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Underwater photo-identification of sicklefin lemon sharks, Negaprion acutidens, at Moorea (French Polynesia)

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Underwater photo-identification of sicklefin lemon sharks, Negaprion acutidens, at Moorea (French Polynesia)

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Abstract

Shark feeding is a controversial recreational activity that may alter shark behaviour. In order to investigate possible behavioural changes at the level of the individual, it is necessary to recognise each shark underwater and in a nonintrusive way. In this study, we tested a protocol based on natural marks on fins, and coloured spots and scars on the body to differentiate individual sicklefin lemon sharks. We found that a feeding group, aggregated for 26 months at a northern location off Moorea Island, comprised 32 animals (19 females and 13 males), identified from 2589 observations made over 541 dives. Post-dive photo-identification of individual sharks was a reliable technique, whereas a high level of skill was required to ensure an instantaneous identification underwater. However, direct underwater identification of individual sharks can be of potential use in shark behavioural studies.

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... Contrary to Palmyra Atoll where C. melanopterus were mainly found inside the lagoon (Papastamatiou et al., 2009b), they were abundant both inside and outside the lagoon at Moorea (French Polynesia), sharing their habitat with the pink whipray Himantura fai Jordan & Seale 1906 within the lagoon (Gaspar et al., 2009), and with sicklefin lemon sharks Negaprion acutidens (Rüppell 1837) (Buray et al., 2009) and grey reef sharks Carcharhinus amblyrhynchos (Bleeker 1856) on the fore-reef. Juvenile C. melanopterus also shared their potential nursery habitat with juvenile N. acutidens as the latter were also caught in the nursery areas, Haapiti and Varari, during this study. ...
... Except for the east coast of southern Africa, maximum sizes for both males and females in Moorea are larger than in previous studies, implying that C. melanopterus densities, or that of other competing species, at Moorea are low or are not limited by food resources. Regarding other competing shark species, the N. acutidens population at Moorea is small (Buray et al., 2009) and C. amblyrhynchos seem to be relatively abundant only at one location in Moorea [Tiki, Fig. 1(b)]. Moreover, these two co-occurring species are not often found in the lagoon (Buray et al., 2009;Gaspar et al., 2009;Clua et al., 2010;Mourier et al., 2012) although C. melanopterus are abundant both within and outside the lagoon. ...
... Regarding other competing shark species, the N. acutidens population at Moorea is small (Buray et al., 2009) and C. amblyrhynchos seem to be relatively abundant only at one location in Moorea [Tiki, Fig. 1(b)]. Moreover, these two co-occurring species are not often found in the lagoon (Buray et al., 2009;Gaspar et al., 2009;Clua et al., 2010;Mourier et al., 2012) although C. melanopterus are abundant both within and outside the lagoon. Therefore, the low level of interspecific competition is likely to be one factor determining the longer L T of C. melanopterus at Moorea. ...
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During a survey of the population of blacktip reef shark Carcharhinus melanopterus in Moorea (French Polynesia) between 2007 and 2011, population structural characteristics were estimated from 268 individuals. Total length (L ) ranged from 48 to 139 cm and 48 to 157 cm for males and females, respectively, demonstrating that the average L of females was larger than that of males. The C. melanopterus population at Moorea showed an apparent spatial sexual segregation with females preferentially frequenting lagoons and males the fore-reefs. Mean growth rate was c. 6 cm year . Males reached sexual maturity at 111 cm L . This study reports on the population characteristics of this widespread carcharhinid shark species and makes comparisons with other locations, confirming high geographic variability in the population structure of the species.
... We deployed the recording system for 90 -120 min a day, depending on meteorological conditions. The sicklefin lemon sharks of this study have been monitored daily for more than 10 years through photo-identification [30] and showed different degrees of attachment to the provisioning site [18]. The robustness and accuracy of the photo-identification method was demonstrated through a long-term monitoring programme [18,30] and was also cross-validated with genetic analyses [29]. ...
... The sicklefin lemon sharks of this study have been monitored daily for more than 10 years through photo-identification [30] and showed different degrees of attachment to the provisioning site [18]. The robustness and accuracy of the photo-identification method was demonstrated through a long-term monitoring programme [18,30] and was also cross-validated with genetic analyses [29]. In the present study, sharks were therefore individually identified according to their body marks, sex and estimated length. ...
... [34]. Each tracked shark could be reliably identified thanks to a record book established in a previous study [30] and that differentiated individuals according to distinctive body marks, estimated size, and sex. We are confident that all sharks present at the provisioning site were ...
Article
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To adapt to their environment, organisms can either directly interact with their surroundings or use social information, namely information provided by neighbouring individuals. Social information relates to the external features of surrounding peers, and little is known about its use by solitary species. Here, we investigated the use of social cues in a solitary marine predator by creating artificial aggregations of free-ranging sicklefin lemon sharks (Negaprion acutidens). Using a novel monitoring protocol, we analysed both dominance interactions and tolerance associations between sharks competing for food in relation with the number, the morphology and the behaviour of rivals. Sharks produced more agonistic displays and spent more time around the bait as competitors were more abundant. Moreover, the morphological attributes of competitors had very limited influence on the structure of shark social interactions. Instead, sharks appeared to establish tolerance relationships with competitors according to their individual behaviour. Furthermore, the more two sharks were observed together at a given study site, the fewer agonistic interactions they exchanged. We discuss these findings as evidence of the use of social cues in a non-gregarious predatory species and suggest directions for future research.
... Because individuals were released on different days, the projected battery life of each tag was used as a standard reference value for the total number of days monitored. All sharks were likely to have survived the tagging process (Buray et al. 2009;Chin et al. 2015) and thus sharks not detected by the array were assumed to have departed. RI values ranged from 0 (no residency) to 1 (high residency). ...
... There was also one instance of fishing mortality, with one N. acutidens recaptured by recreational fishers. High rates of wound healing and survival of internally tagged individuals of our two focal species (Buray et al. 2009;Filmalter et al. 2013;Chin et al. 2015) and multiple recaptures of sharks between 2 and 19 days from release (17%) indicated that declines in detections of tagged sharks likely reflect dispersal to other sites, high rates of natural or fishing mortality or a combination of both, rather than tagging mortality. ...
Article
The benefits of marine protected areas are difficult to estimate for mobile species, but their effectiveness can be increased if essential habitats, such as nursery areas, are protected. In the present study we examined movements of juvenile blacktip reef (Carcharhinus melanopterus) and sicklefin lemon (Negaprion acutidens) sharks in a coastal nursery in northern Australia. Telemetry-derived data were modelled using Brownian bridges and overlaid with maps of habitats and no-take zones. Juvenile N. acutidens were typically residents (≥30 days) of the nursery with small areas of core space use (<1.9km2), whereas juvenile C. melanopterus were non-residents (<30 days) and used larger areas (<5.6km2). Both species exhibited positive selection for sandflats and mangroves, and avoidance of deeper lagoonal and slope habitats. Monthly patterns were examined only for resident N. acutidens, and residency decreased with increasing shark length and varied seasonally for males but not females. Space use showed weak declines with increasing tidal range, and slight increases with mean air pressure, rainfall and shark length. Protecting sandflat and vegetated habitats may increase the efficacy of no-take zones for juvenile N. acutidens, because they exhibit residency and affinity to these features. Conversely, such protection will be of limited benefit for juvenile C. melanopterus, because they exhibit low residency and broader movements.
... Findings also agree with systematic observations of wild black tip reef sharks (Carcharhinus melanopterus) where vitellin scar surface area was shown to decrease by 94% in 24 days in neonatal individuals; a bite wound on an adult closed within 3 days and was completely healed within 40 days; and a major, deep (25 cm across and 3-5 cm deep) wound from a suspected vessel collision closed fully within 27 days (Chin et al., 2015). Similarly, a male sicklefin lemon shark (Negaprion acutidens) was photographed with a 20 cm vertical laceration on the second dorsal fin which had healed significantly within two months and was difficult to distinguish a year later (Buray et al., 2009). Pelagic stingrays (Pteroplatytrygon violacea) have been shown to expel circle hooks and exhibit wound recovery over a 28 day period (François et al., 2019) and shark bites on reef manta rays (M. ...
