Differences In Fish Assemblages Research Articles

Biofouling sponges as natural eDNA samplers for marine vertebrate biodiversity monitoring

Environmental DNA (eDNA) analysis has now become a core approach in marine biodiversity research, which typically involves the collection of water or sediment samples. Yet, recently, filter-feeding organisms have received much attention for their potential role as natural eDNA samplers. While the indiscriminate use of living organisms as ‘sampling tools’ might in some cases raise conservation concerns, there are instances in which highly abundant sessile organisms may become a nuisance as biofouling on artificial marine structures. Here we demonstrate how a sea sponge species that colonizes the moorings of the world's largest curtain of hydroacoustic receivers can become a powerful natural collector of fish biodiversity information. By sequencing eDNA extracted from Vazella pourtalesii retrieved from moorings during routine biofouling maintenance, we detected 23 species of marine fish and mammals, compared to 19 and 15 species revealed by surface and bottom water eDNA respectively, and 28 species captured by groundfish survey in the surrounding area, which are more ecologically impactful and involve higher additional costs. Sponge-based species inventories proved at least as informative as those obtained by traditional survey methods, and are also able to detect seasonal differences in fish assemblages. We conclude that opportunistic sampling of marine sponge biofouling may become an efficient way to document and monitor biodiversity in our rapidly changing oceans.

Freshwater fish diversity and IUCN Red List status of glacial-fed (Bheri) and spring-fed (Babai) rivers in the wake of inter-basin water transfer

Freshwater fish are crucial components of aquatic ecosystems that are affected by a range of anthropogenic activities. Freshwater bodies in Nepal are under different threats affecting biodiversity. Inter-basin water transfer (IBWT) involving damming and diversion of water from one river basin to another is considered a major threat to aquatic biodiversity. Impact assessment of such projects include generation of baseline information on different biotic and abiotic variables. The aim of this study was to generate baseline information on fish diversity from the glacial-fed (Bheri) and the spring-fed (Babai) rivers and their selected tributaries from western Nepal in the wake of the first proposed inter-basin water transfer from the former to the latter. A total of 10 sampling sites, five each from Bheri and Babai River systems, were chosen strategically. Electrofishing was conducted encompassing different seasons in 2018 following the standard method. A total of 32 species with catch per unit effort (CPUE) of 47±24 from Bheri and 42 species with CPUE of 63±52 from Babai River were recorded. Cyprinidae, followed by Nemacheilidae, were the most dominant families in both river systems, and Barilius vagra and Schistura beavani were the most dominant species in both. Species richness and abundance showed a significant difference between rivers, and differences in fish assemblages reflects differences in ecological regimes. Failure to observe migratory species such as Anguilla bengalensis suggests that migratory routes may already have been affected. Of the total 52 species recorded, eight are in the threatened categories of the IUCN Red List and need active conservation measures. The findings provide a reference to assess the impacts of water transfers on fish assemblages in these river systems.

Assessment of the floodplain fishery of Tonle Sap Lake in Cambodia

AbstractAcross the globe, fish stocks have been in decline due to industrialization of fisheries resources, overfishing, pollution, and climate change, thereby warranting more fisheries assessments. The floodplain fishery of Tonle Sap Lake near the Kampong Khleang stilted community in the Chamkar Youn village in Cambodia was evaluated by: (1) characterizing fish assemblage structure and function, (2) highlighting temporal differences in fish assemblage, and (3) assessing potential indicators of fishing‐down‐the‐food‐web by the fishery. Fish trap data from the wet season were used to characterize fish abundance, diversity, species richness, and functional feeding guilds from fish catches in 2014 and 2019. Fish abundance declined 62% and species richness declined between 2014 and 2019. Smaller‐bodied, lower‐trophic level fishes dominated the catch. Our limited findings add insight into the status of a globally important fishery and highlight the need for more local collaborative fishery assessments.

