• Thu. Feb 29th, 2024

Scientists search for solutions to toxin build-up in sharks

BySophie Zweifel

Sep 30, 2017

If animal cruelty isn’t enough of a reason not to eat sharks, then I think this might do the trick. Sharks, as their appearance suggests, are apex predators: they eat other animals. Other animals that have been eating other organisms. All of whom have picked up some level of toxins on their quest for survival.

These toxins, in minute quantities, are relatively harmless; the problem begins when they start to accumulate. And what better way to accumulate up than through the food chain? And where does the food chain ultimately end up?
With sharks. Well, actually it ends up with humans, which is why we should stop eating them.

The Student contacted Dr David Kerstetter, an Assistant Professor at Nova Southeastern University, who specialises in fisheries biology. He has several papers on heavy metal bioaccumulation to his name, and informed us that bioaccumulation in sharks is no new phenomena.

“The issue of mercury contamination goes a long way back. Once it became known it bioaccumulates, it didn’t take long to look for it in all sorts of long-lived species. Some of the earliest papers were from the 1970s.”

Mercury, in humans, is a known neurotoxin, with effects ranging from immune and digestive system damage to memory loss, headaches – and, in severe cases, it can be fatal.

A recent paper led by Dr Neil Hammerschlag even linked the synergistic mixture of β-Methylamino-Lalanine (an amino acid made by a species of cyanobacteria) and methyl-mercury to the onset of Parkinson’s disease and Alzheimers. Surely that is enough of a reason to pass on the shark-fin soup?

It seems that removing harmful levels of mercury from the ecosystem is not a particularly viable option.
Kerstetter wrote: “Removing mercury is difficult, in part because it’s relatively diffuse and in part because of the political challenges in reducing point-sources, which tend to be emissions from power generation facilities burning coal.”

The only light in the tunnel seems to be (that to Dr Kerstetter’s knowledge) sharks do not appear to suffer the same health issues that we do when exposed to high quantities of mercury.

Nonetheless, he did mention that there has not been much research into this, and that “[h]olding large animals in captivity to assess long term neurological changes would be a significant logistical challenge.” Not to mention the difficulty in doing so following the backlash from Blackfish and the overall moral conundrum associated with such endeavours.

Alhough you might never think to eat a shark, there are millions of people around the world that would.

Many of them cling on to the argument of ‘tradition’ to justify the continued slaughter of these magnificent creatures, and if they won’t listen to the call for morality, then we must turn to science.

Kerstetter left us with these final words: “Mercury is one of the bioaccumulates that captures human interest, but it is far from the only one.

“The more substances that we examine each with their own metabolic pathways provides more information on the broader ecology of marine environments, no matter how small or seemingly limited the study.”

It is work, such as his, that is allowing us to garner a greater understanding for the creatures we share our planet with.

And we will need scientists like him to continue looking into the effects our polluting habits are having on the ecosystem at large and how these consequences might feed back to us. It is the circle of life, after all.

Image: Jakob Owen

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