... This may also explain why white sharks exhibited healing rates of several months when recovering from minor abrasions at Guadalupe Island where temperatures range from ∼18-20 • C (Domeier and Nasby-Lucas, 2007) and a reef manta ray occupying a region between ∼ 21-24 • C exhibited slower healing rates (McGregor et al., 2019). Meanwhile, black tip reef sharks and sicklefin lemon sharks in tropical waters exhibit similar healing rates to the whale shark (Buray et al., 2009;Chin et al., 2015). Although whale sharks have been shown to oscillate throughout a broad range of temperatures and perform deep dives into the bathypelagic zone (Tyminski et al., 2015), ...
Article
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Wound healing is important for marine taxa such as elasmobranchs, which can incur a range of natural and anthropogenic wounds throughout their life history. There is evidence that this group shows a high capacity for external wound healing. However, anthropogenic wounds may become more frequent due to increasing commercial and recreational marine activities. Whale sharks are particularly at risk of attaining injuries given their use of surface waters and wildlife tourism interest. There is limited understanding as to how whale sharks recover from injuries, and often insights are confined to singular opportunistic observations. The present study makes use of a unique and valuable photographic data source from two whale shark aggregation sites in the Indian Ocean. Successional injury-healing progression cases were reviewed to investigate the characteristics of injuries and quantify a coarse healing timeframe. Wounds were measured over time using an image standardization method. This work shows that by Day 25 major injury surface area decreased by an average of 56% and the most rapid healing case showed a surface area reduction of 50% in 4 days. All wounds reached a point of 90% surface area closure by Day 35. There were differences in healing rate based on wound type, with lacerations and abrasions taking 50 and 22 days to reach 90% healing, respectively. This study provides baseline information for wound healing in whale sharks and the methods proposed could act as a foundation for future research. Use of a detailed classification system, as presented here, may also assist in ocean scale injury comparisons between research groups and aid reliable descriptive data. Such findings can contribute to discussions regarding appropriate management in aggregation areas with an aim to reduce the likelihood of injuries, such as those resulting from vessel collisions, in these regions or during movements between coastal waters.
... Examples of identifiable features include the distinctive patterns on the dorsal surface of spotted eagle rays Aetobatus narinari (Euphrasen 1790) (Corcoran & Gruber, 1999) and ornate wobbegong sharks Orectolobus ornatus (De Vis 1883) (Carraro & Gladstone, 2006 ), and the natural spot patterns behind their gills of leopard sharks Stegostoma fasciatum (Hermann 1783) (Dudgeon et al., 2008) and whale sharks Rhincodon typus Smith 1828 (Arzoumanian et al., 2005; Meekan et al., 2006). Natural patterns on the fins of Pacific angel sharks Squatina californica Ayres 1859 (Fouts & Nelson, 1999), blacktip reef sharks Carcharhinus melanopterus (Quoy & Gaimard 1824) (Porcher, 2005) and, along with scars and deformities on the fin, in basking sharks Cetorhinus maximus (Gunnerus 1765) (Sims et al., 2000), nurse sharks Ginglymostoma cirratum (Bonnaterre 1788) (Castro & Rosa, 2005 ) and sicklefin lemon sharks Negaprion acutidens (Rüppell 1837) (Buray et al., 2009). The unique shape and spot patterns of the dorsal fin in white sharks Carcharodon carcharias (L. ...
... The longevity and individuality of marks and scars are likely to be species-specific. A photo-ID study on N. acutidens in French Polynesia determined that the uniform colour of the focal species combined with the poor resilience of small spots or colour aberrations resulted in this species being difficult to identify from natural colouration alone (Buray et al., 2009). In other species, even prominent natural spots or patterns are known to alter during an animal's natural growth or change at the onset of maturity (Domeier & Nasby-Lucas, 2006; Dudgeon et al., 2008), while scars, wounds, nicks, scratches and other unnatural marks may transform or completely heal over time (Pratt & Carrier, 2001; Castro & Rosa, 2005; Domeier & Nasby-Lucas, 2006; Marshall & Bennett, 2010a; Anderson et al., 2011). ...
Article
The use of photography to discriminate between individuals in a population using natural markings or aberrations is increasingly being utilized to support field research on elasmobranchs. This non-intrusive method has facilitated investigation of a wide variety of subjects including population composition, abundance estimates, residency and movement, demography and social behaviours. Here the first detailed review of photo-identification as a research technique for sharks and rays is provided, and its assumptions, current applications and potential highlighted. The limitations and practical considerations of photographic studies are also investigated with recommendations on initial survey design and ongoing data collection using current technology. Future directions are also explored with an emphasis on a move towards standardized approaches and automated recognition programmes to facilitate global collaborative work.
... In October 2004, Moorea authorities implemented a Management Plan for the Marine Environment (Plan de Gestion de l'Espace Maritime, PGEM) that restricted sharkfeeding activities to 2 zones. Our specific study area was located at Papetoai on the outer slope of the reef (from 149°50' 670" to 149°51' 389" W); it was selected for its abundance of sicklefin lemon sharks (Buray et al. 2009). At this site, 3 different diving centres feed the sharks between 08:00 and 10:30 h. ...
... The food was released at the end of the dive for the benefit of 1 or sometimes 2 sharks. Data on the presence or absence of sharks were recorded on each dive using natural identification marks on their bodies (Buray et al. 2009), photographed with a digital camera when necessary. Part of the identification process included the determination of sex from the presence or absence of claspers, and total length, estimated visually. ...
Article
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The feeding of marine predators is a popular means by which tourists and tour operators can facilitate close observation and interaction with wildlife. Shark-feeding has become the most developed provisioning activity around the world, despite its controversial nature. Amongst other detrimental effects, the long-term aggregation of sharks can modify the natural behaviour of the animals, potentially increase their aggression toward humans, and favour inbreeding. During 949 diving surveys conducted over 44 mo, we investigated the ecology and residence patterns of 36 photo-identified adult sicklefin lemon sharks Negaprion acutidens. The group contained 20 females and 16 males. From this long-term survey, we identified 5 different behavioural groups that we described as ‘new sharks’ (7), ‘missing sharks’ (4), ‘resident sharks’ (13), ‘unpredictable sharks’ (5) and ‘ghost sharks’ (7). In spite of movements in and out of the area by some males and females, which were probably related to mating, the general trend was that residency significantly increased during the study, particularly in males, showing a risk of inbreeding due to the reduction of shark mobility. Intra- and interspecific aggression was also witnessed, leading to an increased risk of potentially severe bites to humans. Our findings suggest the need for a revision of the legal framework of the provisioning activity in French Polynesia, which could include a yearly closure period to decrease shark behavioural modifications due to long-term shark-feeding activities.
... Diving surveys were implemented on a daily basis representing 1058 days between January 2005 and September 2009 [22] . Based on photo- identification [27], we consistently identified 40 mature sharks (18 males and 22 females ranging from 2.4 to 3.1 meters total length), with an average of 26.75 ± 3.33 individuals sighted per year (24 in 2005, 28 in 2006, 31 in 2007, 29 in 2008 and 24 in 2009). When possible, a fin clip was removed from the dorsal fin of each new shark using a modified spear gun. ...
... Of the 16 microsatellite loci, three did not satisfy Hardy-Weinberg and linkage disequilibrium assumptions. To test our photoidentification technique [27], GENALEX 6 [30] was used to detect potential identical genotypes belonging to resampled individuals. No identical genotype was found confirming the accuracy of our photo-identification technique. ...
Article
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Human pressures have put many top predator populations at risk of extinction. Recent years have seen alarming declines in sharks worldwide, while their resilience remains poorly understood. Studying the ecology of small populations of marine predators is a priority to better understand their ability to withstand anthropogenic and environmental stressors. In the present study, we monitored a naturally small island population of 40 adult sicklefin lemon sharks in Moorea, French Polynesia over 5 years. We reconstructed the genetic relationships among individuals and determined the population's mating system. The genetic network illustrates that all individuals, except one, are interconnected at least through one first order genetic relationship. While this species developed a clear inbreeding avoidance strategy involving dispersal and migration, the small population size, low number of breeders, and the fragmented environment characterizing these tropical islands, limits its complete effectiveness.
... Meekan et al., 2006; Van Tienhoven et al., 2007; Luiz et al., 2008). These studies based on colour patterns photo-ID are reliable because focal animals have at least two distinct colours on specific areas of their bodies (Buray et al., 2009). ...
