An invasion of marauding bronze whaler sharks is threatening the existence of one of the best areas in New Zealand for catching kingfish.

The source of many world record-breaking kingfish, the waters around Volkner Rocks, northwest of White Island in the eastern Bay of Plenty, has fallen victim to a plague of sharks, says a fishing charter boat owner.

Rick Pollock, who has fished in the area for 32 years, says hundreds of sharks are in the area, ranging from an estimated 40kg to a huge 300kg in weight.

The owner-operator of the Whakatane-based gamefishing launch Pursuit said there had always been bronze whalers in the wedge-shaped area cutting into the southwestern side of the Te Paepae o Aotea marine reserve.

But this year they had reached "plague proportions", attacking hooked gamefish much earlier in the season than before and making it virtually impossible to land an intact fish.

The sharks had become so aggressive he would be reluctant to let spear fishermen into the water there, Mr Pollock said. "You'd be asking for problems.

"Previously they have become a hindrance in December or January, but we started our season in early October and had problems immediately.

"You can hook a nice fish, but it will be taken by sharks within a minute.

"On Tuesday, we landed all that was left of a kingfish - the head - and there were 10 sharks in hot pursuit."