The silent killer- the disappearance of the world's estuaries

Posted on January 20, 2009
Written by: Shark Savers

Our impact on the oceans over the last century has been greater than all previous centuries combined. We are quickly changing the oceans’ chemistry, temperature and biodiversity while at the same time, only just beginning to understand these changes' implications. We know so little really; we are still learning about the oceans' important role in our climate, atmosphere, and planet, still exploring their depths, and still discovering their inhabitants. And as we slowly build our knowledgebase, pollution, habitat destruction, global warming and overfishing are ravaging our seas - and all that dwell within.

Sharks sit at the forefront of this lethal combination of catastrophes, vulnerable to each of them. Sharks are being fished at the rate of 100,000,000 sharks per year, with many regional species up to 98% extinct. Bottom-dwelling sharks are chased by trawlers, whose fishing practices are so destructive, the muddy tell-tale signs of the underwater bulldozers demolishing the sea beds can be seen from satellites. And pelagic sharks frequently join the 43 million tons of bycatch caught by fisherman on long-lines and nets. No matter how they are caught, they are brought on board to have their fins sliced off - usually ending with the shark being thrown back into the water to die and rot.

At the same time sharks are being hunted for their fins at unsustainable rates, they are also struggling with the contamination of their environment. Not only have sharks absorbed the highly toxic methyl-mercury which compromises, amongst other things, their ability to reproduce successfully, but now scientists are also finding other strange neuro-toxins (linked to brain diseases like Parkinson's and Alzheimer's) in their flesh. Chemicals, whether dumped or run-off, enter the food chain and become concentrated as they make their way up the food chain. Even the tons and tons of plastics in our ocean - forming two "islands" twice the size of Texas in the Pacific and Indian oceans - are decomposing to a point that the polymer particles, which will take hundreds if not thousands of years to dissipate, are consumed. Some seawater has 7 times more plastic in it than zooplankton, and so this plastic poison also enters the food chain. All of these chemicals are literally poisoning the sharks - and anyone who dares to eat them.

As if not threatened enough, the struggling shark population is also battling with the destruction of habitat. Many sharks and rays rely upon estuaries as nurseries for their young. And sadly, estuaries around the world are under attack. Not only are the fragile ecosystems more susceptible to pollution and overfishing, they are often in areas considered prime real estate. Many estuaries have fallen victim to homes and businesses - either directly or due to the topographical changes urban development force.

The Zambezi Sharks of Southern Africa are one such casualty, for centuries, relying upon toxin-free estuaries to continue their cycle of life. While healthy in the 1960's, the Zambezi Sharks' population, also known as Bull Sharks, has plummeted - missing in large numbers from their usual haunts like Protea Banks. Many attribute this in great part to the disappearance of healthy estuaries. During the last 50 years, one by one, the sharks' birthing places vanished, thanks to river damming, population explosions, and industrial pollution. In fact, reportedly only one estuary remains accessible, protected and healthy enough to serve as a nursery on the eastern coast of South Africa. Shark nets, targeted fishing, and destruction due to ignorant fear or a misplaced sense of competition, combined with an inability to rear healthy young have decimated the population.

Nearby Mozambique and its estuaries are thought to be the Zambezi Sharks' salvation. So we decided to investigate this theory firsthand. On our recent trip, we visited countless estuaries and even dove in two. And the results, for this conservationist, were frightening.

Many of the estuaries we found were polluted from nearby towns and cities, serving as a makeshift waste facility for garbage, industrial waste and untreated sewage. Others had hotels built upon them, with what appeared to be little concern for their impact upon the fragile ecosystem. And more were dried up, with dead mangrove trees serving as the only indicator to the area's previous vivacity, victims to changes in water flows that development and climate change inevitably bring about.

Imagine our excitement when we found a large estuary in Pomene that - from the surface - initially appeared to be healthy. After 6 hours of driving on non-existent roads, we happened upon an isolated estuary in with a hotel perched aside the lovely bay, allowing us to spend five days observing the estuary - from above and under the water.

Our spirits soared as we heard stories of frogfish, sea horses, brindle bass, crabs and even dolphins. And over the next five days, our dives did not disappoint. Swimming through the beautifully healthy sea grass, we found a treasure trove.

Anemones with huge, colorful popcorn shrimp, grasses and sponges entwined with several species of sea horses, black, yellow and orange frog fish lurking about looking for their next meal, beautiful juvenile angelfish displaying the vibrant patterns of youth, sand dollars hairy and purple shuffling on the bottom, and countless varieties of flounders, nudibranchs, scorpionfish, eels, and pipe fish this muck diving veteran had never seen before. We also met several scientists who were busy discovering new species - or species thousands of miles away from their reported home.

What a special place. It was like diving in the macro-heaven Sulawesi, Indonesia - without the garbage.

Our frequent boat trips through the estuary delivered topside sightings of flamingos, humpback dolphins, schools of hunting, large game fish, and even a turtle. Yes, this was a healthy estuary - one that was serving as a nursery and protected area for many species, including sharks no doubt. And one desperately in need of protection.


You see, it wasn't long before our rose colored glasses wore off and we began noticing the locals that descended upon the estuary in full force day after day at low tide. Dozens of women filling bags and bags of razor clams. Fisherman dragging tiny mesh nets through the fragile grass catching fish, eels and everything else in their path, later throwing the precious bycatch not yet realizing its commercial value, like the sea horses, carelessly aside on the beach to die. Crowds of men with long poles who would stab at the water with as much caution as if they were jack hammering a pothole. I couldn't believe my eyes. Day after day, this place was being assaulted. How much longer could it possibly last?

This place, like so many others, is falling victim to our collective ignorance and greed, while we blindly ignore the tremendous consequences upon things needed for our own basic survival. Remove the fish, remove the sharks, kill the fragile ecosystem and we jeopardize far more than a single estuary. We jeopardize the already strained oceans, our life source. And what's worse, this is happening all over the world. Estuaries are threatened with extinction.

Perhaps there is hope for this estuary. The resort manager, Joe, a passionate lover of the oceans, recently convinced Maritima (the governmental agency responsible for protecting their coasts) to come and see the estuary for themselves. Not only did Maritima protect the area in front of the resort - the artificial reef - from gill-netters and agree to assess the impact in three months, but they are considering making the entire estuary a marine protected area. Of course, enforcement is always a challenge - I joined Joe in chasing away fisherman netting where they were not allowed. We also filmed what we saw - both the good and the bad - and are providing it to the government, to further the cause, writing letters to the ministry as well.

Our population is already at levels that are not sustainable from a resource perspective on this planet - so it isn't surprising that in a country where 80% of the people live below the poverty level, it is a mad rush to take whatever they can. Even less excusable is the fact that more wealthy countries seize this as an opportunity to irresponsibly ravage these resources as well, destroying everything including estuaries in their path. The oceans are both our dumping grounds and our endless supply of life irregardless of our stewardship. It is up to those of us who care and can see the big picture, to stop the destruction. Or minimally, fight the good fight and be very noisy while it happens before our very eyes. The sharks, the sea horses, and even our fellow human beings, depend upon it.