Global-Scale Genetic Identification of Hammerhead Sharks: Application to Assessment of the International Fin Trade and Law Enforcement

The future status of sharks is an issue of widespread conservation concern due to declines in many species in the face of high levels of exploitation to satisfy market demands for products, especially fins. Substantial declines in the large-bodied hammerhead sharks, Sphyrna lewini, S. mokarran and S. zygaena, even in regions where some management occurs, indicate that informed conservation measures are warranted for these circumglobally distributed species. Despite the importance of assessing shark catch and trade on a species-specific basis to detect potential overexploitation of individual species, achieving this goal for hammerheads has proven elusive due to difficulties in identification of their products. Here, we present the development and application of a diagnostic, streamlined, five-primer multiplex polymerase chain reaction assay utilizing species-specific primers based on nuclear ribosomal ITS2 for the three hammerhead species throughout their global distribution. Application of this assay to investigations of the fin market confirmed the presence of hammerhead fins in the international trade. A study of the world’s largest fin market in Hong Kong revealed a high concordance between specific Chinese-name trade categories and fins from these three species (‘‘Bai Chun’’ with S. lewini, ‘‘Gui Chun’’ with S. zygaena and ‘‘Gu Pian’’ with S. mokarran), and clear species preferences. This concordance information allows the use of market records for monitoring species-specific trends in trade and exploitation rates. The assay is also proving useful for identification of shark body parts in U.S. fisheries law-enforcement activities. Screening of morphologically identified ‘‘S. lewini’’ from globally distributed areas using this assay with subsequent whole ITS2 sequencing suggests a cryptic species closely related to S. lewini occurs off the SE USA coast

A Streamlined, Bi-Organelle, Multiplex PCR Approach to Species Identification: Application to Global Conservation and Trade Monitoring of the Great White Shark, Carcharodon carcharias

The great white shark, Carcharodon carcharias, is the most widely protected elasmobranch in the world, and is classified as Vulnerable by the IUCN and listed on Appendix III of CITES. Monitoring of trade in white shark products and enforcement of harvest and trade prohibitions is problematic, however, in large part due to difficulties in identifying marketed shark parts (e.g., dried fins, meat and processed carcasses) to species level. To address these conservation and management problems, we have developed a rapid, molecular diagnostic assay based on species-specific PCR primer design for accurate identification of white shark body parts, including dried fins. The assay is novel in several respects: It employs a multiplex PCR assay utilizing both nuclear (ribosomal internal transcribed spacer 2) and mitochondrial (cytochrome b) loci simultaneously to achieve a highly robust measure of diagnostic accuracy; it is very sensitive, detecting the presence of white shark DNA in a mixture of genomic DNAs from up to ten different commercially fished shark species pooled together in a single PCR tube; and it successfully identifies white shark DNA from globally distributed animals. In addition to its utility for white shark trade monitoring and conservation applications, this highly streamlined, bi-organelle, multiplex PCR assay may prove useful as a general model for the design of genetic assays aimed at detecting body parts from other protected and threatened species

The Behavioural and Genetic Mating System of the Sand Tiger Shark, Carcharias taurus, an Intrauterine Cannibal

Sand tiger sharks (Carcharias taurus) have an unusual mode of reproduction, whereby the first embryos in each of the paired uteri to reach a certain size (‘hatchlings’) consume all of their smaller siblings during gestation (‘embryonic cannibalism’ or EC). If females commonly mate with multiple males (‘behavioural polyandry’) then litters could initially have multiple sires. It is possible, however, that EC could exclude of all but one of these sires from producing offspring thus influencing the species genetic mating system (‘genetic monogamy’). Here, we use microsatellite DNA profiling of mothers and their litters (n = 15, from two to nine embryos per litter) to quantify the frequency of behavioural and genetic polyandry in this system. We conservatively estimate that nine of the females we examined (60%) were behaviourally polyandrous. The genetic mating system was characterized by assessing sibling relationships between hatchlings and revealed only 40 per cent genetic polyandry (i.e. hatchlings were full siblings in 60% of litters). The discrepancy stemmed from three females that were initially fertilized by multiple males but only produced hatchlings with one of them. This reveals that males can be excluded even after fertilizing ova and that some instances of genetic monogamy in this population arise from the reduction in litter size by EC. More research is needed on how cryptic post-copulatory and post-zygotic processes contribute to determining paternity and bridging the behavioural and genetic mating systems of viviparous species

