Butterfish – Odax pullus – widely known in New Zealand as Greenbone

Butterfish – Odax pullus – widely known in NZ as Greenbone – Not usually caught on baited hooks but in nets or by spearfishing.

Butterfish are highly regarded in New Zealand as a top table fish.  The fillets are firm white and delicate.  This species is a herbivore.  Its diet consists mostly of kelp.  The bones are green in colour, though sometimes they can be almost black in larger fish. Butterfish are also widely known as greenbone! They have a small parrot-like mouth with small fused teeth.  The inside of the mouth is blue. When young they are a yellowish-brown colour with a whitish stripe along the sides.  Older fish are more dark brown in colour.  Large specimens become a greenish-blue, turning almost black in the largest fish.

They have a small parrot-like mouth with small fused teeth.  The inside of the mouth is blue. When young the fish are yellowish-brown in colour with a whitish stripe along the sides.  Older fish are more dark brown in colour.  Large specimens become a greenish-blue, turning almost black in the largest fish.

Greenbone commonly and grow larger around the South Island.  The average size range is between 30 and 50 cm.  Large specimens can reach 70 cm in length and can weigh up to 5 kg.  The heaviest butterfish are more likely found around the coast of Southland and Fiordland.

They are found in shallow rocky coastal waters down to about 20 meters. They do not generally take baited hooks. Most of those sold in shops are taken in nets. Butterfish are also regularly targeted by recreational divers who catch them by spearfishing. Rocky areas with a lot of kelp like the Kaikoura coast are their typical habitat.

How to Catch Butterfish on Baited Hooks

A small number of recreational anglers target butterfish on rod and line mostly with a float fishing rig, small hooks (size 1/0 and smaller), and either mussel or limpet for bait. Some anglers become very skilled at catching butterfish and use refined methods such as jigging their baited hooks or even spearing them when they come to the surface. They are difficult to catch with hooks and can cause considerable frustration particularly when anglers can see them swimming about in clear water but they just won’t bite! David H. Graham also mentions in his book that one angler found butterfish to bite freely with the garden slater as bait.

Butterfish are hermaphrodites.  They all begin life as females and later change sex to become males. They undergo various changes in colour, fin length, and shape throughout their lives making them sometimes difficult to identify.

David H. Graham, in a Treasury of New Zealand Fishes, found the stomach contents of Greenbone consisted principally of brown kelp and green sea lettuce. He also found worms, whalefeed (shrimp) and other small crustaceans in their stomachs, but these may simply have been taken by chance when feeding on kelp.

Pole Netting Butterfish at Kaikoura

I have seen old black and white photographs of people fishing for butterfish off the rocks near Kaikoura with a large net similar in appearance to a whitebait pole net. Seaweed had been fixed around the circumference of the net opening; perhaps as a means of disguising it. The net was lowered into the water with the long pole in a suitable area, and the butterfish were simply scooped out of the water. I have never seen this done but I can see how it would work. The old black and white photographs of this method being used probably dated from the 40s or 50s. In those days, it was also possible to catch any number of big crayfish right next to the road with little effort.