Diel and Seasonal Changes in the Abundance and Diversity of the Infralittoral Fish Community in the Eastern Central Adriatic

The fish species undergo diel and seasonal changes in coastal (littoral) ocean zones. Many factors affect these seasonal and diel patterns, thus it is difficult to determine which are the most important. Concerning the Adriatic Sea, studies on the temporal changes of fish communities are rare. Therefore, the primary aim of this study was to evaluate, in terms of abundance, diversity and species composition, the diel and seasonal changes in a one-year cycle of the fish community living in the infralittoral zone of the Eastern Central Adriatic and the main drivers affecting them. This study revealed the presence of a very rich and diverse community in the coastal zone of the Eastern Central Adriatic with a total of 63 identified fish species. The results showed that the differences in fish assemblage were more strongly influenced by seasonal variations rather than diurnal variations. The primary environmental factor that drives fish to undertake seasonal variations is water temperature. Considering that many species are important commercial species, especially for small scale fisheries, and taking into account future climate-driven changes that would affect the seasonality of the target species, it is essential that future management will be tailored accordingly and in due time.

Spatiotemporal Variability in Fish Assemblages in a Coastal and Estuarine System in the Tropical Eastern Pacific during the Anthropause

Differences in fish assemblages’ composition and their relationship with the environmental variables were analyzed in the Urías estuarine system, Mexican North Pacific. Environmental variables and fish catches were recorded bimonthly between June 2018 and November 2021, including a period before and during the COVID-19 pandemic. Multivariate analyses were performed in the studied area to define zones based on their environmental, biotic, and abiotic characteristics and the effect of these on the fish assemblages. Two zones were identified, an estuarine with mangrove forest and a surf zone in the coastal area outside the estuarine system. Fish composition, biomass, and diversity (α and β) were evaluated among the factors of the period (before–during COVID-19), climatic seasons, and zones. A total of 5947 fish individuals of 41 species were collected using beach seines as fishing gear. The structure of the fish assemblages was different between zones and periods. Abiotic (temperature, salinity, and total matter suspended), biotic (mangrove area), and temporal (season and period before–during COVID-19) variables had an effect on fish biomass and α diversity, while the results of the β diversity only indicate changes in the nestedness component before–during the lockdown. These results indicate a change in fish assemblages’ structure and composition between periods, which might be a consequence of the limitation of human activities derived from the pandemic, climatic changes, or a combination of both effects. Our results show that fish assemblages in the estuarine systems of the Tropical Eastern Pacific are unique, and there is a need to establish local management strategies for these ecosystems.

Benthic Fish Communities Associated with Posidonia oceanica Beds May Reveal the Fishing Impact and Effectiveness of Marine Protected Areas: Two Case Studies in the Southern Tyrrhenian Sea

The effectiveness of a Marine Protected Area (MPA) is strongly related to its zoning design, management, and surveillance, and fish communities are considered indicators of conservation effects. Posidonia oceanica beds and fish assemblages were studied here to evaluate the fishing impacts and the effectiveness of the Marine Protected Areas (MPAs) of Santa Maria di Castellabate (SMC) and Costa degli Infreschi e della Masseta (CIM) in the South Tyrrhenian Sea, Italy. P. oceanica characteristics were estimated counting and collecting shoots, while fish communities were investigated by visual census. Multivariate analyses were performed to detect differences in fish assemblages among the MPA protection levels and seagrass characteristics. Significant differences in fish communities were observed between the depth and protection levels. The latter are probably due to the zoning design at SMC, which does not allow a spillover effect, and to fishing activities, as showed by the ABC curve results. Trophic analyses suggested the use of longlines at SMC, due to the dominance of planktivorous fish species, and of trammel nets at CIM, due to the great heterogeneity of the fish trophic groups. Shoot density and leaf length were significantly correlated with fish communities. CCA analyses showed omnivorous species, mostly belonging to the Sparidae family, correlated with the highest shoot densities, with their feeding habits mostly directed to crustaceans, while macro- and microinvertivores, mainly belonging to the Serranidae and Labridae families, correlated with the highest leaf lengths, where they sough shelter and feed. In conclusion, the data suggest that a zoning redesign at SMC and an increase in the surveillance of fishing activities at CIM might enhance the effectiveness of these MPAs, highlighting the role of fish community studies in identifying MPA efficiency issues and providing trustful guidelines for their management.

