Remote Underwater Video Research Articles

Do invasive corals alter coral reef processes? An empirical approach evaluating reef fish trophic interactions

Understanding how invasive species affect key ecological interactions and ecosystem processes is imperative for the management of invasions. We evaluated the effects of invasive corals (Tubastraea spp.) on fish trophic interactions in an Atlantic coral reef. Remote underwater video cameras were used to examine fish foraging activity (bite rates and food preferences) on invasive cover levels. Using a model selection approach, we found that fish feeding rates declined with increased invasive cover. For Roving Herbivores (RH) and Sessile Invertivores (SI), an abrupt reduction of fish feeding rates corresponded with higher invasive cover, while feeding rates of Territorial Herbivores (TH) and Mobile Invertivores (MI) decreased linearly with cover increase. Additionally, some fish trophic groups, such as RH, SI and Omnivores (OM), had lower densities in reef sections with high invasive cover. These findings demonstrate that invasive corals negatively impact fish-benthic interactions, and could potentially alter existing trophic relationships in reef ecosystems.

Baited videos to assess semi-aquatic mammals: occurrence of the neotropical otter Lontra longicaudis (Carnivora: Mustelidae) in a marine coastal island in São Paulo, Southeast Brazil

A new record of the neotropical otter (Lontra longicaudis) in the marine environment near the rocky reef of a coastal island in Brazil is described here, being the first published report of a semi-aquatic mammal by baited remote underwater video system. This species is not usually sighted in marine waters away from the mainland coast, and it has never been reported in this environment in this region. This individual may have increased its feeding grounds further offshore as food resources close to the mainland are reduced. Baited videos present a relatively low cost option to understand better these animals existing in different habitats, improving the monitoring for these species and providing valuable information on their distribution, habitat use, and life history.

Are we underestimating elasmobranch abundances on baited remote underwater video systems (BRUVS) using traditional metrics?

Baited remote underwater video systems (BRUVS) are increasingly used to study fish communities, biomass, and animal behaviour. Due to the abundance of BRUVS data, there are many analysis methods. The most commonly used method for analysis of BRUV data is MaxN which refers to the maximum number of individuals observed of a species in a single frame of a video. Here, we present a novel method for BRUVS analysis that involves identifying and counting distinct individuals (MaxIND) to quantify the accuracy of MaxN. Individual oriental bluespotted maskray (Neotrygon orientalis) and the bluespotted fantail ray (Taeniura lymma) were identified on BRUVS by spot patterns, tail characteristics, and sex at three sites in Malaysian Borneo. We demonstrated that MaxIND gave abundances that were 2.4 and 1.1 times higher than MaxN for N. orientalis and T. lymma, respectively. These differences between methods were consistent for each species between sites regardless of the presence of marine reserves. However, differences in abundance estimates from MaxN to MaxIND were apparent between species, indicating that correction factors need to be developed on a species basis to better estimate true abundance. While identifying individuals is time consuming, it provides improved accuracy and information about populations. We therefore recommend the use of MaxIND when rare and endangered species are present, in high density populations, and for behavioural analyses.

Evidence for rapid recovery of shark populations within a coral reef marine protected area

There is limited evidence on the rate at which the shark populations of coral reefs can rebound from over-exploitation, the baselines that might signify when recovery has occurred and the role of no-take Marine Protected Areas (MPA) in aiding this process. We surveyed shark assemblages at Ashmore Reef in Western Australia using baited remote underwater video stations in 2004 prior to enforcement of MPA status and then again in 2016 after eight years of strict enforcement. We found an increase in the relative mean abundance of Carcharhinus amblyrhynchos from 0.16 ± 0.06 individuals h−1 in 2004 to 0.74 ± 0.11 individuals h−1 in 2016, a change that was also accompanied by a shift in the assemblage of sharks to greater proportions of apex species (from 7.1% to 11.9%) and reef sharks (from 28.6% to 57.6%), and a decrease in the proportional abundance of lower trophic level species (from 64.3% to 30.5%). Abundances and trophic assemblage of sharks at Ashmore Reef in 2004 resembled those of the Scott Reefs, where targeted fishing for sharks still occurs, whereas in 2016, abundances and trophic structures had recovered to resemble those of the Rowley Shoals, a reef system that has been a strictly enforced MPA for over 25 years. The shift in abundance and community structure coincident with strict enforcement of the MPA at Ashmore Reef has occurred at a rate greater than predicted by demographic models, implying the action of compensatory processes in recovery. Our study shows that shark communities can recover rapidly after exploitation in a well-managed no-take MPA.