... Nevertheless, some may persist, such as the absence of a dorsal fin spine or cut on the pectoral fin (Figure 1B, c). Although some fish can present great ability to regenerate their tissue, such as the white shark (Domeier & Nasby-Lucas, 2006) and lemon shark (Buray et al., 2009), so far, no information is available about tissue healing time for groupers. We verified that scars on the goliath grouper can fulfil its role as an identification tool for a long time, on specimens that had a significant tissue loss. ...
Article
Full-text available
Herein, we describe the use of scars to photo-identify the goliath grouper,Epinephelus itajara. Three individuals were photoidentified and re-sighted several times at the same site along the Brazilian coast, including the longest report for site fidelity, with more than four years.
... I will however also use the results of a previous study that was conducted in Moorea island between 2005 and 2010. For details about the development of shark feeding in Moorea island, quite similar to the one of Bora-Bora, see Buray, Mourier, Planes, and Clua (2009) and Clua et al. (2010). ...
... Sicklefin lemon sharks have recently become a focal species in shark feeding activities in the eastern Pacific, in particular in French Polynesia (Buray et al., 2009). Sicklefin lemon sharks are not, however, as gregarious as other shark species involved in shark feeding operations, such as the grey reef shark that naturally aggregate in large schools in confined areas (Compagno, 1984). ...
... density or biomass) given the huge bias that is produced for mobile fish, other survey techniques such as mark-recapture (i.e. photo ID or artificial marks), which are currently used for whale sharks394041 as well as white [42,43], sicklefin lemon [44], and grey nurse sharks [45,46] may produce more accurate estimates of absolute density for highly mobile and rare animals. The current application of our simulation model was kept simple, but additional complexities of fish behaviour, habitat, sample area, and survey conditions could be included in AnimDens. ...
Article
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Background: Increasingly, underwater visual censuses (UVC) are used to assess fish populations. Several studies have demonstrated the effectiveness of protected areas for increasing fish abundance or provided insight into the natural abundance and structure of reef fish communities in remote areas. Recently, high apex predator densities (>100,000 individuals x km(-2)) and biomasses (>4 tonnes x ha(-1)) have been reported for some remote islands suggesting the occurrence of inverted trophic biomass pyramids. However, few studies have critically evaluated the methods used for sampling conspicuous and highly mobile fish such as sharks. Ideally, UVC are done instantaneously, however, researchers often count animals that enter the survey area after the survey has started, thus performing non-instantaneous UVC. Methodology/principal findings: We developed a simulation model to evaluate counts obtained by divers deploying non-instantaneous belt-transect and stationary-point-count techniques. We assessed how fish speed and survey procedure (visibility, diver speed, survey time and dimensions) affect observed fish counts. Results indicate that the bias caused by fish speed alone is huge, while survey procedures had varying effects. Because the fastest fishes tend to be the largest, the bias would have significant implications on their biomass contribution. Therefore, caution is needed when describing abundance, biomass, and community structure based on non-instantaneous UVC, especially for highly mobile species such as sharks. Conclusions/significance: Based on our results, we urge that published literature state explicitly whether instantaneous counts were made and that survey procedures be accounted for when non-instantaneous counts are used. Using published density and biomass values of communities that include sharks we explore the effect of this bias and suggest that further investigation may be needed to determine pristine shark abundances and the existence of inverted biomass pyramids. Because such studies are used to make important management and conservation decisions, incorrect estimates of animal abundance and biomass have serious and significant implications.
... Applying reliable methods for assessing shark behaviour is a challenge. We assured the quality of our observations by identifying each individual lemon shark through photo-identification, as detailed in a separate paper (Buray et al. 2009). Our study com-prised a relatively low number of sharks (39), while photo-identification allows independent and reliable diagnoses for much larger numbers, e.g. ...
Article
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.
... maximus (Sims et al. 2000) and spotted raggedtooth sharks Carcharias taurus (Van Tienhoven et al. 2007;Bansemer and Bennett 2008). Even individuals from species with uniform colours could be efficiently identified, e.g. the nurse shark Gynglymostoma cirratum (Castro and Rosa 2005) and the sicklefin lemon shark Negaprion acutidens (Buray et al. 2009). More recently, this technique allowed the collection of critical data about the range of movements for the whitetip reef shark Triaenodon obesus (Whitney et al. 2011). ...
Article
Tiger Sharks, Galeocerdo cuvier, are large top-level predators usually solitary as adults. Observation of their scavenging activity on the carcass of a dead whale offered a rare opportunity for better understanding the pattern of intra-specific behaviour within the aggregations of these large predators. In January 2002, the stranding, subsequent death and consumption of a 17.4m total length (TL) blue whale, Balaenoptera musculus, was observed and filmed in Prony Bay, southern New Caledonia. After three weeks of confinement in the bay, the cetacean was killed by adult bullsharks Carcharhinus leucas. The first adult Tiger Shark was subsequently observed around the carcass after 36h. The fat slicks from the carcass attracted further Tiger Sharks which arrived after an additional 24h. The use of photo-identification on video footage collected during four observation sessions over an eight-day period identified 46 individual Tiger Sharks (primarily adult females between 3.3 and 4m TL) participating in the feeding aggregation. Only four animals were identified in two seperate observation sessions (over two consecutive days), suggesting a short-term residency pattern of several hours (<36h) around the carcass. As the arrival time of Tiger Sharks to the carcass differed, most arrivals of a new participant were followed by a frenzied period of intense intra-specific interaction. Different biting and agonistic behaviours were demonstrated by the Tiger Sharks on the carcass, including three new behaviours previously undescribed for this species. Size and level of aggressiveness appeared to be the determining factors of dominance amongst Tiger Sharks. These observations and analysis demonstrate that systematic study of feeding aggregations supported by photo-identification could contribute to knowledge of large shark ecology when coupled with capture-recapture, genetic fingerprinting and tagging techniques.
... Mourier, unpublished data). Every new shark was recorded on a specific identification sheet, similar to the work done on the sicklefin lemon shark, Negaprion acutidens, in Moorea (Buray et al. 2009). Identification was facilitated by the good visibility of Moorea waters, being relatively stable over time and allowing photography of some shy specimens that remained up to 20 m from the diver. ...
Article
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Large, solitary, marine predators such as sharks have been observed to aggregate at specific areas. Such aggregations are almost certainly driven by foraging and behavioural strategies making space for diverse spatial organizations. Reef-associated shark species often show strong patterns of site fidelity that could be viewed as a prerequisite for sociality. However, there is limited empirical evidence that such aggregations are driven by intrinsic social factors. Association data for blacktip reef sharks, Carcharhinus melanopterus, were obtained from photoidentification surveys conducted in Moorea coral reefs (French Polynesia). We adapted a social network approach to demonstrate evidence of four main communities and two subcommunities within the population. We confronted the resulting structure with candidate explanatory variables. Sharks formed spatial groups characterized by nonrandom and long-term associations, despite opportunities for social relationships to develop between communities. Sex and length of sharks tended to influence assortment at the population and community levels. Individual space use also explained community structure, although spatial assortment was globally weaker than random expectations, suggesting that observed associations were not an artefact of the sampling design or spatial distribution of individuals. We conclude that the observed grouping patterns not only resulted from passive aggregations for specific resources, but rather the communities developed from an active choice of individuals as a sign of sociability. Individual preferences and adaptation to local conditions, as well as demographic, ecological and anthropogenic factors, may explain the social variability between communities. This suggests that a stable grouping strategy may confer substantial benefits in this marine predator.
... The food was released at the end of the dive. Data on presence/absence of individual sharks were recorded for each dive using photo-identification, the size and gender, and natural marks on shark bodies such as scars, notches, missing tissues or coloured spots (Buray et al. 2009). ...
... The food was released at the end of the dive. Data on presence/absence of individual sharks were recorded for each dive using photo-identification, the size and gender, and natural marks on shark bodies such as scars, notches, missing tissues or coloured spots (Buray et al. 2009). ...
Article
Most arguments invoked so far by the scientific community in favour of shark conservation rely on the ecological importance of sharks, and have little impact on management policies. During a 57-month study, we were able to individually recognise 39 sicklefin lemon sharks that support a shark-feeding ecotourism activity in Moorea Island, French Polynesia. We calculated the direct global revenue generated by the provisioning site, based on the expenses of local and international divers. The total yearly revenue was around USD5.4 million and the 13 sharks most often observed at the site had an average contribution each of around USD316 699. Any one of these sharks represents a potential contribution of USD2.64 million during its life span. We argue that publicising economic values per individual will be more effective than general declarations about their ecological importance for convincing policy makers and fishers that a live shark is more valuable than a dead shark for the local economy. Studies monitoring the potential negative ecological effects of long-term feeding of sharks should, however, be conducted to ensure these are also considered. Besides declarations about the non-consumptive direct-use value of sharks, as promoted by ecotourism, the calculation of their other economic values should also benefit shark conservation.
