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The nature of interspecific symbiotic associations is rarely as easily classified as biological textbooks might suggest. The costs and benefits that define these interactions are numerous and often context-dependent (e.g., Cheney and Cote 2005). Nevertheless, identifying and assessing costs and benefits that are either subtle or difficult to measure is important for understanding the evolution of interspecific symbioses (Leung and Poulin 2008).

Wildlife tourism is often extolled for its contribution to conservation. However, understanding the effects of tourism activities on the health of target animals is required to fully assess conservation benefits. Shark tourism operators often use food rewards to attract sharks in close proximity to tourists, but nothing is known about the contribution of these food rewards to the energetic requirements of target species. In this study, hand feeding of bull sharks Carcharhinus leucas was directly observed on 36 commercial shark watching dives in the Shark Reef Marine Reserve (SRMR), Fiji. Mean number of tuna heads consumed per dive by focal individuals ranged from 1.3 to 3.7. Monitored bull sharks consumed an average of ~0.74 heads per provisioning day, and bioenergetics modelling suggests that some sharks might periodically be meeting their full energy requirement from provisioning at the SRMR. Knowing how much individual sharks consume at provisioning sites and how this relates to their energy requirements is crucial in order to better understand the effects of wildlife tourism and its contribution to conservation.

The increasing popularity of marine wildlife tourism (MWT) worldwide calls for assessment of its conservation outcomes and the development of appropriate management frameworks to ensure the conservation of the species and habitats involved as well as the long-term sustainability of this industry. While many studies have examined the positive and/or negative implications of particular forms of MWT, few have attempted to identify factors of concern shared across different types of marine tourism, or examine their implications for sustainability in a broader perspective. We reviewed the existing literature to highlight common impacts on animal behaviour, health and ecology, and to identify successful cases based on minimal negative affects and/or lack of chronic/irreversible impacts on target species or habitats. To ensure the achievement of both economic and ecologic objectives, the following steps should be integrated in MWT management: 1) Increase of research on the biology and ecology of target species/habitat and application of relevant information for the development of suitable policies, frameworks and management strategies; 2) Structured enforcement of existing policies and enhancement of ecological awareness of visitors through active education; 3) Application of an adaptive management framework to continuously improve the codes of conduct employed; 4) Involvement of different stakeholders and local communities in the development and improvement of the MWT activity. Combining these strategies with the extrapolation of frameworks and policies from cases where adverse ecological impacts have been addressed and successfully resolved can further contribute in ensuring the long-term health and conservation of the species/habitats involved in MWT activities.

The oceans are in a state of rapid change – both negatively, due climate destabilization and misuse, and positively, due to strengthening of policies for sustainable use combined with momentum to grow the blue economy. Globally, more than 121 million people enjoy nature-based marine tourism — e.g., recreational fishing, diving, whale watching — making it one of the largest marine sectors. This industry is increasingly threatened by ocean degradation and management has not kept pace to ensure long-term sustainability. In response, individuals within the industry are taking it upon themselves to monitor the oceans and provide the data needed to assist management decisions. Fiji is one such place where the dive tourism industry is motivated to monitor the oceans (e.g., track sharks). In 2012, 39 dive operators in collaboration with eOceans commenced the Great Fiji Shark Count (GFSC) to document sharks (and other species) on 592 dive sites. Here, using 146,304 shark observations from 30,668 dives we document spatial patterns of 11 shark species. High variability demonstrates the value of longitudinal data that include absences for describing mobile megafauna and the capacity of stakeholders to document the oceans. Our results may be used to guide future scientific questions, provide a baseline for future assessments, or to evaluate conservation needs. It also shows the value of scientists collaborating with stakeholders to address questions that are most important to the local community so that they have the information needed to make science-based decisions.

Coastal and estuarine systems provide critical shark habitats due to their relatively high productivity and shallow, protected waters. The young (neonates, young‐of‐the‐year, and juveniles) of many coastal shark species occupy a diverse range of habitats and areas where they experience environmental variability, including acute and seasonal shifts in local salinities and temperatures. Although the location and functioning of essential shark habitats has been a focus in recent shark research, there is a paucity of data from the South Pacific. In this study, we document the temporal and spatial distribution, age class composition, and environmental parameters of young bull sharks (Carcharhinus leucas) in the Rewa, Sigatoka, and Navua Rivers, Fiji's three largest riverine systems. One hundred and seventy‐two young bull sharks were captured in fisheries‐independent surveys from January 2016 to April 2018. The vast majority of the captures were neonates. Seasonality in patterns of occurrence of neonate individuals suggests a defined parturition period during summer. Environmental parameters between the Rewa and the Sigatoka River differed significantly, as did the recorded young bull sharks abundance. According to the surveys, young bull sharks occur in all three rivers with the Rewa River likely representing essential habitat for newly born bull sharks. These results enhance the understanding of bull shark ecology in Fiji and provide a scientific basis for the implementation of local conservation strategies that contribute to the protection of critical habitats., Ecology and Evolution, 9 (13), ISSN:2045-7758

