Whale rescue organisation Project Jonah is calling for volunteers to be trained in marine mammal rescue.

The stranding of a pygmy sperm whale in Wellington on Wednesday was cited as an example of how difficult it can be to manage a stranding and achieve a happy outcome, Project Jonah chief executive Kimberly Muncaster said today.

That whale had to be euthanised after Wellington locals spent more than two hours trying to save it.

Ms Muncaster said while some whales stranded because they were sick or injured, others were healthy and just needed a helping hand back out to sea.

"It can be very difficult to judge the situation and that's why it's so important to call the Department of Conservation or Project Jonah immediately."

She said a stranding could pose potential risks to people trying to help.

"These risks need to be understood and managed.

"The more Kiwis that can be trained in marine mammal rescue, the less likely we are to pose a risk to either human or animal life," Ms Muncaster said.

Project Jonah will kick off another season of whale rescue training in October, with two one-day courses scheduled for Wellington on November 20 and 21.