Can Shark Oil Predict a Hurricane?

Bermuda’s Curious Weather Tradition

As we make our way through another Bermuda hurricane season, we are fortunate to have access to sophisticated and increasingly accurate weather forecasting technology.

The Bermuda Weather Service at weather.bm does an invaluable job of keeping us informed as tropical weather approaches the island — or, better still, skirts safely around us.

But long before satellites, Doppler radar and computer forecasting models, Bermudians learned to look for signs of approaching bad weather in the natural world around them.

Among the most intriguing of these traditions is the shark oil barometer.

For generations, Bermudian fishermen and their families have kept bottles of shark oil as a homespun method of anticipating changes in the weather. Once particularly associated with fishing communities such as St. David’s, examples can still be found hanging around Bermuda today.

The device itself could hardly be simpler.

Traditionally, oil was extracted from a ‘puppy’ shark’s liver, filtered through material such as cheesecloth and sealed inside a glass bottle — sometimes an old wine, rum or spirits bottle. The bottle would then be kept somewhere visible, often outside the house or around a boatyard or fishing area, where changes in its appearance could be observed.

Reading it, however, was another matter entirely.

Reading the Shark Oil

Experienced practitioners learned to interpret subtle changes in both the oil and the sediment that collected at the bottom of the bottle.

In settled weather, the oil was said to remain remarkably clear, sometimes almost transparent, with a layer of sediment resting quietly at the bottom.

As conditions changed, so did the appearance of the bottle.

Small peaks or valleys might develop in the sediment. Increasingly unsettled weather could cause the oil to become cloudy or milky. And when a hurricane threatened, some experienced shark-oil watchers looked for the sediment to swirl or build into a distinctive mushroom-like cone formation.

Exactly what these changes mean — and what causes them — has long been the subject of debate.

Traditional folklore suggests that shark liver oil somehow retained the animal’s ability to sense approaching storms, perhaps helping a shark recognize changing conditions and move into deeper water.

It is a fascinating theory, but modern research has produced a rather different explanation.

In 2015, researchers connected with the Bermuda Institute of Ocean Sciences tested traditionally prepared shark oil under changing atmospheric conditions. They found no significant response to changes in atmospheric pressure alone. Instead, the oil appeared to react much more strongly to changes in temperature.

That does not necessarily make generations of Bermudian fishermen wrong.

The people who learned to “read” shark oil were also experienced observers of their surroundings. They watched the clouds, winds and ocean swells. They knew the sound of the South Shore surf and recognized subtle changes in the sea and sky that might escape a less experienced eye believing that ‘As the oil, so is the sea / As the glass, so is the sky’.

• Watch an Explanation of Shark Oil:  https://www.instagram.com/p/DcgzNnnCYss/
• Learn More About Touring Bermuda: https://bermudaheritagetours.com/best-bermuda-shore-excursions/
• More Bermuda Stories: https://bermudianhistory.com/exploring-the-gibraltar-of-the-west/