Overharvesting of fish has had a significant adverse impact on the mauri and ecological health of the Hauraki Gulf, reducing the availability of kaimoana (seafood) to local communities and Māori. This project developed and tested a bycatch-free fish trap prototype. Objectives were to: 1. Create a viable, sustainable alternative to non-selective commercial set netting practices in the Hauraki Gulf and beyond. 2. Achieve zero bycatch, including non–target fish, marine mammals and seabirds. 3. Enhance the quality and value of commercial fishing catch through passive fishing techniques.

The fish trap was designed by Dave Kellian, a veteran commercial fisherman and environmentalist, with decades of experience in the Hauraki Gulf. Dave was supported by Fraser Stobie from Envirostrat, who led the technical analysis, reporting and project management. The design allowed for passive movement of fish in and out of the trap, and enabled remote trap activation. The contents of the trap were monitored by a submersible camera feed, which was viewable on a home computer. The structure and operation of the trap was designed to be bycatch-proof.

Success criteria were:

• To have zero negative interactions with seabirds and marine mammals.

• To passively attract commercial finfish species within the device.

• To have zero/low volume of non-commercial finfish species within the device.

• To remain structurally intact for the duration of the trial.

• To retain functionality for the duration of the trial.

• To have zero negative interactions with recreational and commercial vessels.

• To be user-friendly.

The device was towed into position by a six metre commercial longline fishing vessel and deployed below the low-tide mark at the mouth of Leigh Harbour in North Auckland (12m water depth), see picture on right of the trap deployed. Data from video recordings inside the trap were used to record fish presence and species.

Key findings were:

• Fish primarily used the device to shelter and to feed, especially in poor conditions. There were no recorded or observed negative interactions with marine mammals or seabirds.

• While several seabird and shorebird species were detected within close proximity (<100m) of the device regularly, none were observed entering the trap.

• Observed fish bycatch was minimal, both in terms of the number of species and total volume. No mortality was recorded while the device’s doors were closed, and no issues were encountered with fish getting ensnared in the mesh.

• No negative interactions were recorded between the device and nearby vessels.

• Although the device was accepted by the majority of the community, the trap was damaged on one occasion where it was clear that someone had cut loose one of the marker buoys. It is not known if this was done to sabotage the device or simply a case of theft, but was an isolated incident.

• Aside from some minor issues, the device and the camera system tolerated the harsh marine conditions well for the entirety of the trial.

Several challenges were encountered during the trial, relating to buoyancy, the heavy weight of the fish trap compounded by biofouling (microorganisms accumulating on wetted surfaces), and voltage differences between the modem and the camera. All of these can be resolved in future iterations.

While the device met most of its success criteria, it failed to catch volumes of fish that would enable this design to become economically viable, and technical challenges limited the ability to test the fish trap at different locations, depths and habitats.

This initial prototype needs to be reworked and tested further to fully realise its potential. This will require funding to redevelop the design and to conduct more in-depth tests of future iterations of the device.