Omnivore’s Dilemma In A Shark Species


A bonnethead shark in the shallows of Florida’s Pine Island Sound. Credit Getty Images

I do not know why it has been so long since we last linked to a story by her, and I will remain on the lookout for more excellent science writing by her, but for now a quick thanks to Veronique Greenwood for this:

The Omnivorous Sharks That Eat Grass

Diminutive bonnethead sharks are the first omnivorous sharks known to science, which could change our understanding of what some sharks eat.


After researchers caught bonnethead sharks for study, they received a daily meal consisting of a wad of seagrass wrapped in a piece of squid, resembling a large inside-out sushi roll. Credit Samantha Leigh

Sharks are not known for their taste for greenery. But at least one species of shark enjoys a salad of sea grass as well as the prey it hunts.

The bonnethead shark, a diminutive species that reaches up to 3 feet in length, lives in the shallow sea grass meadows off both coasts of the Americas. It eats small squid and crustaceans ferreted from the swaying underwater fronds. But, researchers who have carefully monitored everything going in and out of captive bonnetheads say in a study published in Proceedings of the Royal Society B that they also eat large quantities of seagrass. The grass isn’t just passing inertly through the sharks’ guts. They extract nutrition from it just as they do from the meaty portion of their diet. These sharks must, therefore, be reclassified as omnivores — the first omnivorous sharks known to science. Continue reading

Elegance Is Sometimes Overrated

Greenland Shark.jpg

The Strange and Gruesome Story of the Greenland Shark, the Longest-Living Vertebrate on Earth


Using carbon dating and a new method involving proteins in the lens of the eye, Danish scientists have unravelled the mystery of how long Greenland sharks live. Photograph by WaterFrame / Alamy

Apart from Romantic poets and their wannabes, who would wish for elegance at the expense of longevity? Thanks to M. R. O’Connor for this inelegantly titled post:

Greenland sharks are among nature’s least elegant inventions. Lumpish, with stunted pectoral fins that they use for ponderously slow swimming in cold and dark Arctic waters, they have blunt snouts and gaping mouths that give them an unfortunate, dull-witted appearance. Continue reading

Fiji Shark Dive

Photo Credit: Martin Graf,

Photo Credit: Martin Graf,

In an earlier post I wrote about how more and more countries are waking up to the benefits of preserving natural capital, in recognition of the economic value that can be derived through ecotourism. I noted, in particular, the value that can be generated through ecotourism ventures focused on iconic species such as sharks, manta rays, and sea turtles. I cited a number of studies and calculations that demonstrate that the ecotourism value of these animals far outweighs their one-time economic value if harvested for food or body parts.

Earlier this week, I had an opportunity to experience one such venture first hand, via the famous Fiji Shark Dive. Over the course of two dives I was treated to the spectacle of 40+ Bull Sharks and dozens of Blacktip and White Tip Reef Sharks, up close and personal!  What an amazing experience to see these magnificent animals – some upwards of 8 feet long –swimming only inches away.  Click here for a video (check out the background music!) courtesy of Martin Graf, one of the pioneers of the Shark Diving industry, who just happened to be in Fiji this week and was along on my dives. Continue reading

Natural Capital Valuation and Protection of Marine Megafauna

Photo © Fabrice Jaine

I’ve noticed a number of positive and interesting developments as of late in the area of marine species protection, pointing to an increasing recognition, by policymakers, of the value of natural capital and associated ecosystem services, particularly the value arising from ecotourism.

In February of this year, the Government of Indonesia granted full protection to manta rays within its nearly 6 million square kilometer exclusive economic zone (EEZ), making it the world’s largest sanctuary for manta rays. This reverses the trend of the past three decades wherein Indonesia has had the dubious distinction of being home to the world’s largest fishery for sharks and rays. Why the reversal? It seem that studies showing that the ecotourism value of a manta ray is an estimated $1 million over its lifetime, as compared to the onetime value of several hundred dollars for its gill rakers and meat played a key role in persuading policymakers to take action to protect the iconic species.

A few weeks later, the President of Palau announced that the country’s entire 200 nautical mile EEZ will be declared a marine sanctuary and closed to commercial fishing and seabed mining.  This follows a move a few years earlier to declare Palau a shark sanctuary. In explaining the reasoning behind the moves Palau’s president noted that a dead shark is worth several hundred dollars, whereas a live shark is worth $1.9 million in tourism during its life span, and that his country will promote scuba diving, snorkelling and ecotourism as an alternative income to commercial fishing. Continue reading