Chapter 11: Oceans

New Zealand’s marine area

At more than 4.4 million square kilometres, our marine environment is about 14 times larger than our land area. We use our marine area for many purposes, including transportation, fisheries, recreation, and tourism, and value it for its cultural and spiritual significance.

Our economy and the marine environment

Many of New Zealand’s economic activities depend on our marine environment. More than 99 per cent of our exports are transported by sea. Our marine industries are worth an estimated $3.3 billion (about 3 per cent of gross domestic product), including $1.34 billion in fisheries exports.

Marine biodiversity

Our marine environment contains a diverse range of ecosystems, including subtropical and subantarctic waters, inter-tidal estuaries, and seabed trenches.

As much as 80 per cent of New Zealand’s plant and animal species occurs in the marine environment and 44 per cent of these are not found anywhere else in the world. Little is known about many of New Zealand’s marine species.

Impact of human activities

By international standards, New Zealand enjoys abundant marine resources and healthy marine environments offshore where much of the environment is not easily accessible. About 30 per cent of our marine environment, however, is thought to experience some degree of disturbance from human activities.

As our population and technological capability grow, so do the pressures we put on our marine environment.

These pressures include:

• commercial fishing and trawling, which have the greatest impact on our oceans, both inshore and offshore
• increasing land development, which has increased discharges of land-based pollution, stormwater, nutrients, and sediments to the ocean
• marine spills which can put pressure on our marine environment in some areas
• climate change, which is expected to have a significant impact on our oceans and coasts.

Commercial fishing and trawling

In 2006, the commercial fi shing industry caught about 525,000 tonnes of fish in New Zealand waters. Sixty-five per cent of this catch was from fish species that have been scientifically assessed. Of these species, 85 per cent have been sustainably fished. Fifteen per cent have been overfished and rebuilding strategies are in place.

Large commercial vessels conducted about 970,000 seabed trawls between 1990 and 2005. During this period, the area swept by trawls averaged around 55,000 square kilometres each year. Since 1998, the area trawled by large commercial vessels has reduced to about 50,000 square kilometres in 2005, probably due to reductions in the allowable catch for some high-value species. Between 1990 and 2005, an estimated 3.5 million dredges and trawls were undertaken by smaller vessels.

The environmental effects of trawling activity on our seabed are not well monitored.

Water quality at coastal swimming spots

Water quality at our coastal swimming spots is primarily affected by human activity on land. Over the 2006/2007 summer, 80 per cent of the 380 monitored beaches had safe levels of bacteria almost all the time. Only 1 per cent of sites breached bacterial guidelines regularly. Water quality at our beaches appears to have improved in recent years.

Threatened marine species

Of the almost 16,000 known marine species in New Zealand, 444 are listed as threatened. Well-known species of concern include the Hector’s dolphin (both subspecies), New Zealand sea lion, southern right whale, Fiordland crested penguin, and New Zealand fairy tern.

By international standards, a high proportion (62 per cent) of our ocean-going seabirds are listed as threatened. Two species, the Campbell mollymawk and the black petrel, have shown signs of recovery in recent years. However, over the past three years, seven species have had their threatened species status upgraded.

Protecting our marine ecosystems, habitats, and species

A range of measures protect our marine ecosystems, habitats, and species, including marine reserves. Thirty-one marine reserves cover 7 per cent of our territorial sea – a high proportion by Organisation for Economic Co-operation and Development standards. Nearly half of these reserves have been established since 2000, and the area designated as marine reserve has nearly doubled in that same period. However, 99 per cent of our protected area is found in two offshore marine reserves, and some key habitats remain unprotected. Marine reserves are expected to play a signifi cant role in protecting our marine biodiversity.

Fisheries closures are in place for sensitive habitats such as seamounts, and it has been agreed that 30 per cent of the Exclusive Economic Zone will be closed to seabed trawling. Customary restrictions and closures also play an integral part in fisheries management.

Present and future management

In recent years, management of New Zealand’s marine environments has focused on:

• better understanding the wider ecosystem effects of human activities on our marine environment
• establishing a national network of marine protected areas.

Recent years have also seen the emergence of innovative local initiatives for coastal management such as in the Fiordland Marine Area.

In future, increasing attention is likely to be given to the impact of introduced species and climate change on our marine ecosystems, fisheries, and marine species.

