Our Navy has helped nab six boats operating illegally in a traditional fishing ground in Fiji.

It follows maritime patrols carried out with Fijian agencies.

A large quantity of fish was found on board the vessels but had to be thrown back into the sea because of operational and safety concerns.

HMNZS Taupo was involved in the patrols, and Commanding Officer Lieutenant Ben Flight says while it's good to be out there helping Fiji, it's disappointing as well.

"About 50 per cent of the population use fishing as a form of subsistence for food or as part of their income so that could have a huge effect if fish stocks are depleted."