... A trained observer accompa-nied the tourist dives to collect data on all shark species present. Photographs and video footage were taken whenever possible to facilitate individual identification using natural marks and pigmentation [13][14][15]. For this study, the following data were considered: 1) number of C. leucas observed between 2003 and 2009 (recorded on 882 days; mean 6 SD = 126643.3 ...
Article
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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.
... Because of his natural science knowledge, Buray was supervised by CRIOBE Director Serge Planes and CRISP Coordinator Eric Clua from 2006-2010 while undertaking an EPHE 2 qualification on Moorea's lemon shark population. The qualification gave rise to a scientific publication on a recognition method for these sharks using photo identification (Buray et al. 2009). ...
... Wound healing could be reduced in cooler waters owing to reduced metabolic rates, as evident in grey nurse sharks (Bansemer and Bennett, 2010), and may also explain the case in white sharks (Carcharodon carcharias) at Guadalupe Island (∼18-20°C), where 'minor lacerations and abrasions' were visible for several months (Domeier and Nasby-Lucas, 2007). Meanwhile, sicklefin lemon sharks in tropical waters exhibit similar healing rates to blacktip reef sharks (Buray et al., 2009), providing further circumstantial evidence of faster healing rates in warmer waters. While interspecific variation, individual immunology or environmental factors may affect wound recovery, the relative importance of these variables for wound healing in sharks is yet to be explored. ...
Article
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Wound healing is important for sharks from the earliest life stages, for example, as the ‘umbilical scar’ in viviparous species heals, and throughout adulthood, when sharks can incur a range of external injuries from natural and anthropogenic sources. Despite anecdotal accounts of rapid healing in elasmobranchs, data regarding recovery and survival of individuals from different wound or injury types has not been systematically collected. The present study documented: (i) ‘umbilical scar’ healing in wild-caught, neonatal blacktip reef sharks while being reared for 30 days in flow-through laboratory aquaria in French Polynesia; (ii) survival and recovery of free-swimming blacktip reef sharks in Australia and French Polynesia following a range of injuries; and (iii) long-term survival following suspected shark-finning activities. Laboratory monitoring, tag-recapture records, telemetry data and photo-identification records suggest that blacktip reef sharks have a high capacity to survive and recover from small or even large and severe wounds. Healing rates, recovery and survival are important factors to consider when assessing impacts of habitat degradation and fishing stress on shark populations. The present study suggests that individual survival may depend more on handling practices and physiological stress rather than the extent of physical injury. These observations also contribute to discussions regarding the ethics of tagging practices used in elasmobranch research and provide baseline healing rates that may increase the accuracy in estimating reproductive timing inferred from mating scars and birth dates for neonatal sharks based on umbilical scar healing status.
... Applying reliable methods for assessing shark behaviour is a challenge. We assured the quality of our observations by identifying each individual lemon shark through photo-identification, as detailed in a separate paper (Buray et al. 2009). Our study com-prised a relatively low number of sharks (39), while photo-identification allows independent and reliable diagnoses for much larger numbers, e.g. ...
Article
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Brunnschweiler & McKenzie (2010; Mar Ecol Prog Ser 420: 283-284) expressed reservations over the findings of Clua et al. (2010; Mar Ecol Prog Ser 414: 257-266), mostly related to the lack of a reference site or a control group in the methodology. In our study, we distinguished between 39 individuals of sicklefin lemon sharks Negaprion acutidens, mainly based on photo-identification. Our study was based on the field-survey approach, with time (a continuous variable) as the source of variation, and thus a control group was not necessary. We provide here additional data that support the notion that abundance of lemon sharks on the provisioning site was increasing, both in their number and fidelity. We maintain our conclusion that sicklefin lemon shark provisioning off Moorea Island can continue, but should be more intensely controlled.
... The Sicklefin Lemon shark Negaprion acutidens (Rüppell, 1837) is a tropical inshore large (≤ 340 cm total length), stout shark, with a yellowish brown color above, paler below [12]. It is a fish-eating shark, potentially dangerous because of its large size, powerful jaws and dagger-like teeth ( Figure 1); it is normally inoffensive and sluggish but very aggressive when provoked [13]. ...
Article
Introduction: Shark-based ecotourism is significantly developping around the world, often without appropriate management of risk. This activity involves a risk of accidental bites on divers that can be quite severe or even fatal. Objectives: To determine if ecotourism companies’ liability can be engaged in the context of bites on scuba divers in presence of hand-feeding practices, supporting the legitimacy of financial compensation for the victims. Methods: We analyzed the development from the mid-eighties to 2010 of shark-based ecotourism through artificial provisioning practices in Moorea island (French Polynesia) and more specifically the features and motivation of two bites on divers by Sicklefin Lemon sharks. Results: The specific practice of hand-feeding can be considered as a facilitating factor for accidental bites on divers, potentially involving the diving operator’s responsability. Conclusions: Our findings should support the technical work of experts that might be called in such cases.
... Like all animals, elasmobranchs are susceptible to injury through encounters with other animals and, increasingly, humans [e.g., 110]. Several reports have claimed that elasmobranchs, particularly sharks, recover from injuries rapidly and without infection [e.g., [111][112][113][114][115]. However, healing rates have been measured for only a small number of species and are variable among taxa [e.g., 115,116], making it hard to determine a baseline healing rate for comparison. ...
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Elasmobranchs (sharks, skates and rays) are of broad ecological, economic, and societal value. These globally important fishes are experiencing sharp population declines as a result of human activity in the oceans. Research to understand elasmobranch ecology and conservation is critical and has now begun to explore the role of body-associated microbiomes in shaping elasmobranch health. Here, we review the burgeoning efforts to understand elasmobranch microbiomes, highlighting microbiome variation among gastrointestinal, oral, skin, and blood-associated niches. We identify major bacterial lineages in the microbiome, challenges to the field, key unanswered questions, and avenues for future work. We argue for prioritizing research to determine how microbiomes interact mechanistically with the unique physiology of elasmobranchs, potentially identifying roles in host immunity, disease, nutrition, and waste processing. Understanding elasmobranch–microbiome interactions is critical for predicting how sharks and rays respond to a changing ocean and for managing healthy populations in managed care.
... Sharks can be identified using body coloration, patterns or fin notches which are specific to each individual ( Fig. 18.4A). This technique of photo-identification is noninvasive and has been used for many elasmobranch species (Marshall and Pierce 2012) and to track shark and ray associations and movements, including blacktip reef sharks (Mourier et al. 2012), spotted eagle rays Aetobatus narinari (Krause et al. 2009c) and even the sicklefin lemon shark Negaprion acutidens which has a rather homogenous body coloration (Buray et al. 2009). However, other studies on species in which individuals are hard to identify used externally attached visual color-coded tags (Fig. 18.4C;Jacoby et al. 2010;Guttridge et al. 2011) or fluorescent visible implant elastomer tags inserted subcutaneously on the dorsal surface (Fig. 18.4B;Jacoby et al. 2012cJacoby et al. , 2014. ...
Chapter
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In recent decades, network analyses have become ubiquitous in ecology, facilitating our understanding of linkages between paired entities, whether it be genes, proteins, individuals, species, or habitats (Blüthgen et al., 2008; Croft et al., 2008; Krause et al., 2007; Proulx et al., 2005; Wey et al., 2008). Network theory (also known as graph theory) originates from the mathematical and social sciences but has developed concurrently across many disciplines, including computational science, physics, management, genetics, and epidemiology (Newman, 2010), to name but a few.
... Sharks can be identified using body coloration, patterns or fin notches which are specific to each individual ( Fig. 18.4A). This technique of photo-identification is noninvasive and has been used for many elasmobranch species (Marshall and Pierce 2012) and to track shark and ray associations and movements, including blacktip reef sharks (Mourier et al. 2012), spotted eagle rays Aetobatus narinari (Krause et al. 2009c) and even the sicklefin lemon shark Negaprion acutidens which has a rather homogenous body coloration (Buray et al. 2009). However, other studies on species in which individuals are hard to identify used externally attached visual color-coded tags (Fig. 18.4C;Jacoby et al. 2010;Guttridge et al. 2011) or fluorescent visible implant elastomer tags inserted subcutaneously on the dorsal surface (Fig. 18.4B;Jacoby et al. 2012cJacoby et al. , 2014. ...