Land-based pressures on the inshore marine environment and pressures on fisheries stocks are likely to continue to need careful management into the future. Balancing the competing needs of users of our marine area is likely to become more urgent in the future as our population increases and technology advances. Demand will increase for accurate information to help set priorities for the future use and protection of our marine area.

New Zealand’s marine area

New Zealand administers the sixth largest marine area in the world. At more than 4.4 million square kilometres, it is about 14 times larger than our land area (Organisation for Economic Co-operation and Development, 2007).

New Zealand contains an archipelago of more than 330 islands with 18,218 kilometres of coastline (Department of Conservation, 2007) extending from subtropical to subantarctic waters⁷ over 30 degrees of latitude (see Figure 11.1).

^{7 This chapter does not discuss marine areas in New Zealand’s Antarctic territory.}

Figure 11.1: New Zealand’s marine area

New Zealand’s marine area has three key jurisdictional zones, each of which has a different legal regime. The territorial sea extends seaward from the coast to 12 nautical miles offshore. The Exclusive Economic Zone (EEZ) is the area of sea and seabed that extends from 12 to 200 nautical miles offshore. New Zealand has formally lodged the outer limits of its extended continental shelf – the 1.7 million square kilometres of seabed outside New Zealand’s EEZ – with the United Nations Commission on the Limits of the Continental Shelf.⁸ The commission is considering the submission. Once confirmed, the extended continental shelf boundary will be binding on other countries.

^{8 The outer limits of New Zealand’s extended continental shelf remain subject to the delimitation of boundaries with Fiji, Tonga, and possibly France (in respect of New Caledonia).}

Biodiversity in the marine environment

New Zealand’s vast marine area contains a diverse range of marine ecosystems, providing habitats for many species. Scientists have formally identified almost 16,000 marine species in New Zealand waters, although it is estimated that tens of thousands of species may still be undiscovered (Gordon, 2007). According to some estimates, the possible number of species in New Zealand waters could be as high as 65,000 (MacDiarmid, 2007). It is estimated that as much as 80 per cent of New Zealand’s biodiversity occurs in the marine environment (Ministry for the Environment, 2006).

Because of New Zealand’s geographical isolation, our marine area, by international standards, has a comparatively high level of endemism (species that do not occur elsewhere), particularly in isolated areas such as Three Kings Islands and our subantarctic islands (Gordon, 2007). Forty-four per cent of our known marine species are endemic (MacDiarmid, 2006). For example, over half of the 24 species of albatross breed in New Zealand and, of those, nine species breed only in New Zealand (MacDiarmid, 2007).

As a result, New Zealand is considered internationally to be an important contributor to global marine diversity. For example, endemic species include:

• about 95 per cent of the 733 known sponge species
• 84 per cent of bivalves and gastropods (types of marine molluscs)
• 75 per cent of ascidians (commonly known as sea squirts).

In addition, a comparatively high proportion of our seabirds (including half of our albatrosses) and a third of our seaweeds are endemic.

See Chapter 12: Biodiversity for information on land-based and freshwater biodiversity.

Importance of our oceans

Most New Zealanders (90 per cent) live within 50 kilometres of the coastline. We use our marine area for many purposes, including transportation, fisheries, recreation, and tourism, and value it for its cultural and spiritual significance. Māori regard the ocean as a taonga (treasure) integral to their culture and identity. Many coastal areas contain culturally significant sites such as urupā (burial grounds) and tauranga waka (canoe landing sites). The ocean is also an important source of food to many New Zealanders.

Healthy oceans deliver a range of important environmental benefits: they absorb and transfer nutrients and sediments from the land, absorb carbon, and regulate heat transfer from the atmosphere. These functions are critical to sustaining life.

Many of New Zealand’s economic activities are dependent on the sea. In 2006, 99.5 per cent of our exports (by weight) were transported by sea (Statistics New Zealand, 2006b). In 2002, the estimated economic value of marine industries was about $3.3 billion (about 3 per cent of gross domestic product), including earnings from shipping, fisheries and aquaculture, offshore minerals, and government and defence.

Considerable value is also generated from other marine activities, such as tourism, research and education, and marine construction (Statistics New Zealand, 2006a).

Fisheries and aquaculture

Export earnings for fisheries in 2006 were worth $1.34 billion, including $187 million in earnings from salmon and mussel aquaculture (Statistics New Zealand, 2007b). Fisheries and aquaculture employ more than 26,000 people, both directly and indirectly (Organisation for Economic Co-operation and Development, 2007).

