Taking the classroom to the sea in the marine pest fight

In January 2020 a visiting photographer was snorkelling over the estuary mussel bed in the Whangapoua estuary, Aotea Great Barrier when he spotted what he thought was an Asian Paddle Crab (Charybdis japonica) – an aggressive marine pest that reproduces rapidly and predates on our native crabs and shellfish. This incident, which happened on the last remaining estuarine bed of mussels in the Hauraki Gulf, sparked a research project involving senior students from a local school.

Thomas Daly, manager of Envirokiwi which oversees the Okiwi Community Ecology Project on Aotea Great Barrier Island, leads the program which consists of setting traps in the estuary once a month across summer.

Each day a group of around four children and two adults enters the area at low tide. They check a series of twenty traps in the areas they can safely reach on foot, with a kayak as a floating table to process what they find. Five days later they retrieve all the traps and analyse the data they have collected.

While the great news is that no Asian Paddlecrabs have so far been caught in the traps, indicating the species is not well established the students have enjoyed a marvellous learning about biodiversity and biosecurity in the marine environment through involvement in the trapping. They have enjoyed the opportunity to study the bycatch too before releasing it back into the waters of the Whangapaoua estuary.


The Okiwi Community Charybdis Trapping Project is funded by the Aotea / Great Barrier Local Board, and run by Envirokiwi in conjunction with Okiwi Primary School.

Schools interested in including marine biosecurity within their classroom learning can email info@marinepests.nz to find out about a Marine Biosecurity Education Module in development and which will be available shortly.

Photos provided by Thomas Daly, Envirokiwi