Wednesday, May 26, 2010

My Hovercraft is Full of Eels

A spokesperson for EDGE e-mailed me, hoping to get me to plug their fundraiser. I think they do a great job of informing the public about strange animals, and could definitely use your £2 (about $2.88 if the online conversion calculator is correct).

This month’s animal I found after I discovered that the IUCN Redlist highlighted a new species every day. Looking through past Species of the Day, I saw some familiar faces1, and a few new ones. One that caught my eye, featured in January, was the European Eel (Anguilla anguilla).

Image from the BBC

The lifecycle of the European Eel is confusing, surpassing many arthropods in complexity2. Spawning and hatching take place in the Sargasso Sea, the same area that makes up the Bermuda Triangle. As transparent, ribbon-shaped larvae called leptocephali, they eat whatever plankton is available to them. As they grow, the Gulf Stream carries them to the coast of Europe, where they metamorphose into round, but still transparent larvae called glass eels or elvers. Once at the coast, they migrate en masse up rivers and streams. Videos of this seem reminiscent of something you might have seen in a health class.

After finding their way upstream, the eels gain pigment and size in a third metamorphosis, after which they are called yellow eels. Here they spend their time eating small arthropods and growing. Then after a number of years (between five and twenty) they undergo a fourth metamorphosis to adulthood (finally!), gaining larger eyes and a silvery coloration, all the better to survive the open ocean3. However, they have to get to the ocean first, and they will even cross land to get there. Eventually, they find their way back to the Sargasso Sea, mate, die, and the process starts all over again.

There is one main cause for them to go from not listed in 2006 to critically endangered in 2008. They’re delicious. They work as sushi, as soup, smoked, and even as pie. There are eel farms, but those only collect the glass eels and raise them from there. Breeding is still done the old fashioned way, and if that doesn’t increase along with the increased global demand, they will be literally eaten up.

Research into captive breeding (read: more effective farming) is ongoing by fisheries who don’t want to see that size of a drop in a main export. Please don't read that as bitter, as industry support is one of the better methods of conservation. The Monterey Bay Aquarium has set up a program known as Seafood Watch, which educates the public on which seafood is sustainably harvested, and which is being overfished to death. So, watch what you eat.

1 These are some featured animals from the last year that have been posted here: the Goliath Frog, the Vancouver Island Marmot, the Indiana Bat, the Sailfin Lizard, the Brown Hyena, the Boreal Felt Lichen, and the Chinese Giant Salamander.
2Though, their lifecycle isn’t quite as confusing as Malaria. To be fair, I’m not sure I’ve seen any lifecycle as confusing as Malaria.
3Wikipedia says that they lose their stomachs at this stage. I couldn’t verify that anywhere else, but it wouldn’t surprise me. A number of insects do something similar: the larva’s job is to eat; the adult’s job is to breed.