Monday, July 9, 2012

One of the biggest research activities here at CEI is actually shark research, and we have done some pretty interesting projects on local shark populations. Tonight I watched a presentation that was given to some visiting students and thought some of the information might be worth passing along.

Oceanic Whitetip Shark (Carcharhinus longimanus) - courtesy Eric Chen, Wetpixel
According to some of the latest figures, perhaps 73 million sharks are killed each year (from UN data), and some more liberal estimates based on the fact that over 3 in 4 shark kills go unreported puts the figure at perhaps 150 million sharks killed each year (from independent environmental groups). That is half the population of the US, killed in one year. Almost all of these shark kills are just for their dorsal fin, used in Asian markets to produce shark fin soup, which is a sign of affluence. The shark fin has no taste; the soup itself is often flavored chicken or pork - the only discernible difference is the texture. 99% of the Oceanic Whitetip Shark population have disappeared. That is like the population of the Earth going from 7 billion to 70 million, the population of the UK.  And there were certainly not 7 billion Whitetip sharks to begin with. In fact, CEI is the only research institute that collects data on Oceanic Whitetip Sharks in the world, simply because no one else can find them. Sharks are K selected species, which means they have few young in their lives due what was once a stable environment for them to thrive in - like humans. Fishing sharks is like mining minerals - you fish 80% of the sharks, then you will be stuck with 20% of the population as the new baseline, as long as fishing pressure stays consistent (which it doesn't).

However, there are now many shark reserves in the Pacific and Indian island countries, as well as a very recent one  in The Bahamas. Studying Reef Shark population changes over the period from 1980 to 2011, there has been a marked increase in shark population. China has just recently banned shark fin soup at official functions, marking (hopefully) a new direction in which shark fin is viewed. Ensuring shark survival is not just some Romantic crusade to preserve a set of amazing creatures, increased shark diversity and density has a direct correlation to increased coral reef biodiversity and biomass, as sharks prey on weakened fish or fish whose populations have grown too high. Kingman Reef, a US dependency and one of the last truly pristine reefs in the world, has a predator biomass of 85%, 3/4 of which are sharks (from an old NG article,  highly recommend reading). They are some of the most beautiful and awe inspiring inhabitants of the sea, and they deserve our protection. We can't live without them, but they would chug along just fine thank you very much should human disappear tomorrow.

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