Whitebaiters have threatened to shoot, drown and kill Conservation Department ranger Chris Annandale over the years.

Now, with the season's opening day on August 15 fast approaching, DOC Waikato area manager Matt Cook is calling on fishermen to show respect as his staff work to conserve the fishery.

Mr Annandale has some hair-raising tales from his years spent patrolling the Waikato River.

The worst memory is vivid.

He and a partner had stopped their boat at a stand with six nets out, when you're allowed just one, and were busy confiscating them when their owner appeared.

"We had a pontoon stuck out the back and [the whitebaiter] came belting down the river and rammed us and perched his boat on our pontoon directly behind the motor - there was less than a metre separating us. He threatened to climb aboard and kill the both of us. It was very, very tense."

Had the man clipped a log or wave before impact Mr Annandale reckons he'd have been torn in two.

"I just asked him to settle down and said you know I've got your details you will be hearing from us."

The man was prosecuted for having more than one net and being more than 10 metres from it. The police also charged him with wilful damage and threatening behaviour.

It's the same year after year - through "bluster and bravado" people try and get away with fishing illegally.

Drugs, alcohol and money are also part of the scene.

Whitebait sold to fishmongers in South Auckland would get about $65 per kilo while a buyer on the river would pay about $55.

It also depends on the season, in supply and demand terms, and what's happening generally.

When the America's Cup was in Auckland demand soared and a kilo was going for up to $150.

Drugs are a concern too.

"Some people, you'll pull up alongside their stand and look directly in their eyes and if the signals are there you put it in reverse and bugger off out of it," Mr Annandale said.

"They're probably high on P or something and they would probably slide a knife or boat-hook through you without blinking an eye."

Mr Annandale said most fishermen share his view of the regulations and the fishery.

He wants his grandchildren to be able to catch a feed of whitebait as he does.

"If these people pillage it the way they are then that's not going to happen - the majority are waking up to that."

Unfortunately, some aren't.

"Eighty per cent are really good, 15 percent swing either way, and five per cent it doesn't matter what you do. They're never going to change."

Fishing is allowed between 5am and 8pm during the season, from August 15 to November 30, and from 6am to 9pm when daylight saving comes into effect.

- © Fairfax NZ News