Fish and other marine life around Mayor Island have been protected by law for 19 years - but is it making any difference to their numbers?
Dramatic increases in fish sizes and numbers have been recorded in a Tauranga marine reserve after illegal fishing patrols and prosecutions were stepped up.
Annual fish counts have been conducted at Tuhua (Mayor Island) since it was designated a marine reserve in 1993.
For 15 years, those counts returned indifferent results until enforcement was intensified.
Dan Rapson, Tauranga Department of Conservation (DoC) biodiversity ranger, said the link between increased prosecutions and improved fish counts was no coincidence.
"We had a 10-year report in 2004 which brought back quite disappointing results. After that we looked at how we were managing the reserve and DoC decided we needed to up our game on enforcement.
"In 2008, we had a new boat built which enabled us to get out in rougher conditions and meant we were able to do more work out at Tuhua. We definitely upped the ante in terms of prosecutions."
There were just three prosecutions in the first 15 years of the reserve (1993 to 2008). There have been eight in the four years since.
Last week, a 36 year-old Tauranga man pleaded guilty to illegally fishing in a marine reserve and was discharged without conviction at a court hearing in Tauranga. The judge ordered the man to pay $600 to charity, $150 towards court costs and to surrender his fishing rod and reel.
Mr Rapson said there was no excuse for those caught fishing illegally inside the reserve.
"We always hear the same story from people we catch, that they didn't know.
"Well, everyone we've caught had a colour GPS chart with them clearly showing the reserve. The paper charts have this as well, so there's no excuse. Ignorance is not an excuse."
The marine reserve covers an area three square nautical miles north of Tuhua, which lies 35km offshore. Survey graphs supplied by DoC showed the number of legal-sized snapper (above 27cm) per count averaged seven before 2009 and almost trebled, to 19, over the past four years.
"The results post compliance have been much improved," said Mr Rapson.
"They've shown increases in tarakihi, snapper and red moki in terms of the size and number of fish. This is most strongly reflected in the increases in snapper. It's a strong indication of the very positive impact the marine reserve is having."
Keith Gregor is marine studies tutor at the Bay of Plenty Polytechnic and each summer takes about 30 students out to Tuhua to undertake counts. Counts are conducted in two ways: by divers or by baited underwater video (BUV).
Diver counts are undertaken at more than 90 sites, inside and outside the reserve, during a 10-day period. The students dive along a 50-m tape line, on a set compass bearing which is identical each year, and count all fish encountered within a 5-m arc.
BUV surveys, tripods with a fish bait and video camera attached, have been carried out in 2006 and again in 2011.
"We have seen incremental rises over the last four years," said Mr Gregor.
"That's been reflected in both diver surveys and last year's BUV survey. The methods allow us to cover a range of depths and locations. The divers don't go deeper than 20m so typically the cameras will be dropped at depths greater than that."
Mr Rapson said the 2011 BUV survey had seen significant improvements.
"The 2006 BUV survey produced fairly ordinary results but last year they were really good.
"The difference between those counted inside the reserve and those outside was really marked with larger and greater numbers of fish, especially snapper, inside the reserve.
"Sometimes it was really difficult to count because there were just so many fish in the frame."
Mr Rapson said the increase in fish stocks was a "happy by-product" of the work at Tuhua.
"The work is not for the purposes of increasing fish stocks, that's a happy by-product of what we do. The reserve is about putting an area aside for the purposes of the scientific study, without interference from people, with no collecting of shells or seaweed, no external input, interference or development. It was established really to measure the impact of human activity.
"As well as the fish counts, we conduct Benthic surveys which look at life on the seabed - seaweed, sponges, crayfish and the health of that ecosystem.
"The results of that have been more subtle and highlight inter-relationships."