M.S. Marine Biology
Richard E. Spieler
An increase in worldwide industrialized shark fisheries resulting from the growing demand for shark products, especially shark fins in Asian markets, as well as high levels of bycatch mortality associated with multi-species fisheries have raised suspicions of substantial declines in global shark populations. Due to varying responses by individual species to fishing pressure, it has become necessary to manage sharks on a species-specific basis, which requires the collection of more accurate catch and trade data. The accumulation of such data is hindered, however, by difficulties in identifying species from only landed carcasses, body parts, or fins. This is especially true for many of the commercially important carcharhinid (Family Carcharhinidae) sharks, which are easily confused with one another due to strong morphological similarities and overlapping distributions.
The forensic assays described in this thesis expand on a molecular approach developed in the M. Shivji laboratory (Guy Harvey Research Institute, Nova Southeastern University) to resolve these shark species identification issues and allow for rapid and accurate identification of shark body parts. The method involves the development of species-specific primers based on interspecific DNA nucleotide polymorphisms within the nuclear ribosomal internal transcribed spacer 2 (ITS2) locus, and inclusion of these primers in highly streamlined multiplex polymerase chain reaction (PCR) assays. Chapter One describes two separate multiplex PCR assays, each addressing different forensic objectives for U.S. Atlantic and global populations of seven carcharhinid shark species, known as the ridgeback sharks: night (Carcharhinus signatus), dusky (Carcharhinus obscurus), Caribbean reef (Carcharhinus perezi), sandbar (Carcharhinus plumbeus), bignose (Carcharhinus altimus), silky (Carcharhinus falciformis), and tiger (Galeocerdo cuvier). An assay is described in Chapter Two for distinguishing the bull (Carcharhinus leucas) and Java (Carcharhinus amboinensis) shark, carcharhinid species that display high levels of morphological similarity as well as similar habitat preference and distributions. The development of species-specific primers for identification of two additional carcharhinid shark species found in international fin markets, gray reef (Carcharhinus amblyrhynchos) and spottail (Carcharhinus sorrah), is detailed in Chapter Three.
All of the assays and primers presented here have proven effective for various applications in domestic and international fisheries law enforcement, shark species management, and conservation. The efficient, economical, and simple basis of the assay lends itself to widespread routine application in practical contexts, such as collection of species-specific shark catch and trade data and clarification of the extent of species distributions. Further confirmation of the utility of this assay on a global scale is found in the success of this approach and individual primers for identifying dried shark fins from the Hong Kong fin market, confiscated fins from the U.S., South Africa, Guam, and Palau, and unknown identity samples from a Madagascar fishery.
Marcy Henning. 2005. Highly Streamlined PCR-Based Genetic Identification of Carcharhinid Sharks (Family Carcharhinidae) for Use in Wildlife Forensics, Trade Monitoring, and Delineation of Species Distributions. Master's thesis. Nova Southeastern University. Retrieved from NSUWorks, Oceanographic Center. (117)