A comparative analysis of sampling methodologies for assessing abundance and distribution of young-of-the-year groundfishes in nearshore soft-sediment habitats

Groundfishes are important species for commercial, recreational, and tribal fisheries along the Pacific Coast of the United States. Understanding the abundance and distribution of these fishes is necessary for successful fisheries management. Many groundfish species spend at least part of their life cycle in nearshore habitats. However, assessing groundfish species assemblages in nearshore habitats can be limited by the relatively small size of young-of-the-year and subadult life history stages, which may not be quantitatively retained with traditional survey gears. In addition, portions of the innermost nearshore (<55 m water depth) can be inaccessible to vessels employed in trawl surveys. To help improve the fishery-independent data informing the current understanding of nearshore assemblages, we compared catches resulting from two different but spatially overlapping surveys. One is the National Oceanic and Atmospheric Administration’s (NOAA) West Coast Groundfish Bottom Trawl Survey (WCGBTS), which is representative of a typical groundfish survey in USA and EU continental shelf habitats. The other is an ad-hoc beam trawl survey along the Newport Hydrographic (NH) Line – an oceanographically well-monitored sampling line off the Pacific Coast. Our objectives were to evaluate the representativeness of nearshore fish communities in the WCGBTS and to assess if additional nearshore sampling would enhance the WCGBTS. For the purposes of this study, “nearshore” is defined as the continental shelf shoreward of 200 m depth. Examining fish catches and environmental variables from both surveys, we found significant differences in fish assemblages, oxygen, temperature, and salinity based on depth, season, year, and survey type. The WCGBTS is designed and well-suited for sampling subadult and adult groundfishes in trawlable habitat. However, year-round sampling of the beam trawl survey allows it to capture ephemeral environmental conditions better than the WCGBTS. The gear type and sampling location make the beam trawl survey better suited than the WCGBTS for sampling smaller individuals and species that live at shallower depths. The beam trawl survey caught 69 unique species or taxa groups within the comparative data subset, whereas the WCGBTS caught 83. The three most commonly occurring species in the beam trawl survey were Pacific sanddab (Citharichthys sordidus), English sole (Parophrys vetulus), and speckled sanddab (Citharichthys stigmaeus), while the WCGBTS most commonly caught rex sole (Glyptocephalus zachirus), Dover sole (Microstomus pacificus), and spotted ratfish (Hydrolagus colliei). Of the fish with measured lengths, the catch from the beam trawl survey had a mode standard length of 2 cm, contrasted with the mode length (total length, fork length, anal length, and natural length combined) of 22 cm for the WCGBTS. We found that there is a transition in species assemblages right where the WCGBTS ends (about 55 m). Thus, while the surveys overlap in some capabilities, this analysis shows that the beam trawl survey or a similar nearshore survey would complement the WCGBTS, providing an enhanced characterization of groundfish assemblages.

A comparison of fish communities between coves of varying connection to Harlan County Reservoir, Nebraska