Developing indicators and a baseline for monitoring demersal fish in data-poor, offshore Marine Parks using probabilistic sampling

The number of Marine Protected Areas (MPAs) has increased globally as concerns over the impact that human activities are having on the world’s oceans have also increased. Monitoring is a key requirement to determine if MPAs are meeting their objectives. However, many recently declared MPA’s are large, offshore, or form part of an expansive network and spatial information about the habitats, communities and species that they contain is often lacking. This presents challenges for deciding exactly what to monitor and developing strategies on how to monitor it efficiently. Here we examine these issues using the Flinders Marine Park in Australia as a case study. We trial a two-stage version of a spatially-balanced, probabilistic sampling design combined with Baited Remote Underwater Videos (BRUVs) to perform an initial inventory, and we evaluate the potential of six commercially and ecologically important demersal fish as indicators within the Marine Park. Using this approach we were able to (1) quantitatively describe the distribution of the fish species in the Marine Park; (2) establish quantitative and representative estimates of their abundance throughout the Marine Park to serve as a baseline for future monitoring; (3) conduct power analyses to estimate the magnitude of increase we may be able to detect with feasible levels of sampling effort. Power analysis suggested that for most of our potential indicator species, detecting increases in abundance as small as 50% from present values should be feasible if sampling is restricted to a species’ preferred habitat and the same sites are sampled through time. Our approach is transferrable to other regions where monitoring programs must be designed based on limited spatial and biological data, assisting with decisions on what and how to monitor.

First estimates of Greenland shark (Somniosus microcephalus) local abundances in Arctic waters

Baited remote underwater video cameras were deployed in the Eastern Canadian Arctic, for the purpose of estimating local densities of the long-lived Greenland shark within five deep-water, data-poor regions of interest for fisheries development and marine conservation in Nunavut, Canada. A total of 31 camera deployments occurred between July-September in 2015 and 2016 during joint exploratory fishing and scientific cruises. Greenland sharks appeared at 80% of deployments. A total of 142 individuals were identified and no individuals were observed in more than one deployment. Estimates of Greenland shark abundance and biomass were calculated from averaged times of first arrival, video-derived swimming speed and length data, and local current speed estimates. Density estimates varied 1–15 fold among regions; being highest in warmer (>0 °C), deeper areas and lowest in shallow, sub-zero temperature regions. These baited camera results illustrate the ubiquity of this elusive species and suggest that Nunavut’s Lancaster Sound eco-zone may be of particular importance for Greenland shark, a potentially vulnerable Arctic species.

Promising ichthyologic studies in Lake Baikal: fundamental and applied aspects

Promising areas of ichthyologic research in Lake Baikal have been examined. Particular attention is being paid to the technology of remote fsh census, including hydroacoustic methods and the method of quantitative environmental DNA analysis. These technologies may provide information on the status of artifcially reproducible populations in reservoirs for developing a proper fshing strategy. The areas of application of molecular genetic methods for solving applied problems in creating the biological bases of fsheries, studying diseases, associated microflora and parasitic fauna, as well as for identifying fsh feed objects have been determined. Studies aimed at restoring and maintaining the populations of rare and endangered fsh species using artifcial reproduction methods, including breeding, hybridization, hormonal stimulation of spawning producers, cryopreservation of sexual products, individual tagging, etc., are discussed. Prospects of mobile remote underwater video monitoring systems, the EthoStudio software package and the holography method to simulate sensory reaction in studying mechanisms of adaptations of fsh in natural environment and to develop criteria for assessing their stability in aquaculture conditionshave been reviewed. Combining ethological studies and in-depth integrated morphological, molecular-genetic and physiological-biochemical screening of Baikal fsh that would allow to better understand fundamental evolutionary processes responsible for the formation of behavioral adaptations, creation and maintenance of genetic diversity within and between populations in the natural environment, as well as developing recommendations on the introduction of state-of-theart scientifc monitoring approaches into aquaculture are very promising.

