Over the past four years Rainer von Brandis has familiarised himself with a population of the usually timid hawksbill turtle in the Amirante Islands, Seychelles. This has allowed him to observe the turtles behaving naturally in their aquatic environment, revealing just how important they are for the maintenance of biodiversity on coral reefs.
The remote nature of Rainer’s study site, combined with a sound conservation policy in the Seychelles, means it supports relatively healthy turtle numbers. Consequently it has been possible to monitor how the hawksbill turtles function within a coral reef ecosystem outside of the relentless over-exploitation that has left them classified as Critically Endangered by the IUCN. Gradually, Rainer has been able to determine their prey preferences, how much they eat, their habitat requirements and even social interactions.
Reef fish lurk for scraps as a hawksbill turtle dines on sponge. (Photo: Rainer von Brandis)
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Apologies for the notably infrequent posts over the festive period. Rest assured news updates should now return to something approaching regularity, but here’s a brief catch up of stories from the past week or so.
The troubled Copenhagen Climate Change Conference in Denmark concluded on December 18th, yielding what has been reported internationally as a disappointing outcome. Although a deal was eventually reached (essentially aiming to prevent global temperatures from rising more than 2C and pledging financial aid to developing nations) it lacked actual targets for cuts in carbon emissions and there was no agreement on an international, legally binding treaty. The details of the agreement can be found here, whilst more information on how climate change is affecting our oceans can be found here.
More positive news is that the European Commission has elected to close all fisheries for the endangered porbeagle shark, following scientific advice given at the recent European Fisheries Council meeting. Porbeagle sharks, a close relative of the great white, have been heavily targeted both for their fins and meat, but North Atlantic populations have been observed to collapse in recent years. Hopefully effective enforcement will follow this legislation and permit the recovery of porbeagle populations. (more…)
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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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Last week the horizon for Atlantic bluefin tuna grew somewhat darker. Despite dwindling stocks and concerns of extinction, The International Commission for the Conservation of Atlantic Tunas (ICCAT) decided only to reduce quotas by approximately one third instead of suspending the fishery altogether. The aim of limiting tuna catches is to help populations recover and ensure their sustainable exploitation in the future, however, some feel the move by ICCAT to be insufficient and simply a gesture that places interim commercial concerns over long-term interests of both tuna and fishermen. (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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