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... more
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.
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,... more
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 photoidentified 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. Intraand 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.
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.... more
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.
Based on direct observations of free-ranging specimens, the giant manta ray Manta birostris is reported from the Marquesas Islands, the first sighting in French Polynesia. Sightings of its sister species, the reef manta ray Manta alfredi,... more
Based on direct observations of free-ranging specimens, the giant manta ray Manta birostris is reported from the Marquesas Islands, the first sighting in French Polynesia. Sightings of its sister species, the reef manta ray Manta alfredi, are also reported at the most easterly location in the Pacific Ocean. Preliminary individual identification as well as notes on their distribution are also reported.
Conservation of top predators has been emphasized as essential in an ecosystem due to their role in trophic chain regulation. Optimizing conservation strategies for these endangered marine top predators requires direct estimates of... more
Conservation of top predators has been emphasized as essential in an ecosystem due to their role in trophic chain regulation. Optimizing conservation strategies for these endangered marine top predators requires direct estimates of breeding patterns and connectivity as these are essential to understanding the population dynamics. There have been some attempts to investigate breeding patterns of reef sharks from litter reconstruction using molecular analyses. However, direct fine-scale migrations of female sharks for parturition as well as connectivity at a medium scale like between islands remain mostly unknown. We used microsatellite DNA markers and a likelihood-based parentage analysis to determine breeding patterns of female blacktip reef sharks in Moorea (Society Islands, French Polynesia). Most females gave birth at their home island but some migrated to specific nursery areas outside the area they are attached to, sometimes going to another island 50 km away across deep ocean. Our analysis also revealed that females migrated to the same nursery for every birthing event. Many offspring showed a high level of inbreeding indicating an overall reduced population size, restricted movements and dispersal, or specific mating behaviour. Females represent the vectors that transport the genes at nursery grounds, and their fidelity should thus define reproductive units. As females seem to be philopatric, males could be the ones dispersing genes between populations. These results highlight the need to conserve coastal zones where female reef sharks seem to exhibit philopatry during the breeding season.
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 (LT) ranged... more
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 (LT) ranged from 48 to 139 cm and 48 to 157 cm for males and females, respectively, demonstrating that the average LT 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−1. Males reached sexual maturity at 111 cm LT. 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.
The population dynamics of shark species are generally poorly described because highly mobile marine life is challenging to investigate. Here we investigate the genetic population structure of the blacktip reef shark (Carcharhinus... more
The population dynamics of shark species are generally poorly described because highly mobile marine life is challenging to investigate. Here we investigate the genetic population structure of the blacktip reef shark (Carcharhinus melanopterus) in French Polynesia. Five demes were sampled from five islands with different inter-island distances (50–1500 km). Whether dispersal occurs between islands frequently enough to prevent moderate genetic structure is unknown. We used 11 microsatellites loci from 165 individuals and a strong genetic structure was found among demes with both F-statistics and Bayesian approaches. This differentiation is correlated with the geographic distance between islands. It is likely that the genetic structure seen is the result of all or some combination of the following: low gene flow, time since divergence, small effective population sizes, and the standard issues with the extent to which mutation models actually fit reality. We suggest low levels of gene flow as at least a partial explanation of the level of genetic structure seen among the sampled blacktip demes. This explanation is consistent with the ecological traits of blacktip reef sharks, and that the suitable habitat for blacktips in French Polynesia is highly fragmented. Evidence for spatial genetic structure of the blacktip demes we studied highlights that similar species may have populations with as yet undetected or underestimated structure. Shark biology and the market for their fins make them highly vulnerable and many species are in rapid decline. Our results add weight to the case that total bans on shark fishing are a better conservation approach for sharks than marine protected area networks.
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... more
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.
For free-swimming marine species like sharks, only population genetics and demographic history analyses can be used to assess population health/status since baseline population numbers are usually unknown. We investigated the population... more
For free-swimming marine species like sharks, only population genetics and demographic history analyses can be used to assess population health/status since baseline population numbers are usually unknown. We investigated the population genetics of blacktip reef sharks, Carcharhinus melanopterus; one of the most abundant reef-associated sharks and the apex predator of many shallow water reefs of the Indian and Pacific Oceans. Our sampling includes 4 widely separated locations in the Indo-Pacific and 11 islands in French Polynesia with different levels of coastal development. 14 microsatellite loci were analysed for samples from all locations and 2 mitochondrial DNA fragments, the control region and cytochrome b, were examined for 10 locations. For microsatellites, genetic diversity is higher for the locations in the large open systems of the Red Sea and Australia than for the fragmented habitat of the smaller islands of French Polynesia. Strong significant structure was found for distant locations with FST values as high as ~0.3, and a smaller but still significant structure is found within French Polynesia. Both mitochondrial genes show only a few mutations across the sequences with a dominant shared haplotype in French Polynesia and New Caledonia suggesting a common lineage different to that of East Australia. Demographic history analyses indicate population expansions in the Red Sea and Australia that may coincide with sea level changes after climatic events. Expansions and flat signals are indicated for French Polynesia as well as a significant recent bottleneck for Moorea, the most human-impacted lagoon of the locations in French Polynesia.
