Cape Talk, Thursday night

Hours later, they manage to capture a couple. Now there are about 15 people bobbing in the water holding onto huge fishing nets. And in the middle of them, I can see two pink fins. One person suddenly leaps onto the dolphin, and then several others join him.

It looks like they're wrestling with the dolphin and they can weigh up to 200 kilograms. It takes six people to grab the enormous creature and then they carry it to the mud where the vets are waiting, ready to check the dolphin's health. Usually you catch nothing more than a glimpse of a fin, so it's incredible to see the whole golf.

Dolphin out of the water. The dolphin's between grey and pink, and the pink parts are a very faint, dusky pink. And on top of the dolphin's head, it's as if they're wearing a bowler hat. There's a strange round lump, and it's a much longer snout than you'd see in an ocean dolphin. It's as if the creature's smiling. Someone lays a damp towel over her eyes to keep her calm. Yes, this one's a female.

We have to speak quietly so as not to stress the animal further. It's the first time for adults to be out of the water. So it's a kind of abduction. So we try to do this in the best way possible, very quickly. Now the vets are just checking signals, heart rate, the respiration as well. And then we are going to start to take some blood samples.

Within 24 hours, the samples will arrive at the lab in Bogotá, where they'll be analysed for mercury levels and bacterial infections. The team have tagged more than 70 dolphins so they can monitor their movements throughout the Amazon. This is all part of the world's biggest study on river dolphins. Omacha runs these expeditions twice a year.

One in the Amazon and another in the Orinoco, that's a river further north. Each one costs about $14,000 a pop. It's a lot, but the information they gather is crucial to get a clearer picture of the threats dolphins are facing and put pressure on policymakers. Pink River dolphins only reproduce once every four and a half years, so it's amazing when we hear that she's pregnant.