Fish Assemblage Composition Research Articles

Comparing beach seine and gillnet sampling methods in fish assemblages from Southern Brazilian shallow coastal lakes

The aim of this study was to compare littoral zone fish assemblage richness, composition, dominance and size patterns between beach seine and gillnets sampling methods in coastal lakes at Tramandaí river, Southern Brazil. Monthly samples were taken in the littoral zones of six coastal shallow lakes (Itapeva, Quadros, Malvas, Fortaleza, Rondinha and Barros). Dominance and similarity analyses showed differences in species composition, numerical abundance and biomass among the sampling methods. Eleven species were dominant, but only one (Psalidodon aff. fasciatus) was dominant to both sampling methods. Beach seines sampled individuals with a total length ranging from 20 to 80 mm, while gillnets sampled individuals with a total length over 100 mm. An assemblage with high species richness, dominated by small fishes was found in the lake’s margins. In contrast, an assemblage with lower species richness comprised of larger fishes was found in inner areas. The methods are complementary in accessing species richness. Beach seine is a better alternative for monitoring programs as it provides reliable data at lower cost. These results may be useful in the sample design of future research or in the monitoring of ichthyofauna.

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.

Seafloor Terrain Shapes the Three-dimensional Nursery Value of Mangrove and Seagrass Habitats

Mangroves and seagrasses are important nurseries for many marine species, and this function is linked to the complexity and context of these habitats in coastal seascapes. It is also connected to bathymetric features that influence habitat availability, and the accessibility of refuge habitats, but the significance of terrain variation for nursery function is unknown. To test whether seafloor terrain influences nursery function, we surveyed fish assemblages from mangrove and seagrass habitats in 29 estuaries in eastern Australia with unbaited underwater cameras and quantified the surrounding three-dimensional terrain with a set of complementary surface metrics (that is, depth, aspect, curvature, slope, roughness) applied to sonar-derived bathymetric maps. Terrain metrics explained variability in assemblages in both mangroves and seagrasses, with differing effects for the entire fish assemblage and nursery species composition, and between habitats. Higher depth, plan curvature (concavity or convexity) and roughness (backscatter) were negatively correlated with abundance and diversity in mangroves and positively linked to abundance and diversity in seagrass. Mangrove nursery species (6 species) were most abundant in forests adjacent to flats with concave holes, rough substrates and low-moderate depths, whereas seagrass nursery species (3 species) were most abundant in meadows adjacent to deep channels with soft mounds and ledges. These findings indicate that seafloor terrain influences nursery function and demonstrate contrasting effects of terrain variation in mangroves and seagrass. We suggest that incorporating three-dimensional terrain into coastal conservation and restoration plans could help to improve outcomes for fisheries management, but contrasting strategies might be needed for different nursery habitats.

Composition and abundance of fish assemblage in Khor Al-Zubair lagoon, North West of Arabian Gulf

The present study describes the fish assemblages in Khor Al-Zubair lagoon which was located in North West region of Arabian Gulf. The present research was carried out from August 2012 to July 2013 by using various nets. Two environmental factors viz., temperature and salinity were measured during the study period. The total number of individuals collected was 2964. The highest number (513) was recorded in August month and the lowest number (31) was observed in January. Thirty eight species belonging to 28 families of Osteichthyes and two species of Chondrichthyes (Aetobatus narinari and Chiloseyllium grisum) were collected in the region, Mastacemblus mastacembelus and Tilapia zillii were recorded for the first time. The highest number of species (19) was recorded in September while the lowest (8) was noticed in the February month. Three species viz., Thryssa whiteheadi, Liza klunzingeri and L. subviridis formed 43.65 % of the total fish catch. The overall value of diversity index (H), Eveness (D) and Richness (J) were 2.5, 3.4 and 0.8 respectively.

Reef fish assemblages associated to new mat-forming zoantharian communities in the Canary Islands

Proliferations of zoantharians along tropical and subtropical regions are increasingly common and usually associated with anthropogenic impacts and ecosystem degradation. In the Canary Islands, we studied how the dominance in the substrate of Palythoa caribaeorum and Zoanthus pulchellus affected fish communities. For that purpose, we recorded the composition and biodiversity of fish assemblages associated to both zoantharian and macroalgae dominated habitats. In general terms, we found significant reductions of total fish abundance and richness at P. caribaeorum dominated habitats compared with macroalgae stands. However, in terms of trophic structure, there were significant changes within both zoantharian habitats depending on their coverages of the substrate. Herbivores and small invertebrate feeders, which are more adapted to forage in the macroalgae canopy, were less abundant in zoantharian habitats. This study demonstrates that the increasing dominance of zoantharians throughout the archipelago restructure the ecosystems and impact the native fish communities, that may offer a positive feedback for invasive tropical species to thrive.

