Stereo Baited Remote Underwater Video Research Articles

Uso de los Sistemas de Vídeo Estereoscópico Submarino Remoto pelágicos (stereo-BRUV) para el estudio de las tortugas marinas en aguas atlánticas

The pelagic oceanic zone is one of the largest ecosystems on the planet, which is exposed to different anthropogenic pressures. In order to study and promote biodiversity conservation measures on these ecosystems, it is necessary to know the distribution of the species, the use of the habitat, the degree of connectivity and the status of populations. Carrying out such monitoring for pelagic and migratory species is complicated due to the fact that their distribution is not homogeneous and they can be widely distributed in different habitats, as is the case of sea turtles. In recent years, Baited Remote Underwater Stereo-Video (BRUVS) have become a popular tool to assess in a non-intrusive way. This innovative technique can provide us with important new information, in particular for the conservation of sea turtle populations by providing strategic knowledge about areas that have not been thoroughly studied, such as feeding areas and migration corridors in pelagic-coastal zones.

Identifying the drivers of silky shark distribution and an evaluation of protection measures

The silky shark (Carcharhinus falciformis) has experienced a significant population decline associated with intense targeted and incidental fishing pressure. Large marine protected areas (MPAs) are increasingly advocated for the conservation of oceanic species like silky sharks, recognising that the benefits of MPAs to such species depend on a comprehensive understanding of their distribution, abundance and life history. We combined mid-water stereo-baited remote underwater video system (BRUVS) records with environmental, geographic and anthropogenic variables to document the distribution and abundance of silky shark populations, identify the most important predictors of their presence, abundance and body size, and determine if their abundance is greater within MPAs than in locations not designated as MPAs. From 1418 deployments of mid-water BRUVS across three ocean basins, 945 silky sharks were identified at 18 locations, with young-of-year (< 87 cm TL) observed at four of these. Our study revealed generally low abundances of silky sharks as recorded on mid-water BRUVS across their cosmopolitan distribution, although our models identified seamounts as hotspots of abundance. Human pressure was a significant variable within our models, with proximity to human populations and ports being key drivers of silky shark abundance and body size. We did not observe a higher abundance of silky sharks inside MPAs compared to locations not designated as MPAs, suggesting that these MPAs have not been placed in areas where silky sharks remain relatively abundant. We therefore recommend expanding the current MPA network in line with the 30 × 30 initiative to more effectively protect key habitats such as seamounts.

Functional vulnerability and biogeography of reef fish assemblages in the Galapagos Archipelago

The Galapagos archipelago's unique reef biodiversity and fish distribution patterns are well documented. However, reef ecosystem vulnerability to losing functional diversity and the biogeographical drivers of community functional diversity are undescribed. The functional diversity and vulnerability of coastal reef fish communities in the Galapagos were investigated using Baited Remote Underwater Stereo-Video systems (stereo-BRUVs). Relative abundance data for 41,594 individual fish belonging to 121 species was collected, 87 functional entities were identified, and functional diversity and vulnerability estimated based on five functional traits. The influence of spatial and environmental variability and human impact on functional entity composition and richness were also assessed.Galapagos reef fish communities have a high vulnerability to reduced functional diversity if species are lost due to the low redundancy and high sensitivity of reef fish functional entities. However, there may be some ecosystem resilience against species loss from species filling ecologically similar niches instead of redundant species filling the same niche. The functional trait structure and vulnerability of Galapagos reef fish assemblages reflect the known trophic structure of the marine food web. Most functional entities with resilience from redundancy include upper trophic level species with piscivorous diets. Most functional entities that are sensitive and represented by only one species include lower trophic level species. Spatial variables relating to marine environmental variation (from tropical to temperate reef ecosystems) and benthic habitat bottom incline were important predictors of reef fish functional entity distribution. Functional vulnerability may be a concern in marine ecosystems where functional diversity is low, including at higher southern latitudes and western longitudes, the cooler temperate regions and topographically simple marine habitats. Our study raises concerns about the long-term functioning of Galapagos marine ecosystems under present climate change and human management scenarios. We suggest grouping species by functional traits for consideration in the future marine management of Galapagos marine communities.