Sediment berms of various heights have developed in the mouths of several coves within Harlan County Reservoir due to a combination of sediment deposition and lateral drift of eroded sediments. These berms can isolate coves from the main reservoir if the berm height is greater than the water elevation of the reservoir. Previous research in other reservoirs has shown that fish communities may differ in coves based on their connection histories. This study examines similarities and differences in fish assemblages between several disconnected coves and connected coves in Harlan County Reservoir. Connected coves had greater species richness and diversity compared to disconnected coves. Fish communities between cove types were relatively similar based on presence-absence data but notably different based on species abundance. Nonmetric multidimensional scaling ordination showed that fish communities were distinct between cove types. Eleven fish species were indicators of connected coves, and two species were indicators of disconnected coves. Disconnected coves had higher abundances of understudied native species rarely found in the main reservoir, such as Orangespotted Sunfish, Green Sunfish and Black Bullhead. Further research evaluating the influence of water quality, food availability, and duration of isolation is needed to understand the effect of cove disconnection on fish communities. Managers can use this information when planning cove renovations by weighing the costs and benefits of either maintaining ecologically distinct coves versus connecting coves and improving habitat accessibility for reservoir fishes.

Assessing the Spatiotemporal Relationship between Coastal Habitats and Fish Assemblages at Two Neotropical Estuaries of the Mexican Pacific

Differences in fish assemblages’ structures and their relations with environmental variables (due to the variations in sampled seasons, habitats, and zones) were analyzed in two adjacent estuaries on the north Pacific coast of Mexico. Environmental variables and fish catches were registered monthly between August 2018 and October 2020. Multivariate analyses were conducted to define habitats and zones based on their environmental characteristics, and the effect of this variability on fish assemblages’ composition, biomass, and diversity (α and β) was evaluated. A total of 12,008 fish individuals of 143 species were collected using different fishing nets. Multivariate analyses indicated that fish assemblages’ structures were different between zones due to the presence, height, and coverage of distinct mangrove species. Additionally, depth and salinity showed effects on fish assemblages’ diversity (α and β-nestedness), which presented higher values in the ocean and remained similar in the rest of the analyzed zones and habitats. These results and the differences in species replacement (β-turnover) indicate the singularity of fish assemblages at estuaries (even in areas close to the ocean) and the necessity to establish local management strategies for these ecosystems.

Fish diversity reduction and assemblage structure homogenization in lakes: A case study on unselective fishing in China

Unselective fishing involves activities that target the entire assemblage rather than specific fish species, size classes, or trophic levels. This common fishing approach has been in practice for decades in inland waters in China but its implications for biodiversity remain unclear. We addressed this issue by studying fish assemblages in freshwater lakes (five fishing lakes, one reference lake, and a total of 51 sampling sites) between pre- and post-fishing time-periods in Eastern China during 2017–2019. The effects of lake, fishing period, and their interactions on fish abundance, biomass, and diversity indices were assessed. Multivariate analysis was conducted to test for differences in fish assemblages among lakes and between fishing periods. After the implementation of fishing activities, significant reductions in fish species richness, abundance, biomass, and all three life-history strategies (opportunistic, equilibrium, and periodic) were observed in fishing lakes, whereas opposite trends were observed in the reference lake. Compositional similarity of fish assemblages among fishing lakes increased over the three-year monitoring period. Our results suggest that unselective fishing reduces fish diversity and homogenizes fish assemblage structure in lakes. These findings have important implications for protecting both biodiversity and fisheries in inland waters in China and are applicable to other countries or regions that rely on fish as a major food source.

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.

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.

Will fencing floodplain and riverine wetlands from feral pig damage conserve fish community values?

