A launch caught fishing in a marine reserve and divers with undersized scallops were among the busts by police and fisheries officers in a joint operation in the Bay of Islands.

This summer Far North police have borrowed a rigid inflatable boat normally based at Auckland's maritime police unit. It has been getting plenty of use - including the rescue of woman injured when a yacht was smashed ashore on the Cavalli Islands - and last week it was used in another operation with Ministry for Primary Industries to identify illegal fishing.

In particular, boaties were caught and fined for taking undersized and excess scallops, Senior Sergeant Chris McLellan said.

Anglers on a large launch caught fishing in a marine reserve at Deep Water Cove, near Cape Brett, were likely to receive a formal warning.


Marcie Cooke, the ministry's chief compliance officer in Northland, said it was disappointing but the people apprehended were not from the area, did not know about the fishing ban at the cove, and had not caught anything.

The usual response to breaches of that nature was a written warning, she said.

Mr McLellan said people were realising the police were active on the water this summer. The approach of the police boat regularly sparked a flurry of activity as illegal fish and shellfish were thrown back into the water.

Another concern was the number of people diving without flags and vessels travelling at speed through dive zones.

"It's a recipe for disaster," Mr McLellan said.