In 2006, the asset value of fish species managed under New Zealand’s quota management system was estimated to be $3.8 billion, a 40 per cent increase from 1996 (Statistics New Zealand, 2007a). However, New Zealand produces less than 1 per cent of global fisheries output, as much of our EEZ is commercially barren (Organisation for Economic Co-operation and Development, 2007).

Natural factors that affect the marine environment

New Zealand’s marine environment is influenced by its geological history, its isolation, and the action of major ocean currents. Marine life in New Zealand waters is influenced by the range and complexity of our marine habitats.

Longer-term weather cycles also affect New Zealand’s oceans. Together, the atmosphere and the rotation of the earth drive major ocean circulation patterns and climate systems across the world, affecting deepwater and surface currents, sea temperature, sea levels, the productivity⁹ of our oceans, and seawater chemistry.

Natural inflows of nutrients and sediments into coastal ecosystems are an important part of biological, physical, and chemical cycles in New Zealand’s inshore area. Such cycles are the basis for productivity in these areas. The offshore ocean area is primarily influenced by major oceanic currents.

^{9 Productivity is a measure of the amount of life that can be supported in an area. It is driven by the availability of nutrients and light (Pinkerton, 2007).}

Human factors that affect the marine environment

By international standards, New Zealand enjoys abundant marine resources and healthy marine environments (Organisation for Economic Co-operation and Development, 2007). This is particularly so for our deepwater environments which are not readily accessible. It is estimated that about 30 per cent of New Zealand’s marine environment experiences some degree of disturbance from human activities.

Fishing

New Zealand’s inshore and offshore marine areas are generally subject to different human pressures. The largest single pressure on the marine environment in New Zealand is fishing. In particular, large-scale commercial fishing can have a range of ecological effects, such as destroying habitats and removing large numbers of organisms from the area. Both of these effects have long-term impacts on marine ecosystems, including on the marine food chain. Bycatch (the unintended catch of species other than the target fish) also puts pressure on marine species in some fisheries.

Shipping

Other pressures result from the increasing levels of shipping in New Zealand waters. Shipping can bring new marine species into New Zealand waters. While most introduced species (see box ‘More about introduced marine species’) are harmless, some have had localised but significant effects on marine biodiversity (Dodgshun et al, 2007). For example, the sea squirt Styela clava is expected to have a significant negative impact on aquaculture around the Hauraki Gulf and Lyttelton areas unless it is controlled (Biosecurity New Zealand, 2006).

Pollution

The past 60 years have seen increasing levels of pollutants, nutrients, and sediments in the inshore marine environment. This increase is the result of urban and agricultural run-off, road run-off, industrial discharges, and air pollution. Estuaries situated in heavily urbanised catchments often have high levels of chemical pollutants (Auckland Regional Council, 2004). Excessive nutrients, particularly nitrogen, from sewage and land run-off have also caused increased algae growth in many of our coastal areas (Robertson and Stevens, 2007). Litter and debris, both from vessels and land-based activities, can also affect marine organisms and pollute waters and coastlines.

Because of land clearance in catchments, wetland drainage, and land development, average sedimentation rates in estuaries are typically at least 10 times higher than they were before Europeans arrived in New Zealand (Robertson and Stevens, 2007).

Marine mining

The mining of fossil fuels such as oil and gas from under the sea floor can put considerable pressure on marine ecosystems. Oil and gas have been produced from New Zealand’s EEZ since the 1960s, from the oilfields in Taranaki, and new fields in the Great South Basin (Associate Minister of Energy, 2007; Ministry for the Environment, 2005).

To date, the extraction of minerals from the sea floor has not been a large pressure on the marine environment because such exploration has not been consistently economically viable. However, several prospecting licences to mining companies have recently been granted for areas on the Kermadec Ridge. These areas are now being explored (Ministry of Economic Development, 2007).

Coastal development

Habitat degradation or loss due to intensive coastal development is a pressure on the inshore marine area. Vulnerable coastal ecosystems including wetlands, mangroves, and coastal lagoons are most at risk from such habitat changes (United Nations Environment Programme, 2006). Many New Zealanders already live on the coastal margin, but previously undeveloped coastal areas have experienced significant development in the last decade.

See Chapter 1: Environmental reporting for more information on the core national environmental indicators and how they are used.