Baited Remote Underwater Video surveys undercount sharks at high densities: insights from full-spherical camera technologies

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 585:113-121 (2017) - DOI: https://doi.org/10.3354/meps12395 Baited Remote Underwater Video surveys undercount sharks at high densities: insights from full-spherical camera technologies James P. Kilfoil1,*, Aaron J. Wirsing2, Matthew D. Campbell3, Jeremy J. Kiszka1, Kirk R. Gastrich1, Michael R. Heithaus1, Yuying Zhang1, Mark E. Bond1 1Department of Biological Sciences, Florida International University, North Miami, FL 33181, USA 2School of Environmental and Forest Sciences, University of Washington, Seattle, WA 98195, USA 3National Marine Fisheries Service, Southeast Fisheries Science Center, Mississippi Laboratories, Pascagoula, MS 39567, USA *Corresponding author: jkilf001@fiu.edu ABSTRACT: Video surveys are an essential tool for monitoring marine communities. Their use to study elasmobranch populations has dramatically increased over the last decade. However, the restricted field-of-view (FOV) of traditional cameras in these surveys may bias abundance estimates in a number of ways, including saturation at high densities and low detection probability for rare or cryptic species. This study investigated these potential biases using newly developed full-spherical (FS) camera technology. A comparison of 35 Baited Remote Underwater Video surveys (BRUVs), using both FS and traditional cameras, was conducted from July to August 2016 in shallow waters (0.4 to 8.5 m) of Tetiaroa, French Polynesia. Both blacktip reef Carcharhinus melanopterus and sicklefin lemon sharks Negaprion acutidens were quantified from traditional cameras using MaxN and MeanCount methods. These estimates were then regressed against FS cameras counts, which were assumed to more accurately represent site abundance, to test for gear saturation. Detection probabilities of the traditional and FS cameras were assessed using a Bayesian binomial model, with uninformed-uniform priors. Results indicated a significant effect of gear saturation for standard BRUVs as counts on FS cameras increased, regardless of the metric used. Furthermore, traditional cameras had a significantly lower detection probability (mean ± 2 SD: 69.88 ± 0.008%) than FS cameras (81.20 ± 0.007%). Our findings show that traditional cameras are unlikely to adequately discriminate differences in shark relative abundance at high densities. Therefore, standard BRUV techniques that use restricted FOV cameras are likely limited in their ability to provide accurate information to managers once populations have reached particular thresholds of abundance. KEY WORDS: 360° cameras · Detectability · Elasmobranchs · Monitoring · Video surveys Full text in pdf format Supplementary material PreviousNextCite this article as: Kilfoil JP, Wirsing AJ, Campbell MD, Kiszka JJ and others (2017) Baited Remote Underwater Video surveys undercount sharks at high densities: insights from full-spherical camera technologies. Mar Ecol Prog Ser 585:113-121. https://doi.org/10.3354/meps12395 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 585. Online publication date: December 22, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

The effect of artificial light on the community structure of reef-associated fishes at oil and gas platforms in the northern Gulf of Mexico

The northern Gulf of Mexico (GOM) contains almost 2300 oil and gas platforms. While some of these platforms are actively lit, allowing for normal working conditions throughout the night, many are unlit, illuminated only by small navigation beacons to warn vessels of their presence. In addition to producing oil and gas, these structures inadvertently serve as artificial reef habitat for a variety of GOM fish and invertebrate species. Though many fish species have been reported aggregating near these structures, this study is the first to examine changes in fish community structure in response to the structures’ artificial light regimes. Baited remote underwater video (BRUV) surveys were conducted at two lit and three unlit oil and gas platforms off the coast of Louisiana to examine the effect of platform artificial lighting on fish community structure during the day, at night, and during crepuscular periods. Seventeen recreationally harvested species were observed, with red snapper (Lutjanus campechanus) being the most abundant. Statistical analysis indicated that fish community varied significantly with depth, season, type, and season by type interactions. More fish were seen at lit platforms than at unlit platforms, with the majority of individuals identified near the surface. While fish abundance at the surface remained high during the day, the numbers declined at night. This suggests that though fishes are attracted to the vertical relief of the structure, they may be avoiding the artificial light field at the surface either to escape nocturnal predation or to forage away from the platform.

Comparing two remote video survey methods for spatial predictions of the distribution and environmental niche suitability of demersal fishes

Information on habitat associations from survey data, combined with spatial modelling, allow the development of more refined species distribution modelling which may identify areas of high conservation/fisheries value and consequentially improve conservation efforts. Generalised additive models were used to model the probability of occurrence of six focal species after surveys that utilised two remote underwater video sampling methods (i.e. baited and towed video). Models developed for the towed video method had consistently better predictive performance for all but one study species although only three models had a good to fair fit, and the rest were poor fits, highlighting the challenges associated with modelling habitat associations of marine species in highly homogenous, low relief environments. Models based on baited video dataset regularly included large-scale measures of structural complexity, suggesting fish attraction to a single focus point by bait. Conversely, models based on the towed video data often incorporated small-scale measures of habitat complexity and were more likely to reflect true species-habitat relationships. The cost associated with use of the towed video systems for surveying low-relief seascapes was also relatively low providing additional support for considering this method for marine spatial ecological modelling.

