humpback whales

A Sea Shepherd helicopter spotted the vessel yesterday, with two harpoon ships nearby.

"They're hit with an explosive harpoon that goes straight into their body, hooks come out and shrapnel is sent through their body, it's a terrible bloody death … these whales can take up to 30 or 40 minutes to die," Jeff Hansen from Sea Shepherd said.

The marine conservation group said the Japanese crew quickly covered the whale with a tarpaulin.

Whale watching operator Magical Niue Sea Adventures has been working with local and international researchers to try and understand where the whales came from and where they are going.

This is done by photo identification and DNA analysis which is compared with other countries the whales visit in the region throughout the season.

The owner of Magical Sea Adventures, Rami Oved says research aside this year has been really good for business.