Conservation benefits of a marine protected area on South African chondrichthyans

Chondrichthyans are threatened worldwide due to their life-history traits combined with a plethora of anthropogenic impacts that are causing populations to collapse. Marine Protected Areas (MPAs) are a conservation option, but their efficacy for chondrichthyans is still unclear. Conservation efforts might be challenging especially in developing countries, due to a lack of resources and monitoring and limited data and stakeholder support. Here Baited Remote Underwater Stereo-Video systems (stereo-BRUVs) were deployed inside and outside a small partially protected MPA (Robberg MPA, Western Cape, South Africa) to assess the status of cartilaginous fishes’ assemblages and to investigate the potential benefits derived from the presence of a marine reserve. Overall, 19 chondrichthyan species in 11 different families were observed. Chondrichthyans were observed in 78.5% of the sites and, of these, 89.7% of the MPA sites showed at least one chondrichthyan, while only in the 67.5% of surrounding exploited sites a cartilaginous fish was sighted. The presence of the MPA had a significant effect on the relative abundance of batoids, threatened species and local endemics, with more observations inside the MPA than outside, indicating the potential benefit of marine reserves on species that are more vulnerable to fishing pressure. Relative abundance was generally higher inside the bay than in the exposed area, and both relative abundance and species richness decreased significantly with depth. The analysis of the body length showed that the 35.5% of species had an average body length below maturity length, indicating that the area might be used as nursery ground for different species. This study provides evidence that MPAs, even though small and partially protected, can provide benefits for chondrichthyans, specifically to threatened species, endemic species and lesser-known species. Importantly, different environmental parameters must be considered to maximize the benefits an MPA can provide.

Habitat and Marine Reserve Status Drive Reef Fish Biomass and Functional Diversity in the Largest South Atlantic Coral Reef System (Abrolhos, Brazil)

The effects of fishing have been documented across coral reefs worldwide. No-take marine reserves do not only act as a conservation tool but also allow an opportunity to study impacts of fishing, by acting as control sites. In addition, well-planned and well-managed no-take marine reserves (NTRs) provide conservation benefits that are essential to marine biodiversity and ecosystem-based management. The Abrolhos Marine National Park, off the tropical Brazilian coast, protects part of the largest coral reef system in the South Atlantic. To investigate the effects of fishing on reef fish richness, abundance, biomass, and functional diversity of the fish assemblage, we compared sites across two protection levels considering the variation in habitats (Fringing Reefs—Protected; Pinnacles Reefs—Protected; and Coastal Reefs—Open Access), using Baited Remote Underwater Stereo-Video systems (stereo-BRUVs). We adjusted generalized additive mixed models of fish assemblage characteristics with protection levels and environmental variables, such as topographic complexity (mean relief and relief variation), visibility, and benthic cover percentage. Inside NTRs, we found higher total biomass and biomass of fishery target species and carnivores, specifically for the Carcharhinidae (sharks) and Epinephelidae (groupers) families, indicating direct fisheries effects on these groups. In contrast, the ecological parameters of non-target fish were positively correlated with habitat characteristics, including mean relief and variance of relief. Moreover, fish functional diversity was higher within NTRs, demonstrating an even distribution of functional entities. The presence of large mobile predators and the overall higher biomass of carnivores inside the NTR indicate the effect of fishing exclusion. Our results point to the value of NTRs to study the effects of fishing and achieve biodiversity conservation and suggest the importance of using remote sampling methods to assess large mobile predators.