Sharks are a diverse group of mobile predators that forage across varied spatial scales and have the potential to influence food web dynamics. The ecological consequences of recent declines in shark biomass may extend across broader geographic ranges if shark taxa display common behavioural traits. By tracking the original site of photosynthetic fixation of carbon atoms that were ultimately assimilated into muscle tissues of 5,394 sharks from 114 species, we identify globally consistent biogeographic traits in trophic interactions between sharks found in different habitats. We show that populations of shelf-dwelling sharks derive a substantial proportion of their carbon from regional pelagic sources, but contain individuals that forage within additional isotopically diverse local food webs, such as those supported by terrestrial plant sources, benthic production and macrophytes. In contrast, oceanic sharks seem to use carbon derived from between 30° and 50° of latitude. Global-scale compilations of stable isotope data combined with biogeochemical modelling generate hypotheses regarding animal behaviours that can be tested with other methodological approaches., This research was conducted as part of C.S.B.’s Ph.D dissertation, which was funded by the University of Southampton and NERC (NE/L50161X/1), and through a NERC Grant-in-Kind from the Life Sciences Mass Spectrometry Facility (LSMSF; EK267-03/16). We thank A. Bates, D. Sims, F. Neat, R. McGill and J. Newton for their analytical contributions and comments on the manuscripts.

Population declines in shark species have been reported on local and global scales, with overfishing, habitat destruction and climate change posing severe threats. The lack of species-specific baseline data on ecology and distribution of many sharks, however, makes conservation measures challenging. Here, we present a fisheries-independent shark survey from the Fiji Islands, where scientific knowledge on locally occurring elasmobranchs is largely still lacking despite the location’s role as a shark hotspot in the Pacific. Juvenile shark abundance in the fishing grounds of the Ba Estuary (north-western Viti Levu) was assessed with a gillnet-and longline-based survey from December 2015 to April 2016. A total of 103 juvenile sharks identified as blacktip Carcharhinus limbatus (n = 57), scalloped hammerhead Sphyrna lewini (n = 35), and great hammerhead Sphyrna mokarran (n = 11) sharks were captured, tagged, and released. The condition of umbilical scars (68% open or semihealed), mean sizes of individuals (±SD) (C. limbatus: 66.5 ± 3.8 cm, S. lewini: 51.8 ± 4.8 cm, S. mokarran 77.4 ± 2.8 cm), and the presence of these species over recent years (based on fishermen interviews), suggest that the Ba Estuary area is a critical habitat for multiple species that are classified as “Near Threatened” or “Endangered.” Specifically, the area likely acts as a parturition ground over the studied period, and potentially as a subsequent nursery area. We identified subareas of high abundance and found that temperature, salinity and depth acted as small-scale environmental drivers of shark abundance. The data suggests a tendency for species-specific spatial use, both horizontally (i.e., between sampling areas) and vertically (i.e., across the water column). These results enhance the understanding of shark ecology in Fiji and provide a scientific basis for the implementation of local conservation strategies that contribute to the protection of these threatened species

Sharks are an important component of coastal fisheries. Accordingly, the impacts of small-scale shark fisheries are likely significant, but data, including socio-economic drivers, are often scarce. Fiji features active but largely unregulated and unmonitored artisanal fisheries. Data suggest that the country's small-scale shark fisheries have the potential to become more targeted. This study considers the socio-economic value of shark fisheries across stakeholder groups. In 2017, semi-structured interviews were conducted with 211 fishers throughout Fiji, out of which 66.8% reported catching sharks of 11 species. Of those who caught sharks, 19.9% stated to release them dead or alive, while 78.7% retained the sharks. Various reasons were cited for shark retention with the most common explanation being to meet dietary needs. Only 19.8% of the participants who retained sharks sold them, yet fishers who gain additional income from the sale of sharks had significantly higher mean maximum catch rates compared to fishers who retained sharks for consumption. Fewer fishers reported selling shark fins compared to a previous comparable survey. This study indicates a decreasing relevance of small-scale coastal shark fisheries for income generation but an increasing utilisation of shark meat as a substitute for traditional food fishes.