... Territory size of individuals can be assessed using a variety of techniques, from underwater telemetry, to mark-recapture, camera trapping or individual identification (Lucas & Baras, 2000). Individual identification in fishes is commonly based on natural marks or body-facial patterns and can be an alternative to more costly methods (e.g., genetic) for identifying individuals in species that display variation in external characters such as body colour pattern, typical scares or marks (Buray et al., 2009;Dala-Corte et al., 2016). ...
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The site fidelity of ballan wrasse Labrus bergylta was studied using photo‐identification and external tagging. Five male individuals were observed to defend the same small territory composed of a few rocks during several reproductive seasons spanning 2 to 15 years. These results provide one of the strongest indications of long‐term very fine‐scale site fidelity in marine fishes. This article is protected by copyright. All rights reserved.
... For example, empirical studies on teleosts have shown faster generation of new tissue in warmer versus cooler waters [37]. Observations on wild elasmobranchs lend support to this idea, with slower healing rates of small abrasions and cuts in white sharks in colder waters [21] compared with sicklefin lemon sharks Negaprion acutidens [38] and blacktip reef sharks in tropical waters [18]. All observations for manta ray #0018 were from Bateman Bay, which is towards the latitudinal extent of the tropics. ...
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Increasing vessel traffic in the marine environment due to commercial and recreational activities has amplified the number of conflicts with marine animals. However, there are limited multi-year observations of the healing rate of marine animals following vessel strike. Here we document the healing rate of a reef manta ray Mobula alfredi, following lacerations caused by a propeller along the pectoral fin. We demonstrate a high healing capacity, with wound length following a negative exponential curve over time. Lacerations healed to 5% of the initial wound length (i.e. 95% closure) within 295 days. The wounds appeared to stabilise at this point as observed more than three years following the incident and resulted in a distinctive scarring pattern. Examination of an extensive photo-identification catalogue of manta rays from the Ningaloo Coast World Heritage Area showed that the scarring pattern occurs more frequently than previously recognised, as the wounds had been previously attributed to failed predation attempts. This study provides baseline information for wound healing from vessel strike in reef manta rays and indirect evidence for increased vessel strikes on manta rays within the Ningaloo Coast World Heritage Area. We discuss the implication for spatial and behavioural management of vessels around manta rays.
... Photo identification (hereafter photo-ID) of individuals using natural marks is often used in conjunction with capture-recapture methods, minimising the need for invasive techniques (e.g., sub-dermal tags; Arzoumanian et al., 2005;Harvey et al., 2003;Harvey & Shortis, 1995;Würsig & Würsig, 1977). Photo-ID capture-recapture has successfully been employed on numerous chondrichthyan species, including but not limited to whale sharks (Rhinchodon typus, Holmberg et al., 2009;Speed et al., 2008), great white sharks (Carcharadon carcharias, Chapple et al., 2011;Ryklief et al., 2014), C. maximus (Gore et al., 2016), raggedtooth sharks (Carcharias taurus, Van Tienhoven et al., 2007) and sicklefin lemon sharks (Negaprion acutidens, Buray et al., 2009). ...
Article
The broadnose sevengill shark (Notorynchus cepedianus) is a common high trophic level predator around coastal New Zealand. Data on the ecology of the species in New Zealand are severely lacking and anthropogenic impacts are unquantified. To partially address this, we undertook a study of the demographics of a population at Stewart Island. Sampling trips were carried out seasonally from winter 2016 to spring 2017. A baited underwater video system (BUV) was deployed on 133 occasions (mean = 22.2 deployments per season) in a shallow coastal embayment to capture underwater video of N. cepedianus for photo‐ID of individuals. N. cepedianus was detected on all but one deployment. Images extracted from video recorded the presence of 149 different individuals. Capture‐recapture analysis of these data using robust design methods indicated a seasonal trend in abundance of the population using the study area, ranging from 34 (95% CI = 21 ‐ 55) during winter 2016, to 94 (95% CI = 44 ‐ 199) during spring 2017. This study presents the first data on demographic parameters of N. cepedianus in New Zealand.
... Population estimates of basking shark, Cetorhinus maximus [25], and great white shark, Carcharhinus carcharius [26], have been made based on individual recognition through quality images of dorsal fins. Photo-identification based on images captured by divers or fishers has also been used in ecological studies of blacktip reef shark, C. melanopterus [27], Greenland shark, Somniosus microcephalus [28], nurse shark, Ginglymostoma cirratum [29], sicklefin sharks, Negaprion acutidens [30], broadnose sevengill shark, Notorynchus cepedianus [23], and whale shark [31,32], as well as flapper skate, Dipturus intermedius [33]. In addition, BRUVS have been used to monitor the presence and size [34], as well as site fidelity [11], of individually identified sharks. ...
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Baited Remote Underwater Video Stations (BRUVS) are widely used for monitoring relative abundances of fishes, especially sharks, but only the maximum number of individuals seen at any one time (MaxN) is usually recorded. In both the Cayman Islands and the Amirante Islands, Seychelles, we used photo-ID to recognise individual sharks recorded on BRUVS videos. This revealed that for most species the actual numbers of separate individuals (IndN) visiting the BRUVS were significantly higher than MaxN, with, for example, ratios of IndN to MaxN being 1.17 and 1.24 for Caribbean reef, Carcharhinus perezi, and nurse, Ginglymostoma cirratum, sharks in the Cayman Islands, and 2.46 and 1.37 for blacktip reef, C. melanopterus, and grey reef, C. amblyrhynchos, sharks, respectively, in the Amirantes. Further, for most species, increasing the BRUVS deployment period beyond the 60 min normally used increased the observed IndN, with more than twice as many individuals in the Cayman Islands and >1.4 times as many individuals in the Amirantes being recorded after 120 min as after 60 min. For most species, MaxN and IndN rose exponentially with time, so data from different deployment periods cannot reliably be compared using catch-per-unit-effort (CPUE) calculated as catch-per-unit-time. In both study areas, the time of first arrival of individuals varied with species from <1 min to >2 h. Individually identifiable sharks were re-sighted after up to 429 days over 10 km away in the Cayman Islands and 814 days over 23 km away in the Amirantes, demonstrating that many individuals range over considerable distances. Analysis of Cayman re-sightings data yielded mean population estimates of 76 ± 23 (SE) and 199 ± 42 (SE) for C. perezi and G. cirratum, respectively. The results demonstrate that, for sharks, the application of both photo-identification and longer deployment periods to BRUVS can improve the precision of abundance estimates and provide knowledge of population size and ranging behaviour.
... Monitoring the demographics and distribution of a species through the identification and tracking of individuals provides researchers with knowledge essential to take informed conservation actions (Legge et al. 2018). One popular technique to monitor mobile fauna is through the photographic identification of individuals using unique variations in natural markings and patterns including dorsal fin morphology (Gubili et al. 2009), spot patterns (Meekan et al. 2006) and colouration or scars (Buray et al. 2009). This has been applied to a wide range of marine animals, including elasmobranchs (Speed et al. 2007, van Tienhoven et al. 2007, Marshall & Pierce 2012. ...
Article
Monitoring the demographics and movement patterns of mobile marine species underpins appropriate management and conservation strategies. Photographic identification of whale sharks Rhincodon typus based on individual variations in spot patterns is a widely used technique for monitoring of populations, but relies on the untested assumptions that these variations in spot patterns are unique to each shark and can be reliably detected using photo-matching software. This study validated the accuracy of photo-identification technique by manually determining the number of photo-identified individuals showing mismatched genetic profiles created for the individuals using 12 microsatellite markers. Results from 154 photographic and genetic identifications of whale sharks were 100% concordant, showing the uniqueness of spot patterns to each shark and high accuracy of the photo-identification technique. Based on these techniques, we observed an annual resighting rate of approximately 10% at Ningaloo Reef, Western Australia, between 2016 and 2018, showing evidence that variations in spot patterns did not change over a time scale of years. Our study shows that the photographic identification technique provides a reliable means to recognise individuals and monitor whale sharks through time.
