Eric Clua

Reef-fidelity and migration of tiger sharks, Galeocerdo cuvier, across the Coral Sea.

Knowledge of the habitat use and migration patterns of large sharks is important for assessing the effectiveness of large predator Marine Protected Areas (MPAs), vulnerability to fisheries and environmental influences, and management of shark–human interactions. Here we compare movement, reef-fidelity, and ocean migration for tiger sharks, Galeocerdo cuvier, across the Coral Sea, with an emphasis on New Caledonia. Thirty-three tiger sharks (1.54 to 3.9 m total length) were tagged with passive acoustic transmitters and their localised movements monitored on receiver arrays in New Caledonia, the Chesterfield and Lord Howe Islands in the Coral Sea, and the east coast of Queensland, Australia. Satellite tags were also used to determine habitat use and movements among habitats across the Coral Sea. Sub-adults and one male adult tiger shark displayed year-round residency in the Chesterfields with two females tagged in the Chesterfields and detected on the Great Barrier Reef, Australia, after 591 and 842 days respectively. In coastal barrier reefs, tiger sharks were transient at acoustic arrays and each individual demonstrated a unique pattern of occurrence. From 2009 to 2013, fourteen sharks with satellite and acoustic tags undertook wide-ranging movements up to 1114 km across the Coral Sea with eight detected back on acoustic arrays up to 405 days after being tagged. Tiger sharks dove 1136 m and utilised three-dimensional activity spaces averaged at 2360 km3. The Chesterfield Islands appear to be important habitat for sub-adults and adult male tiger sharks. Management strategies need to consider the wide-ranging movements of large (sub-adult and adult) male and female tiger sharks at the individual level, whereas fidelity to specific coastal reefs may be consistent across groups of individuals. Coastal barrier reef MPAs, however, only afford brief protection for large tiger sharks, therefore determining the importance of other oceanic Coral Sea reefs should be a priority for future research.

Business partner or simple catch? The economic value of the sicklefin lemon shark in French Polynesia

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.

Economic valuation of ecosystem services from coral reefs in the South Pacific: taking stock of recent experience.

The economic valuation of coral reefs ecosystem services is currently seen as a promising approach to demonstrate the benefits of sustainable management of coral ecosystems to policymakers and to provide useful information for improved decisions. Most coral reefs economic studies have been conducted in the United States, Southeast Asia and the Caribbean, and only a few have covered the South Pacific region. In this region, coral reefs are essential assets for small island developing states as well as for developed countries. Accordingly, a series of ecosystem services valuations has been carried out recently in the South Pacific, to try and supply decision-makers with new information. Applying ecosystem services valuation to the specific ecological, social, economic and cultural contexts of the South Pacific is however not straightforward. This paper analyses how extant valuations address the various management challenges of coral reef regions in general and more specifically for the South Pacific. Bearing in mind that economic valuation has to match policy-making contexts, we emphasize a series of specific considerations when conducting and applying ecosystem services valuation in South Pacific ecological and social contexts. Finally, the paper examines the decision-making situations in which extant valuations took place. We conclude that, although ecosystem valuations have been effectively used as a means to raise awareness with respect to coral reef conservation, methodologies will have to be further developed, with multidisciplinary inputs, if they are to provide valuable inputs in local and technical decision-making.

The Capture and Culture of Post-Larval Fish and Invertebrates for the Marine Ornamental Trade

Governments, non-government organizations, and other stakeholders are striving to develop practices, policies, and vehicles to make the tropical marine ornamental trade sustainable. Small-scale fisheries based on post-larval capture and culture (PCC) promise to contribute to this goal by (1) removing the risk of damaging corals (inherent in harvesting adults of target species established on reefs) by collecting post-larvae with light traps, nets, and purpose-built temporary shelters as they settle from the plankton to the substrate; and (2) translating the high mortality of post-larvae at settlement into high rates of survival in culture. Possible concerns about overfishing of post-larvae, harvesting the juveniles after they have run the gauntlet of predation at settlement, and the large proportion of bycatch can be eliminated or greatly alleviated by restricting the size and quantity of fishing gear, designing it to retain bycatch alive, and releasing bycatch at times and places that minimize predation. However, special caution is needed when PCC is used at small, isolated islands with self-replenishing populations. Although PCC is environmentally friendly, its contribution to the ornamental trade is expected to be limited. Large variation in the abundance and species composition of settling post-larvae among years, the logistics and costs of operating labor-intensive operations in remote locations, and competition with responsible enterprises harvesting wild adults or producing ornamentals in hatcheries are expected to constrain the viability and market share of dedicated PCC enterprises. PCC is expected to have the greatest uptake by part-time artisanal fishers in developing countries with infrastructure for exporting marine ornamentals. Such fishers are more immune to temporal variation in the supply of post-larvae—they can engage in PCC when valuable post-larvae are abundant and switch to other sources of income when they are scarce. Livelihood opportunities for smallholders could be enhanced through promotion of the environmental benefits of PCC among hobbyists maintaining marine ornamentals.

Unprovoked Fatal Shark Attack in Lifou Island (loyalty Islands, New Caledonia, South Pacific) by a Great White Shark, carcharodon carcharias

The case of a fatal, unprovoked shark attack is reported and analyzed. The incident took place on the 30th of September 2007, in the lagoon of Luengoni Bay, Lifou Island (Loyalty Islands, New Caledonia). A young French woman who was snorkeling was severely bitten on the right thigh and died of hemorrhage. An analysis based in particular on the size and color of the shark, the characteristics of the wounds, and the behavior of the shark before and after the bite suggests that the aggressor was a great white shark, Carcharodon carcharias.

Blacktip reef sharks, Carcharhinus melanopterus, have high genetic structure and varying demographic histories in their Indo‐Pacific range

For free‐swimming marine species like sharks, only population genetics and demographic history analyses can be used to assess population health/status as 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. Four‐teen microsatellite loci were analysed for samples from all locations and two 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.

Behavioural patterns of a Tiger Shark (Galeocerdo cuvier) feeding aggregation at a blue whale carcass in Prony Bay, New Caledonia

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 17.4 m 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 36 h. The fat slicks from the carcass attracted further Tiger Sharks which arrived after an additional 24 h. 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 4 m 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 (<36 h) 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.

Microsatellite Analyses of Blacktip Reef Sharks (Carcharhinus melanopterus) in a Fragmented Environment Show Structured Clusters

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.

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.

Features and motivation of a fatal attack by a juvenile white shark, Carcharodon carcharias, on a young male surfer in New Caledonia (South Pacific)

We present the case of a non provoked fatal shark attack on a 19-year old male surfer in New Caledonia. Several severe bites removed the right arm and all flesh from the right thigh, provoking a quick hypovolemic shock that was fatal. The information provided by a witness and the analysis of a partial bite on the right calf allowed us to identify a 2.7 m TL (est. length) white shark as responsible for this attack. The features of the attack are consistent with a young predator motivated by hunger and the development of its predatory skills.