Gigantic sunfish weighing a tonne caught and released by scientists off the coast of Spain

A sunfish so big two cranes were needed to winch it aboard a ship has been caught in Spain.

Scientists in Spain captured and released the beast measuring a whopping 3.2 metres from fin to fin.

The bizarre species has a distinctive disc-like body that gives it the appearance of all head and very little tail.

The specimen caught by researchers off the coast of Ceute on October 4 weighed in at a tonne, and measured 2.9 metres and length and 3.2 metres from fin to fin.

Marine biologists trapped the fish in an underwater chamber and hauled it aboard their vessel using cranes.

A diver aids the sunfish as it is released and swims off into the deep. Credit: Estación de Biología Marina del Estrecho (Ceuta) – Universidad de Sevilla

The Station of Marine Biology of the University of Seville team took measurements before releasing the fish back into the waters off the coast of Ceuta on October 4.

Researchers from the US Marine Biology Laboratory, led by Professor José Carlos García Gómez, together with colleagues from Switzerland, are working on monitoring the population of sunfish that pass through Ceuta, Sevilla University said.

They are working to identify the morphological and genetic differences between the “Mola mola” and the “Mola Alexandrini” species.

The specimen caught off the coast of Ceuta belongs to the “Mola Alexandrini” species, researchers said.

The sunfish is one of the heaviest known bony fish in the world.

They are known to bask on their sides on the sea's surface, in behaviour scientists believe may be a strategy of "thermal recharging" following feeding dives into deeper, colder water.