Hong Kong - The waiter serves up a generous helping of hyperbole with his sales patter as he points to a giant garoupa gawping out of the glass of a neon-lit fish tank on the pavement outside a seafront restaurant in Hong Kong.

"This is a very special fish - it is more than 100 years old," he says, gesturing to the fish struggling to turn its metre-long body in the confines of the tank.

"If you want to eat it, it will cost you around HK$500,000 (64,500 US dollars). You will need a very big party."

For months now, this magnificent creature has been on show to passers-by, working its way onto hundreds of snapshots as it tries to circle in the tank that suddenly became its home after decades cruising the inky, limitless depths of the Indian Ocean.

Capture brought no quick death for this and dozens of other large exotic fish crammed into tanks lining the pavement in seafood restaurants across Hong Kong and Asia.

The taste among Asian diners for exotic fish appears defiantly recession-proof. Falling fish stocks and rising prices have if anything, it seems, sharpened people's appetite for luxury seafood.

However, the increasingly popular practice of enticing customers to restaurants with the display of huge fish in small tanks is troubling animal welfare experts.

The Society for the Protection of Cruelty to Animals (SPCA) in Hong Kong has likened it to the way caged leopards or shackled elephants were displayed in the city's colonial days half a century ago.

SPCA executive director Sandy Macalister said of the display of garoupa in Hong Kong's restaurants: "These wonderful animals, which since the 1940s have lived and bred in the coral depths, now lie behind thick distorting glass in a narrow tank on the footpath.

"If a passerby or a restaurant patron knew that these magnificent creatures were more than 65 years old, would that make a difference?"

Macalister believes laws should be changed to stop big fish being put on public display in cramped conditions by restaurants. "The problem is that until very recently, no one has really understood fish in the same way that no one understands lobsters and crabs," he said.

"In fact they have sophisticated brains, and animal welfare science shows that they are feeling things we never knew they felt.

"Some of those fish you see outside restaurants have probably been around since the 1940s. They are used to swimming around freely in the depths. The next thing they know, they are in a tank on a footpath. It's cruel and it must be terrifying for them."

Expert research suggests that in spite of common misconceptions, fish have memories and feelings similar to other animals, according to Macalister, meaning that being kept for months or years in a hugely restricted space amounts to a sublime form of torture for a mature adult fish.

"The only thing with a fish is it can't express it," he said. "They learn, and they have memories, and they can identify people. They feel stress and they feel pain. People used to believe fish couldn't remember anything for longer than three seconds, but we know now that isn't true."

Macalister said that as the law currently stood, it was very difficult for prosecutions to be brought. "The issue is defining what is too small in terms of a tank," he said. "If the fish has clean water and he has got the space to move around, then it's not prosecutable under law."

Marine biologist Yvonne Sadovy of the University of Hong Kong said the notion that fish feel pain and stress was becoming increasingly accepted in academic circles.

"There has been a big question over whether fish feel pain and how they respond," she said. "Fish are vertebrates like us. They have a backbone and a lot of the biology and physiology have some similarities to us. The nervous system and hormonal system in some ways are very similar.

"I think most biologists would say there is absolutely no reason to believe they would not feel pain. How they perceive it is obviously incredibly difficult to know, but you pick up a fish and take it out of water and put a hook in its mouth and it struggles.

"There is something clearly uncomfortable and not right and that fish is perceiving stress in some way.

"There have been studies of fish in mariculture environments where stress levels are measured by hormones when they are crowded and not fed properly, and chemicals associated with stress are very high.

"There is no reason to think that they don't feel pain, In fact, that would have to be the assumption, unless it can be shown that they do not."

Professor Sadovy has examined how large fish are treated in Hong Kong and said: "The way they are handled is pretty awful. They are there for the spectacle and to attract people to the businesses.

"They often have abrasions. I guess when they are shipped and often moved over large areas, they get banged around.

"Outside restaurants, I've actually seen these fish physically thrown from one net to another. People stand on the tanks and pick one up in a net and throw it to another tank like a game of lacrosse."

Professor Sadovy said: "We used to put lions and tigers in tiny cages in the past. With fish, we still don't treat them like we do other animals that we have come to have more respect for. Fish always get left until last."

As far as Macalister is concerned, a public debate and a review of the law on the treatment of fish is urgently needed. "We should start the discussion today," he argued. "Otherwise future generations might wonder how we could have been so inhumane." (dpa)