Crayfish numbers at Astrolabe Reef (Otaiti) have been hammered since the exclusion zone around the Rena wreck was lifted, a local dive operator says.
Jared Ross, owner of Tauranga Dive, has been diving the reef regularly since about 2014. In that time, Mr Ross said he had seen the number of crayfish in the shallower parts of the reef grow exponentially to the point where a wall was "just crawling" with the crustaceans.
On his last dive, about a month ago, Mr Ross said he did not see any crayfish.
"The crayfish have been wiped out from when it was opened until now.
He said that in his opinion the reason for that was commercial fishing.
Mr Ross said the stock levels would probably be "okay" by national standards, but replenishment had taken "five steps backwards" to a pre-Rena state.
"Now, it replicates what a normal coastline looks like."
Phil Ross, a University of Waikato marine ecologist based at the Coastal Marine Field Station at Sulphur Point, agreed marine life had been fished back to a pre-Rena state and that the reef was now in a similar state to the rest of the Bay coastline.
Dr Ross, who is part of the team tasked with monitoring the ecological effects of the Rena grounding, said the reef was still teeming with life, just not necessarily with commonly harvested species.
"I don't think it's unexpected. It takes a long time for things to accumulate and it doesn't take long to fish it down."
Dr Ross said from his observations, there were fewer crayfish than previously, but that was probably the only observable difference.
Daryl Sykes, the executive officer of the New Zealand Rock Lobster Industry Council, said there would be a number of explanations for why the numbers of crayfish had reduced.
All the legal lobsters may have been caught, or the behavioural patterns of the lobsters might be coming in to play.
Mr Sykes said that at this time of year, females would be "in berry" and protective of their egg clusters, so would go into shelter. Males also went into moult and were incredibly vulnerable to predators, he said.
"There is a reasonable explanation that they've been caught, and there's nothing wrong with that. The catch limit is set to make sure the lobsters aren't overfished.
"There are stringent measures in place because populations across the Bay of Plenty have been in decline for a number of years."
Mr Sykes said the industry had voluntarily reduced its catch limit this season for this reason.
Russ Hawkins, who operates Fatboy Charters and is the club captain of the Mount Maunganui Underwater Club, said the reef was seasonal and at this time of year, there were no real numbers of pelagic fish around.
Mr Hawkins did not believe there had been any impact on fish stocks at the reef.
Te Atarangi Sayers was one of the drivers behind an application to the Ministry for Primary Industries to have a temporary exclusion zone in place at the reef for two years with the aim of applying for Otaiti to become a marine reserve.
Mr Sayers applied for the temporary closure in January, hoping if it was granted it would be in place before the exclusion zone was lifted in April, but was yet to get a response from the ministry.
A Ministry for Primary Industries spokesperson said the ministry was considering the request for a temporary fishing closure over the waters around the reef.
The spokesperson said fish stocks were not monitored during the navigation exclusion zone because that was put in place for the MV Rena recovery.