Ecological Links between Pelagic and Mesophotic Reef Fishes in an Oceanic Archipelago of the Equatorial Atlantic Ocean

Geographic isolation, a relatively low species richness and high endemism make oceanic islands excellent natural laboratories for ecological and evolutionary studies. Here we used Baited Remote Underwater stereo-Video systems (stereo-BRUVS) to investigate the taxonomic, trophic and size structures of fish assemblages from pelagic and mesophotic reef ecosystems in the smallest archipelago of the equatorial Atlantic Ocean, the Saint Peter and Saint Paul’s Archipelago (SPSPA). The occurrence of steep reef walls favors studies on the ecological connections between pelagic and reef ecosystems. We performed five pelagic stereo-BRUVS deployments and fourteen benthic stereo-BRUVS deployments, totaling 1440 min of footage. We recorded 14 species from eight families in the pelagic ecosystem, with Carangidae and Balistidae as the most diverse families. The most abundant species were Elagatis bipinnulata (Quoy and Gaimard, 1825), Melichthys niger (Bloch, 1786), and Caranx crysos (Mitchill, 1815), which together accounted for over 75% of the total relative abundance. The carnivores were the most diverse and abundant trophic group. On the mesophotic reefs, 41 taxa were recorded, with carnivores and planktivores being the most diverse, whereas omnivores were the most abundant. Here, the most abundant species were M. niger, Azurina multileneata, Chromis vanbebberae, Seriola rivoliana, Caranx lugubris and Stegastes sanctipauli. Nine species were recorded in both ecosystems, with Melichthys niger, Caranx lugubris and S. rivoliana being the main species linking them (i.e., occurring in both). These species are known to forage in both pelagic and mesophotic reef ecosystems, and thus represent potential ecological links between them. Such links combined with the endangered status of some species, suggest the need for an integrated management strategy in this remote archipelago.

Depth and benthic habitat influence shallow and mesophotic predatory fishes on a remote, high-latitude coral reef

Predatory fishes on coral reefs continue to decline globally despite playing key roles in ecosystem functioning. Remote atolls and platform reefs provide potential refugia for predator populations, but quantitative information on their spatial distribution is required to establish accurate baselines for ongoing monitoring and conservation management. Current knowledge of predatory fish populations has been derived from targeted shallow diver-based surveys (<15 m). However, the spatial distribution and extent of predatory fishes on outer mesophotic shelf environments has remained under described. Middleton Reef is a remote, high-latitude, oceanic platform reef that is located within a no-take area in the Lord Howe Marine Park off eastern Australia. Here we used baited remote underwater stereo video to sample predatory fishes across lagoon and outer shelf habitats from depths 0-100 m, extending knowledge on use of mesophotic depths and habitats. Many predatory fish demonstrated clear depth and habitat associations over this depth range. Carcharhinid sharks and Carangid fishes were the most abundant predators sampled on Middleton Reef, with five predatory fishes accounting for over 90% of the predator fish biomass. Notably, Galapagos shark (Carcharhinus galapagensis) and the protected black rockcod (Epinephelus daemelii) dominated the predator fish assemblage. A higher richness of predator fish species was sampled on reef areas north and south of the lagoon. The more exposed southern aspect of the reef supported a different suite of predator fish across mesophotic habitats relative to the assemblage recorded in the north and lagoonal habitats, a pattern potentially driven by differences in hard coral cover. Biomass of predatory fishes in the more sheltered north habitats was twice that of other areas, predominantly driven by high abundances of Galapagos shark. This work adds to the growing body of literature highlighting the conservation value of isolated oceanic reefs and the need to ensure that lagoon, shallow and mesophotic habitats in these systems are adequately protected, as they support vulnerable ecologically and economically important predator fish assemblages.

