Rotorua Lakes residents have taken freshwater crayfish poaching concerns into their own hands.
But some have been in the wrong, the Ministry for Primary Industries says.
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The ministry was recently contacted about "incidents at Rotorua lakes between locals and visitors who were gathering kōura".
"Unfortunately without being well informed of the rules the locals have taken the kōura catch and tipped it back into the water because they thought it was illegal to take kōura using scuba."
The ministry said it contacted "a number of concerned locals, advised them of the rules".
The Te Arawa Lakes Trust has also received "numerous reports" from Lake Rotoiti and Lake Ōkataina residents about large illegal takes of kōura - a threatened species.
The trust's environment manager, Nicki Douglas, told the Rotorua Daily Post, "The trust was first notified of these illegal takes three weeks ago, including reports that some of these were well in excess of the 50 kōura allowed per person."
She said residents had "attempted to intervene".
"We would urge people to consider their own health and safety first and to contact the relevant authorities who will take appropriate action."
She said Fisheries New Zealand had been notified but no charges had been laid so far, and it was "critical for people to note down any information relating to the vehicle(s) and people involved".
The Ministry for Primary Industries had asked lakes residents to call the poacher hotline if they suspected illegal activity, so fisheries officers could respond.
It said officers would be patrolling Rotorua lakes this summer.
Kōura populations are in gradual decline, the Department of Conservation said, and many did not reach adulthood.
However, currently people gathering kōura were allowed 50 per day.
They could be caught with pots, traps or baited lines but the most common method was hand gathering.
Scuba diving for kōura was currently allowed and was becoming increasingly popular.
Rotorua freshwater fisheries scientist Dr Ian Kusabs told the Rotorua Daily Post at this time of year female kōura carried juveniles under their tails before releasing them into shallower waters.
"Basically if you take the mothers at this time there are no juveniles to continue the population in the future."
He said catfish in Lake Rotorua and Lake Rotoiti were eating juvenile kōura, putting pressure on the populations there.
"It is now even more important to look after the kōura populations in the lakes where catfish are not present such as Rotomā, Tarawera and Ōkataina.
Tightening the rules
The Te Arawa Lakes Trust had been working on proposed bylaws for the lakes to put restrictions on the size, quantity, and methods of harvesting taonga species such as kōura.
The bylaw proposed a total closure of the kōaro (small native freshwater species) fishery, it limits cultural harvesting of the six Te Arawa freshwater taonga species and bans people from scuba diving for them.
The proposed bylaws were developed by Te Komiti Whakahaere, the Te Arawa Fisheries Committee, which sits within Te Arawa Lakes Trust.
The Ministry for Primary Industries called for public submissions on the proposed bylaws in March 2018, and the trust was waiting on final notification from the agency around implementing the bylaws.
"We all want the same thing – to protect our taonga for the future. These bylaws will go a long way to help us achieve that," Nicki Douglas said.
• The freshwater crayfish have a hard shell-like skin that they moult. There are two species found only in New Zealand. Kōura in the North Island and Marlborough, Nelson and the West Coast of the South Island are slightly smaller and have less hairy pincers than those found in the east and south of the South Island and on Stewart Island.
• They live in streams, lakes, and ponds, and even in swamps and get oxygen from water through their gills. They shelter between stones but can burrow into mud. They stay hidden during the day. Their dark brown colouring serves as camouflage.
• They are scavengers that feed on leftovers that float by in the water or settle on the bottom including old leaves and small insects. This helps recycle leftover materials and clean up waterways on a small scale.
• Large trout are known to eat kōura, as do shags.
• Females produce eggs between April and December, and carry them under their abdomen until they hatch. Babies cling to their mothers with their pincers until they are nearly 4mm long. They are fully grown after four years.
• Populations are decreasing in some areas because of habitat modification and land-use intensification. Predation by introduced species and harvesting for human consumption has also reduced their numbers.
• Fencing off waterways and ponds from stock and planting native vegetation along the edge of waters supports kōura conservation.
Source: Department of Conservation