We quantified temporal changes in blood plasma δ13C and δ15N values collected from recaptured juvenile blacktip reef sharks (Carcharhinus melanopterus, n = 14) and sicklefin lemon sharks (Negaprion acutidens, n = 4) at liberty in Moorea,... more
We quantified temporal changes in blood plasma δ13C and δ15N values collected from recaptured juvenile blacktip reef sharks (Carcharhinus melanopterus, n = 14) and sicklefin lemon sharks (Negaprion acutidens, n = 4) at liberty in Moorea, French Polynesia for 10-50 days, and juvenile bull sharks (Carcharhinus leucas, n = 7) at liberty in the Florida Coastal Everglades for 34–127 days to investigate shifts in assimilated biomass from energy reserves and consumed biomass. Blacktip reef and bull sharks exhibited significant changes in plasma δ13C as they grew, with a mean Δ δ13C/cm total length ± SD of 0.41‰/cm ± 0.72 and–0.82‰/cm ± 0.67. While low sample sizes precluded statistical analyses, sicklefin lemon exhibited a change of 0.49‰/cm ± 0.77. Blacktip reef sharks and bull sharks also exhibited significant shifts in δ15N values − mean Δ δ15N/cm TL ± SD = − 0.23‰/cm ± 0.59, and − 0.24‰/cm ± 0.20; shifts in δ15N values for sicklefin lemon sharks averaged 0.19‰/cm ± 0.52. When data were normalized across species (accounting for species-specific difference in δ13C and δ15N ranges), no significant difference were found in the rate of δ15N change between bull and blacktip reef sharks, but mean changes in δ13C/day among blacktip reef and sicklefin lemon sharks (~ 1%/day) were twice as fast as bull sharks (~ 0.5%/day). Comparisons between plasma and muscle isotope values in bull sharks yielded similar results to comparisons of plasma isotope values — rapid changes in δ13C and δ15N. The magnitude and direction of changes in δ13C and δ15N values, however, were not uniform among individuals within each species, suggesting intraspecific variation in trophic interactions within the shark nurseries studied. Further studies quantifying shifts in energy pathways may contribute to elucidating the factors that shape foraging development in sharks and variation in trophic interactions within shark nurseries.
Le gouvernement de Polynésie française s’est engagé en novembre 2013 à protéger au moins 20% des eaux polynésiennes d’ici 2020. En juin 2014, plus de 50 associations de Polynésie française ont soutenu cet objectif à travers le message... more
Le gouvernement de Polynésie française s’est
engagé en novembre 2013 à protéger au moins 20%
des eaux polynésiennes d’ici 2020. En juin 2014, plus
de 50 associations de Polynésie française ont
soutenu cet objectif à travers le message de la
pirogue Hokule’a. Les îles Australes présentent des
opportunités de conservation majeures, avec une
richesse extraordinaire des écosystèmes marins et
un intérêt marqué de la population des îles pour la
protection de leur patrimoine. De juin à décembre
2014, les conseils municipaux des cinq îles habitées
des Australes ont voté une délibération appelant à la
création d’une grande Aire Marine Protégée (AMP)
dans les eaux de leur archipel. Le gouvernement a
entendu ce message et annoncé en novembre 2014
la création future d’une grande AMP dans les eaux
des Australes, lors du Congrès Mondial des Parcs à
Sydney. En mai 2014, le gouvernement de Polynésie
française a invité The Pew Charitable Trusts à
travailler sur un état des lieux scientifique de
l’environnement marin des Australes ; le présent
ouvrage vise à répondre à cette requête. L’objectif de
ce rapport est d’établir un diagnostic détaillé et
partagé des connaissances disponibles sur le milieu
marin de l’archipel des Australes, du littoral jusqu’à
l’océan du large, et des relations entre les insulaires
des Australes et leur environnement marin. Cet état
des lieux participatif et pluridisciplinaire offrira un
socle de connaissance solide sur lequel pourront être
définies des mesures de conservation adaptées, par
le gouvernement et les populations locales.
A better understanding of the key ecological processes of marine organisms is fundamental to improving design and effective implementation of marine protected areas (MPAs) and marine biodiversity. The movement behavior of coral reef fish... more
A better understanding of the key ecological processes of marine organisms is fundamental to improving design and effective implementation of marine protected areas (MPAs) and marine biodiversity. The movement behavior of coral reef fish is a complex mechanism that is highly linked to species life-history traits, predation risk and food resources. We used passive acoustic telemetry to study monthly, daily and hourly movement patterns and space use in two species, Schoolmaster snapper (Lutjanus apodus) and Stoplight parrotfish (Sparisoma viride). We investigated the spatial overlap between the two species and compared intra-specific spatial overlap between day and night. Presence-absence models showed different diel presence and habitat use patterns between the two species. We constructed a spatial network of the movement patterns, which showed that for both species when fish were detected by the array of receivers most movements were made around the coral reef habitat while occasionally moving to silt habitats. Our results show that most individuals made predictable daily crepuscular migrations between different locations and habitat types, although individual behavioral changes were observed for some individuals across time. Our study also highlights the necessity to consider multiple species during MPA implementation and to take into account the specific biological and ecological traits of each species. The low number of fish detected within the receiver array, as well as the intraspecific variability observed in this study, highlight the need to compare results across species and individuals to be used for MPA management.
Expedition Pakaihi I Te Moana was conducted in 2011 to the Marquesas Islands, lying between 07°50ʹ S and 10°35ʹ S latitude and 138°25ʹ W and 140°50ʹ W longitude. The expedition combined extensive col-lections and visual censuses of the... more
Expedition Pakaihi I Te Moana was conducted in 2011 to the Marquesas Islands, lying between 07°50ʹ S and 10°35ʹ S latitude and 138°25ʹ W and 140°50ʹ W longitude. The expedition combined extensive col-lections and visual censuses of the shore fish fauna. A total of 74 species are added as new records for the Marquesas Islands; the coastal fish fauna of the Marquesas Islands is increased from 415 to 495 species and the number of endemic species is increased from 48 to 68 species. This increases the per-centage of species-level endemism for the Marquesas Islands to 13.7%, ranking as the third highest region of endemism for coral reef fishes in the Indo-Pacific. Only two other peripheral regions, the Hawai’ian Islands and Easter Island, have higher values.
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... more
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.
