichthyes and Osteichthyes) from the Pécs-Danitzpuszta sand pit (Mecsek Mts, Hungary)

Chondrichthyans and osteichthyans are widely reported from marine sediments of the Central Paratethys, not only by sporadic occurrences, but also by complex, diverse fish assemblages. Here we present a rich fish fauna from the upper Miocene (Pannonian, Tortonian) lacustrine sediments exposed in the Pécs-Danitzpuszta sand pit, in the SW Pannonian Basin. Altogether 22 227 specimens were investigated, and they could be classified into 17 chondrichthyan and 16 osteichthyan taxa. Among the chondrichthyans Odontaspididae (55.51%) and Myliobatidae (14.4%) are the most abundant, while the bony fishes are dominated by the Sparidae (77.07%). The limonitic, yellow, coarse-grained, gravelly sands yielded an extremely large amount of isolated fish fossils. A considerable part of the vertebrate material of the sands is likely reworked from older, middle Miocene (Badenian and Sarmatian, i.e. Langhian and Serravallian) sediments. The late Miocene calcareous marls underlying the sands also yielded a variety of fish remains. From these remains, associated and articulated latid bones are coeval with the sediment and suggest freshwater and brackish conditions in the area, in accord with other biotic data. Other, isolated fossils, namely teeth, otoliths, cycloid scales and jaw elements of Gadidae, Gobiidae, Sparidae and Latidae could be reworked and thus have a very limited paleoecological significance. Based on habitat preferences of extant relatives, all chondrichthyans and most osteichthyan taxa found in the sands must be of Badenian origin. The abundant remains allow for some conclusions on the environmental conditions during the Badenian. They refer to a shallow, coastal environment with tropical-subtropical climate with connection to more open water habitats. Remains of some osteichthyan taxa were found in coprolites, showing that these taxa were part of the food chain as prey items. Sirenian ribs and odontocete limb bones bearing tooth marks refer to trophic relations between marine mammals and large sized macropredatory sharks. The Pécs-Danitzpuszta record of shark-attributed bite marks on bones of marine mammals is the second of the Badenian of the Central Paratethys. Acipenserids and latids of the sands, linked to brackish and/or freshwater environments, could originate from any Miocene stratigraphic units.

Supplemental habitat is reservoir dependent: Identifying optimal planting decision using Bayesian Decision Networks

Environmental management often requires making decisions despite system uncertainty. One such example is mudflat mediation in flood control reservoirs. Reservoir mudflats limit development of diverse fish assemblages due to the lack of structural habitat provided by plants. Seeding mudflats with agricultural plants may mimic floodplain wetlands once inundated and provide fish habitat and achieve habitat management objectives. However, planting success is uncertain because of unpredictable water level fluctuations that affect plant survival and growth. Decision support tools can account for uncertainty that influences decision outcomes and reduce the risk in reservoir mudflat planting decisions. We used Bayesian decision networks and sensitivity analyses to quantify uncertainty surrounding mudflat plantings as supplemental fish habitat in four northwest Mississippi reservoirs. When averaged across all uncertainty, planting was the optimal decision only in Enid Lake. Response profiles indicated planting decisions depended on elevation contours within Enid, Sardis, and Grenada reservoirs. No planting was optimal at all elevations for Arkabutla Lake. These results provide a quantified basis for establishing best management practices and identify key system states that influence decision outcomes. The process used in this study to evaluate planting decisions can be applied to any reservoir by modifying reservoir dependent inputs to evaluate planting decisions to provide supplemental fish habitat.

Geomorphology variables predict fish assemblages for forested and endorheic rivers of two continents.

Stream fishes are restricted to specific environments with appropriate habitats for feeding and reproduction. Interactions between streams and surrounding landscapes influence the availability and type of fish habitat, nutrient concentrations, suspended solids, and substrate composition. Valley width and gradient are geomorphological variables that influence the frequency and intensity that a stream interacts with the surrounding landscape. For example, in constrained valleys, canyon walls are steeply sloped and valleys are narrow, limiting the movement of water into riparian zones. Wide valleys have long, flat floodplains that are inundated with high discharge. We tested for differences in fish assemblages with geomorphology variation among stream sites. We selected rivers in similar forested and endorheic ecoregion types of the United States and Mongolia. Sites where we collected were defined as geomorphologically unique river segments (i.e., functional process zones; FPZs) using an automated ArcGIS‐based tool. This tool extracts geomorphic variables at the valley and catchment scales and uses them to cluster stream segments based on their similarity. We collected a representative fish sample from replicates of FPZs. Then, we used constrained ordinations to determine whether river geomorphology could predict fish assemblage variation. Our constrained ordination approach using geomorphology to predict fish assemblages resulted in significance using fish taxonomy and traits in several watersheds. The watersheds where constrained ordinations were not successful were next analyzed with unconstrained ordinations to examine patterns among fish taxonomy and traits with geomorphology variables. Common geomorphology variables as predictors for taxonomic fish assemblages were river gradient, valley width, and valley slope. Significant geomorphology predictors of functional traits were valley width‐to‐floor width ratio, elevation, gradient, and channel sinuosity. These results provide evidence that fish assemblages respond similarly and strongly to geomorphic variables on two continents.