The four national environmental indicators for oceans are:

• fish stocks under the quota management system
• seabed trawling in deep waters
• water quality at coastal swimming spots
• marine areas with legal protection.

Understanding how these indicators change will allow us to respond better to existing and emerging pressures on our marine resources.

Fish stocks under the quota management system

The first indicator provides information on fish stocks under the quota management system. To report on this indicator, the following are measured:

• proportion of total commercial catch (by weight) from assessed fish stocks under the quota management system
• status of assessed fish stocks under the quota management system.

Assessed fish stocks

Assessed fish stocks are fish species for which there is enough information to scientifically determine the status of the stock.

Each year, some of New Zealand’s fish stocks are assessed to determine the status of the stock relative to a target level and to ensure the total allowable catch for that stock is set at a sustainable level. Assessment of a fish stock requires significant amounts of data, so it is not always cost-effective or practical to conduct full assessments of all stocks. Therefore, the most valuable and most vulnerable species in any given year are prioritised for assessment.

Status classification

The status of New Zealand fish stocks are classified as:

• near or above target biomass levels: the stock is highly likely to have been sustainably fished
• probably near or above target biomass levels: the stock has probably been sustainably fished
• possibly near or above target biomass levels: the stock is more likely than not to have been sustainably fished
• below target biomass levels: the stock is likely to have been overfished, and recovery plans are in place
• unknown: there is not enough data to ascertain the status of the stock.

Seabed trawling in deep waters

The second indicator provides information on seabed trawling in deep waters. To report on this indicator, the following are measured:

• the area ‘swept’ (the area trawled over by a vessel towing gear along or near the seabed) by commercial trawlers, which are required to report their position by latitude and longitude
• the types of fish expected to be found in areas that have been swept.

This indicator shows only where there has been seabed trawling and the amount of trawl effort in those areas. It does not provide any information on the impact of the trawl on the sea floor environment.

Data collected from Trawl Catch Effort Processing Returns

Seabed trawling in deep waters is reported on using data collected from commercial forms called Trawl Catch Effort Processing Returns (TCEPRs) from 1990 to 2005. These returns are required from all commercial trawlers longer than 28 metres and some smaller vessels that are required to report their position.¹⁰

Most small vessels do not have to complete TCEPRs, so an estimated 3.5 million dredges and trawls are not reported over the same period. In some inshore areas, the effects of dredging and trawling by small vessels can be significant.

^{10 Fisheries (Reporting) Regulations 2001, Regulation 11(1).}

Data reported for ‘fishing years’

Trawling effort is reported by ‘fishing year’, which runs from 1 October to 30 September of the next year. For ease of reference, a fishing year takes its name from the second of the two calendar years. For example, because most of the 1989–1990 fishing year is in 1990, it is referred to as the 1990 year.

Reporting on trawl effort

About 970,000 TCEPR trawls were reported in the 16 years from 1990 to 2005. These include bottom trawling and trawling using mid-water gear close to the seabed. The area swept for each trawl is estimated using the reported start and end positions of the trawl, and estimates of the ‘doorspread’ (effective width) of the trawl gear.

To report on trawl effort, the area inside the Exclusive Economic Zone (EEZ) is divided into a grid of 25-square-kilometre cells (National Institute of Water and Atmospheric Research, 2007). For each cell, the sum of the area swept (square kilometres) can be calculated. In a particular fishing year, a cell may have a total swept area of zero square kilometres (that is, it was untrawled) or, for example, 100 square kilometres, indicating that, on average, the area of the cell was trawled four times.

The trawl effort can then be analysed against the Demersal Fish Community Classification (see box ‘More about the Demersal Fish Community Classification’) to see what types of fish community are likely to have been most affected by seabed trawling in New Zealand.

Water quality at coastal swimming spots

The third indicator provides information on water quality at coastal swimming spots – referred to as ‘recreational water quality’. To report on this indicator, concentrations of enterococci bacteria at coastal swimming spots are measured.

Enterococci indicate the presence of faecal material in coastal waters. During summer months, concentrations of enterococci are measured, usually once a week, at monitored beaches, and the results are compared with national guidelines.

Recreational water quality can be affected by effluent run-off from farmland and human wastewater discharges. Seawater that has been contaminated with human or animal effluent can carry a variety of disease-causing organisms. These can pose health risks to people using coastal beaches for activities like swimming, sailing, and surfing. Very young children, the elderly, or people with impaired immune systems are particularly vulnerable.

