Matt Baker and Shauna Lowry are near Colchester on the Essex coast. Matt ventures to Mersea Island to meet Richard Haward, a seventh-generation oyster fisherman. They head out to sea, where Matt learns about the decline of the native oyster and finds out how the local fishermen are joining forces with the Wildlife Trust to help save them. He also learns that native oysters are not just a key indicator of habitat quality, but that the habitat they help create is as valuable as coral reef. Shauna Lowry returns to the River Colne, where five years ago Countryfile saw the start of a big project to return water voles to the wild. She sees for herself the success of the project and the vigilance needed to keep predatory mink at bay. Shauna also meets Stig - the first dog in the world specially trained to help sniff out water voles. And then there is Lola, the puppy learning the ropes from Stig. It is also getting busy down on Adam's farm as he welcomes the latest arrival - a full-grown Berkshire pig. While dogs might well be loving companions to millions of people across UK, Tom Heap finds out the devastating impact on livestock they can have when they get loose on a farm. And actor Nina Wadia talks about her favourite bit of the countryside.