SOSF funded Professor Mahmood Shivji of the Guy Harvey Research Institute and Save Our Seas Shark Centre at Nova Southeastern University has been tracking the international trade in shark fins using methods that wouldn’t look out of place in an episode of Crime Scene Investigation. By sequencing mitochondrial DNA of both wild shark populations and fins in markets it is possible for Mahmood and his team to tell where in the world the fins at market came from – a process called ‘genetic stock identification’.
Most recently they have been able to identify that 21% of scalloped hammerhead fins sampled from Hong Kong markets were actually sourced from western Atlantic populations, where the species is already listed as endangered by the IUCN. The samples from the western Atlantic also identified three subdivisions within the population due to particular sequences being geographically segregated, indicating that breeding females either remain close, or home back, to their natal region of origin for parturition.
Hammerhead shark at market. Photo by Dan Beecham.
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It was recently revealed via genetic analyses that the already critically endangered common skate (Dipturus batis) in Europe is in fact two different species: the flapper and blue skate (D. intermedia and D. flossada). Consequently catches of the smaller, more resilient blue skate have in fact been masking the more rapid decline of the flapper skate, dramatically reducing the perceived population size. Dr Iglesias, who led the study, stated:
‘The threat of extinction for European Dipturus together with mislabelling in fishery statistics highlight the need for a huge reassessment of population for the different Dipturus species in European waters. Without revision and recognition of its distinct status the world’s largest skate, D. intermedia, could soon be rendered extinct.’ (more…)
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Great white sharks are capable of travelling large distances over relatively short periods of time, but a recent publication has found that the white sharks of the North Pacific have over time formed a genetically distinct population despite their ability to undertake transoceanic migrations. Essentially there is no interbreeding between white sharks from the North Pacific and those from other regions such as Australia and South Africa.
“Individuals persistently return to the same network of coastal hotspots following distant oceanic migrations and comprise a population genetically distinct from previously identified phylogenetic clades.” state the authors of the article published in Proceedings of the Royal Society B. They used a combination of acoustic and satellite tags, as well as tissue samples for DNA analyses, to demonstrate this strong homing behaviour that has presumably generated this genetic isolation from other populations, frequenting areas such as Hawai’i, the coast of California and a mid ocean spot termed ‘white shark café’. (more…)
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