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  • International fishing involves some really big numbers. There are an estimated 4.6 million fishing vessels in the world. Most of these are small and local, but there are around 64,000 large vessels (24 m or longer) that operate in marine waters. Oceans cover 70% of the Earth and over 80% of the Southern Hemisphere. These are enormous areas to monitor. Seafood is a valued commodity, so how do we ensure that marine fishing is sustainable, responsible and regulated?

    Tracking vessels with automatic identification systems (AIS)

    International waters are governed by the International Maritime Organization (IMO). The IMO requires all large ships to use an automatic identification system (AIS). AIS uses the vessel’s GPS or sensor built in to the AIS unit to transmit information including:

    • the vessel’s name, unique marine identity number and call sign
    • the type of vessel (fishing, cargo or passenger)
    • the vessel’s size
    • the vessel’s position on the sea
    • its course of travel and speed.

    The AIS broadcasts the vessel’s position continuously – every 2–12 seconds – in order to avoid collisions at sea. Satellites pick up this information and relay it to ground stations, so even vessels in remote parts of the ocean are tracked.

    AIS is also used by smaller craft. More than 400,000 AIS devices broadcast their vessels’ identities and locations annually.

    Dark vessels

    Vessels that do not want to be tracked switch off their AIS systems. They ‘go dark’ and are known as dark vessels. It is estimated that illegal and/or unregistered fishing vessels cost the global economy up to NZ$36 billion per year. Dark vessels are not limited to fishers. The ships may also be involved in transferring illegal goods or smuggling drugs or people.

    Protecting our territorial waters and our fish species

    Countries that border the sea have territorial waters. A very long time ago, this distance was 3 nautical miles (about 5.5 km) – the range of a cannon shot! In more modern times, the distance was 12 nautical miles (nmi) until 1982 when the United Nations established an international framework to create exclusive economic zones (EEZ) that stretch 200 nmi from the coastline.

    Before the change to an EEZ, most of New Zealand’s commercial fishing was inshore within the 12 nmi range. The ocean beyond that was fished – uncontrolled – mostly by Japanese, Taiwanese, Korean and Soviet fishing vessels. Once the EEZ was established, New Zealand’s zone grew to more than 4 million km².

    The New Zealand Government introduced the Quota Management System in 1986 to protect and manage fishing areas and fish stocks. Commercial fishers are required to have a permit. They must also provide reports on lots of things including fish catch numbers, non-fish species or protected fish species, disposal, processing and landing and report on monthly harvest returns. Prior to this system, it was difficult for authorities to limit the number of commercial fish species that were caught.

    The New Zealand Government has also signed international treaties and agreements to manage international fisheries and/or areas of the ocean.

    New technology to help monitor the seas

    The area within New Zealand’s EEZ is truly vast. In addition to managing fisheries, it’s also important to monitor marine protected areas and help with maritime emergencies. Satellite technologies have been a game changer in helping to monitor and manage the seas.

    Xerra Earth Observation Institute has developed Starboard® Maritime Intelligence, a software platform that helps New Zealand and other countries monitor their national waters for activities like illegal fishing and dark vessels. Starboard combines data from AIS, satellites and computer models to analyse and investigate vessels and marine areas of interest. Starboard tracks where vessels have travelled, where they’ve docked and their movements near other ships.

    Xerra uses satellites that have synthetic aperture radar (SAR) instruments on board. SAR emits radar waves that strike the steel surface of a vessel and then ping back to the satellite. SAR has real advantages over optical imagery (photos) – it isn’t blocked by clouds and it does not require someone to be able to see a vessel amongst the camouflaged background of the waves.

    Build a satellite to find dark vessels

    Have a go at building a fit-for-purpose satellite to be able to catch these illegal fishing vessels! Choose the ‘Dark fishing vessels’ scenario. Once you’ve received the SAR data in ©Starboard, use this activity to analyse whether any dark vessels are operating in this part of the Tasman Sea.

    Activity ideas

    In the Fisheries role-play activity, students take on the role of a stakeholder in New Zealand fisheries. In their role, they decide whether they agree or disagree with the statement ‘there are plenty of fish in the sea’.

    Fishing is a very important industry in New Zealand, and we have one of the largest territorial waters in the world. Use this timeline to take a look at some of the historical aspects of fisheries in New Zealand.

    Useful links

    The Office of the Prime Minister’s Chief Science Advisor reports on commercial fisheries in 2020.

    Visit the Ministry for Primary Industries website for maps of New Zealand fisheries and information about international fisheries management.

    Read about the work of Xerra and Starboard Maritime Intelligence.

    Watch Starboard Maritime Intelligence’s video Uncover hidden maritime activity with Starboard.

    Meet Xerra head of product and design Andy Hovey in this Stuff article. Follow up with this news article and video looking the success of Xerra, in detecting up to 100 dark vessels during a Pacific fishing surveillance operation.


    This resource has been produced with funding from the Ministry of Business, Innovation and Employment and the support of the New Zealand Space Agency.

      Published 25 July 2022 Referencing Hub articles
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