Potential and limitations of applying the mean temperature approach to fossil otolith assemblages

Evaluation of the impact of climatic changes on the composition of fish assemblages requires quantitative measures that can be compared across space and time. In this respect, the mean temperature of the catch (MTC) approach has been proven to be a very useful tool for monitoring the effect of climate change on fisheries catch. Lack of baseline data and deep-time analogues, however, prevent a more comprehensive evaluation. In this study, we explore the applicability of the mean temperature approach to fossil fish faunas by using otolith assemblage data from the eastern Mediterranean and the northern Adriatic coastal environments corresponding to the last 8000 years (Holocene) and the interval 2.58–1.80 Ma B. P. (Early Pleistocene). The calculated mean temperatures of the otolith assemblage (MTO) range from 13.5 to 17.3 °C. This case study shows that the MTO can successfully capture compositional shifts in marine fish faunas based on variations in their climatic affinity driven by regional climate differences. However, the index is sensitive to methodological choices and thus requires standardized sampling. Even though theoretical and methodological issues prevent direct comparisons between MTO and MTC values, the MTO offers a useful quantitative proxy for reconstructing spatial and temporal trends in the biogeographic affinity of fossil otolith assemblages.

Global patterns and drivers of beta diversity facets of reef fish faunas

AbstractAimExploring the relationships between the different facets of beta diversity and both past and current environmental conditions can unveil the processes that have shaped spatial patterns of biodiversity. In the marine realm, large‐scale patterns and processes of beta diversity have been less investigated. Our study aimed to investigate the patterns and drivers of multiple facets of beta diversity and its components, contrasting pairs of reef fish assemblages among marine realms.LocationTropical reefs.TaxonReef fishes.MethodsBased on trait data and phylogenetic relationships for 5182 tropical reef fish species, we calculated compositional differences between pairs of reef fish assemblages across the Atlantic, the Tropical Eastern Pacific (TEP) and the Indo‐Pacific realms. We also applied a partitioning approach to distinguish between the turnover and nestedness components. We then evaluated the relative importance of several variables related to historical and contemporary environmental conditions in shaping spatial patterns of beta diversity using Constrained Analysis of Principal coordinates (CAP) models.ResultsBoth the turnover and the nestedness components contributed to total phylogenetic and taxonomic beta diversity in the TEP and Indo‐Pacific realms, while the turnover component was found to be more important in the Atlantic realm. In contrast, total trait beta diversity displayed very low values and was primarily explained by the nestedness component. Taxonomic and phylogenetic differences in the composition of tropical reef fish assemblages were influenced by both historical and contemporary factors or solely by historical variables.Main conclusionsOur results suggest that past climate changes and historical contingency left an imprint in the present‐day composition of tropical reef fish assemblages. The very low levels of trait beta diversity indicate that reef fish assemblages display similar trait composition even among geographically distant assemblages with contrasting evolutionary histories, which may result from environmental filtering or evolutionary convergence, or the combination of both processes.

Contrasted spatio-temporal changes in the demersal fish assemblages and the dominance of the environment vs fishing pressure, in the Bay of Biscay and Celtic Sea

Climate change and resource exploitation represent strong selection pressure affecting the spatio-temporal dynamics of marine assemblages that ensure food provision for humans. However, such dynamics remain poorly documented, and their drivers unclear. Here, we investigate changes in fish assemblages of two key European fishing areas, the Bay of Biscay (BoB) and the Celtic Sea (CS), during the last two decades. We quantify the relative contribution of change in energy (i.e. temperature and trophic resources), habitat (depth, substrate, oxygen) and fishing pressure to explaining observed spatial and temporal variations in fish diversity. We used long-term scientific surveys to evaluate the spatio-temporal changes in species richness (SR), abundance and composition of demersal fish (Actinopterygii) assemblages at different spatial scales combined with a range of regression models and variance partitioning. Diversity patterns showed greater variability in space than in time: SR weakly changed over time, while compositional dissimilarity showed local patterns of taxonomic homogenization in the CS and differentiation in the southern BoB, where local assemblages were becoming more similar and dissimilar over time, respectively. Energy funnelled through small pelagic species as a potential trophic link affecting the dynamics of demersal assemblages was the most important driver, while habitat and fishing pressure had limited importance. Our study revealed contrasted dynamics of demersal fish assemblages at a regional scale that were best explained by the dynamics of small pelagic species. Direct effects of environmental forcing and fishing pressure were limited in both regions which have a long history of fishing and still remain relatively buffered from global warming effects. This research paved the way to combine methods inspired by biogeography with scientific monitoring surveys to detect spatio-temporal dynamics of fish assemblages and their drivers in marine ecosystems under multiple pressures.