Offshore platforms as novel ecosystems: A case study from Australia’s Northwest Shelf

The decommissioning of offshore oil and gas platforms typically involves removing some or all of the associated infrastructure and the consequent destruction of the associated marine ecosystem that has developed over decades. There is increasing evidence of the important ecological role played by offshore platforms. Concepts such as novel ecosystems allow stakeholders to consider the ecological role played by each platform in the decommissioning process. This study focused on the Wandoo field in Northwest Australia as a case study for the application of the novel ecosystem concept to the decommissioning of offshore platforms. Stereo‐baited remote underwater video systems were used to assess the habitat composition and fish communities at Wandoo, as well as two control sites: a sandy one that resembled the Wandoo site pre‐installation, and one characterized by a natural reef as a control for natural hard substrate and vertical relief. We found denser macrobenthos habitat at the Wandoo site than at either of the control sites, which we attributed to the exclusion of seabed trawling around the Wandoo infrastructure. We also found that the demersal and pelagic taxonomic assemblages at Wandoo more closely resemble those at a natural reef than those which would likely have been present pre‐installation, but these assemblages are still unique in a regional context. The demersal assemblage is characterized by reef‐associated species with higher diversity than those at the sand control and natural reef control sites, with the pelagic community characterized by species associated with oil platforms in other regions. These findings suggest that a novel ecosystem has emerged in the Wandoo field. It is likely that many of the novel qualities of this ecosystem would be lost under decommissioning scenarios that involve partial or complete removal. This study provides an example for classifying offshore platforms as novel ecosystems.

Assessing the size selectivity of capture gears for reef fishes using paired stereo-baited remote underwater video

All methods used to sample fish populations exhibit some degree of size selectivity, whether due to the physical properties of the gear, behavioral responses to the gear, or the spatial distribution of the targeted population. In most stock assessments, selectivity functions are assumed and their parameters estimated due to a paucity of empirical data necessary to estimate selectivity. However, incorrect assumptions about selectivity functions can impart significant bias, ultimately affecting assessment outcomes. In 2016, a study was conducted to assess the size selectivity of three fishery-independent survey methods for reef fish in the U.S. South Atlantic: (1) a chevron trap survey, (2) a standardized repetitive timed drop hooked-gear survey, and (3) an unstandardized hooked-gear survey designed to mimic industry fishing practices. Each survey method was paired with a stereo-baited remote underwater video (S-BRUV) camera, which was treated as a comparative reference, considering that it is the least selective of the four gears used. A total of 93 stations were sampled with all gear types, and size data were analyzed for three managed reef fishes: red snapper, Lutjanus campechanus (all gears), black sea bass, Centropristis striata (all gears), and vermilion snapper, Rhomboplites aurorubens (all gears except chevron traps). For red snapper, all three capture gears showed dome-shaped selectivity, the degree of doming being more pronounced for chevron traps as evidenced by a decreasing capture probability for individuals over ~500 mm FL. Despite the largest red snapper (> 800 mm FL) being observed more often on S-BRUV, mean size of red snapper was generally smaller on S-BRUV than for either hooked-gear survey, indicating that hooked-gears capture proportionally fewer smaller red snapper. For black sea bass, there was evidence of flat-topped selectivity for all gear types, but chevron traps captured smaller individuals on average than did hooked gears. For vermilion snapper, both hooked gears exhibited dome-shaped selectivity. Given these results it’s clear that improper assessment of selectivity can lead to poor assumptions about the sampled population. Therefore, when the selectivity function of a particular gear type is not explicitly known, studies that directly estimate selectivity should be conducted to reduce assumptions applied to assessments. This study demonstrates the utility of non-destructive video surveys to complement and evaluate the selectivity functions of standard fisheries assessment methods. Furthermore, efforts to broaden the spatial scale of this study’s survey methods, expand the species to be examined, validate collected life history data, and determine the potential influence of interannual recruitment variability on observed selectivity patterns are necessary to better understand selectivity processes for all reef fishes assessed in the region.

High functional diversity in deep-sea fish communities and increasing intraspecific trait variation with increasing latitude.

