Baited Remote Underwater Video Research Articles

Minimum soak times of Baited Remote Underwater Video needed to assess the status of a coral reef fish community in the northern Gulf of Aqaba

Fishing pressure and other human impacts are increasing throughout much of the Red Sea. We assessed the minimum soak time and status of the coral reef fish community in the Aqaba Marine Park, Jordan prior to its official redesignation as a Marine Reserve in 2020 using baited remote underwater video (BRUV). A total of 86 species from 27 families were recorded in 15 deployments, comprising 60 hours of video. A minimum soak time of 150 minutes was found necessary to sufficiently estimate overall species richness. For richness of commercially valuable families, shorter soak times of 60 minutes were adequate, likely resulting from increased attraction of this largely piscivorous group to the bait plumes. A 30-minute soak time was adequate to assess the maxN of commercially valuable families. Our results indicate that the Aqaba Marine Reserve was overfished prior to its establishment as a reserve, as we recorded no large predators and not a single individual from Carcharhinidae, Haemulidae, Lutjanidae, or Scombridae. Other predator families like Epinephelinae, Lethrinidae, and Carangidae were relatively rare with low maxN. Our results provide a useful point of comparison to assess whether the coral reef fish community will recover as a result of enhanced management action and reduced fishing pressure.

Spatial variability in the structure of fish assemblages associated with Laminaria hyperborea forests in the NE Atlantic

Understanding fish-habitat associations is critical for ecosystem-based approaches to management and conservation. Kelp species, which are estimated to inhabit around 25% of the world's coastline and underpin highly productive and biodiverse ecosystems, are widely recognised as important nursery and foraging habitats for coastal fish species. However, quantitative assessments of fish assemblages within kelp forests are lacking for many regions. Here, we used Baited Remote Underwater Video (BRUV) and Underwater Visual Census (UVC) to quantify fish assemblages in Laminaria hyperborea forests at eight shallow subtidal rocky reefs that spanned 9° of latitude in the United Kingdom (UK). Fish assemblages were a ubiquitous and conspicuous component of kelp forest communities at all sites. BRUV surveys recorded marked regional-scale variability, with latitudinal shifts in assemblage structure and particularly distinct assemblages recorded in southwest England. These patterns were largely due to greater abundances of Pollachius spp. (i.e. saithe and pollock) in northern regions and higher numbers of Gobiusculus flavescens (two-spotted goby) and labrid species (i.e. rock cook, goldsinny and ballan wrasses) in southern regions. Unlike BRUVs, UVC surveys did not detect significant regional-scale variation in assemblage structure but did detect significant site-level differences, highlighting differences between the two techniques. BRUV surveys also recorded clear latitudinal trends in richness, with more taxa recorded at lower latitudes. Fish assemblages in the NE Atlantic have been, and will continue to be, impacted by ocean warming and fishing activities. Greater spatiotemporal coverage of kelp forest surveys and ongoing robust monitoring is needed to better understand and manage future ecological changes.

Fine-scale variation in the proximity of baited remote underwater video stations (BRUVS) to rocky reefs reveals changes in the structure of temperate fish assemblages

We investigated changes in the structure of coastal fish assemblages in Northern Patagonia, Southwestern Atlantic, by using baited remote underwater video stations (BRUVS) deployed at increasing distances from rocky reefs: 0–5 m, 15–20 m and 50–60 m. We estimated species richness and abundance (total and by preferred habitat type) and searched for diagnostic species in each distance range. We recorded 14 taxa across 11 families in 19 areas surveyed. Species richness and abundance were higher on reef ledges and decreased with distance from them, at a finer spatial scale than previously reported. Acanthistius patachonicus and Sebastes oculatus were indicative of reef ledges; they were less abundant at 15–20 m and disappeared at 50–60 m. Callorinchus callorynchus and Odontesthes spp. occurred only at distances >15–20 m from the reefs, while Galeorhinus galeus was distributed homogeneously throughout the surveyed area. Our findings have practical implications for monitoring ecotone demersal habitats with BRUVS.