Benthic habitat and fish assemblage structure from shallow to mesophotic depths in a storm-impacted marine protected area

Baseline ecological studies of mesophotic coral ecosystems are lacking in the equatorial Indo-West Pacific region where coral reefs are highly threatened by anthropogenic and climate-induced disturbances. Here, we used baited remote underwater video to describe benthic habitat and fish assemblage structure from 10 to 80 m depth at Apo Island, a well-managed marine protected area in the Philippines. We conducted surveys 2 yr after two storms (in 2011 and 2012) caused severe damage to shallow coral communities within the no-take marine reserve (NTMR) of Apo Island, which led to declines in fish populations that had built up over three decades. We found that hard coral cover was restricted to 30 m) was dominated by sand/rubble and rock (dead coral) with low cover of soft corals, sponges and macroalgae. Storm damage appeared to have reached the deepest limit of the fringing reef (40 m) and reduced variability in benthic structure within the NTMR. Species richness and/or abundance of most trophic groups of fish declined with increasing depth regardless of storm damage. There were differences in taxonomic and trophic structure and degree of targeting by fisheries between shallow and mesophotic fish assemblages. Threatened shark species and a fish species previously unreported in the Philippines were recorded at mesophotic depths. Our findings provide a first glimpse of the benthic and fish assemblage structure of Philippine coral reef ecosystems across a wide depth gradient. This work also underscores how a combination of limited coral reef development at mesophotic depths close to shallow reefs and severe habitat loss caused by storms would result in minimal depth refuge for reef fish populations.

A tale of two islands: Decadal changes in rocky reef fish assemblages following implementation of no-take marine protected areas in New South Wales, Australia

Marine Protected Areas (MPAs) are used worldwide as a management tool for the protection of marine biodiversity. To assess decadal changes in rocky reef fish assemblages following MPA protection, fish assemblages were monitored regularly in the Port Stephens-Great Lakes Marine Park (PSGLMP), New South Wales, Australia, using Baited Remote Underwater Video (BRUVs) comparing between fished and non-fished zones. Spatial and temporal heterogeneity of fish assemblages and fishery targeted species were assessed from 2006–2016 at two no-take zones at Broughton and Fingal Islands, and compared with nearby fished areas. A total of 102 species from families was observed over the study, with fish assemblage response being dependent on both the spatial scales of MPA zoning and locations within the park, and the temporal scales assessed. Five fishery targeted families, Labridae, Scorpaenidae, Sparidae, Monacanthidae and Cheilodactylidae, increased in relative abundance within no-take zones, compared with fished zones, although the response was variable among families and between locations. While abundance increased at both locations following the implementation of no-take zones, a significant zoning effect was only detected at Broughton Island, with the Labridae and Sparidae displaying the greatest increases in relative abundance within the no-take zone. This study demonstrates that the response of fish assemblages and targeted fishery families to the implementation of no-take MPA zones varies both temporally, and between locations. Differences in the assemblage response between locations are likely driven by the size and habitats within the no-take zones and these factors need to be adequately considered in MPA planning.

Reef accessibility impairs the protection of sharks

Abstract Reef sharks are declining world‐wide under ever‐increasing fishing pressure, with potential consequences on ecosystem functioning. Marine protected areas (MPAs) are currently one of the management tools used to counteract the pervasive impacts of fishing. However, MPAs in which reef sharks are abundant tend to be located in remote and underexploited areas, preventing a fair assessment of management effectiveness beyond remoteness from human activities. Here, we determine the conditions under which MPAs can effectively protect sharks along a wide gradient of reef accessibility, from the vicinity of a regional capital towards remote areas, using 385 records from baited remote underwater video systems and 2,790 underwater visual censuses performed in areas open to fishing and inside 15 MPAs across New Caledonia (South‐Western Pacific). We show that even one of the world's oldest (43 years), largest (172 km2) and most restrictive (no‐entry) MPA (Merlet reserve) on coral reefs has between 17.3% and 45.3% fewer shark species and between 37.2% and 79.8% fewer shark abundance than remote areas in a context where sharks are not historically exploited. On coral reefs situated at less than 1 hr of travel time from humans, shark populations are so low in abundance (less than 0.05 individuals per 1,000 m2) that their functional roles are severely limited. Synthesis and applications. Remote areas are the last sanctuaries for reef sharks, providing a new baseline from which to evaluate human impacts on the species. However, there is no equivalent close to human activities even in large, old and strongly restrictive marine protected areas. As such sharks deserve strong protection efforts. The large, no‐entry marine protected areas, close to humans, offer limited benefits for reef shark populations, but provide more realistic conservation targets for managers of human‐dominated reefs. The exclusion of human activities on a sufficiently large area is key to protect reef shark populations. However, this strategy remains difficult to apply in many countries critically depending on reef resources for food security or livelihood.

