At one point, I have to move the microphone away from my mouth to spare Hughie, our pilot, and Gavin, our photographer, the sounds of my screams. I can't help it. It's something about falling out of the sky sideways, hurtling towards the water that brings it on.

(Note from the pilot: Alex is a just a helicopter newbie. This is a standard turning manoeuvre, completely safe... And we didn't need the microphone to hear her screaming.)

We must be about 170m (300ft) high. It's stunning. All around is blue, as far as the eye can see, fading into a cloudy haze. I can confirm from up here that the earth is in fact round. We watch as a group of fishing boats round up tuna from their big net into a cage. There are little people snorkelling inside the net. They're making sure that it doesn't get caught under the boats, because that would kill the tuna. A ship on either side pulls the net tighter and tighter and eventually the tuna swim into the cage.

From the air, I can see how big the tuna are. And these ones aren't even as large as what they were catching a few years ago. Bluefin tuna are amazing. They can grow up to 700 kg and can out swim a great white shark. The ones in the net are swimming around in a great silver ball. But this is just about the end of their life as kings of the sea. From here, they'll be towed in the cage to a ranch for fattening. Some will not survive the journey. Those that do will end up being chopped into little pieces and served on a sushi platter.

While we're hovering above the boats, some of our activists are onboard, talking to the captain and first mate, who command the fleet. Here's the report from the 'ground':

These fishermen are very friendly. The company owns about 34 boats in the region, including fishing vessels and tug boats. The ship we've been invited aboard is opulent. Activists are asked to take off their shoes, to walk on the wooden deck. In Turkish tradition, you always take your shoes off when you enter someone's home. Our hosts invite us into the air-conditioned lounge and offer us tea, little cakes and, remarkably, rose-scented refresher towels. I don't know how we got here, but I'm not complaining about getting away from the heat for a while.

Our hosts are kind enough to offer us a tuna to BBQ. We politely decline.

Turkey has a quota of about 1,000 tonnes for fishing bluefin tuna in the Mediterranean, but a farming capacity of over 9,000. Our hosts tell us that they fill their farms with fish from other countries. They also buy quotas from countries such as Libya. The only problem is that Libyan fleets fish well over their quota and engage in a lot of unreported fishing. Basically the 'quota' that they're selling to the Turkish fleets is simply a piece of paper. It means nothing.

This is a good example of how hard it is to keep track of who is fishing where and how much.