Low-impact rearing of a commercially valuable shellfish: sea-based container culture of European lobster Homarus gammarus in the United Kingdom

There is increasing interest in the aquaculture of high-value shellfish species such as European lobster Homarus gammarus. Recent years have seen the development of extractive rearing equipment requiring no additional feed input, including novel sea-based container culture (SBCC) systems designed specifically for lobster mariculture. Here, we report the results of a study which assessed the impact of SBCC systems on the local ecology surrounding a pilot-scale lobster farm (Lobster Grower) integrated into an existing mussel farm in St Austell Bay, Cornwall, UK, across 2 monitoring surveys. We assessed the impact of SBCC systems on the macrobenthic, epifaunal, and mobile species ecology across the study area through benthic grab sampling, drop-down camera, and baited-remote underwater video (BRUV) monitoring. We detected no changes to local sediment composition around SBCC systems, nor changes in macrobenthic diversity or community structure. Increased detritus and biodeposition originating from SBCC systems may be attracting increased epifaunal scavengers, while the presence of the containers and associated infrastructure may act as fish-aggregating devices and provide additional foraging opportunities for mobile fish. These extractive systems may provide low-impact and low-carbon opportunities for coastal mariculture in the face of increased global demand for shellfish.

Small marine reserves provide conservation benefits for coastal sharks in southern New Zealand

Abstract With the increasingly imperilled status of shark populations, there is a pressing need to evaluate management solutions. Given the threats posed by fishing, marine reserves (MRs) present a promising option. Ata Whenua (Fiordland) in the South Island of Aotearoa/New Zealand is an ideal location to investigate this phenomenon owing to the presence of several shark species in coastal MRs. One‐hundred and sixty‐seven baited remote underwater video deployments were made in five MRs. A multi‐model inference approach using generalized linear modelling was used to assess the combined effect of the MRs on two trophic groups of coastal sharks. Generalized linear modelling was used to assess the effect of protection on, firstly, the presence of broadnose sevengill sharks (Notorynchus cepedianus), while accounting for variations in environmental variables, and secondly, the combined relative abundance of mesopredatory sharks detected (spiny dogfish, Squalus acanthias; school shark, Galeorhinus galeus; and carpet shark, Cephaloscyllium isabellum). Mesopredators had a higher relative abundance in MRs by a factor of 2.5 and there was a strong significant effect of protection, suggesting that MRs have led to an increase in their abundance or a change in distribution. In contrast, there was no effect of protection detected for sevengill sharks. It is concluded that the relatively small (<40 km2) MRs sampled do not provide conservation benefits for a large, mobile shark, but that they are potentially large enough to offer protection for mesopredatory sharks with smaller home ranges. To be effective for shark conservation, we therefore recommend that MRs need to be appropriately sized for the ranging behaviour of the target species for protection.

Further Insights into Invasion: Field Observations of Behavioural Interactions between an Invasive and Critically Endangered Freshwater Crayfish Using Baited Remote Underwater Video (BRUV).

Competitive behavioural interactions between invasive and native freshwater crayfish are recognised as a key underlying mechanism behind the displacement of natives by invaders. However, in situ investigations into behavioural interactions between invasive and native crayfish are scarce. In Australian freshwater systems, the invasive Cherax destructor has spread into the ranges of many native Euastacus species, including the critically endangered Euastacus dharawalus. Staged contests between the two species in a laboratory setting found E. dharawalus to be the dominant competitor, however, this has yet to be corroborated in situ. Here, we used baited remote underwater video (BRUV) to examine in situ intra- and inter-specific behavioural interactions between E. dharawalus and C. destructor. We sought to evaluate patterns of dominance and differential contest dynamics between the species to provide indications of competition between the two species. We found E. dharawalus to be dominant over C. destructor based on pooled interspecific interaction data and size-grouped interactions where C. destructor was the smaller opponent. Alarmingly, however, when C. destructor was within a 10% size difference the dominance of E. dharawalus was lost, contrasting with the outcomes of the laboratory-staged study. In addition, we report that small C. destructor initiated significantly more contests than larger conspecifics and larger E. dharawalus, a pattern that was not observed in smaller E. dharawalus. Further, intraspecific interactions between C. destructor were significantly longer in duration than intraspecific interactions between E. dharawalus, indicating a willingness to continue fighting. Concerningly, these outcomes point towards inherent and greater aggressiveness in C. destructor relative to E. dharawalus and that only larger E. dharawalus hold a competitive advantage over C. destructor. Therefore, we conclude that C. destructor represents a substantial threat to E. dharawalus through competitive behavioural interactions. Further, due to the disparity between our findings and those produced from laboratory-staged contests, we recommend the use of in situ studies when determining the behavioural impacts of invasive crayfish on natives.

