Actor Leonardo DiCaprio has teamed up with Google to create a new satellite-based surveillance system to spy on illegal fishing.

The technology, which is being provided free online so members of the public can monitor the oceans for activity, is aimed at combating overfishing around the world.

Fish stocks in many parts of the world are perilously low after being over exploited and despite international agreements on what can be caught, many are still overfished illegally.

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Google has teamed up with two conservation groups and actor Leonardo DiCaprio to create technology that allows the public to monitor the activity of commercial fishing vessels around the world (pictured). It uses satellite, radar and transponder data

HOW THE TRACKER WORKS Currently, Global Fishing Watch does not include every vessel on the ocean, only those that broadcast data from the Automatic Identification System, collected by satellite and terrestrial receivers. It was initially designed mainly as a safety mechanism to avoid collisions. Many of the world's largest fishing vessels are required by the International Maritime Organization to use AIS. But AIS can be turned off if the boat operator is doing something illegal. However, such on-off actions would likely be apparent by tracing the boat's appearing and disappearing tracks. This can help to highlight illegal activity. Future versions of the technology may even include tagging data for marine animals, so that the paths of whales and sharks and other fish might be visible alongside the vessel activity. This could help to reveal if vessels are targetting vulnerable stocks. Advertisement

The technology, called Global Fishing Watch, is designed to provide an eye in the sky that constantly searches for this activity.

By providing the information free online, marine conservation campaigners hope citizens will be able to play their part in looking for illegal activity.

'This unprecedented technology is available to everyone in the world,' DiCaprio said at the launch of the software at the US State Department in Washington.

'This platform will empower citizens across the globe to become powerful advocates for our oceans.'

Around two thirds of global fish stocks are overexploited or depleted according to the UN Food and Agriculture Organisation.

Illegal fishing is estimated to account for 35 per cent of the global wild marine catch and causes yearly losses of £17.7 billion ($23.5 billion).

Some of the planet's largest fish, including tuna and swordfish, now have populations that are below 10 per cent of their historical level.

Using satellite technology combined with radar aboard boats, the new platform allows people to trace the paths of 35,000 commercial fishing vessels in almost real time.

Actor Leonardo DiCaprio (right), who is a strong campaigner for the environment, unveiled the new project at the US State Department along with US Secretary of State John Kerry (left)

Dedicated: The actor at the announcement

By focusing on areas of interest they should also be able to spot vessels operating there illegally.

The $10 million project has been set up by three partner groups – Google, environmental imaging non-profit SkyTruth and marine conservation group Oceana.

Actor DiCaprio has long been a campaigner for the environment and last week premiered a new documentary about climate change.

His Leonardo DiCaprio Foundation is one of the main financial backers of the Global Fishing Watch project, after it put in £4.54 million ($6 million).

The system allows information like protected marine areas, territorial waters and the country that vessels are from to be visualised (pictured). In the example above the Spanish fleet is in blue, the Japanese in green and the Korean in red

The technology uses the Automatic Identification System carried by large fishing vessels to track their location (illustrated). This means suspicious activity can be carefully monitored. In the past it was rarely noticed if these were turned off but the new project will highlight this

Since 1999 his foundation has channelled £45 million ($59.6 million) into projects to protect vulnerable wildlife and ecosystems.

Global Fishing Watch is being an attempt to crowdsource the fight against illegal fishing.

Jacqueline Savitz, vice president for US oceans at Oceana, said the platform will 'revolutionise the way the world views commercial fishing.'

She said it could provide vital data for governments to monitor and enforce fishing restrictions, for journalists investigating suspicious activity and for the public to help track illegal activity.

However, the data will be provided by satellite company Orbcomm with a three day delay, meaning it will not be possible to use it to instantly catch any criminals.

The technology can reveal that vessels from all around the world can cluster in fishing areas, such as around South Georgia Island in the example pictured

The online software also highlights protected marine areas (shown in green above) and highlights when vessels are operating within their borders

'We think it is going to have a lot of impact, first of all just the deterrent effect of vessels knowing that we could see them if they are doing something they are not supposed to be doing,' Ms Savitz said.

For instance, users could zero in on a marine protected area and see if any boat tracks have crossed into waters where they should not have been.

One could scan the map for any evidence that large vessels are fishing in areas that are reserved for small-scale fishermen.

Overfishing is a growing problem around the world, with about two-thirds of fish stocks in the high seas either over exploited or depleted (stock image)

Vessels can be tracked by name or by country, or by traffic inside exclusive economic zones.

The paths of ships are visible, including zigzag paths that could indicate vessels are avoiding shore to offload their catch on to other ships undetected, or that other illegal operations or human rights abuses may be under way.