The environmental health of Auckland's Hauraki Gulf is either worse or no better than three years ago, according to most of the measures used.
The Hauraki Forum has released its latest review of how the largely protected marine and wildlife sanctuary is faring.
In one area, the number of wading birds has declined by half, while a large amount of plastic litter is still entering the coastal environment.
The report also says fisheries management rules are keeping stocks of some fish well below natural levels, causing big declines in species and habitat diversity.
Hauraki Forum chair John Tregidga is calling for more investment in protection and enhancement, and wants to increase the area protected.