Multidecadal changes in the demersal community structure in an urban bay: Shift from a bottom- to a top-heavy pyramid

Fish community structures in urban bays have changed over time as a result of anthropogenic activities, leading to changes in species richness, diversity, fish assemblage composition, and abundance. Tokyo Bay is one of the most eutrophic urban bays in Japan, and hypoxia occurs every summer in the bottom water of the bay. Accordingly, the demersal community in the bay has undergone drastic changes in taxonomic composition over the past several decades. We analyzed data from a bottom trawl survey spanning 35 years to characterize multidecadal changes in the slopes of body size spectra of the demersal community in Tokyo Bay, as a reliable index to represent shifts in community structure. We found that the community shifted from bottom-heavy pyramids in the past (1977–1995) to top-heavy pyramids in recent years (2003–2019) due to a decrease in the biomass of small-sized crustaceans and an increase in the biomass of large-sized elasmobranchs. Human-induced hypoxia can promote the formation of top-heavy pyramids, as it decimates the number of small-sized individuals. The existence of energy subsidies to large-sized individuals from the inner-shallow and outer bay areas as well as the pelagic community provides a possible explanation for the persistence of top-heavy pyramids.

The effect of hierarchical environmental structure and catchment-scale land cover on fish assemblage composition in streams from the Brazilian south-eastern rain forest

The effect of hierarchical environmental structure and catchment-scale land cover on fish assemblage composition in streams from the Brazilian south-eastern rain forest

Evaluating effects of partial fishing closures on the composition and structure of estuarine fish assemblages

Partial fishing closures are an integral component of contemporary aquatic resource conservation and fisheries management. This study examined whether assemblages of fishes differed between partially closed (PC) estuaries that permit recreational fishing compared to fully fished (FF) estuaries that permit commercial and recreational fisheries. Fish assemblages were quantitatively sampled in a standard and stratified manner using a multimesh gillnet and beam trawl that sampled different ichthyofaunal components in two PC and two FF estuaries across three years, ∼ six to eight years post commercial fishing closure and PC implementation. There was no global support for the hypothesis that assemblages, diversity and numbers of fishes would differ between PC and FF estuaries. Assemblages significantly and consistently differed among individual estuaries regardless of estuary management category. Differences between PC and FF estuaries in terms of numbers of species and individuals were inconsistent across years, with more species (gillnet) and individuals (trawl) occurring in PC estuaries in only one of three years. Only one species (Gerres subfasciatus) was more abundant (gillnet) in the PC category, most likely due to reduced fishery harvests. In contrast, juveniles of three harvested species (G. subfasciatus, Rhabdosargus sarba and Acanthopagrus spp.) occurred in greater numbers (trawl) in FF estuaries, potentially a result of strong recruitment and estuary-specific environmental conditions. This study demonstrated the complexity, and potential scale-dependent ecological and fishery-related constraints, in comparatively examining the effects of different fishery management arrangements on fish assemblages across estuary systems.

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.

Freshwater fishes of the Río de la Plata: current assemblage structure

Abstract Few studies have addressed the composition of fish assemblages of the freshwater Río de la Plata (RdlP) and have only been limited to species lists gathered over the last two centuries. As such inventories have never been reviewed or validated by fish sampling, the richness and structure of RdlP fish assemblage are poorly known. Hence, we conducted an exhaustive literature review and a fieldwork in six coastal points of Argentina to update the species composition and determine the hierarchical structure of the fish assemblage. From the 206 species registered in the literature, 48 were not confirmed, 13 were absent, five were taken as synonymized species, 29 were supported by literature and 107 were confirmed; one was an established exotic species, and three were a non-established exotic species. The findings reported here suggest that the fish assemblage currently comprises 141 species, including four new records. Analysis of fieldwork data in number and weight of fish captured resulted in an assemblage hierarchical structure of five dominant, 22 frequent, and 45 rare species; 16 dominant, 11 frequent, and 45 rare taxa, respectively. These results could be used as baseline to monitor, manage, and preserve neotropical fish species in their southern distribution boundary.

