Dolphin and whale watch cruises are one of the most popular tourist attractions in Auckland, New Zealand.

This writer had an opportunity to see and video dolphins gliding along the Explore NZ vessel in April 2012.

However, this thriving money earner is being jeopardised by the threat of extinction by 2030 for one dolphin sub-species - the Maui dolphin. Scientists from the Society for Marine Mammalogy (SMM) in the U.S. said that the population of the world's smallest dolphin sub-species has gone down to only 55.

The Maui dolphin could only be found in the waters of the North Island's west coast in New Zealand.

The society wrote a letter to New Zealand Prime Minister John Key, pointing out that based on scientific data, five dolphins die yearly due to being entangled in fishing nets. It sought a ban on trawling and gillnetting, a fishing method, in the country's marine habitat.

"In a situation such as this one, involving a critically endangered sub-species, delay to resolve uncertainty could have dire, irrevocable results . . . I encourage you to act quickly and decisively to provide the leadership in marine conservation that the world expects of your country," SMM President Helene Marsh wrote in her letter to Mr Key dated Feb 11.

The warning echoed the plea made by the International Whaling Commission in July 2012 for Wellington to extend maritime protection zones for dolphins. The New Zealand government had actually started to review in 2012 protection measures but has yet to release the measures it would take.

Also endangered are the Hector's dolphins which are found only around New Zealand but whose population had dwindled to 7,000 from 30,000 because of nylon fishing nets used by fishermen since the 1970s.