Quantifying use of kelp forest habitat by commercially important crustaceans in the United Kingdom

AbstractKelp forests are regarded as important nursery and foraging habitats for commercially important species of finfish and shellfish despite an absence of fishery-independent data in many regions. Here, we conducted targeted surveys at 12 subtidal reefs, distributed across 9° of latitude in the UK, using three complementary techniques (Underwater Visual Census (UVC), Baited Remote Underwater Video (BRUV) and deployment of prawn pots) to quantify the abundance of crustaceans within kelp forests. Commercially important species were recorded at all sites; Cancer pagurus (brown/edible crab) and Necora puber (velvet swimming crab) were the most abundant and commonly observed, although Maja brachydactyla (spider crab), Homarus gammarus (European lobster) and Palaemon serratus (common prawn) were also recorded. The abundance of some species exhibited pronounced regional variability, with higher abundances of C. pagurus within northern regions and, conversely, higher abundances of M. brachydactyla and P. serratus within southern regions. Each sampling technique yielded similar spatial patterns for the most abundant species but had varying sensitivity to some species. Most individuals observed were juvenile or sub-adults, suggesting kelp forests serve as important nursery grounds for commercially and ecologically important crustaceans. Further monitoring efforts, conducted across greater spatiotemporal scales and in different habitat types, are needed to provide a robust baseline against which to detect changes and to inform management and conservation actions.

Fish community assessment of shelf-edge artificial reefs along east-central Florida

Artificial reef development is a popular management tool used to enhance fish stocks, mitigate degradation or loss of natural habitats, and provide additional recreational opportunities. In Florida, artificial reef development is a top priority of the Florida Fish and Wildlife Division of Marine Fisheries Management’s Artificial Reef program; however, despite their popularity and support, our scientific understanding of how artificial reefs ecologically facilitate marine fisheries is limited in certain habitats. This is especially true of the many artificial reefs along Florida’s central east coast, which has received sporadic assessment over the past few decades. The objective of this study was to conduct a fishery-independent assessment of the reef fish communities inhabiting the artificial reef sites off central east coast Florida using a combination of vertical longline sampling (VLL) and baited remote underwater videos (BRUV). Red snapper (Lutjanus campechanus) and vermilion snapper (Rhomboplites aurorubens) had the largest catch-per-unit-effort (CPUE) during VLL sampling, with red snapper CPUE significantly greater on rubble artificial reefs deeper than 40 m and vermilion snapper CPUE significantly greater on artificial reefs shallower than 30 m. A total of 62 fish species were observed on BRUVs, and community analysis indicated that red snapper, vermilion snapper, and tomtate (Haemulon aurolineatum) contributed the most to differences in community composition. Red snapper had the greatest abundance on sites deeper than 40 m, while vermilion snapper and tomtates had greater abundance on sites shallower than 30 m; all three species were more abundant during summer. This study provides the first quantitative assessment of reef fish communities on artificial reefs along central east coast Florida. Further monitoring is encouraged to unravel possible interactive effects of reef type and other environmental factors on fish assemblages, although it is evident that the reefs sampled support multiple managed fisheries species.

