Thousands of hatchery-bred barramundi are to be poured into the Johnstone River, near Innisfail in far north Queensland.

The micro-tagged barramundi fingerlings are part of a research project being run by the Queensland Department of Employment, Economic Development and Innovation to determine if fish stocking methods in rivers and impoundments are delivering the best possible results for barramundi enthusiasts.

The project aims to provide information to community stocking groups and managers on how best to plan and implement stocking programs.

A microtag is only about 1mm long and a special machine is used to inject it into the cheek muscle of the 50mm long fish before it is released.

A special scanner, similar to the wands used at airport security checks, is needed to detect their presence.

The tags allow researchers to identify if a barramundi caught in the river was originally stocked there.