Marine areas with legal protection

The fourth indicator provides information on marine areas with legal protection. To report on this indicator, the following are measured:

• the percentage of New Zealand’s territorial sea in marine reserves
• the percentage of each class of the Coastal Biogeographic Regions Classification protected by marine reserve.

Marine reserves

Marine reserves are fully protected areas established under the Marine Reserves Act 1971. Until a Marine Protected Area network is established (see box ‘Government action on protecting the marine environment’ later in this chapter), this indicator will report on marine reserves within the territorial sea. Wider marine protection mechanisms, including those in the EEZ, are not reported on using this indicator.

Department of Conservation records are used to report on the size and location of marine reserves in New Zealand’s territorial sea. By comparing this information with the Coastal Biogeographic Regions Classification (which divides New Zealand’s territorial sea into 13 regions), we can show the percentage of each class of coastal biogeographic region protected by a marine reserve.

Image: Courtesy of the Department of Conservation.

Threatened marine species

Information on the state of New Zealand’s threatened marine species is included in this chapter to present a more rounded picture of our oceans.

This includes information about:

• marine species on New Zealand Threat Classification lists
• migratory marine mammals and seabirds on the International Union for the Conservation of Nature and Natural Resources (IUCN) Red List of Threatened Species.

New Zealand Threat Classification lists

The New Zealand Threat Classification lists classify all threatened and potentially threatened species that breed in New Zealand waters.

The classification uses information on population size, the range of the species, and population trends to determine the level of threat.

The classification system groups threatened species into the following three categories:

• acutely threatened: nationally critical, nationally endangered, or nationally vulnerable
• chronically threatened: in serious decline or gradual decline
• at risk: sparse or range-restricted.

International Union for the Conservation of Nature and Natural Resources Red List of Threatened Species

The IUCN Red List classifies threatened and potentially threatened species across the world. This chapter focuses on the species of marine mammals and seabirds on the IUCN Red List that migrate through New Zealand waters.

The IUCN Red List groups threatened species into the three categories of:

• critically endangered: considered to be facing an extremely high risk of extinction in the wild
• endangered: considered to be facing a very high risk of extinction in the wild
• vulnerable: considered to be facing a high risk of extinction in the wild.

Limitations of the indicators

The limitations of the indicators for oceans are explained below.

The two fisheries indicators do not measure:

• the environmental effects of fishing and trawling on marine ecosystems
• the effects from fishing activities on fish species that are not within the quota management system.

The recreational water quality indicator measures the water quality only at monitored beach sites, which may or may not be representative of recreational water quality elsewhere in New Zealand. In addition, beaches are often monitored only when there is a known problem with water quality.

The marine protection indicator does not measure how effective marine reserves are at protecting threatened marine species.

Fisheries

Fishing is the most widespread human activity in the marine environment. Recreational, customary, and commercial fishing occur along a significant proportion of the New Zealand coastline and in several areas within our Exclusive Economic Zone (EEZ).

More than 1,300 commercial fishing vessels operate in New Zealand’s marine environment (Ministry of Fisheries, 2007c). The commercial fishing sector accounts for the most significant proportion of the annual fisheries catch, catching 525,000 tonnes of fish in the 2006 fishing year. This includes fish caught both inside and outside of the New Zealand quota management system, including hoki, squid, jack mackerel, southern blue whiting, barracouta, and orange roughy. These species make up 60 per cent of the total catch by weight.

One hundred and thirty species are commercially fished in New Zealand. Of these, 96 species, comprising 618 fish stocks, are managed under New Zealand’s quota management system (Ministry of Fisheries, 2007c). About 40 species have quota management system allowances for customary Māori fishers, and a similar number have allowances for recreational fishers (Ministry of Fisheries, 2007a).

While the quota management system ensures good information is collected about commercial fishing in New Zealand, recreational fishing catches are not formally reported. However, surveys are periodically conducted to estimate the quantity and type of species caught. For some fish stocks, the recreational take represents a large proportion of the total catch. For example, in the year ending 30 September 2005, the estimated recreational catch for blue cod in some management areas, such as the Marlborough Sounds, far exceeded the commercial landings (Ministry of Fisheries, cited in Statistics New Zealand, 2007a).

The quota management system also cannot track and report on unregulated and illegal fishing in New Zealand waters. Illegal fishing can limit the availability of fish for all fishers, particularly high-value species such as rock lobster and pāua.

