A PIECE OF GLASS?
POSTED 17 FEBRUARY 2007
© WRITTEN AND ILLUSTRATED BY PEARLY BEACH ONLINE

One Saturday (13 August 2005) my family and I went for our usual walk along the beach at Pearly Beach.

My brother was retrieving some fishing-line that had been left lying around, when he saw a piece of glass glinting in the setting sun. As he picked it up, he let out a squeal and, dropping the glass, exclaimed, "It's alive!"

We then proceeded to take a closer look, and discovered two tiny eyes looking at us from a totally transparent, rubbery, ribbon-like body, about 7cm in length.

After getting home and consulting a couple of our fish books, we concluded that the piece of "glass" we had found was in fact an eel larva, Leptocephalus, commonly known as a glass eel.

To identify what species of eel the Leptocephalus would grow into, we painstakingly counted its muscle-bands, which look like a very fine fish backbone. I counted 106 excluding a few at either end that were too small to decipher. According to our books, it's most likely a South African Fresh-water Eel, or Paling (Anguilla mossambica), which has between 100 and 105 vertebrae.

These eels have an amazing life cycle. The fully-grown adult eels breed in the sea in deep water. The transparent little Leptocephalus hatch and make their way back to the coast, changing into small eels, known as Elvers, along the way. After entering a river, the Elvers grow to become sexually mature, and when this happens, they change colour and are known as Silver Eels. At this stage they return to their breeding ground in the sea, where they die after laying their eggs. And so the cycle begins again.

 — We came across another glass eel in August 2006, and will look out for them again this year.