Bull sharks Carcharhinus leucas use estuarine and riverine systems as nursery habitat. The Shark Reef Marine Reserve (SRMR) on the southern coast of Viti Levu, Fiji, is well-known for its adult bull shark population. The species’ seasonal departure from the SRMR is related to reproductive activity, but nursery grounds have not yet been identified on the southern coast of Viti Levu. In order to further identify and characterise bull shark habitats in Fiji, 49 teeth were collected from bull sharks encountered at the SRMR and measured for their trace element concentrations, and 22 of them for oxygen isotopic composition in the phosphate group of bioapatite. The trace element analyses yielded relatively high Na, Mg, Sr, and F and low Ba concentrations for all the teeth supporting formation in marine environment. The phosphate oxygen isotope data concur with this result and the data evidently show that these teeth developed under marine condition relating to the temperature and oxygen isotopic composition of Fiji’s coastal waters. Therefore, the investigated teeth show no signs of freshwater habitat. Our results do not support the hypothesis that bull sharks enter freshwater habitats, at least not for longer time periods, during their absence from the SRMR. Additionally, the bull shark teeth had unexpectedly high zinc concentration at the very edge of the enameloid. This cannot be explained by environmental factors; therefore the high Zn content is interpreted here as a result of biological process, a reflection of enzyme (i.e., KLK4) related organic matter removal and enhanced crystallization during tooth maturation.

Eight whale sharks tagged with pop-up satellite archival tags off the Gulf of California, Mexico, were tracked for periods of 14–134 days. Five of these sharks were adults, with four females visually assessed to be pregnant. At least for the periods they were tracked, juveniles remained in the Gulf of California while adults moved offshore into the eastern Pacific Ocean. We propose that parturition occurs in these offshore waters. Excluding two juveniles that remained in the shallow tagging area for the duration of tracking, all sharks spent 65 ± 20.7% (SD) of their time near the surface, even over deep water, often in association with frontal zones characterized by cool-water upwelling. While these six sharks all made dives into the meso- or bathypelagic zones, with two sharks reaching the maximum depth recordable by the tags (1285.8 m), time spent at these depths represented a small proportion of the overall tracks. Most deep dives (72.7%) took place during the day, particularly during the early morning and late afternoon. Pronounced habitat differences by ontogenetic stage suggest that adult whale sharks are less likely to frequent coastal waters after the onset of maturity.

Environmental Conservation, 37 (1), ISSN:0376-8929, ISSN:1469-4387

Limited information is available on artisanal and subsistence shark fisheries across the Pacific. The aim of this study was to investigate Fiji’s inshore fisheries which catch sharks. In January and February 2013, 253 semi-directive interviews were conducted in 117 villages and at local harbours on Viti Levu, Vanua Levu, Taveuni, Ovalau and a number of islands of the Mamanuca and Yasawa archipelagos. Of the 253 interviewees, 81.4% reported to presently catch sharks and 17.4% declared that they did not presently catch any sharks. Of the 206 fishers that reported to catch sharks, 18.4% targeted sharks and 81.6% caught sharks as bycatch. When targeted, primary use of sharks was for consumption or for sale. Sharks caught as bycatch were frequently released (69.6%), consumed (64.9%) or shared amongst the community (26.8%). Fishers’ identification based on an identification poster and DNA barcoding revealed that at least 12 species of elasmobranchs, 11 shark and one ray species (Rhynchobatus australiae) were caught. This study, which is the first focused exploration of the shark catch in Fiji’s inshore fisheries, suggests that the country’s artisanal shark fisheries are small but have the potential to develop into larger and possibly more targeted fisheries.

Ctr Ecol Evolut &Environm Changes, Azorean Biodivers Grp, Angra Do Heroismo, Azores, Portugal

Shark-based tourism that uses bait to reliably attract certain species to specific sites so that divers can view them is a growing industry globally, but remains a controversial issue. We evaluate multi-year (2004-2011) underwater visual (n = 48 individuals) and acoustic tracking data (n = 82 transmitters; array of up to 16 receivers) of bull sharks Carcharhinus leucas from a long-term shark feeding site at the Shark Reef Marine Reserve and reefs along the Beqa Channel on the southern coast of Viti Levu, Fiji. Individual C. leucas showed varying degrees of site fidelity. Determined from acoustic tagging, the majority of C. leucas had site fidelity indexes >0.5 for the marine reserve (including the feeding site) and neighbouring reefs. However, during the time of the day (09:00-12:00) when feeding takes place, sharks mainly had site fidelity indexes

Pop-up satellite archival tags (PSATs) are electronic devices attached externally to aquatic animals that collect data such as light-level, pressure and temperature. After the PSAT has popped off and floats to the sea surface, archived data are transmitted via the Argos satellite system to the user, eventually providing insight into the spatial ecology of the study animals. Raw data received via the Argos satellite system are either processed directly by the manufacturer of the tag, or the tag manufacturer provides the user with custom-made analysis software, both resulting in data conditioned in files that can then be used for further analysis. Here I argue that insufficient knowledge by users about how PSATs record, archive and transmit data can be problematic. I revisit a dataset previously published from adult bull sharks Carcharhinus leucas to give an example of how erroneous depth and temperature data can slip into the peer-reviewed literature. I encourage PSAT users to engage in personal communication with tag manufacturers in order to understand how PSATs record, archive, process and transmit data. I argue that scientists must accurately report what data from PSATs they included and/or excluded in the analysis in order to avoid the publication of incomplete data.