Video surveys of sea snakes in the mesophotic zone shed light on trends in populations

Declines in abundance of sea snakes have been observed on reefs throughout the Indo-Pacific, although the reasons are unknown. To date, surveys have occurred on shallow reefs, despite sea snakes occurring over a large depth range. It is not known if populations of sea snakes in deep habitats have undergone similar declines. To address this, we analysed deep-water video data from a historical hotspot of sea snake diversity, Ashmore Reef, in 2004, 2016, and 2021. We collected 288 hours of video using baited remote underwater videos and a remotely operated vehicle at depths between 13 and 112 m. We observed 80 individuals of seven species with Aipysurus laevis (n = 30), Hydrophis peronii (n = 8), and H. ocellatus (n = 6) being the most abundant. Five of the species (A. duboisii, A. apraefrontalis, H. ocellatus, H. kingii, and Emydocephalus orarius) had not been reported in shallow waters for a decade prior to our study. We found no evidence of a decline in sea snakes across years in deep-water surveys, although abundances were lower than those in early shallow-water surveys. A comparison of BRUVS data from 2004 and 2016 was consistent with the hypothesis that predation by sharks may have contributed to the loss of sea snakes in shallow habitats. Our study highlights the use of underwater video to collect information on sea snakes in the mesophotic zone and also suggests that future monitoring should include these depths in order to capture a more complete representation of habitats occupied.

Mesophotic Reefs of the Largest Brazilian Coastal Protected Area: Mapping, Characterization and Biodiversity

Mesophotic reefs are poorly known worldwide despite their great ecological relevance and management importance for coral reef conservation strategies. To aid in filling this gap, we conducted a pioneering, large-scale survey, covering a total of around 315 miles in length, in the largest Brazilian coastal Marine Protected Area (MPA) Costa dos Corais. From the digital bathymetry model (30 to 50 m depth) generated by a multibeam echo sounder, we selected areas of greater geomorphological diversity for a detailed investigative expedition of mesophotic ecosystems. Various sampling techniques were used: single-beam echo sounders for detailing the relief, a remotely operated underwater vehicle (ROV) for habitat type investigation, baited remote underwater video (BRUV) for collecting images of the fish community, and scuba diving to perform transects describing the benthic and fish community. We analyzed reef environments from 20 to 68 m deep. As a result, we present the mapping and geomorphological characterization of two compartments of mesophotic reefs at 21–45 m depth and an image library of mesophotic ecosystems with the species description and indications of whether it is a new record in the region. Biodiversity data were collected covering eight species of sponges, with greater abundance for Ircinia spp., Aplysina spp., and Xestospongia muta; eight from corals, mainly Siderastrea spp. And Montastrea cavernosa; and 68 species of reef fish, with the Labridae family (including Scarinae—11 species) being the richest. Our results demonstrate the importance of mesophotic reefs for MPA Costa dos Corais reef biodiversity and, with that, the need to protect these areas through the application of local conservation strategies, such as the creation of “no-take zones”.

Stable, Semitransparent, and Self‐Powered Conjugated‐Polymer/CsPbI2Br UV–vis–NIR Photodetector Improved by Thiamine Additive

AbstractTransparent/semitransparent perovskite photodetectors hold great promise for next‐generation optoelectronic devices due to their attractive photoelectric properties and transparency. However, most previously reported transparent perovskite photodetectors require an external power supply and are unstable under relatively high humidity ambient conditions. To address these issues and realize improved performance, this study demonstrates a semitransparent self‐powered broad photodetector based on an inorganic CsPbI2Br perovskite/conjugated‐polymer hybrid structure with a thiamine hydrochloride additive. By optimizing the concentration of the thiamine hydrochloride additive, the main crystal exposure of the CsPbI2Br film changes from the (200) to the (110) plane orientation and can remain stable for more than 10 d in the air with 60%–70% humidity. The corresponding device exhibits a broad response spectrum up to a wavelength of 950 nm, a fast response speed (200/580 µs), a high responsivity (0.32 A W−1), and a large detectivity (4.4 × 1013 Jones). The improvement is mainly due to thiamine hydrochloride controlling the crystal growth to realize the desired crystal plane orientation and reduce the crystal size, which in turn improves the phase stability and optoelectronic properties of CsPbI2Br.

