New catfish control option to be investigated

2:07 pm on 9 August 2020

The Bay of Plenty Regional Council has given the goal of eradicating brown bullhead catfish from Lake Rotoiti and Rototua another boost.

A brown bullhead catfish

NIWA says the brown bullhead catfish which was introduced to New Zealand in 1877. (file picture) Photo: CC 4.0 BY-NC-ND / NIWA

Catfish stir up sediment and prey on small native fish, fish eggs and are known to eat and compete with kōura, native freshwater crayfish.

The biological control method involves releasing sterile male catfish into lakes to disrupt reproduction by causing catfish eggs to be left unfertilised.

Bay of Plenty Regional Council biosecurity manager Greg Corbett said that the preliminary investigations into using the control method showed there was strong potential for catfish biological control in the Rotorua Te Arawa Lakes.

"It's early days and while it has been used successfully overseas, at this stage the focus is purely on investigating the method further and determining how it could be applied in Lakes Rotoiti and Rotorua.'

"We have a good base understanding of the behaviours and impacts of catfish following the completion of six separate research projects in the last two years, so investigating the viability of biocontrol as a long term solution for catfish population control is a natural next step," Corbett said.

Te Arawa Lakes Trust environment manager Nicki Douglas said the application of mātauranga Māori will be an integral part of the project, which has been dubbed 'Catfish Killas'.

"We know that catfish are having a devastating effect on kōura and other taonga species," she said.

"Including mātauranga Māori-based research into this work will ensure that the research, implementation and monitoring of biocontrol incorporates kaupapa Māori assessments in decision making," Douglas said.

NIWA has already completed an initial feasibility study of biological control of catfish and modelling has indicated that suppression or even eradication of the species might be possible.

Corbett said ultimately the long term health of the Rotorua Te Arawa Lakes and its freshwater biodiversity is the top priority for everyone involved.

Douglas said the role of the Te Arawa Catfish Killas will continue to be crucial in the future to control catfish numbers.

"Biocontrol takes time and the incredible mahi of our Catfish Killas will be needed for a long time yet.''

Next steps for the project involve proof of concept work in a laboratory-based environment, working with regulatory agencies to determine permitting requirements, and commissioning of post-graduate research projects.

Engaging with Te Arawa hapū and iwi as well as community consultation throughout the Rotorua Te Arawa Lakes area will be an integral part of the project development.

Biological control does not involve genetic modification and the activity is regulated by multiple central government agencies in New Zealand.

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