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The extent of the global human footprint [ 1 ] limits our understanding of what is natural in the marine environment. Remote, near-pristine areas provide some baseline expectations for biomass [ 2, 3 ] and suggest that predators dominate, producing an inverted biomass pyramid. The southern pass of Fakarava atoll—a biosphere reserve in French Polynesia—hosts an average of 600 reef sharks, two to three times the biomass per hectare documented for any other reef shark aggregations [ 4 ]. This huge biomass of predators makes the trophic pyramid inverted. Bioenergetics models indicate that the sharks require ∼90 tons of fish per year, whereas the total fish production in the pass is ∼17 tons per year. Energetic theory shows that such trophic structure is maintained through subsidies [ 5–9 ], and empirical evidence suggests that sharks must engage in wide-ranging foraging excursions to meet energy needs [ 9, 10 ]. We used underwater surveys and acoustic telemetry to assess shark residency in the pass and feeding behavior and used bioenergetics models to understand energy flow. Contrary to previous findings, our results highlight that sharks may overcome low local energy availability by feeding on fish spawning aggregations, which concentrate energy from other local trophic pyramids. Fish spawning aggregations are known to be targeted by sharks, but they were previously believed to play a minor role representing occasional opportunistic supplements. This research demonstrates that fish spawning aggregations can play a significant role in the maintenance of local inverted pyramids in pristine marine areas. Conservation of fish spawning aggregations can help conserve shark populations, especially if combined with shark fishing bans.
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Shark social behavior has received little attention to date, despite its considerable interest for shark conservation and the mitigation of human-shark conflicts. It provides new insights on the ecological effects of shark provisioning activities, and can also contribute to shark bite prevention.
Thesis
Photographic identification of unique patterning on individual animals within a species is a nonintrusive and powerful technique for gathering information on population size, movement, behaviour, and life-history specifications for wild populations. Photo-ID is dependent on reliably reidentifying individuals through visible marks which are stable over extended periods of time. Flapper skate (Dipturus cf. intermedia) have distinguishable patterns on their dorsal surface which are unique to each individual. Due to historic mislabelling of the species and confusion with the blue skate (Dipturus cf. flossada), flapper skate are now critically endangered where there are relict populations. The suitability of flapper skate for photo-ID was tested in this paper by assessing the visual variance of the dorsal surface in terms of spot pattern and injury. It was shown that the software HotSpotter could reidentify individuals over the maximum time frame available in the database (1602 days), and that the majority of individuals (81%) were recaptured within a year of their last capture event. The quality of the photo data was insufficient to quantify any possible variance of spot pattern over a short period (1098 days), however it was concluded that there was no significant change in spot pattern that would impede future matching efforts if the recapture rate was ≥1098 days.
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Sharks were collected over 2 years (six field trips) from the offshore prawn trawling grounds in Albatross Bay (7-45 m depth), from shallow (< 5 m) nearshore waters, and from the adjacent inshore waters of the Embley River estuary. Stomachs from 11 shark species were collected and analysed gravimetrically (% dry weight). Four species (Carcharhinus cautus, C. dussumieri, C. tilstoni and Rhizoprionodon acutus) were represented in all three regions. Seven general food categories (Mollusca, Penaeidae, Brachyura, Stomatopoda, Other Crustacea, Teleostei and Other) were used to describe their diets. Nearly all sharks were primarily piscivorous, and the teleost diet is discussed in detail. Hemigaleus microstoma was not piscivorous and cephalopods represented 94.7% of its diet. Teleostei constituted less than 70% of the diet for three other species: C. amblyrhynchos offshore (64.3% Teleostei, 18.6% Penaeidae, 11.6% Mollusca), C. dussumieri offshore (52.5% Teleostei, 21.8% Stomatopoda, 10.1% Penaeidae), and R. acutus nearshore (59.3% Teleostei, 17.6% Cephalopoda, 10.3% Brachyura). Offshore, there was a strong correlation between estimates of consumed prey biomass and of trawled prey biomass, suggesting that these sharks feed in a density-dependent manner.
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In an initial telemetry study we examined patterns of activity and space-utilization by the lemon shark, Negaprion brevirostris, using manual ultrasonic tracking. Nine sharks were tracked intermittently for periods of 1-8 days: The longest continuous tracking segment lasted 101 h. Total activity space per individual ranged from 9-93 km2, as determined by the maximum-area polygon method. All sharks tracked at Bimini showed some degree of site attachment. The two largest sharks tracked elsewhere, did not remain in the area of tagging but made deepwater excursions. At Bimini, sharks tracked during the day were located eastward of their nighttime activity spaces. They moved westward over the flats at sunset and back eastward at sunrise. These sharks appeared to use the sun as an orientation cue. The tracks of two sharks fitted with speed-sensing transmitters demonstrated that swimming speeds were two times faster than the corresponding point-to-point rates of movement. The highest rates of movement were recorded at evening and morning twilight periods: the average nighttime rate was higher than the daytime rate—although statistical significance could not be established. Underwater and aerial observations showed lemon sharks to be associated with each other, with other sharks and with teleosts. Findings are interpreted in light of current information on space utilization, diel activity, social grouping, and energetics.
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A systematic, reliable method for identifying white sharks, Carcharodon carcharias Linnaeus, from underwater photographs was developed and applied to examine site fidelity at Guadalupe Island, Mexico (29˚N, 118˚W). The most reliable features for repeat identification in multiple years were the pigment patterns on the gill flaps, pelvic fins, and caudal fins. Pigment patterns in all three regions were asymmetrical on the right and left sides making it necessary to photograph both sides to catalog each individual. However, once cataloged, an individual could be re-identified using a partial body image. Using this method, 73 individuals were identified between 2001 and 2005. Site fidelity was indicated through repeated annual sightings of individuals with 78% of the identified sharks observed over at least 2years. Males were found to arrive at Guadalupe Island as early as July and females in September. Peak abundances at the site occurred August–December. The sex ratio was not significantly different from unity in 2002, 2004, and 2005. This monitoring technique has shown Guadalupe Island to be an important white shark aggregation site in the eastern Pacific.
Article
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We assessed information on the population structure of the nurse shark, Ginglymostoma cirratum, at Atol das Rocas, northeastern Brazil, through underwater observations. Based on photographic records of natural distinctive marks for individual recognition, we used probabilistic estimators (Petersen–Bailey and Jolly–Seber) to assess population size. We found that 46% of the sharks (194 individuals) had distinctive marks. The population size was estimated in 368 individuals, using the Petersen–Bailey estimator, and 339 individuals using the Jolly–Seber estimator.
Article
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The diets of one ray species (Rhinobatus typus) and three shark species (Carcharhinus cautus, Negaprion acutidens, Rhizoprionodon acutus) undergo size-related changes and differ among these species in the nearshore waters of a large subtropical embayment (Shark Bay) in which these elasmobranchs are abundant, thereby reducing the potential for competition for food within and among these four species. R. typus fed almost exclusively on penaeid prawns and portunid crabs, which is reflected in its narrow dietary breadth, whereas different species of teleosts constituted a major component of the diets of each size class of the three shark species. The prey consumed by the three shark species was diverse, with representatives of 15 teleost families being consumed by C. cautus and substantial volumes of cephalopods being ingested by that species and R. acutus. The pronounced differences in the diet of the single ray species and three shark species reflect differences between a bottom-dwelling and more pelagic life, and between modes of feeding and relative mouth sizes. The relative contributions of the different species of teleost to the diets of the three shark species varied. Thus, although each of these species fed on atherinids, labrids and sillaginids, C. cautus also consumed substantial amounts of platycephalids and terapontids and R. acutus and N. acutidens also ingested considerable amounts of clupeids. Furthermore, R. acutus, which is the only one of the four species that typically occurs over seagrass, was the only species that fed on the centropomid Psammoperca waigensis, which is very abundant in seagrass meadows. However, the sparid Rhabdosargus sarba, which lives in unvegetated areas, was never ingested by R. acutus, but was consumed by C. cautus and N. acutidens. As the individuals of R. typus increased in size, they progressively consumed proportionately smaller volumes of the penaeid prawns Penaeus merguiensis and Melicertus latisulcatus and relatively greater volumes of the portunid crab Portunus pelagicus, which is slightly larger and has a harder exoskeleton. In addition to teleosts, large C. cautus ingested substantial volumes of portunid crabs and ophidian reptiles, presumably sea snakes, while large N. acutidens also fed on the ray R. typus.
