Scientists have shed new light on what's driven the decline of snapper in Auckland's Hauraki Gulf

Successive stocktakes have painted a grim picture - with numbers plummeting by more than 80 percent since the arrival of humans to the area.

For centuries, snapper relied on estuaries with low saline levels - but the industrial revolution brought deforestation, agricultural expansion and urban development.

That led to increased sedimentation and excessive nutrients in estuaries, in turn causing habitat loss, reduced water quality and heightened turbidity.

Researchers say these changes, worsened by over-fishing and new pests, forced snapper to other habitats.