Fish Composition and Diversity of Four Coral Reefs in the South China Sea Based on Hand-Line Catch

To improve the overall understanding of the fish diversity and spatial patterns of major coral reefs in the South China Sea, fish assemblage composition, dominant species, biodiversity indices, and multivariate analysis of community structure were reported for four major coral reefs based on hand-line survey data in May and September 2018. A total of five orders, 21 families, 45 genera and 121 species of fish were recorded with Perciformes (78.5%) being the most diverse. The highest number (5) of dominant species was found near Chenhang Island while the lowest (2) number was detected at Zhubi Reef. The highest abundance index (7.21) occurred at Zhubi Reef, while the Shannon–Wiener diversity (4.80), Pielou’s evenness (0.81), and Simpson’s dominance (0.95) indexes were all highest at Qiliangyu Island. Based on cluster analysis and non-metric multi-dimensional scaling (NMDS), fish communities varied more spatially than seasonally. Our results led us to hypothesize that the habitat complexity and level of anthropogenic disturbance were the main factors affecting the composition of reef-dwelling fish on each coral reef. Topography was likely responsible for most variation in the spatial pattern of fish diversity.

Evaluation of fish assemblages’ composition in the Euphrates River, southern Thi-Qar province, Iraq

Fish assemblage composition in the Euphrates River southern Thi-Qar province was assessed from January to December 2018. Various fishing methods were used to collect the samples. A total of 3010 specimens of bony fishes were caught represented 17 species, 17 genera, ten families and six orders. The species included ten native fish species and seven exotic fish species. The Abu mullet Planiliza abu was the most abundant species formed 26.21% of the total caught, blue tilapia Oreochromis aureus 19.30%, Prussian carp Carassius gibelio 17.48% and Redbelly tilapia Coptidon zillii 13. 29% of the total number of species. The dominance index (D3) value of the highest abundance represented by three fish species that preside the study area forming 62.99%, there are P. abu, O. aureus and C. gibelio. The occurrence of fish species contained seven fish species formed 92.03% of the total species caught. Seasonal fish species comprised of three fish species included 6.51% and occasional fish species contained seven species represented 1.46% of the total number of species. The diversity index values appear as poor ranged from 1.59 in December to 2.07 in April. Richness index values pointed to disturbing status, varied from 1.21 in September to 2.00 in May. Evenness index tends to be balanced, fluctuated from 0.79 in June to 0.91 in February and July. The present study verified the prevalence of the small-sized tolerance fish species represented by one native and three exotic species, with rarely or absence of the keystone native fish species of fish communities predominating the south of Iraq.

Antagonistic effects of seawalls and urban sedimentation on epilithic algal matrix (EAM)-feeding fishes

Marine urbanisation often results in the proliferation of artificial coastal defences and heavy sedimentation, adversely impacting coral reef systems in tropical coastal cities. Knowledge of how motile organisms, such as reef fish, respond to novel human-made habitats and high sedimentation is limited. Here, we examine the role of sloping granite seawalls in supporting reef fishes that utilise the epilithic algal matrix (EAM) as a food resource. We surveyed fish assemblages and feeding activities on seawalls and reef flats, and conducted a field experiment to examine the effects of sediment on EAM feeding rates. Seawalls and reef flats supported distinct fish assemblage composition with significantly greater feeding activity on seawalls. However, reduced feeding activity on EAM with elevated sediment loads suggests that urban sedimentation may limit the utility of this novel feeding ground for nearshore communities. These findings illustrate the complexities and interactive effects of anthropogenic changes driven by coastal urbanisation.

Insights on the fish assemblages of seamounts and banks in the southern Tyrrhenian Sea (western Mediterranean Sea): implications for the conservation of deep-sea environments