Article
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Population size and structure of whale sharks (Rhincodon typus) remain unknown despite their economic importance to targeted tourism and fisheries and their 2002 listing on CITES Appendix II. Here, we present results from the first whale shark population study in the Western Hemisphere and describe the inherent difficulties of assessing populations using catch-independent methods in free-ranging sharks. From 1998 to 2003, we identified 106 whale sharks using their distinctive scars and spot patterns following 521 encounters at a predictable seasonal aggregation on the Mesoamerican Barrier Reef linked to snapper spawning aggregations at Gladden Spit, Belize. Encountered sharks measured a mean total length of 6.3 m ± 1.7 m S.D. and a range of 3.0–12.7 m (n = 317). Sexual and size segregation is suggested: 31% of encountered sharks (n = 162) were sexed, of which 86% were immature males. Between 1999 and 2002, 70 sharks were tagged with 72 conventional tags and measured sharks (n = 63) possessed a mean length of 6.0 m ± 1.6 m S.D. (range 3.0–9.7 m). Growth rates for three resighted sharks ranged from an estimated 0.03–0.70 m year−1. Resightings of tagged sharks elsewhere on the Mesoamerican Barrier Reef indicate that the population is not resident at Gladden Spit and is shared with two other sites possessing seasonal aggregations: Isla Contoy, Mexico and Utila, Honduras. Monitoring whale shark populations at Gladden Spit and the other aggregation sites on the Mesoamerican Barrier Reef underpins the region's lucrative and burgeoning whale shark tourism and is key to their local and international conservation.
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Sharks and rays are thought to have a large number of independent origins of live-bearing. We examined evolutionary transitions to live-bearing and maternal input to embryos in this subclass by optimizing reproductive characters onto a composite phylogeny. Egg-laying (40 per cent of all species) is the likely ancestral reproductive mode for this clade, and there is evidence that live-bearing has evolved independently 9–10 times and maternal input 4–5 times. Most transitions (12–15) have been toward live-bearing with provisioning limited to yolk. These have occurred from egg-laying ancestors or live-bearing taxa that provide maternal input to embryos. Only 2–3 transitions have occurred in the other direction, i.e. away from yolk-only bearing. Egg-laying has evolved from live-bearing ancestors in skates, Rajidae (25 per cent of all species) and possibly in the zebra shark, Stegostoma fasciata. Thus, although there has been an overall trend toward the evolution of live-bearing in elesmobranchs, the evolution of additional maternal input has been extremely labile.
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Effective approaches for the management and conservation of wildlife populations require a sound knowledge of population demographics, and this is often only possible through mark-recapture studies. We applied an automated spot-recognition program (I3S) for matching natural markings of wildlife that is based on a novel information-theoretic approach to incorporate matching uncertainty. Using a photo-identification database of whale sharks (Rhincodon typus) as an example case, the information criterion (IC) algorithm we developed resulted in a parsimonious ranking of potential matches of individuals in an image library. Automated matches were compared to manual-matching results to test the performance of the software and algorithm. Validation of matched and non-matched images provided a threshold IC weight (approximately 0.2) below which match certainty was not assured. Most images tested were assigned correctly; however, scores for the by-eye comparison were lower than expected, possibly due to the low sample size. The effect of increasing horizontal angle of sharks in images reduced matching likelihood considerably. There was a negative linear relationship between the number of matching spot pairs and matching score, but this relationship disappeared when using the IC algorithm. The software and use of easily applied information-theoretic scores of match parsimony provide a reliable and freely available method for individual identification of wildlife, with wide applications and the potential to improve mark-recapture studies without resorting to invasive marking techniques.
Article
Elasmobranch reproductive behavior has been inferred from freshly caught specimens, laboratory examinations of reproductive structures and function, or determined from direct observations of captive or free swimming wild animals. Several general behaviors have been described including seasonal sexual segregation, courtship and copulation. Courtship behavior was inferred for many species from the presence of scars and tooth cuts on the female's body, and noted in more detail from underwater observations. Copulation has been directly observed in captive settings for several species of elasmobranchs in large aquaria, and in the wild for three species of urolophids and for Triaenodon obesus and Ginglymostoma cirratum. A detailed ‘case history’ of nurse shark reproductive behavior is presented that may be used as a template for future work on shark reproductive behavior of other species. Our studies, using diver identifiable tags and in situ behavioral observations, provide unprecedented information on social structure and mating behavior in this species. Since 1993, 115 G. cirratum, 45 adults and 70 juveniles have been tagged in the Dry Tortugas, Florida. Observations show that adult males visit the study site every year with three males dominant. Individual adult females visit the study area to mate in alternate years. Polygyny and polyandry are common. Future research on reproductive behavior of elasmobranchs should address questions on male access to females, sexual selection and dominance hierarchies.
Article
Lemon sharks Negaprion brevirostris were sampled in the Atol das Rocas, a nursery area, on nine occasions from March 1999 to October 2003, during which 157 individuals were tagged and 35 were recaptured. The male : female sex ratio of captured individuals was 1 : 1�12. Mean � S.D. growth rates were 24�7 � 3�4 cm year�1 in total length (LT), 20�7 � 3�2 cmyear�1 in fork length, and 19�5 � 2�7 cmyear�1 in precaudal length. There was no significant difference in growth rates between males and females. Mean � S.D. increase in mass was 2565 � 762 g year�1. The von Bertalanffy growth parameters estimated by the Fabens method based on LT were: k ¼ 0�077, L1 ¼ 399�9 cm and t0 ¼ �2�16. Despite the large variation of environmental conditions, particularly of tidal range and currents, and the lack of protective mangrove cover in the nursery area at Atol das Rocas, juvenile lemon sharks grew relatively faster than at other nurseries. Such rapid growth could be a response to abundant food availability or high risk of predation by adults that enter the nursery area.
Ten species of shark belonging to three families were recorded from Aldabra Atoll. Carcharhinus melanopterus and Negaprion acutidens were the most abundant species in the lagoon, while Carcharhinus albimarginatus was the most common shark outside the reef. Twelve hundred sharks of six species were tagged and individual recapture rates varied from 15 to 34%. Some specimens of C. melanopterus were caught up to seven times. All five species for which recapture data were available are restricted in their movements at Aldabra. C. melanopterus in particular is very localized, normally remaining in an area of a few square kilometres. Length increment data obtained from tagging demonstrated a slow growth rate for C. melanopterus, averaging 3.5 cm a-1, with no detectable difference between the growth rates of small and large individuals. Limited data for juvenile Negaprion and C. albimarginatus indicated average growth rates of 12.5 and 8.8 cm a-1 respectively. Population densities calculated for several areas in the lagoon varied from 19 to 198 C. melanopterus per square kilometre. It is suggested that C. melanopterus may be food-limited at Aldabra owing to the intensity of intra- and inter-species competition. C. melanopterus and Negaprion have restricted and almost identical reproductive cycles at Aldabra. C. melanopterus females mature at 110 cm total length and breed every second year giving birth to about four pups after a 10-11 month gestation period. Stomach contents of the more abundant species indicate that fish are the most important item in the diet, except for Nebrius concolor which feeds principally on octopus.
Article
We used photo-identification to produce estimates of population size and structure of whale sharks Rhincodon typus at Ningaloo Reef, Western Australia. We analysed photographs of whale sharks taken from 1992 to 2004. A combination of spot and stripe patterns behind the last gill slit and forward of the dorsal fin (lateral view), and distinctive scars and marks on the body and fins were useful for identifying individual sharks. These patterns appeared to be unique to individuals and distinctive markings could be recognized on some sharks for more than a decade. From 581 photographs, 159 individuals were identified. Of these, 74% were male, 16% were female and 10% were of indeterminate gender. Photographed sharks ranged in estimated size from 3 to 10 m total length (TL). The size distribution of sharks was bimodal with a large peak at 8 m and a smaller peak at 6 m TL. Sixty individuals were resighted during the study. Of these, 46 were resighted at different times during the same year (sometimes on multiple occasions) up to 4 mo after they were initially photographed, and 33 were resighted (4 on >2 occasions) in different years. The interval between inter-annual resightings was typically 1 to 3 yr; however, 2 sharks were resighted after a period of 12 yr. We estimated the super population of whale sharks that visit Ningaloo Reef to consist of approximately 300 to 500 individuals (95% confidence interval) based on closed population models, or 320 to 440 based on Jolly-Seber open-population models. Our study shows that photo-identification offers a practical, non-invasive and non-destructive means to obtain data on the population size and demography of whale sharks.