Variation in both inter‐ and intraspecific traits affects community dynamics, yet we know little regarding the relative importance of external environmental filters versus internal biotic interactions that shape the functional space of communities along broad‐scale environmental gradients, such as latitude, elevation, or depth. We examined changes in several key aspects of functional alpha diversity for marine fishes along depth and latitude gradients by quantifying intra‐ and interspecific richness, dispersion, and regularity in functional trait space. We derived eight functional traits related to food acquisition and locomotion and calculated seven complementary indices of functional diversity for 144 species of marine ray‐finned fishes along large‐scale depth (50–1200 m) and latitudinal gradients (29°–51° S) in New Zealand waters. Traits were derived from morphological measurements taken directly from footage obtained using Baited Remote Underwater Stereo‐Video systems and museum specimens. We partitioned functional variation into intra‐ and interspecific components for the first time using a PERMANOVA approach. We also implemented two tree‐based diversity metrics in a functional distance‐based context for the first time: namely, the variance in pairwise functional distance and the variance in nearest neighbor distance. Functional alpha diversity increased with increasing depth and decreased with increasing latitude. More specifically, the dispersion and mean nearest neighbor distances among species in trait space and intraspecific trait variability all increased with depth, whereas functional hypervolume (richness) was stable across depth. In contrast, functional hypervolume, dispersion, and regularity indices all decreased with increasing latitude; however, intraspecific trait variation increased with latitude, suggesting that intraspecific trait variability becomes increasingly important at higher latitudes. These results suggest that competition within and among species are key processes shaping functional multidimensional space for fishes in the deep sea. Increasing morphological dissimilarity with increasing depth may facilitate niche partitioning to promote coexistence, whereas abiotic filtering may be the dominant process structuring communities with increasing latitude.

Latitude, depth and environmental variables influence deepwater fish assemblages off Western Australia

Continental shelf and upper slope fishes are important global resources which have significant economic and biodiversity values. Understanding the drivers of their abundance and distribution are fundamental to guide sustainable fisheries management arrangements. Deepwater demersal fish assemblages were sampled between depths of 91–570 m at six locations along the Western Australian coastline spanning 17° of latitude (i.e. 17–34°S at the Rowley Shoals, Montebello Islands, Ningaloo Reef, Abrolhos Islands, Perth Canyon and South West Capes) using Baited Remote Underwater Stereo-Video systems (stereo-BRUVs, n = 417 deployments). A total of 5965 individual fishes were identified belonging to 252 species and 92 families. Assemblage composition data were modelled against in-situ habitat data, temperature, salinity, current speed, and current direction. Multivariate statistical analyses revealed that fish assemblage composition was predominantly influenced by latitude (9.5% of variation), depth (7.3%) and salinity (7.2%). Three distinct assemblages were defined in response to latitude; a tropical, a sub-tropical and a southern temperate bioregion. Species richness declined with increasing latitude, and average biomass was highest in the southern bioregion. A mid-depth peak in biomass and lengths indicated the dominance of meso-predator species in the 300–399 m depth range. The information provided by this study on the factors influencing the abundance and distribution of fish assemblages over an exceptionally broad depth and latitudinal range along a continuous coastline will be useful for predicting the effects of future climate shifts on this and similar teleost species occupying tropical and temperate oceans elsewhere.

Mangrove fish assemblages reflect the environmental diversity of the Galapagos Islands

Mangroves are important habitats for a variety of ecologically, commercially and culturally important fishes. However, little is known about their role within the Tropical Eastern Pacific (TEP), and particularly in the Galapagos Archipelago, the westernmost limit for mangroves in the Americas, and the only oceanic islands in the TEP where mangroves are present. We describe patterns of fish composition in the 2 Galapagos bioregions where mangroves are present and assess potential environmental factors influencing fish community composition. Underwater Visual Census and Stereo Baited Remote Underwater Video stations (stereo-BRUVS) were used to sample fish communities. We identified 35029 fish representing 93 species, 67 genera and 36 families. Pomacentridae, Mugilidae, Haemulidae and Lutjanidae were the most common families. Juveniles made up 43% of the fish, 30 species were of importance to local artisanal fisheries and 80% of species were associated with reef habitats, suggesting mangroves in Galapagos may provide nursery habitats for economically valued species. Fish assemblage composition varied across bioregions, with 6 taxa responsible for driving these differences, including species of economic importance:Lutjanus novemfasciatusandMycteroperca olfax. Species richness was 17% higher in the Central-Southeastern than in the Western region; while higher species richness, Shannon-Wiener diversity and Pielou’s evenness were detected with BRUVS than through visual censuses. Our results highlight the role of mangroves as a habitat for a unique fish community composed of young, endemic and commercially important species, whose composition is likely driven by the isolation of the islands and its location in a convergence zone.

