In this section, we describe the state of our marine environment and how it is changing over time. We provide information about the sustainability of fisheries and biodiversity.
Sustainability of fisheries
Our commercial fisheries are sustainably managed, and overfishing is decreasing
Overfishing occurs when the rate of harvesting a fish stock exceeds the rate at which it can naturally replenish. We can understand how sustainably our fish populations are being fished in two ways: first, by assessing the proportion of fish caught from stocks subject to overfishing; second, by assessing the proportion of stocks (ie fish populations) that are subject to overfishing.
In 2014, the proportion of fish caught (landings) from stocks subject to overfishing was less than 5 percent. This is a decrease from about 10 percent in 2009/10.
Between 2009 and 2014, the proportion of stocks subject to overfishing fell from 25 percent to 14 percent (from 19 of 76 assessed stocks, to 16 of 114 assessed stocks; see figure 40). This is partly due to a 20 percent reduction in the number of stocks subject to overfishing between 2013 and 2014. However, it is also due to more stocks being assessed each year, bringing the proportion of stocks subject to overfishing down.
Bycatch and trawling remain a pressure on our fisheries and other marine life.
This graph shows the tonnes of landed catch from overfished and not overfished stocks annually between 2009 and 2014. Visit the MfE data service for the full breakdown of the data.
For more information see: The pressures on our marine environment section.
For more detail see Environmental indicators Te taiao Aotearoa: State of fish stocks.
This section presents information about the state of our marine biodiversity: seabirds, marine mammals, fish and reptiles, and invertebrates. The state of these species provides a good indication of the overall health of the marine environment.
Most indigenous seabird species are threatened with or at risk of extinction
New Zealand has 92 resident indigenous seabird species and subspecies, which is the highest number of endemic seabirds in the world (Croxall et al, 2012). (‘Resident’ refers to indigenous species that breed in New Zealand.)
Thirty-two (35 percent) of our indigenous resident seabird species or subspecies are threatened with extinction. Twelve (13 percent) of these are classified as nationally critical (meaning they face the highest risk of extinction). Another 51 species (55 percent) are at risk of extinction.
Between 2005 and 2011, the risk of extinction increased for seven species of seabird, while it improved for one species, the Chatham petrel.
Fishing bycatch is the main pressure on seabirds.
For more detail see Environmental indicators Te taiao Aotearoa: Conservation status of seabirds and shorebirds.
Some marine mammal species are threatened with extinction
New Zealand waters are home to 30 species and subspecies of resident indigenous marine mammals.
Eight of these species (27 percent) are threatened with extinction, and between 2005 and 2008–11, the extinction risk increased for one mammal species, the New Zealand sea lion.
The orca, Māui’s dolphin, Bryde’s whale, New Zealand sea lion, and southern elephant seal are considered nationally critical. The Māui’s dolphin is estimated to have 55 individuals remaining that are over one year of age (those less than a year old are not monitored) (Hamner et al, 2012).
Nine species (30 percent) of marine mammals are considered to be not threatened. For one of these species, the New Zealand fur seal, the population is recovering.
Conservation status of fish and reptiles is uncertain
We do not have recent information on the conservation status of marine fish. The Department of Conservation completed the last assessment of their conservation status in 2005. At that time, two of the 204 resident species assessed – the great white shark and basking shark – were classified as being in gradual decline, while 18 species were assessed as sparse. However, the system for assessing conservation status has changed since 2005 (Hitchmough et al, 2007).
Turtles and sea snakes also visit our waters and, while they are considered indigenous, their conservation status is not assessed because they do not breed in New Zealand’s marine environment.
Many marine invertebrates are at risk of extinction
There is limited information available about the conservation status of marine invertebrates such as rock lobster, pāua, pipi, sponges, and corals. Of an estimated 12,000 species, 415 were assessed (Gordon et al, 2010; Freeman et al, 2014).
Of the assessed species, 11 (2.7 percent) were classified as threatened with extinction. A further 324 species (78 percent) were considered to be at risk of extinction, principally because they are naturally uncommon – that is, they are naturally restricted to certain habitats (Freeman et al, 2014).
Heavy metal levels in estuary sediment are generally low
The concentration of heavy metals in most estuary sites monitored between 2010 and 2014 was at levels considered unlikely to have adverse ecological effects on species living on the estuary seafloor. Heavy metals accumulate on the seafloor and have the most direct impact on species that live there.
Lead levels at 94 percent of sites were unlikely to have adverse effects. Levels of zinc, cadmium, and copper were unlikely to have adverse effects at 92 percent, 95 percent, and 89 percent of sites, respectively.
Levels at 1percent of monitored sites for bothcadmium and zinc (four sites each)exceeded levels likely to cause adverse ecological effects on species living on the estuary seafloor.
For more detail see Environmental indicators Te taiao Aotearoa: Heavy metal load in sediment.