Saturday, 31 March 2012

Eels

I've just been reading a marvellous book by Tom Fort, fishing correspondent for the British Financial Times (the Financial Times has a fishing correspondent? I hear you ask) called The Book of Eels. 

I've always been aware of eels.  One of my early Australian memories is going with my family and some neighbours for a swim and picnic on the Logan River.  Us kids (I must have been about eight) were terrified to discover there was a large eel in the swimming hole, so our neighbour stuck a bit of sausage on the end of his fishing line and five minutes later the eel was writhing furiously in a bucket. 

Later attempts at eel capture were less successful.  My mates and I used to play down at Stable Swamp Creek behind the Sunnybank train station.  Once during the wet season when the creek was bulging with recent rains we saw a huge eel.  We were convinced it was four feet long.  They can actually grow this big, but it's also possible it grew in the telling.  We went back later with home-made spears to try and catch it but we never saw it again.  Perhaps it was lurking on the bottom, as eels do, munching on yabbies, or perhaps it had made its way down to Oxley Creek and the Brisbane River and eventually reached its breeding grounds  in the Coral Sea.

I still see them now, lurking under the bridge at Ekibin Creek waiting for scraps thrown to the ducks, or cruising the pond in the Botanic Gardens.  I've read a little about them from time to time with Rachel Carson's Under the Sea Wind giving me the first hint that there was something more to their life than mooching around in freshwater streams and ponds and exciting local children.  Fort's book, however, took my knowledge to a whole new level.

There are about fifteen species of freshwater eel in the world.  The ones I see are almost certainly the speckled long-finned eel Anguilla reinhardtii, like this one currently resident in Calamvale Creek just a little south of Stable Swamp Creek.  Fort, as befits an Englishman, focuses mainly on the European eel Anguilla anguilla and its North American counterpart Anguilla rostrata.  Not surprisingly for a fishing correspondent, much of his book is about the eel fishing industry and it opened up a whole new world to me.  Here in Australia we tend not to eat eels much, and we think of them mainly as lurking presences.  Yet in Europe and North America their status as a dietary staple goes back to prehistoric times, with the remains of neolithic fish traps still standing in British rivers.  The figures he gives for historic catches in the main European and North American eel fisheries are astounding, with literally millions of eels taken from rivers such as the Severn and Thames in England, the Loire in France, the St Lawrence in Canada and the Delaware in the USA, and lakes like Lough Neath in Northern Ireland and Commachio in Italy.  These huge catches have gone on year after year for centuries, with remarkably few changes to methods anywhere except France. 

The eel's life cycle is quite remarkable.  The eels we see in our lakes and streams are mostly maturing specimens - females mainly travelling upstream while the smaller males stay at the river mouth.  Yet after perhaps 15 or 20 years of quiet mooching, adult eels feel the call of reproduction and head downstream, transforming as they go into saltwater creatures and making the journey to deep-sea breeding grounds.  Anguilla and rostrata breed in the Sargasso Sea, that expanse of weed and calm water in the Altantic.  Australian eels have a similar ocean breeding ground in the Coral Sea near New Caledonia.  Presumably here the males and females mate and produce trillions of offspring.  I say presumably, because the detective work required to deduce this part of their lifecycle was onerous.  Adult eels are rarely caught at sea because they don't feed in this phase of their life and somehow elude trawl nets.  The breeding grounds were largely found by trial and error, with the redoubtable Danish ichthyologist Johannes Schmidt honing in on the Sargasso by following the trail of smaller and smaller larvae.  However, neither he nor his successors succeeded in observing adult eels in the act of copulation, nor in fishing up fertilised eggs.

Following their birth, the tiny eel larvae or "thin-heads" - little leaf-shaped fishes - ride the ocean currents back towards their freshwater homes, carried in huge numbers on the warm streams and growing slowly as they go.  As they approach the river mouths they transform, taking on the typical cylindrical shape, first of all as clear fishes known as "glass eels" and then gaining pigment as they swim upstream as "elvers" to find a home patch of water in which to mature.

It is during these two migrations - the autumn run of the mature "silver eels" downstream, and the spring "elver run" back upstream - that most eels are caught.  Historically they have migrated in huge enough numbers for fisherman to net and trap them in a frenzy and still have enough get through in each direction to maintain the species.  Mature eels and elvers are caught primarily for the table, glass eels primarily to stock fish farms.  No-one has yet succeeeded in breeding eels in captivity, but a rich fish farm diet and warm water can have them mature in two years instead of the natural 15, feeding the insatiable Japanese appetite for eel meat.

Yet all is not well in the world of eel fishing.  After centuries in which the supply was seemingly inexhaustible, numbers have fallen away steadily in the last few decades.  Like the many ocean species whose decline Richard Ellis documents, numbers are collapsing, and the European eel is now listed as critically endangered by the International Union for the Conservation of Nature. The same body lists the American and Australian species as "not evaluated" which may mean no-one has yet cared enough to look. 

Unlike oceanic species such as cod and tuna, this seems a little more complex than a case of uncontrolled factory fishing risking the resource that sustains it.  Certainly there is some of that, with the glass eel fisherman of the Loire fishing longer hours with wider nets to catch the few remaining specimens and fish farmers desparately paying huge sums for a dwindling supply of larvae.  Yet other factors also play their part.  A parasite is spreading through world eel stocks, origin only guessed at.  The dams and hydro turbines serve as major barriers to eel migration.  In the 19th Century, Londoners' use of the Thames as a sewer made the river so toxic eels were unable to migrate through the estuary.  Changes to ocean currents may be preventing many eel larvae reaching their home river mouths.

Whatever the reasons may be the trend, and its similarity to the trends for so many species, is disturbing.  Eels are robust, adaptable creatures.  They are not fragile niche fishes vulnerable to the tiniest change in climate or habitat.  They live everywhere, they are are so common that we take them for granted.  They have seemed invincible for so long.  If they are endangered, what other creatures will follow?

1 comment:

Stephen said...

Reading, studying, and now a great essay on eels! Change of career on the way?