Removal of bottom-towed fishing from whole-site Marine Protected Areas promotes mobile species biodiversity

Marine habitats are being altered by anthropogenic pressures, influencing the diversity and distribution of species. Marine Protected Areas (MPAs) are increasingly used as spatial management tools to mitigate these human impacts on marine systems, but levels of protection vary. MPAs that exclude bottom-towed fishing activities from all habitats within their boundaries while still allowing static gear fishing, taking a “whole-site approach”, have shown benefits in terms of increasing biodiversity and biomass on reef habitat. In this study we use Baited Remote Underwater Videos (BRUVs) to quantify differences in mobile species assemblage composition, diversity and abundance on mixed sediment habitats inside and outside three MPAs adopting this whole-site approach within Jersey's territorial waters. Greater numbers of taxa were recorded within all three MPAs compared to nearby unprotected areas, with an average of 4.9 ± 1.8 taxa observed per deployment inside the MPAs compared to 3.9 ± 1.7 taxa outside the MPAs. No significant difference was observed in the overall abundance. The proportion of presence of two indicator species (Labridae Spp. and juvenile bream Spondyliosoma cantharus) was greater within the MPAs than the nearby unprotected areas. IUCN threatened and vulnerable shark species were observed on more BRUVs inside the MPAs, while IUCN threatened and vulnerable ray species were present on fewer BRUVs in the MPAs, but both occurred in too few numbers to statistically assess. Not all species responded positively to the MPAs, with scavenging species such as spider crab (Maja brachydactyla) recorded in lower numbers in two out of the three MPAs compared to the nearby unprotected areas. BRUV surveys that have been used to survey MPAs that exclude bottom-towed fishing in Europe are sparse and have primarily focussed on reef habitat. This study provides the first account of how this whole-site approach for mixed sediment habitats in three MPAs affects mobile species. These results evidence the merit of an ecosystem-based approach to MPA management for species of both conservation and commercial importance.

Insights into elasmobranch composition, abundance, and distribution in the Bocas del Toro Archipelago, Panama using fisheries-independent monitoring

There are very little data on Central America and the Western Caribbean elasmobranch populations. Here we present the first results of standardized fisheries-independent monitoring of sharks and rays in Panama's Bocas del Toro Archipelago over four consecutive years. Using baited remote underwater videos (BRUVs), underwater visual census (UVC), and scientific longline, we provide baseline data on the composition, relative abundance, distribution, and demographics of seven shark species and six rays observed during the study. Observations differed among methods and habitats, with BRUVs (n = 148) more effective for assessing shark diversity and abundance and UVC (n = 108) more effective for assessing ray abundance. Nurse sharks (Ginglymostoma cirratum) and southern stingrays (Hypanus americanus) were the most commonly observed species overall (frequency of occurrence = 30.4 and 18.9%, respectively). Depth, temperature, and protected area status significantly affected the relative abundance of sharks and rays based on UVC and BRUV data. The use of scientific longlines (n = 55) highlighted the lagoon habitat as a potential nursery site for blacktip sharks (Carcharhinus limbatus), with juvenile (average total length = 113 cm) individuals representing 58% of longline captures. The results provide a current baseline for elasmobranch communities that can further aid in the conservation and management of these species nationally and regionally.

Preliminary evidence of early Reef Cube® enhancements to mobile benthic ecosystems

Reef Cubes® are ecological engineering units, intended to restore biodiversity while serving functions to marine engineers. Ecological engineering must be backed by quantitative scientific evidence. Here, preliminary results of the Reef Enhancement for Fisheries at Aquaculture Sites (REFAS) project are presented. 11 Clusters of Reef Cubes® were deployed in June 2021. Sampling was undertaken before and after in the Spring and Autumn of 2021, in daylight and at night-time. Guided Baited Remote Underwater Video Station (BRUVS) surveys were completed with a modified BlueROV2. All mobile benthic and demersal species were identified during a 30-minute window and quantified in terms of Max-N. Biodiversity indices, rarefaction curves and multivariate community compositions were compared at reef and non-reef sites before and after build. Average species richness, Pielou’s evenness, Simpson’s and Shannon’s indices were similar between reef and non-reef sites. Seasonal increases of total abundance and total species were found, and these were significantly greater at reef sites. There were also significant differences in the community compositions of the reef and non-reef sites that were not observed before the build. These results are significant for the implications of using Reef Cubes® and indicate that Reef Cubes® could be a potential tool for biodiversity remediation.

