African freshwater eels - new tools in environmental education
Dr Jim Cambray
Eels - few other animals have life cycles which depend on maintaining
extensive pathways through oceans, estuaries and freshwater habitats. Life
cycles which take so long to complete. Break one link in that cycle and an
entire generation of eels might disappear. Dr Jim Cambray discusses the life
cycles of these amazing creatures and how their story can be used towards
effective environmental education.
The health of our freshwater systems is an index of the health of our
environment as a whole.
Three thousand of the 10 000 known freshwater fish species in the world are
in danger of extinction in 30 years time. South Africa has a high number of
threatened freshwater fish species. As far as we know none of the species of
freshwater eels which occur in southern Africa are at the present threatened.
However, the precautionary principle needs to be applied as we do not know
enough about these fish.
There are 16 species of freshwater eels, family Anguillidae, in the
world. We have four of these species in southern Africa. In terms of commercial
fisheries they are divided into a potential of 7 eel fisheries around the world
of which the African one is the last 'virgin' eel fisheries to be fished. It is
worrying that two of the six eel fisheries being fished are in trouble due to a
variety of factors. Detailed and long-term research is required on the African
eels before they are exploited. Their numbers might already be severely reduced
due to impoundments along our rivers, water abstraction, pollution, alien
invasive predaceous fish species such as black bass and catfish and a host of
other changes which we have done to our river systems which are the 'life-blood'
of the freshwater eels. If they go below a certain critical number they might
just disappear and their journey will be no more!
Slippa and Slippery
Freshwater eels have a very interesting life cycle which takes them on a long
journey from their spawning grounds in the ocean north of Madagascar to high up
in some of our river systems and then back again to the ocean off Madagascar to
spawn. In Cambray's freshwater fish surveys he met many farmers who have seen
the little elvers and the large eels in their rivers and thought that the eels
bred in the rivers. Their lack of knowledge about the life history of these fish
prompted Cambray to write an educational booklet on African freshwater eels.
The booklet is entitled "Slippa and Slippery - The adventures of two
freshwater eels on the long swim for survival." In this booklet the story
of the fascinating life history of our freshwater eels is told. The booklet is
written in a story format with a father telling his two children about how two
eels, Slippa and Slippery, make their way from the spawning grounds off the
coast of Madagascar to a river system in South Africa and then back again to
spawn. Many problems and dangers are encountered along the way including
anglers, alien fish, crabs, weirs, poachers and even an Albany Museum
ichthyologist! Many of these encounters are based on actual experiences I have
had or observed along the river over the past 20 years. This booklet is well
illustrated by the talented wildlife artist, the late Ray Black. At the end of
the booklet are a number of fun activities which will help to reinforce the
understanding of the eels life history. There is a quiz, a board game, an eel
life history and teamwork exercise, eel life history puzzle and the freshwater
eel geography lesson. In addition to this booklet on freshwater eels there is a
pack of informative overhead notes which can be used by teachers. There is also
a useful glossary and a section on interesting eel facts. Did you know that some
Europeans used to think that skin rubbed with eel oil caused one to see fairies!
The life history cycle of freshwater eels
Our four African freshwater eels breed in the ocean off Madagascar. The eggs
develop into larval eels called leptocepalli (singular leptocephallus) and are
leaf like and float with the currents along the African coast. They change into
glass eels which are see through and one can see the internal organs of the
fish. They sense the freshwater and move into our river systems and become a
brownish grey. They move at night up the river systems with females travelling
the furthest upstream. Males may stay as long as 8-10 years in freshwater and
females up to 20 years. This is why they are called freshwater eels as they
spend the majority of their life in freshwater BUT have to migrate out to sea to
The four African eels provide a great challenge to us all for they provide a
true test of functioning ecosystems and public responsibility.
Few other animals have life cycles which depend on maintaining
"extensive pathways" through oceans, estuaries and freshwater
habitats. Life cycles which take so long to complete. Break one link in that
cycle and an entire generation of eels might disappear.
Responsibility for this life cycle rests with all who share any part of the
"extensive pathway". While a pollution event on the high seas would
require national input - the effect of "uninformed persons" should not
be discounted. For example - injudicious (sp) chemical spraying for mosquitoes
outside a holiday home on an estuary; a flooded cattle dip or a diesel spill
from a hospital boiler. There is also the likelihood of over fishing by
commercial concerns. All feasible human errors with possible long term effects.
This book is intended to make South Africans aware of the wondrous, but
easily disturbed, life-cycle of our African freshwater eels.
Booklet available from the Albany Museum @ R10 plus postage. Contact:
J.Cambray@ru.ac.za; phone Pat Black @ 046 6222312; Fax: 046 6222398.
Freshwater environmental education resources from WWF, Sharenet and the
Makana Biodiversity Centre of the Albany Museum