Installation of feral pig (Sus scrofa) exclusion fences to conserve and rehabilitate coastal floodplain habitat for fish production and water quality services remains untested. Twenty‐one floodplain and riverine wetlands in the Archer River catchment (north Queensland) were surveyed during postwet (June–August) and late‐dry season (November–December) in 2016, 2017, and 2018, using a fyke net soaked overnight (~14–15 hr) to test: (a) whether the fish assemblage are similar in wetlands with and without fences; and (b) whether specific environmental conditions influence fish composition between fenced and unfenced wetlands. A total of 6,353 fish representing twenty‐six species from 15 families were captured. There were no wetland differences in fish assemblages across seasons, years and for fenced and unfenced (PERMANOVA, Pseudo‐F < 0.589, p < .84). Interestingly, the late‐dry season fish were far smaller compared to postwet season fish: a strategy presumably in place to maximize rapid disposal following rain and floodplain connectivity. In each wetland, a calibrated Hydrolab was deployed (between 2 and4 days, with 20 min logging) in the epilimnion (0.2 m) and revealed distinct diel water quality cycling of temperature, dissolved oxygen and pH (conductivity represented freshwater wetlands), which was more obvious in the late‐dry season survey because of extreme summer conditions. Water quality varied among wetlands in terms of the daily amplitude and extent of daily photosynthesis recovery, which highlights the need to consider local conditions and that applying general assumptions around water quality conditions for these types of wetlands is problematic for managers. Though many fish access wetlands during wet season connection, the seasonal effect of reduced water level conditions seems more overimprovised when compared to whether fences are installed, as all wetlands supported few, juvenile, or no fish species because they had dried completely regardless of the presence of fences.

A New Method for Standardizing Inland Fish Community Surveys: Characterizing Habitat Associated with Small-Bodied Fish Species, Abundance, and Size Distributions in a Highly Modified Estuary

Monitoring fish assemblages in estuary environments is often difficult to standardize due to habitat complexity and gear-specific selectivity. This is further compounded by conventional sampling methods which require fish handling that might cause stress or mortality. To ameliorate these issues, we developed the Single-Platform Aquatic Species and Habitat Sampling System (Platform), an integrated and mobile concentrator net and live box prototype, coupled with a range of physical monitoring equipment. The long-term goal of the Platform is to employ non-invasive sampling techniques such as video and eDNA; however, our aim in this study was to test the Platform’s ability to sample across different habitat types and detect differences in fish assemblages. We investigated the utility of the Platform over a short time period (2 mo) in a relatively small and complex embayment within the highly modified San Francisco Estuary, California. We were able to identify clear physical distinctions among estuary/delta habitat types and detect habitat segregation by ecological groups of sampled fishes with the Platform. The Platform also detected discernable ontogenetic shifts (i.e., size differences) within estuary habitats of commonly observed fish species. These initial results demonstrate the Platform’s ability to contrast fish density, size, and species diversity, which sets the stage to advance more passive monitoring techniques, including video and eDNA methods. The Platform has the potential to fill a methodological gap in non-invasive surveying of small-bodied fish across a range of estuarine habitats, warranting further investigation of potential applications.

Freshwater reserves for fisheries conservation and enhancement of a widespread migratory fish

AbstractAs management tools, freshwater reserves are under‐represented in protected area networks for fisheries conservation and enhancement. This is surprising considering that freshwater ecosystems, and the biodiversity they support, are among the most threatened worldwide.We compared freshwater reserve types established to prevent overexploitation of migratory galaxiids (mostly īnangaGalaxias maculatus) from fishing and evaluated their performance as reproductive reservoirs. We studied 10 streams classified into three a priori types: (a) closed, (b) partially closed and (c) open streams.Closed streams had greater abundances, biomasses and egg production ofG. maculatusdespite having a greater proportion of smaller fish compared to partially closed and open streams. Community‐level analyses indicated differences in fish assemblages between closure types. Large, native, predatory fish (longfin eelAnguilla dieffenbachii, shortfin eelAnguilla australisand giant kōkopuGalaxias argenteus) were more common in closed streams.Overall, there were notable reserve effects related to closed streams. There was slight evidence that partially closed streams conferred some fisheries benefits compared to streams open to fishing. While the limited number of reserve streams warrants some caution in conclusions, partial closures may still be worthwhile as a management tool where complete closure to fishing is not feasible.Closures can be effective in increasing fish numbers, albeit at a cost of smaller sized individuals, most likely because of density‐dependent processes relating to food and habitat. Despite clear benefits in total egg production of populations in closed streams, it remains unclear how these benefits may translate across the full life history of the annualG. maculatus.Synthesis and applications. We demonstrate that freshwater reserves have many of the ‘reserve effects’ observed in more common marine reserves, but there are also important differences. Stream closure should be considered as one potential management tool that is unlikely to be effective unless stream habitats are returned to more pristine states. Our effort to evaluate the explicit effects of different reserve types across different spatial scales is the first we know of for migratory freshwater fishes, providing useful insights for adjusting the current reserve network and establishing new reserves.