Survey of Nautilus pompilius Linnaeus, 1758 (Cephalopoda) from Siquijor Island and Dalaguete–Alcoy in the Philippines Using Baited Traps and Baited Remote Underwater Video Systems (BRUVS)

Survey of Nautilus pompilius Linnaeus, 1758 (Cephalopoda) from Siquijor Island and Dalaguete–Alcoy in the Philippines Using Baited Traps and Baited Remote Underwater Video Systems (BRUVS)

Unoccupied aerial video (UAV) surveys as alternatives to BRUV surveys for monitoring elasmobranch species in coastal waters

Abstract Effective conservation strategies are founded by baseline information on abundance and diversity estimates. Method choice can influence the success of baseline surveys as method performance is variable and needs to be selected based on habitat and taxa. Here, we assess the suitability of unoccupied aerial vehicle (UAV) surveys, specifically multi-rotor “drones”, and baited remote underwater video (BRUV) surveys in shallow-water habitats to quantify elasmobranch abundance and diversity in the Saudi Arabian central Red Sea. Our results show that the number of elasmobranchs h−1 observed using UAV surveys exceeded that of BRUV surveys by two orders of magnitude, indicating that the increased spatial coverage of UAV surveys is beneficial for long-term monitoring projects. BRUV surveys detected a greater number of species within reef habitats, whereas UAV surveys detected a greater number of species within sandflat habitats, indicating the value of multi-method approaches for regional biodiversity studies. Here, we provide the first insight into elasmobranchs associated with sandflat habitats in Saudi Arabia, emphasising the importance of these habitats to stingrays and the need for further information on elasmobranch habitat use to better inform management and conservation efforts in the face of rapid coastal developments across the Red Sea.

Habitat-specific fish fauna responses to different management regimes in the largest coral reef complex in the South Atlantic

While marine protected areas (MPAs) are increasing worldwide, it is still needed to assess the effectiveness of those already consolidated. Methods and ecological assessments to understanding integrated and habitat-specific management regimes are still scarce and insufficient for policy implications and biodiversity conservation. Through Baited Remote Underwater Video (BRUV), we used fish assemblages as proxy of ecological and managerial status in two reef habitat types along three protection levels at Abrolhos Bank - the largest and most biodiverse coral reef complex of the South Atlantic. We found completely distinct responses in the fish fauna between the top (shallow) and bottom (deep) habitats of the unique “chapeirões” pinnacle reef formations. In the most protected zone (no-take), higher richness and abundance of commercial fish and more diverse trophic structure was observed. Particularly, large (sharks and groupers) and small carnivores (snappers) were more abundant and distributed more homogeneously over both reef habitats in the strictly enforced no-take zone. Abundance of these top-predators decreased from the low enforcement no-take zone to the multiple use area, where they were often absent while their typical preys (primary and secondary consumers) were thriving, notably in the top habitats. These outcomes highlight the importance to focus investigations not selectively on a single habitat type or depth zone in order to properly assess MPA effectiveness. Consequently, the monitoring and protection of fish species supported by marine spatial planning may benefit from an improved understanding of ecological functioning provided by MPA performance.