Distribution and ontogenetic habitat shifts of reefassociated shark species in the northeastern Caribbean

Understanding how reef-associated sharks utilise coastal reef habitats throughout their ontogeny is essential for their effective management. In this study, we assessed the distribution of sharks in the northern Caribbean Netherlands (Saba, Saba Bank and St Eustatius) and ontogenetic shifts in habitat and depth use of the 2 most observed species: Caribbean reef shark Carcharhinus perezi and nurse shark Ginglymostoma cirratum. We used stereo baited remote underwater video (stereo-BRUV) surveys at 376 sites. A total of 126 shark sightings (6 species) were recorded, with C. perezi (n = 72) and G. cirratum (n = 42) most frequently observed. The probability of recording at least 1 shark per deployment ranged from 0.19 to 0.37 and is comparable with shark occurrences in the small number of other stereo-BRUV studies in the Wider Caribbean Region. Habitat type was the most important factor driving reef-associated shark occurrences, with the highest probability of observing C. perezi and G. cirratum in soft-coral habitat. Additionally, occurrences of C. perezi were significantly influenced by the management zone, with highest probabilities of occurrence in no-fishing zones. Almost all observed reef-associated sharks (95.6%) were juveniles, indicating that the study area may be a nursery area. Overall, both species were observed in deeper waters with increasing size, indicating ontogenetic shifts in depth use. Our findings imply that protected areas should not be limited to a single habitat or depth, but focus on protecting a large area with the range of habitats and depths necessary for reef-associated sharks to complete their life cycle.

Assessing the Relative Selectivity of Multiple Sampling Gears for Managed Reef Fishes in the Eastern Gulf of Mexico

AbstractFishery‐independent data are important for the effective management of reef fishes in the eastern Gulf of Mexico. Proper characterization of selectivity, or the effectiveness of each type of sampling gear in capturing a species or a size‐class, is essential to ensure that assessment models treat various sources of data appropriately. In this study, we analyzed fishery‐independent data that was collected using stereo‐baited remote underwater video (S‐BRUV) arrays, chevron traps (TRAP), and two types of hooked gear (repetitive timed‐drop [RTD] and vertical longline [VLL]) to assess gear‐related differences of species composition and size selectivity of managed reef fishes in the eastern Gulf of Mexico. Significant differences were detected in the assemblage structures of reef fishes in relation to region, gear type, and depth. Overall, eight managed species were identified as contributing to the top 70% of the assemblage structure for each gear type. Stereo‐baited remote underwater video had the highest abundances for most of the species and the highest number of species captured, while VLL had the lowest. Two economically and ecologically important species (Red Grouper Epinephelus morio and Red Snapper Lutjanus campechanus) were common to all four gear types, and the size selectivity of these two species generally overlapped. However, significant differences among gear types were detected. Unimodal selection curves for hooked gears indicated that size of Red Snapper and Red Grouper increased as hook size increased. These data provide insight on species and size selectivity of multiple gears, which will contribute to future survey design and aid in the management of reef‐fish populations.

