Ocean Park's performing whales and dolphins are one of its most popular attractions. Last year, more than 85 per cent of visitors watched the Ocean Theatre show. But local and overseas animal welfare groups say marine mammals should not be on display for the amusement of the public. The Royal Society for the Prevention of Cruelty to Animals (RSPCA) in Hong Kong said performing shows exploited the creatures. At the recent Tokyo Aquarium Congress, the Japanese Dolphin and Whale Action Network distributed a leaflet describing the country's aquariums as 'cruel'. At Ocean Park, chief dolphin trainer Harriet Chiu Lai-har said the mammals were not forced to perform. 'The tricks are basically what they do in the wild. We do a bit of modifying and show it to the audience.' Ocean Park has two whales and nine dolphins which perform, and two calves. Trainers spend over a year developing a close relationship with the creatures. 'We need to spend plenty of time with them, then the animals and the trainers know each other very well so neither is afraid of the other. You have to keep calm. You respect them and they respect you. After time, you can recognise each animal's character,' Chiu explained. The performing is encouraged by positive reinforcement when tricks are successful. 'It's like teaching children, you praise them for what they do well,' she said. 'It's very satisfying. They look playful, active, interested and happy.' But Doreen Davies, executive director of the RSPCA, argued: 'I don't think they do in the wild what they do in Ocean Park. We object to performing animals. It's just exploiting them. There's no educational value to it, and we're against it just as we would be against circuses.' Marine ecologist Brian Morton, of the University of Hong Kong, is also against performing dolphins. 'I think [marine parks] should be fulfilling a different role,' he said. 'They should keep local animals, so local people can see what's in their waters, and they should be engaging in education much more.' Jo Ruxton, of the World Wide Fund for Nature in Hong Kong, commented: 'To the dolphins it's like a tiny prison, and it's very sad. 'But the point is it's been done, and now we have to do the best we can. '[The Ocean Park staff] are very caring towards their animals, and they've really brought the plight of whales and dolphins to people's attention. They've made people care about their plight in the wild.' The dolphins at Ocean Park were caught in Indonesia, many by fishermen concerned that they would destroy fish stocks. No new dolphins have been brought to Ocean Park since 1987, according to the park's chief veterinarian Reimi Kinoshita. The Post recently reported that Ocean Park had been criticised in an Asian Marine Biology article for poor survival rates of its marine mammals in the past. Few of the 139 mammals caught in the wild to stock Ocean Park since 1974 are alive today. The park's management blame start-up problems for the early casualties. Ocean Park now has an advanced veterinary laboratory to look after its marine mammals' health. 'They can mask signs of disease very well. In the wild, if you show signs of weakness, you'll be eaten,' Kinoshita said.