Insights Into Insular Isolation of the Bull Shark, Carcharhinus leucas (Müller and Henle, 1839), in Fijian Waters

The bull shark (Carcharhinus leucas) is a large, mobile, circumglobally distributed high trophic level predator that inhabits a variety of remote islands and continental coastal habitats, including freshwater environments. Here, we hypothesize that the barriers to dispersal created by large oceanic expanses and deep-water trenches result in a heterogeneous distribution of the neutral genetic diversity between island bull shark populations compared to populations sampled in continental locations connected through continuous coastlines of continental shelves. We analyzed 1,494 high-quality neutral single nucleotide polymorphism (SNP) markers in 215 individual bull sharks from widespread locations across the Indian and Pacific Oceans (South Africa, Indonesia, Western Australia, Papua New Guinea, eastern Australia, New Caledonia, and Fiji). Genomic analyses revealed partitioning between remote insular and continental populations, with the Fiji population being genetically different from all other locations sampled (FST = 0.034–0.044, P \u3c 0.001), and New Caledonia showing marginal isolation (FST = 0.016–0.024, P \u3c 0.001; albeit based on a small sample size) from most sampled sites. Discriminant analysis of principal components (DAPC) identified samples from Fiji as a distinct cluster with all other sites clustering together. Genetic structure analyses (Admixture, fastStructure and AssignPOP) further supported the genetic isolation of bull sharks from Fiji, with the analyses in agreement. The observed differentiation in bull sharks from Fiji makes this site of special interest, as it indicates a lack of migration through dispersal across deep-water trenches and large ocean expanses

Widespread Use of Migratory Megafauna for Aquatic Wild Meat in the Tropics and Subtropics

Wild animals are captured or taken opportunistically, and the meat, body parts, and/or eggs are consumed for local subsistence or used for traditional purposes to some extent across most of the world, particularly in the tropics and subtropics. The consumption of aquatic animals is widespread, in some places has been sustained for millennia, and can be an important source of nutrition, income, and cultural identity to communities. Yet, economic opportunities to exploit wildlife at higher levels have led to unsustainable exploitation of some species. In the literature, there has been limited focus on the exploitation of aquatic non-fish animals for food and other purposes. Understanding the scope and potential threat of aquatic wild meat exploitation is an important first step toward appropriate inclusion on the international policy and conservation management agenda. Here, we conduct a review of the literature, and present an overview of the contemporary use of aquatic megafauna (cetaceans, sirenians, chelonians, and crocodylians) in the global tropics and subtropics, for species listed on the Appendices of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). We find that consumption of aquatic megafauna is widespread in coastal regions, although to varying degrees, and that some species are likely to be at risk from overexploitation, particularly riverine megafauna. Finally, we provide recommendations for CMS in the context of the mandate of the Aquatic Wild Meat Working Group.Additional co-authors: Jeffrey W. Lang, Sigrid Lüber, Charlie Manolis, Grahame J. W. Webb and Lindsay Porte

Fishing for profit or food? Socio-economic drivers and fishers` attitudes towards sharks in Fiji

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