Benthic Habitats, as Derived from Classification of Side‐Scan‐Sonar Mapping Data, Are Important Determinants of Reef‐Fish Assemblage Structure in the Eastern Gulf of Mexico

AbstractIncreasingly restrictive management regulations have greatly reduced the utility of fishery‐dependent data for characterizing temporal changes in the abundance of managed fish populations, so fishery‐independent data are becoming more important for the accurate assessment of stock status. A notable downside to fishery‐independent data is the high cost of conducting surveys, and efforts to maximize survey efficiency are critical given ongoing reductions in agency funding. We conducted a pilot study to explore the utility of classifying side‐scan‐sonar mapping data to provide a practical a priori characterization of reef habitat in the eastern Gulf of Mexico. An analysis of side‐scan‐sonar mapping data identified five distinct reef habitat types (low‐relief hard bottom, mixed hard bottom, fragmented hard bottom, ledges, and potholes) that were subsequently sampled with stereo baited remote underwater video (S‐BRUV) arrays and trap‐mounted GoPro cameras. The permutational analysis of variance indicated that the assemblage structure of reef fish differed significantly (P &lt; 0.01) among all of the pairs of habitats except ledges and fragmented hard bottom; assemblage structure did not differ among cameras (P = 0.45). Overall species richness and diversity were significantly higher in the habitats with greater vertical relief, as were the abundances of several economically and ecologically important reef fishes, although many taxa were observed across all of the habitat types. Benthic habitats that are identified from side‐scan‐sonar mapping data are important determinants of reef‐fish assemblage structure and may prove to be useful as a stratification scheme for reef‐fish surveys, although additional research is necessary to explore the transferability of these results to the rest of the eastern Gulf of Mexico.

First underwater sighting of Shepherd\u2019s beaked whale (Tasmacetus shepherdi)

Here we describe the first underwater sighting of Shepherd’s beaked whale (Tasmacetus shepherdi). Two individuals were observed together on video footage obtained via mid-water stereo-Baited Remote Underwater Video Systems (BRUVS) deployed off the coast of Inaccessible Island, Tristan da Cunha, in the South Atlantic. This observation constitutes the first recorded live sighting of this species in the waters of Tristan da Cunha since 2002 and provides further evidence for the persistence of a population of this species in the region. The observed individuals lacked the dark flipper stripe observed in previous descriptions, indicating that the species may exhibit greater variation in pigmentation than previous records indicate. The planned implementation of a marine reserve in the region along with the current low level of fishing pressure and remote location of this archipelago provide a good context to ensure the appropriate management and protection of this rare species. The recent establishment of an ongoing mid-water stereo-BRUVS monitoring programme, in concert with other methods targeted at marine mammals, may yield further information about this little known species and aid in informing management decisions in the future.

Network of small no-take marine reserves reveals greater abundance and body size of fisheries target species.

No-take marine reserves (NTRs), i.e. areas with total fishing restrictions, have been established worldwide aiming to promote biodiversity and ecosystem conservation. Brazil has 3.3% of its exclusive economic zone protected by 73 different NTRs, however, most of them currently lack scientific knowledge and understanding of their ecological role, particularly regarding rocky reefs in subtropical regions. In this context, this study aimed to contrast a network of NTRs with comparable fished sites across a coastal biogeographic gradient to investigate the effect of fishing and habitat variability on the abundance and body size of rocky reef fish. We used Baited Remote Underwater stereo-Video (stereo-BRUVs) and Diver Operated stereo-Video (stereo-DOVs) systems to simultaneously sample reef fish and habitat. Model selection and results identified habitat and biogeographic variables, such as distance from shore, as important predictor variables, explaining several aspects of the fish assemblage. The effect of protection was important in determining the abundance and body size of targeted species, in particular for epinephelids and carangids. Conversely, species richness was correlated with habitat complexity but not with protection status. This is the first study using these survey methods in the Southwestern Atlantic, demonstrating how a network of NTRs can provide benchmarks for biodiversity conservation and fisheries management.

