Identification of the population genetic structure of Carcharhinus longimanus (oceanic white tip shark or brown Milbert's shark) using mitochondrial DNA markers

Abstract

Even though sharks are the largest fishes in the world with their size varying size and behaviour, they were over exploited and most of them were at the fear of extinction. Among these Carcharhinus longimanus, an epipelagic bottomless shark considered as at the point of extinction were IUCN Red list points out this shark as a “vulnerable” species at global level. In order to implement the management measures for these species which require the information regarding its population in interoceanic regions. Population genetics can be characterized as the study of how hereditary variance is dispersed among the species and population on a very basic level (Hansen, 2003). Assessment of genetic makeup and variability of fish stock is important for scientific management of fishery, conservation and rejuvenation of endangered species. Mitochondrial DNA (mtDNA), which in general possess a five to ten times greater variability than single copy nuclear genes hence, served as a powerful tool for elucidating population structures studies. Among the 150 specimens of C. longimanus sequenced, we obtained sequences ranging from 720 base pairs were obtained 12 polymorphic sites yielding 13 haplotypes. Genetic differentiation among the populations of C. longimanus from Indian Ocean was revealed as a non-significant statistical analysis. Vital insights were gained from this study indicating lack of significant substructuring and its capability to migrate across large expanses of Open Ocean. The capability to migrate may provide it with some buffering against habitat loss and climate change, but excessive fishing is a danger to its populations. Globally sharks are in danger due to their inherent vulnerabilities like long gestation time and reduced number of offsprings coupled with over fishing. Our study also corroborated the findings of shark decline, as decline in genetic diversity is an indicator of decrease in resilience capacity. The present study calls for restrictions on its fishery so that populations will get sufficient time to replenish and consequently their resilience is ensured in the face of changing oceans.