World Marine Data - Page 5

Extreme wave indexes estimate the occurrence of extreme wave events in coastal and oceanic waters. Extreme wave indexes estimate the number of times a significant wave height exceeds one of three threshold values for at least 12 hours in 24 marine regions. The three wave-height thresholds are four metres, six metres, and eight metres.
This indicator estimates the exceedances of wave-height thresholds for each year from 2008 to 2015 in oceanic areas around New Zealand.
Significant wave height is a measure of the ‘typical’ wave height in a place over a time period. It is four times the standard deviation of the water surface if, for example, you were to measure water moving up and down a jetty piling for an hour. The largest individual wave will typically have a height around twice the significant wave height.
We use three wave-height thresholds because of the regional variation in extreme wave events. In general, the north experiences less exposure to consistently strong winds, and the waves generated by them, than the south. Four-metre tall waves are considered extreme in the northern-most parts of New Zealand but are more common in the south. For the southern-most parts of New Zealand, eight-metre waves better represent extreme wave events.

Along with sea lions, fur seals, and dolphins, seabirds are the protected species most directly affected by fisheries in New Zealand waters (exclusive economic zone and territorial sea). Estimating seabird deaths from bycatch in commercial fishing is one way of assessing the pressure some seabird species face from current fishing practices. About one-third of our 92 resident seabird species and subspecies are considered to be threatened with extinction. We report on the risk of death from commercial fishing for 70 seabird species and subspecies.
The estimated annual seabird bycatch in trawl and longline fisheries is reported for Salvin’s albatross to illustrate effects on a threatened bird species with a very high risk of fishing-related death.
This data has been significantly revised since that reported in Environment Aotearoa 2015, with the estimated total bycatch of seabirds increasing by nearly 1400 birds (30 %) on average across the comparable years 2002/3 – 2012/13. This revision is due to an updated and more unified modelling approach being applied by the data providers. For further information about this revision please see our Marine domain 2016 webpage or Abraham and Richard (unpublished).

New Zealand has a diverse range of marine mammal species and subspecies, including whales, dolphins, seals, and sea lions. Marine mammals are indicator species for the state of our marine environment. The conservation status of a species relates to its risk of extinction.
Many of these species are endemic (only found in) to New Zealand. They are apex species (near the top of the food chain) and can thrive only if their ecosystems are healthy. A decreasing population can indicate that the ecosystem is degrading. Marine mammals played an important part in New Zealand history; in the past whales and seals were hunted in great numbers. Now we have a rapidly-growing whale- and dolphin-watching industry.

New Zealand waters have at least 117 species of chondrichthyans (sharks, rays, and other cartilaginous fish species). They are particularly vulnerable to overfishing because they are long-lived, mature slowly, and have a low reproductive rate. Chondrichthyans are important for healthy ocean ecosystems, and reporting their commercial catch and bycatch helps us understand the sustainability of our fisheries.

Seabed trawling and dredging, when fishing nets or dredges are towed near and along the seabed, can physically damage seabed (benthic) habitats and species. It can also stir up sediment from the seabed, shading (in shallow waters) or smothering marine species. This measure focuses on coastal areas (waters shallower than 250m). Focusing on coastal benthic habitats is important as these face multiple threats (for example, from land-based activities) in addition to fishing

Seabed trawling and dredging, when fishing nets or dredges are towed near and along the seabed, can physically damage seabed (benthic) habitats and species. It can also stir up sediment from the seabed, shading (in shallow waters) or smothering marine species. This measure focuses on coastal areas (waters shallower than 250m). Focusing on coastal benthic habitats is important as these face multiple threats (for example from land-based activities) in addition to fishing.

Seabed trawling and dredging (where fishing gear is towed near or along the ocean floor) can physically damage seabed (benthic) habitats and species. These fishing methods can also stir up sediment from the seabed, creating sediment plumes that can smother sensitive species. Recovery times for affected habitats and species depend on their sensitivity and the area affected by trawling or dredging. Bottom trawling is carried out on or near the seabed in both shallow and deep waters. Dredging is carried out on the seabed in shallow waters and targets marine creatures such as scallops. This measure focuses on deepwater areas (waters deeper than 200m).

Seabed trawling and dredging (where fishing gear is towed near or along the ocean floor) can physically damage seabed (benthic) habitats and species. These fishing methods can also stir up sediment from the seabed, creating sediment plumes that can smother sensitive species. Recovery times for affected habitats and species depend on their sensitivity and the area affected by trawling or dredging. Bottom trawling is carried out on or near the seabed in both shallow and deep waters. Dredging is carried out on the seabed in shallow waters and targets marine creatures such as scallops. This measure focuses on deepwater areas (waters deeper than 200m).

Seabed trawling and dredging (where fishing gear is towed near or along the ocean floor) can physically damage seabed (benthic) habitats and species. These fishing methods can also stir up sediment from the seabed, creating sediment plumes that can smother sensitive species. Recovery times for affected habitats and species depend on their sensitivity and the area affected by trawling or dredging. Bottom trawling is carried out on or near the seabed in both shallow and deep waters. Dredging is carried out on the seabed in shallow waters and targets marine creatures such as scallops. This measure focuses on deepwater areas (waters deeper than 200m).

The marine economy shows the contribution marine-based economic activities make to the New Zealand economy as measured by gross domestic product (GDP). Measuring the marine economy shows how New Zealand’s marine environment is used to generate economic activity and how this changes over time. However, these activities can also be a source of pressure on New Zealand’s marine environment.