Seascape connectivity of temperate fishes between estuarine nursery areas and open coastal reefs

Abstract While estuaries are considered valuable nurseries for many harvested fish species, little quantitative data exist about the spatial scales over which estuaries supply individuals to coastal reefs and how this influences coastal metapopulations. Quantifying this connectivity between estuaries and coastal reefs will assist the sustainable management of fisheries and key fish habitat. This information is particularly pertinent considering estuaries world‐wide are experiencing degradation and habitat loss. We examine how the relative abundance and body length of three exploited fishes (Chrysophrys auratus, Pseudocaranx georgianus and Nemadactylus douglasii) varied in relation to the proximity and size of the nearest estuary, predicting that estuarine dependent species (i.e. C. auratus) would be smaller and more abundant on reefs close to large estuaries. As a network of ‘no‐take’ marine reserves exist across the study area, we also assessed for reserve effects and if these were influenced by the proximity and size of estuaries. Fish assemblages were surveyed using baited remote underwater video systems deployed on 629 rocky reefs across 417 km of coastline in south‐eastern Australia. As predicted, C. auratus were smaller and more abundant on reefs adjacent to estuaries (<8.5 km), which is consistent with the species being heavily reliant on estuaries as nursery habitats. Neither the length nor abundance of N. douglasii and P. georgianus were influenced by the proximity or size of estuaries. Marine reserves consistently had higher abundances and larger C. auratus, regardless of their proximity to estuaries. However, reserve effects were more variable for both N. douglasii and P. georgianus. Synthesis and applications. Our results suggest that the dispersal of subadult Chrysophrys auratus from estuarine nurseries to coastal reefs occurs across relatively small spatial scales, highlighting that conserving the ecological functioning of estuaries is paramount to sustaining recruitment to nearby coastal fisheries. Estuary size and proximity had little influence on populations of both Nemadactylus douglasii and Pseudocaranx georgianus as these species are not greatly dependent on estuaries. We also found that the proximity to estuaries did not enhance reserve effects, instead these effects were consistent across the study area.

Depth and habitat are important drivers of abundance for predatory reef fish off Pemba Island, Tanzania

Coral reefs across the world face significant threats from fishing and climate change, which tends to be most acute in shallower waters. This is the case off Pemba Island, Tanzania, yet the effects of these anthropogenic stressors on the distribution and abundance of economically and ecologically important predatory reef fish, including how they vary with depth and habitat type, is poorly understood. Thus, we deployed 79 baited remote underwater videos (BRUVs) in variable water depths and habitats off Pemba Island, and modeled the effects of depth and habitat on abundance of predatory reef fish. Predatory reef fish types/taxa were significantly predicted by depth and habitat types. Habitats in relatively deeper waters and dominated by hard and soft corals hosted high species richness and abundance of predatory reef fish types/taxa compared to mixed sandy and rubble habitats. The findings add to the growing evidence that deep waters around coral reefs are important habitats for predatory reef fish. Thus, careful management, through effective area and species protection measures, is needed to prevent further depletion of predatory reef-associated fish populations and to conserve this biologically important area.

Functional diversity of reef fish assemblages in the Galapagos Archipelago

The Galapagos Archipelago's unique reef biodiversity and distribution patterns are relatively well understood compared to the study of local functional diversity processes. We investigated functional diversity patterns in coastal reef fish communities using stereo Baited Remote Underwater Videos systems (stereo-BRUVs). We collected relative abundance data based on 41,594 individual fish belonging to 121 reef fish species and assessed functional diversity using seven functional traits and a combination of functional alpha-diversity and beta-diversity indices. We found differences between bioregions; however, we observed no differences in reef fish assemblages between the geographic strata (distinct habitat types) within regions. Low functional alpha-diversity within assemblages but high environmental variability at small spatial scales has resulted in a consistent moderate functional beta-diversity between assemblages and high functional diversity at an archipelago-wide scale. While there is a low diversity of functional roles, the most abundant species represent a few distinct and supportive functional roles in Galapagos reef ecosystems. Such functional roles likely have redundancy; however, many other functional roles are likely under-represented and vulnerable. The variable functional diversity between Galapagos bioregions facilitates an ecological interpretation that supplements traditional species diversity indices. Therefore, we suggest a combination of species compositions and functional diversity metrics be used in the future management of Galapagos marine communities.