Temporal stability in a protected and isolated fish community within marine parks surrounding Lord Howe Island

Remote oceanic islands often display high levels of biodiversity and endemism, making them important locations for marine parks aimed at conserving biodiversity. To determine whether marine parks are reaching conservation objectives requires consistent assessments of their effectiveness through time. Lord Howe Island and Balls Pyramid are World Heritage listed remote oceanic islands in the Tasman Sea that support a diverse assemblage of fishes including many endemic and protected species. To conserve the region’s unique marine biodiversity, state and Commonwealth marine parks including no-take zones and partially protected zones open to line fishing were established. After approximately 5, 9 and 13 years of protection of shelf habitat we tested for changes in the marine park’s fish assemblage across management zones through time using baited remote underwater video systems (BRUVs). We detected no difference in total fish abundance, diversity, or assemblage composition between management zone types. The relative abundance of targeted carangids, yellowtail kingfish and silver trevally were 2 and 1.6 times greater in no-take zones than partially protected zones respectively, however, the substantial variation in their abundances among locations and sites meant that these differences were not statistically significant. No clear difference in the relative abundance of endemic, near-endemic and protected species were observed between management zone types. Generally, the abundance and diversity of fishes varied most among locations, sites and sampling years. The overall lack of difference in the fish assemblage between management zone types and its stability through time suggests current anthropogenic threats are relatively minor, and the marine park’s condition is reasonably healthy. Future surveys of the marine park’s fish assemblage will be valuable to test for body-size differences between zone types and to monitor trends in condition, particularly in response to possible changes in the number, frequency and intensity of anthropogenic threats.

Fish assemblages associated with natural, transplanted, artificial, and accidental reefs in Puerto Rico

When accompanied with well-informed management actions, active restoration strategies such as coral gardening and deployment of artificial reef structures can help mitigate negative effects of human impact on fish assemblages associated to natural reefs. However, ecological patterns of variation of fish assemblages associated with artificial reefs are poorly understood. From mid-April 2018 to mid-June 2019, we compared fish assemblages associated to one of four types of reef structures: natural reefs (NR), transplanted reefs (TR; i.e., Acropora palmata colonies), concrete modules or restoration reefs (RR), and accidental reefs (AC; submerged docks and shipwrecks) across twelve sites around Puerto Rico. Response variables were abundance, biomass, and number of species per sample and these were correlated with environmental factors that could influence the observed patterns of spatial and temporal variation in fish assemblages. Despite natural seasonal fluctuations, differences in fish assemblages between reef types were generally greater than differences among sites, although less obvious between TR and NR. Based on these results, and on the assumption that the general aim of artificial reef deployment is to mimic natural reef function, we highlight the need for management strategies that are tailored to site-specific or reef-specific goals and needs. Our study reinforces the importance of multivariate statistics to recognize patterns of spatial and temporal variation at the smallest spatial scales, understand ecosystem function, and to improve the effectiveness of management actions concerning active restoration strategies like coral gardening and creation of artificial reef habitats.

Bycatch from seagrass fisheries: implication for conservation

Fishing activities conducted on seagrass bed to capture fishes and other seagrass associated fauna are very massive especially in the Pacific regions and undeveloped countries. This is due to the high abundance of economically important species associated to seagrasses, and additionally, seagrass area is the most accessible fishing ground throughout the year and with low capital. Seagrass meadows are importance habitat to support an abundance and diverse fish assemblages that form the basis for artisanal fisheries, which are vital in maintaining food security of coastal community in the regions. The seagrass fishery is considered a small-scale, multi-species and multi-gear fisheries. One of the fishing gear used in this fishery is traditional permanent fish trap called “sero”. Bycatch from some small-scale fisheries have been reported such as from trawls, traps, gill nets, and longline fisheries. This study aimed to identify bycatch species from “sero”, a type of seagrass fisheries which is in the form of fish fences with nets positioned on intertidal area of seagrass bed to the subtidal for approximately 200m. The result shown the bycatch from this fisheries was dominated by either low value fishes or invaluable and even toxic fishes for consumption, such as the puffers (Tetraodontidae and Diodontidae), juveniles of Apogonidae and Chaetodontidae. Additionally, sharks, turtles, and rays were also found in the bycatch. This result should be put into consideration as the bycatch would have an ecological consequences on the population, predator-prey relationship, and ecosystem resilience to stressor in general. Information from this study will be important for sustainable small-scale fisheries management and seagrass conservation, and therefore, further research into bycatch reduction in this fishery would be desirable.