Correction: Drivers of abundance and spatial distribution of reef-associated sharks in an isolated atoll reef system.

[This corrects the article DOI: 10.1371/journal.pone.0177374.].

Efficacy of remote underwater video cameras for monitoring tropical wetland fishes

Remote underwater video (RUV) cameras are commonly used in marine environments to sample fish, but to date have infrequently been used in freshwater environments. We tested the utility of a range of underwater video camera deployments (floating/benthic and fixed/moving) for surveying fish assemblages within tropical wetland habitats of Kakadu National Park, Australia. RUV cameras in both fixed and moving configurations were able to detect a range of fish species in various habitat types, with shy and/or flighty species readily detected. Cameras also performed well in a variety of conditions, although dense macrophytes posed a challenge for all video deployment types. RUV camera survey data compared favourably to two traditional fish survey techniques (visual census and pop netting). However, fixed camera deployments more closely resembled data collected via traditional techniques; whereas moving RUV deployments were consistently lower than any other method. We find that RUV cameras are a valuable monitoring and sampling technique for assessing freshwater fish assemblages in tropical wetlands, and are especially useful where remoteness, difficult access, variable water quality, complex habitats and interactions between humans and dangerous aquatic life can limit the use of other traditional fish sampling techniques.

Bubble Curtains: Herbivore Exclusion Devices for Ecology and Restoration of Marine Ecosystems?

Herbivorous fishes play a critical role in maintaining or disrupting the ecological resilience of many kelp forests, coral reefs and seagrass ecosystems, worldwide. The increasing rate and scale of benthic habitat loss under global change has magnified the importance of herbivores and highlights the need to study marine herbivory at ecologically relevant scales. Currently, underwater herbivore exclusions (or inclusions) have been restricted to small scale experimental plots, in large part due to the challenges of designing structures that can withstand the physical forces of waves and currents, without drastically altering the physical environment inside the exclusion area. We tested the ability of bubble curtains to deter herbivorous fishes from feeding on seaweeds as an alternative to the use of rigid exclusion cages. Kelps (Ecklonia radiata) were transplanted onto reefs with high browsing herbivore pressure into either unprotected plots, exclusion cages or plots protected by bubble curtains of 0.785 m2 and 3.14 m2. Remote underwater video was used to compare the behavioural response of fishes to kelps protected and unprotected by bubble curtains. Kelp biomass loss was significantly lower inside the bubble curtains compared to unprotected kelps and did not differ from kelp loss rates in traditional exclusion cages. Consistent with this finding, no herbivorous fishes were observed entering into the bubble curtain at any point during the experiment. In contrast, fish bite rates on unprotected kelps were 1621 ± 702 bites hr-1 (mean ± SE). Our study provides initial evidence that bubble curtains can exclude herbivorous fishes, paving the way for future studies to examine their application at larger spatial and temporal scales, beyond what has been previously feasible using traditional exclusion cages.

Epibenthic and mobile species colonisation of a geotextile artificial surf reef on the south coast of England.

With increasing coastal infrastructure and use of novel materials there is a need to investigate the colonisation of assemblages associated with new structures, how these differ to natural and other artificial habitats and their potential impact on regional biodiversity. The colonisation of Europe’s first artificial surf reef (ASR) was investigated at Boscombe on the south coast of England (2009–2014) and compared with assemblages on existing natural and artificial habitats. The ASR consists of geotextile bags filled with sand located 220m offshore on a sandy sea bed at a depth of 0-5m. Successional changes in epibiota were recorded annually on differently orientated surfaces and depths using SCUBA diving and photography. Mobile faunal assemblages were sampled using Baited Remote Underwater Video (BRUV). Distinct stages in colonisation were observed, commencing with bryozoans and green algae which were replaced by red algae, hydroids and ascidians, however there were significant differences in assemblage structure with depth and orientation. The reef is being utilised by migratory, spawning and juvenile life-history stages of fish and invertebrates. The number of non-native species was larger than on natural reefs and other artificial habitats and some occupied a significant proportion of the structure. The accumulation of 180 benthic and mobile taxa, recorded to date, appears to have arisen from a locally rich and mixed pool of native and non-native species. Provided no negative invasive impacts are detected on nearby protected reefs the creation of novel yet diverse habitats may be considered a beneficial outcome.

