Here's an animated satellite map showing every large commercial fishing vessel in the Atlantic Ocean between 2012 and 2013:

Here's the same map, only centered on the Pacific Ocean:

And here's a map breaking vessels down by country of origin. Spanish boats are in blue. Japanese boats are in green. Korean boats are in red:

These nifty maps come from Global Fishing Watch, a new collaboration between the conservation group Oceana and the non-profit SkyTruth. The project makes use of Google's mapping software to track commercial fishing. So far, they've been able to spot more than 25,000 large vessels in all.

The project's creators hope the tool can eventually be used to catch boats that are operating illegally — say, fishing in protected marine areas — in order to help prevent overfishing and the collapse of global fish populations.

How to track illegal fishing boats from space

Overfishing has become a major problem in many parts of the world. Commercial boats have now become so skilled at catching fish — using sonar, GPS, and other technologies — that some fisheries are on the verge of collapse.

Worldwide, some 28.8 percent of assessed fish populations are now over-exploited, according to the UN's Food and Agriculture Organization. And that's starting to have adverse effects. Between 1996 and 2012, the global wild marine catch actually declined — humans were working harder and harder to catch fewer and fewer fish. (Fish farming is making up the gap.)

Many countries have tried to alleviate this problem by placing limits on fishing — either by setting quotas on catches or protecting certain areas to allow fish populations to recover. But many of these rules get undermined by fishing boats operating illegally. Boats that either operate in restricted areas, ignore quotas, catch prohibited species, or misreport their catches cost the industry an estimated $10 billion to $23 billion per year.

Illegal fishing has undermined fish protections — but it's always been hard to track

Illegal fishing has always been hard to track, however. And that's where Global Fishing Watch comes in. As this Oceana report (pdf) explains, all large vessels on the ocean are required to use an Automatic Identification System that broadcasts the ship's identity, location, and so forth. The project's creators then developed an algorithm that analyzed these boats' movements and could figure out which boats were fishing boats.

The system isn't perfect. It sometimes mistakes other vessels for fishing boats and can't currently track smaller boats that aren't required to use the Automatic Identification System. (Oceana has called on the International Maritime Organization to expand these requirements to smaller vessels.) But the system can potentially help countries tell if, say, a large trawler or longliner is operating in a protected marine area — or an area where it doesn't have a license.

Right now, the Global Fishing Watch maps still display data from 2012 and 2013. But its creators are planning to release a public version soon that anyone can use and that will show data from a few days back — far more useful for enforcement purposes.

Are these boats fishing illegally?

In its report, Oceana gives a few examples of how its mapping system can help track suspicious fishing behavior.

Throughout 2013, for instance, five different Russian trawlers appeared to enter the protected Dzhugdzhursky State Nature Reserve — a refuge for salmon that's supposed to be a "no-take" area. Yet in September, the Russian trawler Komarovo appeared to be making movements consistent with fishing:

Another map caught a ship operating in Fiji's exclusive economic zone. The Ugulan, a longliner, was not in the registry to fish in this area. But it also appeared to be making movements consistent with fishing:

Granted, all this data is from a year ago, so it's impossible to know for certain what these boats were doing. Oceana's report says that these examples help demonstrate that the Global Fishing Watch project can identify ships in restricted areas, unlicensed ships operating suspiciously, ships that mysteriously appear to turn off their tracking information, or multiple ships using the same identification number.

The system can identify ships operating suspiciously

Here's the vision for the final project, from its website: "Global Fishing Watch will be available to the public, enabling anyone with an internet connection to monitor when and where commercial fishing is happening around the globe. Citizens can use the tool to see for themselves whether their fisheries are being effectively managed. Seafood suppliers can keep tabs on the boats they buy fish from. Media and the public can act as watchdogs to improve the sustainable management of global fisheries. Fisherman can show that they are obeying the law and doing their part."

This isn't the first time satellite mapping is being used for environmental purposes. One of the groups behind the project, SkyTruth, has also used satellite data to track the size of the BP oil spill in 2010 and keep tabs on natural gas flaring in North Dakota.

Further reading: Over at Wired, W. Wayt Gibbs has a great piece on the backstory behind Global Fishing Watch and how it came to be.