Reply to: Shark mortality cannot be assessed by fishery overlap alone

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Methamphetamine Use and Methicillin-Resistant Staphylococcus aureus Skin Infections

Drug use may be contributing to the spread of MRSA in a rural southeastern US community

Reply to: Caution over the use of ecological big data for conservation

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Global Spatial Risk Assessment of Sharks Under the Footprint of Fisheries

Effective ocean management and conservation of highly migratory species depends on resolving overlap between animal movements and distributions and fishing effort. Yet, this information is lacking at a global scale. Here we show, using a big-data approach combining satellite-tracked movements of pelagic sharks and global fishing fleets, that 24% of the mean monthly space used by sharks falls under the footprint of pelagic longline fisheries. Space use hotspots of commercially valuable sharks and of internationally protected species had the highest overlap with longlines (up to 76% and 64%, respectively) and were also associated with significant increases in fishing effort. We conclude that pelagic sharks have limited spatial refuge from current levels of high-seas fishing effort. Results demonstrate an urgent need for conservation and management measures at high-seas shark hotspots and highlight the potential of simultaneous satellite surveillance of megafauna and fishers as a tool for near-real time, dynamic management

Efficient PCR-Based Identification of Shark Products in Global Trade: Applications for the Management and Conservation of Commercially Important Mackerel Sharks (Family Lamnidae), Thresher Sharks (Family Alopiidae) and Hammerhead Sharks (Family Sphyrnidae).

Shark populations worldwide are suspected to be in severe decline due to domestic and international markets for trade in shark products, especially dried fins in Asian markets, and as a result of bycatch mortality in multi-species fisheries. The management of sharks on a species-specific basis has become imperative for shark conservation, particularly in regions where numerous species are heavily fished, because sharks with differing life-history characteristics respond differently to exploitation. However, many commercially exploited sharks are morphologically similar and not easily identifiable to the species level. This problem is exacerbated when it comes to identifying detached fins, processed carcasses (logs), and filets or steaks at the dock or in trade. To address these species-identification problems and make available an accurate but practical, DNA-based forensic method for use in conservation and management of sharks, I have developed a highly streamlined genetic assay based on multiplex polymerase chain reaction (PCR) and species-specific primers derived from interspecific DNA sequence differences in the nuclear ribosomal internal transcribed spacer 2 (ITS2) locus of sharks. This forensic assay allows accurate identification of body parts from ten shark species commonly exploited worldwide for their meat and/or fins. In this thesis, I report on the development and use of this assay in the form of two separate suites of species-specific PCR primers that can be used in a high-density multiplex format to achieve rapid and accurate species identification. Chapter 1 of this thesis describes a suite of species-specific primers and multiplex PCR assay that simultaneously distinguishes among seven pelagic shark species: four species of mackerel sharks: shortfin mako (Isurus oxyrinchus), longfin mako (Isurus paucus), porbeagle (Lamna nasus) and salmon (Lamna ditropis); and the three species of alopiid (thresher) sharks: common thresher (Alopias vulpinus), bigeye thresher (Alopias superciliosus) and pelagic thresher (Alopias pelagicus). The second species-specific primer suite, described in chapter 2, simultaneously identifies the three globally distributed and most commercially important species of hammerheads: the great hammerhead (Sphyrna mokarran), scalloped hammerhead (Sphyna lewini) and the smooth hammerhead (Sphyrna zygaena). The species-specific PCR primers and forensic approach described here provide an efficient, straightforward technique that can be used in conservation and management relevant contexts where large volumes of samples need to be screened quickly. Preliminary testing of dried fins from the Hong Kong market and confiscated fins from U.S. and South African law enforcement activities suggests that this genetic technique will be useful for large-scale survey applications, such as monitoring the species composition of the fin trade as well as improving fisheries law enforcement capabilities. The efficient nature of the general forensic approach reported here may also make it useful as a model applicable to monitoring trade in other wildlife products on a global scale