Deep-reef fish assemblages of the Great Barrier Reef shelf-break (Australia)

Tropical mesophotic and sub-mesophotic fish ecology is poorly understood despite increasing vulnerability of deeper fish assemblages. Worldwide there is greater fishing pressure on continental shelf-breaks and the effects of disturbances on deeper fish species have not yet been assessed. Difficult to access, deeper reefs host undocumented fish diversity and abundance. Baited Remote Underwater Video Stations (BRUVS) with lights were used to sample deeper habitats (54–260 m), in the Great Barrier Reef (GBR), Australia. Here we describe fish biodiversity, relative abundance and richness, assessing the prediction that depth would drive assemblage structure in the GBR. Distinct groups of fishes were found with depth whilst overall richness and abundance decreased steeply between 100 and 260 m. Commercially-valuable Lutjanidae species from Pristipomoides and Etelis genera, were absent from shallower depths. Few fish species overlapped between adjacent depth strata, indicating unique assemblages with depth. We also detected new location records and potential new species records. The high biodiversity of fish found in shelf-break environments is poorly appreciated and depth is a strong predictor of assemblage composition. This may pose a challenge for managers of commercial fisheries as distinct depth ranges of taxa may translate to more readily targeted habitats, and therefore, an inherent vulnerability to exploitation.

Residency and movement patterns of an apex predatory shark (Galeocerdo cuvier) at the Galapagos Marine Reserve.

The potential effectiveness of marine protected areas (MPAs) as a conservation tool for large sharks has been questioned due to the limited spatial extent of most MPAs in contrast to the complex life history and high mobility of many sharks. Here we evaluated the movement dynamics of a highly migratory apex predatory shark (tiger shark Galeocerdo cuvier) at the Galapagos Marine Reserve (GMR). Using data from satellite tracking passive acoustic telemetry, and stereo baited remote underwater video, we estimated residency, activity spaces, site fidelity, distributional abundances and migration patterns from the GMR and in relation to nesting beaches of green sea turtles (Chelonia mydas), a seasonally abundant and predictable prey source for large tiger sharks. Tiger sharks exhibited a high degree of philopatry, with 93% of the total satellite-tracked time across all individuals occurring within the GMR. Large sharks (> 200 cm TL) concentrated their movements in front of the two most important green sea turtle-nesting beaches in the GMR, visiting them on a daily basis during nocturnal hours. In contrast, small sharks (< 200 cm TL) rarely visited turtle-nesting areas and displayed diurnal presence at a third location where only immature sharks were found. Small and some large individuals remained in the three study areas even outside of the turtle-nesting season. Only two sharks were satellite-tracked outside of the GMR, and following long-distance migrations, both individuals returned to turtle-nesting beaches at the subsequent turtle-nesting season. The spatial patterns of residency and site fidelity of tiger sharks suggest that the presence of a predictable source of prey and suitable habitats might reduce the spatial extent of this large shark that is highly migratory in other parts of its range. This highly philopatric behaviour enhances the potential effectiveness of the GMR for their protection.

Erratum to: Application of systematic adaptive cluster sampling for the assessment of black sea bass Centropristis striata abundance

In this study, we applied systematic adaptive cluster sampling (SACS) to assess the abundance of black sea bass Centropristis striata on hard bottom habitats in the Mid-Atlantic Bight (MBA; USA). We used a remote underwater video system to obtain video recordings of black sea bass from 25 June to 6 August 2013 within a 25-square nautical mile (nmi2) sampling region. Data in the form of fish counts were collected from video recordings and used to estimate parameters including sample means and population totals of black sea bass for two adaptive cluster sampling estimators and a single systematic sampling estimator. The precision and relative efficiencies of the parameter estimates were also calculated and compared. In total, two adaptive cluster samples were encountered within the sampling region. Sample means and population totals were largest for the systematic sampling (SS) estimator while the adaptive sampling estimators produced parameter estimates with the lowest variances and highest precision. Our results indicated that SACS was more efficient and advantageous with respect to sampling costs [i.e., sampling time (hours) and travel distance (kilometers)] than SS alone for assessing the abundance of clustered populations of C. striata on hard bottom habitats in the MBA.