A recreational fisherman has been left gobsmacked after pulling up a prize blue cod, only to find the bloated fish had been gorging on salmon feed.

Martin Pinder said fish feed pellets used in salmon farms spilled out of the gut as he began to fillet the fish on board his boat in the Marlborough Sounds. He had been fishing about 800 metres from the Ngamahau salmon farm in the Queen Charlotte Sound.

\"If there are other fish species dining on fish feed, it would be interesting to know if they are getting accustomed to eating it.\"

Pinder said the pellets might have drifted through the cage wire at high tidal flow before the salmon had a chance to eat it. Blue cod obtained most of their food from the sea floor, he said.

\"They are bottom dwellers, they eat anything and they hoover a lot up from the sea floor. \"I\'ve caught others in the same spot but none have been bloated like this one.\"

Pinder said the discovery of the fish feed also had him questioning if the feed was harming the native fish stock in the Marlborough Sounds.

By Mike Watson, Stuff. Read the full story.