Are basking sharks eating plastic? We went to find out.

Posted by Luke Massey — 31 May 2017 at 4:24pm - Comments
All rights reserved. Credit: © Will Rose / Greenpeace
Crew on the Beluga II search for basking sharks on the west coast of Scotland

“Basking sharks!”

At 5am, these words shatter the silence in the sleeping quarters on the lower deck of the ship.

The crew burst into life, wrestling on clothes, cameras, binoculars.

Up on the helm, eyes pace back and forth across the expansive blue of Gunna Sound – a known feeding ground for these gentle giants off the west coast of Scotland – searching for the elusive fins which moments before pierced the water.

And then… nothing.

The fins are nowhere to be seen. As our drone camera buzzes overhead, the deck is ringed with bleary eyed campaigners, photographers, videographers, and even the cook, all staring through binoculars into an ocean of nothing.

Although it’s not nothing, of course. Below the surface, the waters between Mull and Tiree are teeming with life: minke whales, grey seals, bottlenose dolphins, a cornucopia of marine life, and the thing the basking sharks are here for, plankton.

That was day one of our search for basking sharks while aboard the Beluga II, a Greenpeace ship on an expedition researching the impact of ocean plastic on some of the UK’s most precious wildlife.

There are fears that basking sharks could be particularly susceptible to the effects of plastic pollution in our seas. They’re what are called “filter feeders”, which means pretty much what you’d expect. With their huge gaping mouths (they’re the second largest fish in the world after the whale shark) they can process up to a whopping 1,800 tons of water every hour, filtering out the water and keeping the zooplankton, alongside invertebrates and tiny fish.

While the impact of entanglement in plastic and fishing gear is well-documented, not much is known about the threat of microplastic pollution to basking sharks, so as part of our End Ocean Plastics voyage, we’re sampling the water for microplastics in the area where they feed. To do that, we place a “manta net” at the surface of the water, filtering it in much the same way as the sharks do. In fact, sailing at around 2 knots, our manta processes around 1,000 tons of water an hour, similar to a young female basking shark.

The samples we collect are logged and stored on board and will be sent to the Greenpeace Research Laboratories, based at Exeter University, for further tests. We’ll get a detailed analysis later on this year, but even to my untrained eye I’ve seen tiny bits of visible plastic in the samples. There could be many more, smaller, microplastics not visible to the human eye, which we’ll find out through our lab work. But my gut feeling is that these water samples don’t give much cause for optimism.

That shouldn’t be surprising to us. Every single minute, the equivalent of a rubbish truck full of plastic ends up in the ocean. So many beautiful beaches we’ve passed in the 10 days while I’ve been aboard the Beluga II have been littered with plastic bottles, bags and packaging. And when those big plastics enter the ocean, they break down over time into microplastics – getting eaten by all kinds of marine life.

But I was telling you about basking sharks…

Days go by. Poor weather hits. For days on end the crew is out searching, hoping. The wonderful people at the Hebridean Whale and Dolphin Trust, based in nearby Tobermory, offer assistance, news of sightings, and even cups of tea when we’re back on land. With years of experience monitoring basking sharks in the region, their help is invaluable and they’re lovely to boot.

Our final day in Gunna Sound arrives and the weather breaks – a beautiful sunrise and blue skies, clearing the grey, the wind, and the rain of the preceding days. Whispers over breakfast: could this be our lucky day?

We don’t have to wait long. “Fins port side!” the call comes in and everyone scrambles to action stations. And there they are, three large fins bobbing along less than 100m from the ship. It’s a phenomenal sight. After days of convincing yourself that dark crested waves or bobbing sea birds are in fact shark fins: the real deal is unmistakeable.

The drone whooshes up, and peering over the drone operators shoulder into his viewfinder I see this incredible creature breaking the surface, seven or eight metres long, gently swaying its tail, mouth yawning open and gills undulating as it takes in its gulpfuls of Tiree’s finest seawater.

While the other two dive and disappear, the Beluga II gently keeps up with our remaining companion for the next half hour, following its movements and documenting it, and as we slow to a halt it even drifts in towards us. Quiet descends on deck, punctuated by occasional oohs and awws, like people gathering around a newborn baby, as all eyes remain fixed on this perfect moment.

About Luke Massey

I'm Luke and I'm a Press and Communications Officer at Greenpeace UK, mostly covering oceans issues.

Follow Greenpeace UK