Article
Basking shark (Cetorhinus maximus) movement patterns and growth rates over annual cycles remain entirely unknown. Here the re-sighting of a female identified by a highly distinctive first dorsal fin, after a 3·1 year period is described. Our results show this individual foraged at the surface in coastal areas off south-west England in at least two of four summer seasons and increased in total length by 2·4 m over this period. The growth increment observed was similar to that predicted from the growth model for this species.
Article
Lemon sharks Negaprion brevirostris were sampled in the Atol das Rocas, a nursery area, on nine occasions from March 1999 to October 2003, during which 157 individuals were tagged and 35 were recaptured. The male : female sex ratio of captured individuals was 1 : 1Á12. Mean AE S.D. growth rates were 24Á7 AE 3Á4 cm year À1 in total length (L T), 20Á7 AE 3Á2 cm year À1 in fork length, and 19Á5 AE 2Á7 cm year À1 in precaudal length. There was no significant difference in growth rates between males and females. Mean AE S.D. increase in mass was 2565 AE 762 g year À1 . The von Bertalanffy growth parameters estimated by the Fabens method based on L T were: k ¼ 0Á077, L 1 ¼ 399Á9 cm and t 0 ¼ À2Á16. Despite the large variation of environmental conditions, parti-cularly of tidal range and currents, and the lack of protective mangrove cover in the nursery area at Atol das Rocas, juvenile lemon sharks grew relatively faster than at other nurseries. Such rapid growth could be a response to abundant food availability or high risk of predation by adults that enter the nursery area.
Article
Pieces of skin together with scales measuring 7×7 mm were removed from a mature Nurse Shark and a mature Leopard Shark. In the following 2 weeks the wound area secreted mucus, later it contracted and the epidermis regenerated, then it expanded again and newly formed scales erupted. Most of the scar area was covered with scales after 4 months. In the regenerated dermal skeleton the scales show a high degree of variability in that they are much larger and much more complex than the scales of control areas. The repair scales are no longer arranged in diagonal rows and are not so perfectly oriented in a caudal direction as the control scales. Wolpert's concept of positional information in pattern formation can explain this type of regeneration behaviour. The fact that regeneration of the dermal skeleton is not perfect leads to the assumption that the flow of positional information was temporarily inhibited by the surgery. The present experiment does not indicate whether the anomalous repairscales will eventually be replaced by normal scales if the flow of positional information is readjusted. The author found, however, several skin samples in his own collection which showed a certain kind of anomaly in the dermal skeleton. While the shapes of all the scales were normal, in some small areas the scales did not point in caudal direction but formed an angle with the caudal direction. They were all oriented parallel to each other. It can be assumed that these small areas are old scars. This leads to the finding that size, shape, and variability of the scales that replace the repair scales are normal and that the scar area gains a new polarity which is at an angle to the original polarity. To test these conclusions a new excision would have to be made. It would probably take 2 years until all the repair scales were replaced.
Article
Mark–recapture techniques are an important tool for estimating population parameters of vagile organisms. However, the application of marks (tags) to crustaceans is problematic due to tag-loss during moulting of the exoskeleton. Accordingly, we investigated the use of external colour patterns to distinguish (via photographic identification) individuals of a common marine crustacean (painted crayfish, Panulirus versicolor). Colour patterns were found to be highly polymorphic and individually unique, such that all crayfish in a sample of 59 could be individually identified. When 30 of these crayfish were recaptured after 6–36 months at liberty, colour patterns were unchanged, despite moulting during the inter-census period. It was concluded that (1) photographic identification is an effective method for tracking P. versicolor through time and space, and (2) this method of identification may be useful in capture–recapture investigations of other invertebrate species that display polymorphic colour patterns. This result is significant given the logistical, ecological and ethical problems of attaching tags to crustaceans, as well as invertebrates in general.
Article
Captive and wild Carcharias taurus were used to assess whether spots present on their flanks were suitable as natural tags for individual shark recognition. Photographic images of seven captive sharks taken at monthly intervals for 14 months and at 3 years after the start of the study indicated that spot numbers, positions and sizes did not change. Eighty-nine wild sharks were photographically re-captured at least once subsequent to their initial image-capture; fourteen were re-photographed at least 23 months subsequent to their initial image-capture and a single individual after 14 years. Unique physical marks (e.g. partial fin loss) on six wild sharks were used to validate the pattern recognition process by providing unambiguous identification of individuals independently of their spots. Preliminary visual identification data on the eastern Australian C. taurus population show how spatial and temporal information on individual sharks can be collected without recourse to conventional tagging to address key questions about this species’ ecology and population biology.
Article
Tissue responses to the application of Rototags and Jumbo Rototags in the first dorsal fin of Carcharhinus melanopterus, C. obscurus and C. plumbeus were examined. The acute response included tissue tearing and haemorrhage and was present by 5 days post-tagging. The intermediate response had begun by 20 days post-tagging and continued beyond 207 days. This response involved decreased red blood cell activity as the inflammatory response commenced. The chronic response had begun by 301 days and was complete by 553 days with a layer of fibrous connective tissue walling off the tag. External damage to the fin was caused by continued abrasion by the tag. Repair scales were observed at 242 days using scanning electron microscopy and were confirmed histologically in 61- and 553-day samples. Repair scales were not seen in areas of continuous abrasion. No infection was observed in tissues surrounding the wound. Disruption of the fin surface was observed due to abrasion by the tag, but did not appear to cause a severe tissue reaction. The tissue responses observed were consistent with a normal, but relatively slow, healing in the vicinity of the tag wound. Use of Rototags or Jumbo Rototags appears to be an efficient way of marking elasmobranchs with minimal damage to the shark. (C) 1998 The Fisheries Society of the British Isles.
Article
Selection acting on large marine vertebrates may be qualitatively different from that acting on terrestrial or freshwater organisms, but logistical constraints have thus far precluded selection estimates for the former. We overcame these constraints by exhaustively sampling and repeatedly recapturing individuals in six cohorts of juvenile lemon sharks (450 age-0 and 255 age-1 fish) at an enclosed nursery site (Bimini, Bahamas). Data on individual size, condition factor, growth rate and inter-annual survival were used to test the 'bigger is better', 'fatter is better' and 'faster is better' hypotheses of life-history theory. For age-0 sharks, selection on all measured traits was weak, and generally acted against large size and high condition. For age-1 sharks, selection was much stronger, and consistently acted against large size and fast growth. These results suggest that selective pressures at Bimini may be constraining the evolution of large size and fast growth, an observation that fits well with the observed small size and low growth rate of juveniles at this site. Our results support those of some other recent studies in suggesting that bigger/fatter/faster is not always better, and may often be worse.
-Identification of humpback whales by fluke photographs
  • Baxter B Brazier O
  • Perkins J Kraus S
  • Whitehead H
KATONA S., BAXTER B., BRAZIER O., KRAUS S., PERKINS J. & WHITEHEAD H., 1979. -Identification of humpback whales by fluke photographs. Behav. Mar. Anim. Cur. Persp. Res., 3: 33-44.
Wound healing in sharks. Form and arrangement of repair scales
REIF W.-E., 1978. -Wound healing in sharks. Form and arrangement of repair scales. Zoomorphologie, 90: 101-111.
Site fidelity and behavior of sharks at a long-term shark feeding dive site
  • Scharfer A
SCHARFER A., 2003. -Site fidelity and behavior of sharks at a long-term shark feeding dive site. J. Undergr. Res., 5(3): online o n l y. h t t p : / / w w w. c l a s. u f l. e d u / j u r / 2 0 0 3 1 2 / p a p e r s / paper_scharfer.html. (Consulted Dec. 2007).
Shooting whales (photographically) from small boats: An introductory guide. In: Individual Recognition of Cetaceans: Use of Photo-identification and Other Techniques to Estimate Population Parameters
  • A Mizroch S
  • A Bigg M
MIZROCH S.A. & BIGG M.A., 1990. -Shooting whales (photographically) from small boats: An introductory guide. In: Individual Recognition of Cetaceans: Use of Photo-identification and Other Techniques to Estimate Population Parameters (Hammond P.S., Mizroch S.A. & Donovan G.P., eds), pp. 39-40. Cambridge: International Whaling Commission.