The slimy, sausage-shaped members of the starfish family have no local market but are a valuable commodity in China as both a culinary delicacy and a medicinal ingredient. Entering mainland China from around the world via Hong Kong, some varieties can fetch up to $6,000 per kilogram. In China – the world’s biggest sea cucumber market – there are no natural populations remaining, according to marine biologist and sea cucumber expert Dr Mercedes Wanguemert. The problem in West Africa, says Dr Wanguemert, is a lack of information. “No-one knows the species being fished or the size of the stocks,” she tells the BBC. In tropical areas such as Liberia, “a maximum of 10% of the population can be caught in order to maintain healthy levels”. Sea cucumbers play a critical role in keeping marine ecosystems healthy. Sierra Leone’s sea cucumber stocks have been over-fished, forcing the divers to prospect further afield. It is a common trend: some 70% of the world’s sea cucumber fisheries are either fully or over-exploited.