AbstractFish assemblages inhabiting a complex of south Tyrrhenian seamounts and banks were characterized using a remotely operated vehicle (ROV). Fish distribution was assessed through surveying 15 ROV transects. Video segments of each transect were split into two bathymetric ranges, above and below 200 m depth. In total 28 fish taxa belonging to 22 families were recorded. The number of species observed at the Marettimo Banks and the Aceste Seamount was higher compared with the Tiberio and Scuso Seamounts. The number of species recorded in the shallow part (<200 m depth) of the Marettimo Banks and the Aceste Seamount was higher than in the deeper zone (>200 m). Assemblages were numerically dominated byAnthias anthias,Callanthias ruberandHelicolenus dactylopterus. The occurrence of some elasmobranchs of conservation concern, such asSquatina aculeata,Hexanchus griseus,Squalus blainvilleandGaleus melastomus, was noteworthy. Differences in fish assemblage composition were observed between the Aceste Seamount and the other sites and especially between the two bathymetric ranges. The fish distribution pattern showed significant relationships with bottom slope and some substrate types. A large occurrence of lost fishing gear characterized the sites closest to the coast (the Marettimo Banks and the Scuso Seamount), providing, along with scanty observations of commercially important fishes, evidence of heavy fishing activities. The adoption of conservation and management actions in the investigated seamounts and banks, such as their inclusion in the Natura 2000 network, would be very helpful to protect some threatened elasmobranchs and restore valuable deep-sea habitats.

Marine fish assemblages of Eastern Brazil: An update after the world's largest mining disaster and suggestions of functional groups for biomonitoring long-lasting effects

When the Fundão dam collapsed in Brazil, 50 million m3 of iron ore tailings were released into the Doce river, resulting in the world's largest mining disaster. The contaminated mud was transported 668 km downstream of the Doce river and reached the Atlantic Ocean 17 days after the collapse. Seven months later, there was evidence that the tailings had reached the largest and richest coral reef formation in the South Atlantic Ocean. This study provides the first description of species composition, abundance, and diversity patterns of fish assemblages in estuaries, coastal areas, and coral reefs affected by the rupture of the mining dam in the Doce river. A linear mixed model (GLMM) was used to evaluate the influence of salinity on fish abundance across estuarine and coastal ecosystems. In addition, based on functional traits related to habitat use and feeding habits, this study identified fish species suitable as bioindicators of the long-lasting effects of this major mining disaster. Bottom trawls were used to sample five estuaries and their respective coastal areas, and a visual census was employed to sample five reef areas, representing an impact gradient. A total of 269 species were recorded in all three habitats, but only seven were shared among them. The results showed lower similarity in assemblages among estuarine areas compared to the coastal and reef areas. Species composition among estuaries and reef ecosystems was more heterogeneous. In contrast, coastal habitats exhibited high homogeneity. Salinity had no statistically significant effect on fish abundance either in estuaries (p = 0.22) and along the coast (p = 0.14). Twelve fish species were identified as suitable bioindicators for evaluating the long-lasting effects of resuspension of contaminated sediments. These species are commonly found in the ecosystems under the influence of the disaster inhabiting potentially contaminated substrates and substrate-associated benthic preys.

Uncharted coral reefs from the Inhambane Province, Mozambique

Mozambique has the third-largest coastline in the western Indian Ocean with a large and diverse reef area. Those reefs provide food and income for a large proportion of coastal communities but remain scarcely studied. As a baseline assessment, we sampled four uncharted shallow reefs (Baixo Africa, Baixo Zambia, Pomene and Baixo Silvia) within a 56 km stretch line from 5 to 32 meters deep. The fish abundance and assemblage composition were assessed by underwater visual census (25x2m, n = 112). The benthic community was characterized by digital images (0.5x0.5m, n = 164) and the invertebrate megafauna by direct counting (25x2m, n = 52). A total of 209 reef fish species was observed, with similar mean richness (22.4 ± 7.2 species.100 m−2) at all reefs. Invertivorous (n = 79) and planktivorous fish species (n = 36) represented 55% of species total. Trophic composition was similar among sites and with large contribution of planktivores. The presence of large shoals (>100 ind.100 m−2, e.g., surgeonfish, fusiliers, snappers) and large-bodied fishes (>90 cm) (e.g., groupers) was a clear indication of local productivity and health conditions of reefs. Seventy-nine taxa were observed on the benthic cover with the largest richness found at Baixo Silvia (28.5 ± 7.4, species.100m −2, mean ± SD). Turf algae dominated the benthos (31.5% ± 16.4) at all sampled reefs. Coral cover was variable between sites (9.3 – 25.8%), dominated by branching and plate corals, and <1% of colonies showed signs of diseases/bleaching. The baseline assessment indicated large biomass of fishes and negligible evidence of large impacts on coral formations which indicated a good conservation status of those areas. Based on these findings, a marine protected area is proposed for establishment in collaboration with environmental authorities and the local community.

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.