Niwa's primary scientist for biodiversity and biosecurity Dennis Gordon said the creature was a type of salp, which moves through the ocean by contracting and pumping water through its gelatinous body.
Salps played an important role in the food chain because they were able to feed on the smallest organism which were captured in internal filters.
"They can eat the smallest plant plankton and can even eat bacteria so they can exist in parts of the ocean where nothing else can live. The significance of that is they are an intermediary in the food chain,'' Dr Gordon said.
They were also an important food source for some fish, sea turtles and seals, and were far more nutritious than jellyfish.
They were not as rare as one might think and had an amazingly rapid reproductive rate - some salps could double their population in just a day.
However they were not often spotted because of their highly-effective camouflage.
"Their transparency is quite remarkable,'' Dr Gordon said.
The creature Mr Fraser pulled up was about as big as they got.