Coral reefs, 29 (4), ISSN:0722-4028, ISSN:1432-0975

An optimal search theory, the so-called Levy-flight foraging hypothesis1, predicts that predators should adopt search strategies known as Levy flights where prey is sparse and distributed unpredictably, but that Brownian movement is sufficiently efficient for locating abundant prey2, 3, 4. Empirical studies have generated controversy because the accuracy of statistical methods that have been used to identify Levy behaviour has recently been questioned5, 6. Consequently, whether foragers exhibit Levy flights in the wild remains unclear. Crucially, moreover, it has not been tested whether observed movement patterns across natural landscapes having different expected resource distributions conform to the theory’s central predictions. Here we use maximum-likelihood methods to test for Levy patterns in relation to environmental gradients in the largest animal movement data set assembled for this purpose. Strong support was found for Levy search patterns across 14 species of open-ocean predatory fish (sharks, tuna, billfish and ocean sunfish), with some individuals switching between Levy and Brownian movement as they traversed different habitat types. We tested the spatial occurrence of these two principal patterns and found Levy behaviour to be associated with less productive waters (sparser prey) and Brownian movements to be associated with productive shelf or convergence-front habitats (abundant prey). These results are consistent with the Levy-flight foraging hypothesis1, 7, supporting the contention8, 9 that organism search strategies naturally evolved in such a way that they exploit optimal Levy patterns.

Based on direct observation of a free-ranging specimen and access to a jaw from a caught animal, the bull shark, Carcharhinus leucas, is reported from Tonga, South Pacific, for the first time. This finding extends the known geographical distribution of this species in the South Pacific.

4 páginas, 3 figuras, J.M. Brunnschweiler is supported by the Save Our Seas Foundation, the Shark Foundation Switzerland, Project AWARE (UK) and he acknowledges the Swiss National Science Foundation Grant no. 11 9305/1 for partial funding during the preparation phase of this manuscript. I. Sazima thanks the CNPq for essential financial support. N. Queiroz was funded by Fundac¸˜ao para a Ciˆencia e a Tecnologia (FCT) Grant SFRH/BD/21354/2005. S. J. Pierce is supported by Casa Barry Lodge, Project AWARE (UK), PADI Foundation, and the Save Our Seas Foundation. Fran Saborido and Juan Santos are gratefully acknowledged for technical assistance and advice. The valuable comments from two anonymous referees that substantially improved this manuscript are greatly appreciated

The sharksucker, Echeneis naucrates, attaches to a variety of hosts including teleost fish, elasmobranchs, marine turtles, and mammals. We list 18 additional hosts not previously recorded for this species, including the first report of its attachment to a conspecific and review the possible role of the relationship between echeneid fish and their hosts. The attachment of E. naucrates to a conspecific represents an addition to known hosts for this species, but it remains unclear if remoras are a habitual host for conspecifics.

This paper describes the first determination of water-escape velocities in free-ranging sharks. Two approximations are used to estimate the final swimming speed at the moment of penetrating the water surface. Blacktip sharks were videotaped from below the surface and parameters were estimated by analysing the sequences frame by frame. Water-escape velocities averaged 6.3 m s−1. These velocities for blacktip sharks seem accurate and are similar to estimates obtained for other shark species of similar size.

A recent study by Clua et al. (2010; Mar Ecol Prog Ser 414:257-266) that looks at the behavioural response of sicklefin lemon sharks Negaprion acutidens to underwater feeding for eco- tourism purposes has a number of methodological and semantic problems that complicate the evalu- ation of the results and raise questions about the conclusions. Main issues are the lack of a control, the use of non-defined terms to characterize observed behaviours, and statements not supported by data. Unwarranted conclusions include the notion that behavioural changes were caused by the human interference, the link between intraspecific aggression and the feeding process, and the loss of genetic variability as a consequence of the aggregating effect of shark feeding.

Shark tourism has become increasingly popular, but remains controversial because of major concerns originating from the need of tour operators to use bait or chum to reliably attract sharks. We used direct underwater sampling to document changes in bull shark Carcharhinus leucas relative abundance at the Shark Reef Marine Reserve, a shark feeding site in Fiji, and the reproductive cycle of the species in Fijian waters. Between 2003 and 2009, the total number of C. leucas counted on each day ranged from 0 to 40. Whereas the number of C. leucas counted at the feeding site increased over the years, shark numbers decreased over the course of a calendar year with fewest animals counted in November. Externally visible reproductive status information indicates that the species' seasonal departure from the feeding site may be related to reproductive activity., PLoS ONE, 6 (1), ISSN:1932-6203