Giants in the River

At virtually every public aquarium I've been to, the emphasis has been on the ocean.  Which makes sense, I suppose.  Saltwater covers about three-quarters of the surface of the planet.  The seas and oceans are home to some of the most popular of aquatic animals - dolphins and sharks, seals and penguins, octopuses and sea turtles.  All of this emphasis on the ocean, however, does mean we pay less attention to the freshwater habitats of our planet - the lakes and rivers and streams.

There are some freshwater animals which are featured prominently in zoos - otters, hippos, crocodilians - but freshwater fish tend to be overlooked in aquariums.  This is unfortunate, since the freshwater habitats are home to some of the most exciting and unique fish species on earth.  Also, some of the most endangered.

There's been a lot of awareness raised lately about the threats facing oceanic fish - global climate change, coral reef die-offs, overfishing.  In some ways, I feel like the freshwater fish have the rawer deal.  Their habitats are smaller and more localized, leaving them more vulnerable to threats.  They also tend to butt up against our habitats - farms, factories, and cities - leaving them vulnerable to pollution (yeah, I know, the ocean gets polluted too, but at least it dilutes a little with its massive size).  Rivers are dammed.  Invasive species are transported from one lake to another.  Like I said, it's a rough deal.

Among the most fascinating of freshwater fish are the river giants - the biggest fish found in their rivers and lakes across the world.  These include the arapaima, the Mekong catfish, the alligator gar, and the Australian freshwater stingray, among others.  These fish are the living legends of their native waterways - and like legends, their very existence is being thrown into doubt.  The biggest fish in a river or lake tend to be the ones that are fished out the quickest, and many of these river giants are becoming increasingly rare.  Fish, like reptiles, grow for as long as they live, and not many are surviving long enough to achieve giant status anymore.  Furthermore, the ones that are taken are often likely to be the biggest, meaning their genes for "bigness" are being removed from the population, resulting in survival of the runtiest.

Shark conservation has gotten a tremendous boon in recent years from the amount of attention paid to them. They are the stars of every aquarium and the subjects of countless TV documentaries (some better or more accurate than others).  An obstacle that many giant freshwater fish are facing is that no one knows that they are even there, let alone that they need our help.  A decent number of aquariums and zoos feature displays of Amazonian fish.  Considerably less attention goes to Asian river fish... or Australian... or even North American.  One of the most exciting captive breeding and reintroduction projects going on in this country right now is the work being done with sturgeons.  No one is really talking about it.

Recently, I visited the National Geographic museum in Washington, DC, currently playing host to an exhibit called "Monster Fish."  I watched video clips, played with interactives, observed some baby alligator gars in a tank and, when no one was looking, played on the life-sized fiberglass models of the giant fish.  All I could think of was how cool it would be to have seen some of these fish - adult, huge versions of them - in real life, to watch a six-meter sawfish cruise by, or go eye-to-eye with a gnooch, just one of the monster fish I'd never heard of before entering the exhibit.

It would be great for more aquariums to devote some exhibit space to the imperiled freshwater fish of the world, maybe even start some captive-breeding programs that could be used to replenish some of the more endangered species.  Don't get me wrong, sharks and dolphins are cool.  But to look at the lazy river that runs alongside my zoo and through my town and to wonder what kind of behemoth used to lurk beneath the waves there?  That makes me look at the river in a way I never did before.