A coherent, representative, and bioregional marine reserve network shows consistent change in rocky reef fish assemblages

AbstractWorldwide, several countries have established coherent, representative, and large‐scale networks of marine reserves to conserve biodiversity. Very few have, however, published systematic assessments of the ecological responses to this network protection, hindering broad understanding of their generality, utility, and efficacy. We present data collected from systematic sampling of rocky reef fish assemblages at sites across a network of 27 no‐take marine reserve areas (NTMR) and 27 partially protected areas (PPA) nested within multiple marine parks (regional networks) across three Australian bioregions spanning &gt;1000 km of coastline (7° latitude) to test the generality of ecological change across this network. We also sampled 18 reference areas (outside of the marine parks) to provide an independent assessment of potential NTMR effects and also to assess whole marine park effects. Baited remote underwater video (BRUV) was used to sample fishes between depths of 20–40 m over austral winters in four years (2010, 2011, 2015, and 2016). Despite substantial bioregional differences in fish assemblages, large and consistent effects of NTMR protection were detected across all bioregions for a key commercially and recreationally harvested species, Chrysophrys auratus (pink snapper). There were substantial increases in relative abundance of C. auratus in NTMR compared with fished zones through time (effect sizes &gt;150%). The wider assemblage of targeted fish (excluding C. auratus) only showed relatively small effects of protection (~11%) with trends observed for site‐attached wrasses (labrids) and planktivores (e.g., commercially fished Scorpis lineolata) that are recreationally and commercially harvested. Furthermore, the relative abundance of non‐target or by‐catch species generally did not differ among management zones across the bioregional network. These results highlight how NTMR can be used to assess the ecological effects of fishing and wider environmental management, and can be incorporated into ecosystem‐based management for reef species more generally. Importantly, the provision of robust evidence of the performance and generality of NTMR over large‐spatial scales (e.g., bioregions) provides greater confidence in the expected outcomes from marine reserve networks as a conservation management approach.

Changes in Fish Assemblages after Dike Construction in the Saemangeum Area

In the Saemangeum area, construction of a dike began in 1991 and was completed in 2006; desalination is currently being conducted. In order to investigate the influence of dike construction on fish assemblages, we analyzed the changes in fish assemblages using fish monitoring data accumulated before, during, and after construction of the Saemangeum Dike. Analysis of changes in the salinity of the Saemangeum Reservoir between 1997 and 2014 revealed that the overall salinity decreased, and this pattern became evident after completion of the dike. Long-term changes in fish assemblages were also confirmed in freshwater areas (Mankyeong and Dongjin Rivers) and the Saemangeum Reservoir. In freshwater areas, different fish assemblages were collected before and after dike construction according to NMDS analysis, and the proportion of freshwater fish continuously increased during analysis of ecological types. In the Saemangeum Reservoir, differences in fish assemblages were observed before, during, and after dike construction (PERMANOVA, F = 2.5325, P = 0.017). Moreover, the numbers of families and species decreased during dike construction; in terms of species composition, the proportion of brackish water fish increased, while that of marine fish decreased. Currently, a salinity gradient exists in the Saemangeum area between the rivers and the dike, and the M1-3 and D1-3 sites were classified as freshwater sites. Desalination is expected to increase freshwater areas in the future; as the change will happen over a very long period of time, differentiated management plans for each site of the Saemangeum area should be implemented through continuous monitoring.

