The La Paz situation is the worst one lately, but it is just the tip of the iceberg.

Naomi Rose Dolphin specialist

However, just five weeks later the dolphin was dead, a post mortem revealing that she was suffering from ulcers in her belly.

Luna's death has sparked a passionate debate over the effect that swimming with humans has on the dolphins and over the conditions in which they are kept.

Lucrative business

Aquariums offering the opportunity to swim with dolphins are popular throughout the world, with tourists willing to part with large sums of money for the experience.

In Mexico they have spread at an enormous rate thanks to a steady flow of wealthy tourists, a ready supply of dolphins and little, if any, government regulation of the capture and keeping of dolphins.

In a country where tourism is a vital part of the economy, a trained dolphin is valued at around $60,000 (�42,000).

But critics say that conditions in many of the aquarium facilities are poor, with the water too shallow or unclean and badly-managed feeding systems. They also say the animals are not given sufficient rest.

Moratorium ordered

"The La Paz situation is the worst one lately, but it is just the tip of the iceberg," said Naomi Rose, a dolphin expert at the Humane Society of the United States.

Javier Enriquez Serralde, the owner of the Dolphin Learning Centre - where Luna died - denied that the conditions in which she was kept are to blame. Mr Serralde said that she had the ulcers and other chronic problems before arriving at the centre.

But Mexico's Environment Minister, Victor Lichtinger, has ordered an evaluation of the facility. He has also placed a moratorium on capturing dolphins in Mexican waters and on the opening of more dolphin parks.