Sunday, May 2, 2010

It's Eel-ectric!

Once upon a time, Bexie was digging some juicy, dark, clay-heavy soil out of the mostly dried out duck pond muck to use in a salad green garden bed.

duck pond...  the upper few centimeters of earth are dried out and crusty, but the muck below is juicy, blank, and dense.

And then...  out of the corner of her eye...  she saw a large worm slither under the upturned soil.

A really large worm.

A REALLY large worm!

hint:  they're not worms

There were baby eels living in the muck of the dried out duck pond!  And not just one eel--in only a few minutes, we liberated a half-dozen from only the top 20 centimeters of soil in a square meter patch.  They thrashed about and were really difficult to grab until they dried out a little.  We forced them to slither into the mouth of a jug of water.  When we turned the water jug upside down and the contents went plop-plop-plop-plop into the creek, some of the baby eels just rested on the sediment for a while.  I reached into the water and ran a finger along its spine.   It was unexpectedly soft and oh-so-slimy.  Now I understand the saying, "slippery as an eel"...  it's descriptive and very true!

Jon postulates that the eels swam into the duck pond during the last wet season.  The last time Tuateawa had any rain of note was a great storm and flood in November of 2009.  This means that the eels had been in the muck for at least 4 months, and perhaps as long as 7 or 8 months!!!

When we got home, I cracked open one of our books about New Zealand natural history from our library.  I wanted to know how on earth these fish could live out of the water!  What I learned was more bizarre than I could have imagined.

(Begin eel tangent)

There are three species of eel in New Zealand; my little friends were probably long-finned eels.  The long-finned eel is involved in what can only be described as an epic adventure.  At some point in its life--around 23 years for a male, 34 years for a female--something triggers the long-finned eel to leave its comfortable home in a New Zealand river and swim 10,000 km/ 6,200 miles to the tropical Pacific waters.  Scientists don't know what triggers the eels to migrate, nor do they know exactly to where they migrate.  But once they arrive at their breeding grounds, they mate...  and die.  And that's it for the adult eel.

Eels go through several transformations before adult eels can begin their migrations.  The eggs laid in the warm Pacific waters hatch into larvae ("leptocephalus"), only 60 mm/ 2 inches in length.  These little creatures float in the ocean currents for up to 15 months before making their way back to New Zealand.  As they approach the coast, they transform into translucent "glass eels," perhaps triggered by the scent of fresh water pouring from the rivers into the sea.  Once they make their way into fresh water, they transform yet again, growing additional internal organs, into dark baby eels called "elvers."

Eels in general are incredibly long lived.  A 22 lb/ 10 kg eel might be 60-70 years old...  and reliable reports describe female eels weighing 52 lbs/ 24 kg!  Eels are also prodigious climbers (I just knew I felt an affinity with them :-).  Young eel "elvers" making their way upriver have been reported scaling dams greater than 130 feet/ 40 meters, and even conquering waterfalls up to 65 feet/ 20 meters.  Basically, eels can move across any damp surface.

(End eel tangent!)

i'm going to pretend that he is smiling because he knows he's going back to the water in the creek

Getting back to my original question:  I don't know.  I couldn't find an answer to the question of eels--fish--living out of water for long periods of time.  The mysteries of the earth and the water!  (Any marine/ conservation biologists care to comment?)  The eel incident shows again that our efforts in the valley, such as our man-made duck pond, are indeed creating new habitats for plants and animals.

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