STREAM FISH IN THE ARIPUANÃ RIVER UPSTREAM AND DOWNSTREAM OF THE DARDANELOS-ANDORINHAS WATERFALL COMPLEX, STATE OF MATO GROSSO, BRAZIL

The Aripuana River basin is part of one of the most biodiverse hydrographic basins on the planet; however, the lack of information on fish diversity in the basin is notable, particularly upstream to the Dardanelos and Andorinhas waterfalls complex. For this study, we sampled 50 m stretches of 71 streams in the Aripuana River basin, upstream and downstream of the Dardanelos and Andorinhas waterfalls complex. Sampling occurred in the drought period in 2013 and 2014. A total of 11,334 specimens were capture, belonging to five orders, 21 families and 80 species. Among the 80 species, 71 were caught in the downstream and 45 in the upstream region. Overall, there were 36 species in both upstream and downstream samples, 35 exclusive to the downstream segment, and nine were restricted to the upstream region. Despite the low levels of current knowledge, at least 15 endemic fish species could be present in the Aripuana River basin, and four from these 15 species were sampled in this study. Dardanelos and Andorinhas waterfalls complex are important barriers and we found significant differences in fish assemblage between upstream and downstream regions.

The influence of protection and temperature on subtropical reef fish assemblages in Cape Byron Marine Park

Abstract Diver‐held video transect surveys at a subtropical reef complex in eastern Australia documented a significant difference in the fish assemblages eight years after the area was closed to fishing. Average sea temperatures at depth were 1–3°C warmer during the second survey period, and autumn averaged 5–6°C warmer than spring. Large differences in fish assemblages between the seasons in 2006 were not observed in subsequent 2014 surveys. Rather than any general shift towards greater topicalisation of the assemblage in warmer conditions, the difference between the assemblage sampled in the coldest sample period and the three warmer periods was a lower frequency of occurrence of both tropical and non-tropical species and decreased asymptotic species richness. Species that were otherwise rare, which consisted of a higher proportion of tropical species, were more likely to be absent in colder conditions. This was particularly so at the deepest and coldest location. Therefore, in this region warmer waters tend to increase the richness and abundance of most fish, but particularly rare tropical species. Protection from fishing since 2005 also contributed to the inter‐year differences with increased abundance of most fishery‐targeted species regardless of climatic affinities in 2014.

Contrasting distribution and foraging patterns of herbivorous and detritivorous fishes across multiple habitats in a tropical seascape

Understanding drivers behind patterns of functionally important groups of fishes is crucial for successful management and conservation of tropical seascapes. Herbivorous fishes are the most prominent consumers of marine primary production which can have profound effects on reef resilience. We explored environmental variables affecting distribution and foraging patterns of herbivorous and detritivorous fish assemblages (siganids, acanthurids and parrotfish) across distinct shallow-water habitats (coral reefs, macroalgae beds and seagrass meadows) during September–November 2016 at Mafia Island, Tanzania (8°00′S, 39°41′E). We performed underwater visual census to quantify fish assemblages, measured habitat features, deployed macroalgal assays and conducted inventories of grazing scars. Multi-dimensional scaling and mixed-effects linear models were used to evaluate differences in fish assemblages and environmental variables influencing abundance and foraging patterns of fishes. Fish communities of focal functional groups differed among habitats. Abundance of herbivores and detritivores as well as relative browsing and scraping was highest on coral reefs compared to macroalgae and seagrass meadows. Adult fish were more abundant on coral reefs while juveniles were abundant in macroalgal beds. Coral cover and crustose coralline algal cover had a positive effect on the abundance of fish in coral reef areas, while macroalgal cover had a negative effect. Contrastingly, in macroalgae habitats, macroalgal cover had a positive effect on the abundance of parrotfish. These results highlight the importance of considering connectivity between macroalgal beds and coral reefs through ontogenetic shifts in habitat use by primarily microphagous parrotfish and of incorporating a range of habitats within coastal management plans.