First record of prickly shark Echinorhinus cookei (Pietschmann, 1928) (Chondrichthyes: Echinorhinidae) in French Polynesia (Eastern Tropical Pacific)

International audienceA submarine dive allowed the observation of a mature male individual of the prickly shark Echinorhinus cookei (Pietschmann, 1928) at –500 m depth on the outer slope of the barrier reef off the island of Moorea (Society Islands, French Polynesia). This identification extends the range of this species in the Eastern Tropical Pacific, between Hawaii in the West and the Peruvian coasts in the East

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

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-dentification 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.7 page(s

Genetic network and breeding patterns of a sicklefin lemon shark (Negaprion acutidens) population in the Society Islands, French Polynesia.

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

Behavioural response of sicklefin lemon sharks Negaprion acutidens to underwater feeding for ecotourism purposes

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. 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.10 page(s

Effects of provisioning on shark behaviour : reply to Brunnschweiler & McKenzie (2010)

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.4 page(s

Citizen science provides valuable data to evaluate elasmobranch diversity and trends throughout the French Polynesia's shark sanctuary.

Observers of the Polynesian Shark Observatory (ORP), a citizen science network organized mainly through the Polynesian dive centers, collected an unprecedented amount of data from more than 13,916 dives spanning 43% of the islands of French Polynesia between July 8, 2011, and April 11, 2018. The objective for this type of data collection, which is not accessible within the standard research context, was to provide a unique dataset, and the opportunity to explore the specific diversity, distribution, seasonality and abundance of many elasmobranch species spread out throughout the territory of French Polynesia. Since the data are based on random citizen observations, the spatial distribution was biased toward the most frequented sites and islands where scuba diving is most developed. Overall, the increase in observed abundance of rays and sharks observed in French Polynesia, and the three most sampled islands as well as the high specific diversity recorded for the region, provide first evidence on the effectiveness of the French Polynesia's Shark Sanctuary, established in 2006. These data, collected randomly by the volunteers, also provide insights into potential movement patterns and site fidelity of some of the more commonly observed species. While no final conclusions can be drawn, it is clear that the network of volunteers that regularly contributes information to the Polynesian Shark Observatory plays a very important role in the delivery of much needed data for conservation and management action, as well as providing perspectives for new directions in research on sharks and rays in French Polynesia

Female reproduction inferred from parentage assignment.

<p>Litters are shown by years for each female with the assigned father(s) and juvenile(s). Sampled individual adult sharks are indicated in bold. Mothers and fathers inferred through genotype reconstruction by the program COLONY are identified by #ID and *ID, respectively. Colour of juveniles refers to their sampling nursery site (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0073899#pone.0073899.s001" target="_blank">Figure S1</a>). Note that juvenile Tet5 was sampled in 2008 in Tetiaroa but was assigned to the birth year 2007 due to its size (110 cm) corresponding to an age-1 juvenile, while subadult Sub1 was sampled in 2008 at the size of 125 cm and subsequently assigned to year of birth 2006. Finally, Tet1 was assigned to an unknown year as we were not able to determine its year of birth.</p

Patterns of distribution in internal relatedness values (IR).

<p>(A) IR values across the maturity stage of individuals (categories: juvenile < 100 cm, immature = 100-199 cm and mature > 200 cm). (B) IR values of newborn sharks (cohorts) across years. Box plots show the median (line within the boxes), mean (white diamond) and interquartile ranges IQR (boxes). Raw data points are indicated by black circles.</p

Genetic network of the sicklefin lemon shark population from Moorea and Bora Bora.

<p>(A) Map of the study location. (B) The genetic network of adult lemon sharks. Each individual is indicated by a node labelled by shark ID. Circles and squares indicate females and males respectively and symbol size is indicative of the body length of the shark. Node colour corresponds to the three defined residency groups. Dyads sharing a first-order genetic relationship are connected by a line, with line thickness indicating the strength of the genetic relationship (proportional to R values). A ‘spring embedding’ algorithm with node repulsion for laying out the nodes’ positions [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0073899#B38" target="_blank">38</a>] was used to cluster densely connected nodes together with less connected nodes placed around the edge. (C) Genetic degree (number of first-order genetic relationships an individual has) distribution within the population.</p

Inference of reproductive cycle from underwater surveys.

<p>(A–D) A two-year reproductive cycle as displayed by female F11 which was pregnant in 2007 (A), then entered in a resting period (B) and mated in 2008 as shown by dermal bite wounds on its flanks (C), and was pregnant again in 2009 (D). (E–F) Female F01 is pregnant in 2008 (E) and is followed by males M10 and M31 in a courtship behavior just after parturition in 2008 (F).</p