Peak in biomass driven by larger-bodied meso-predators in demersal fish communities between shelf and slope habitats at the head of a submarine canyon in the south-eastern Indian Ocean

This study investigated variations in the composition and biomass of demersal fish assemblages over a 570-metre depth gradient on the temperate, lower west coast of Australia (32° S) in the south-eastern Indian Ocean. Fish assemblages were sampled using Baited Remote Underwater Stereo Video systems (stereo-BRUVs, n = 284 deployments) from shallow waters around a mid-shelf island (Rottnest Island) to the continental slope within a submarine canyon (Perth Canyon). A total of 9013 individual fishes (i.e. ΣMaxN) belonging to 179 species and 75 families were identified. Multivariate statistical analyses revealed three distinct fish assemblages associated with the continental shelf (5–199 m), margin (200–300 m) and upper slope (300–570 m). A distance-based linear model revealed that among environmental covariates, benthic biota (sessile invertebrates and macroalgae) accounted for the highest proportion of variation in fish assemblage composition (16.9%) followed by depth (12.5%) and seabed relief (10.5%). Generalised additive models indicated higher biomass of fish associated with habitats characterised by benthic biota. Species richness decreased with increasing depth across the continental shelf but remained constant with increasing depth on the continental slope. Average fish length was not correlated with depth but was greatest at 200–400 m depth. The continental margin and upper slope habitats revealed a distinct change in assemblage composition as well as a peak in biomass of species that was dominated by larger-bodied meso-predators at the continental margin. The trends exhibited in fish assemblage characteristics across this broad depth range can inform ecosystem based management for deepwater fisheries resources.

An Assessment of Mobile Predator Populations along Shallow and Mesophotic Depth Gradients in the Hawaiian Archipelago

Large-bodied coral reef roving predators (sharks, jacks, snappers) are largely considered to be depleted around human population centers. In the Hawaiian Archipelago, supporting evidence is primarily derived from underwater visual censuses in shallow waters (≤30 m). However, while many roving predators are present or potentially more abundant in deeper strata (30–100 m+), distributional information remains sparse. To partially fill that knowledge gap, we conducted surveys in the remote Northwestern Hawaiian Islands (NWHI) and populated Main Hawaiian Islands (MHI) from 2012–2014 using baited remote underwater stereo-video. Surveys between 0–100 m found considerable roving predator community dissimilarities between regions, marked conspicuous changes in species abundances with increasing depth, and largely corroborated patterns documented during shallow water underwater visual censuses, with up to an order of magnitude more jacks and five times more sharks sampled in the NWHI compared to the MHI. Additionally, several species were significantly more abundant and larger in mesophotic versus shallow depths, which remains particularly suggestive of deep-water refugia effects in the MHI. Stereo-video extends the depth range of current roving predator surveys in a more robust manner than was previously available, and appears to be well-suited for large-scale roving predator work in the Hawaiian Archipelago.

Mesophotic Depth Gradients Impact Reef Fish Assemblage Composition and Functional Group Partitioning in the Main Hawaiian Islands

Mesophotic coral ecosystem (MCE) research has increased considerably in recent years, as MCEs may provide partial insulation from the effects of climate change, localized anthropogenic stressors, and may dampen fishing pressures for target species depleted in shallower waters. However, few studies have examined coral reef fish assemblages and functional groups across shallow water to mesophotic depth gradients. In the Main Hawaiian Islands, we investigated coral reef fish communities between 0 and 100 m using baited remote underwater stereo-video. While significant community shifts were detected when transitioning from shallow water to mesophotic depths, relative abundance and species richness remained highest between 0 – 30 m. Mobile invertivores and generalist macropiscivores were exceptions, recording higher abundance and richness values in deeper waters. Depth, habitat complexity, and percent cover of unconsolidated sediment and macroalgae were the main reef fish community drivers in multivariate regression and distance-based linear models. Finally, several target species were more abundant and/or larger in deeper waters, suggesting stock assessment and resource management strategies are incomplete without the incorporation of mesophotic portions of stocks.