Image: Nature’s Pic Images.

Māori fisheries

Māori have a significant interest in New Zealand fisheries, controlling more than 35 per cent of the commercial fishing industry.

Māori also control the customary take of marine species provided for under the Fisheries (Kaimoana Customary Fishing) Regulations 1998 and Fisheries (South Island Customary Fishing) Regulations 1999.

Tangata kaitiaki or tiaki (customary-take guardians)

Iwi and hapū elect tangata kaitiaki or tiaki (customary-take guardians) for each area, whom the Minister of Fisheries then appoints formally.

Tangata kaitiaki may authorise any individual to take fisheries resources for customary use from within the rohe moana (coastal and marine area) for which the tangata kaitiaki have been appointed.

Iwi must report catches regularly to the Ministry of Fisheries so customary use can be factored in when annual catch limits are set.

Customary fisheries restrictions and closures

Provision for customary fisheries restrictions and closures is made under the Fisheries Act 1996 (Ministry of Fisheries, 2007a). This includes the use of rāhui, mātaitai reserves, and taiāpure.

Rāhui is a traditional marine management tool that temporarily closes an area. Tangata whenua may ask for mātaitai reserves (special management areas) and taiāpure (locally managed fishing areas) to cover some of their traditional fishing grounds or areas that have cultural and spiritual significance.

Within mātaitai reserves, tangata kaitiaki set the rules for customary and recreational fishing. Generally, commercial fishing is banned within mātaitai reserves. However, tangata kaitiaki may recommend that some types of commercial fishing be allowed (Taylor and Buckenham, 2003).

Taiāpure are local fisheries in coastal waters that recognise the special significance of the area to local iwi or hapū, either as a source of seafood or for spiritual or cultural reasons. Taiāpure give Māori greater say in the management of their traditionally important areas.

A major difference between mātaitai reserves and taiāpure is that commercial fishing is often allowed in taiāpure (Department of Conservation, 2007).

Status of commercial fish stocks

In 2006, 65 per cent by weight of all commercial catches were from fish stocks where enough information was available to assess the stock status (99 fish stocks).¹¹

The remaining 35 per cent comprised 519 stocks, the status of which could not be assessed because of insufficient information. For many of these fish stocks, there is presently no way to assess their status, as long-term data is needed for a meaningful assessment. Many of these stocks record catches of less than 10 tonnes each year, so they are not considered at risk of over-fishing.

Table 11.1 shows that of the 99 assessed fish stocks, 85 per cent (84 fish stocks) are near or above target biomass levels. This includes all stocks in the ‘near or above’, ‘probably near or above’, and ‘possibly near or above’ target level categories.

The remaining 15 per cent of assessed fish stocks are below target levels. Rebuilding strategies are in place for these fish stocks. They include, for example, orange roughy in the Puysegur area (which has been closed to fishing since 1997) and rig (a shark-like species) in areas where the allocated catch has been reduced.

^{11 The 65 percent excludes arrow squid, the annual catch limit for which is more than 100,000 tonnes. The unusual life cycle of the arrow squid prevents a meaningful stock assessment being made. However, current levels of fishing are expected to be sustainable (Ministry of Fisheries, pers comm).}

Table 11.1: Status of assessed fish stocks under the quota management system relative to target levels, 2006

Data source: Adapted from Ministry of Fisheries, 2007b.

Seabed trawling

Trawling on or near the sea floor is the most widespread fishing activity in the New Zealand marine area that physically affects the seabed. From 1990, trawl effort by vessels required to report accurate fishing locations (TCEPR vessels) increased from fewer than 40,000 sweeps by trawls per year by about 127 vessels to a peak in 1998 of almost 80,000 sweeps per year by 173 vessels. In 2005, this number had dropped to nearly 55,000 sweeps per year by 94 vessels.

At the same time, the total area swept increased from 35,000 square kilometres in 1990 to a peak of more than 67,000 square kilometres in 1998. On average, the total area swept remained between 55,000 and 62,000 square kilometres in subsequent years until 2004 (see Figure 11.2). By 2005, the area swept had decreased to about 50,000 square kilometres, probably due to reductions in the total allowable catch for some species.

On average, around 55,000 square kilometres were trawled each year between 1990 and 2005.

Figure 11.2: Commercial trawling effort (total area swept in square kilometres) by trawl catch effort processing returns (TCEPR) vessels, 1990–2005