Since the first hook caught the first fish perhaps 40,000 years ago, technology has raced with increasing speed to extract more and more fish from the oceans. Most big fish are long gone and fishing vessels are inexorably hauling in the rest—sometimes legally, sometimes not.

But on Friday, American non-profits SkyTruth and Oceana, supported by Google, unveiled a prototype program called Global Fishing Watch that will eventually allow anyone with a computer to observe which vessel is fishing where—and perhaps infer whether they are poaching or not.

“Our goal is to make the invisible visible," John Amos, the president of SkyTruth, told me. The tiny company based in Shepherdstown, West Virginia, made a name for itself by acquiring and releasing satellite pictures that showed that the amount of oil flowing from the Deepwater Horizon oil rig was greater than BP was claiming at the time.

According to the team, it will be possible for experts to go online and zoom into areas like marine reserves where fishing is forbidden or coastal areas where it’s restricted to vessels with permits by next March.

The program is based on the Automatic Identification System (AIS), originally a voluntary collision-avoidance system for ships that relies on VHF transmitters aboard vessels that transmit their position, identity, and speed continuously to other ships and to satellites. “Global Fishing Watch enables the user to see the global fishing fleet in both space and time, and in any part of the world,” said David Manthos of SkyTruth.

Right now, the plan is to give access to that data to fisheries managers, non-profits, and researchers only. But if they get additional funding to pay for the raw satellite data and for further engineering the system to process billions of data points a year, the team would be able to invite anyone to sign on. To make that possible they’d need somewhere between $3 and $5 million more over the next two years, according to Jackie Savitz, VP for U.S. oceans at Oceana. Broadening access will allow more people to pressure the governments who would already have access to the information into investigating what everybody saw. That’s different from today’s system, where only some people get satellite information, and those people might not be willing to do anything with it. “Now there’s no public pressure at all,” explained Savitz.

AIS transponders aren’t foolproof—they can be turned off and manipulated. But Amos of SkyTruth said that even vessels that choose to turn them off will trigger alerts and find it hard to escape detection and questioning when they turn them on again or reach a port.

Poaching of fish is not a major problem in the U.S. or Europe, but these countries consume mostly imported fish. Experts I talked to predict this new transparency would increase fishing revenue in some poor countries, reduce overfishing in others and, most importantly, insure that the huge no-take areas that have been appearing around the world in the past few years are actually left alone, allowing overfished populations of marine life to grow back in health and numbers inside them.

Without measures like this, fish could soon become a very scarce commodity. Today’s fish stocks are vastly smaller than they were just a century ago. Dirk Zeller, senior scientist of the Sea Around Us research program at the University of British Columbia in Vancouver, estimates that the combined weight of table fish like cod and tuna in the ocean has dropped anywhere from 60 to 90 percent over the last century. “The global catch is declining because the fish stocks have shrunk so much in spite of the fact that technology makes it easier and easier to catch fish in deeper, more remote waters,” he said.

Many countries ban foreign fleets from fishing close to shore, because they deprive coastal people of their main source of protein. But often these governments have no way to enforce those bans. Now they will at least be able to identify the vessels fishing over the horizon who should be fined or forced to pay for fishing licenses.

For example, in offshore West Africa, one of the most productive coasts in the world, Chinese and other foreign vessels routinely fish without permits. Identifying them would allow those governments to oblige them to pay the standard license fees or face expulsion and possible fines. “This will increase their income and maybe allow some countries to decrease their catch without losing money,” he said.

Identifying poachers is a big step forward, but it’s still a long way from arrest and confiscation. Still, it’s likely to considerably expand the number of 300 vessels that are already blacklisted by international authorities because they were caught poaching. These vessels have a difficult time selling their catch and are sometimes even not allowed into ports.

But Daniel Pauly, a professor of fisheries also at UBC, warns that since fishing permits are not public in most countries, it’s difficult for an observer far away to tell whether a given vessel that’s fishing in a country’s waters is doing so legally or not. “In Africa, it’s not hard to get a piece of paper, a permit, from a corrupt fisheries official,” he said. “In Asia, there are industrial fisheries with more financial clout, so to make them back down when they’re caught red-handed is not obvious.” So it's too early to tell exactly to what extent poor, coastal countries will benefit practically from the learning the identities of the vessels that are stealing their fish, the experts say.

There is a much clearer consensus that the most likely beneficiaries of the Global Fishing Watch are likely to be the giant no-fishing reserves that have multiplied in the last decade in places like the Northwestern Hawaiian Islands, the Indian Ocean’s Chagos Islands, three U.S. possessions in the Pacific, and the Chilean waters off Easter Island. Huge areas off the Cook Islands, Palau, and New Caledonia may join their ranks.

The most valuable of these, because it has the most fish by far, is Kiribati’s Phoenix Islands Protected Area, located on in the so-called Equatorial tuna belt, southwest of Hawaii. The size of California, it’s scheduled to become closed to commercial fishing on January 1, 2015.* It’s also likely the most promising for satellite-based monitoring. “It’s an ideal candidate,” said Brian Sullivan, manager of Google’s Ocean and Earth Outreach program.

Keeping people from illegally fishing in protected areas is key to allowing populations of fish to grow back. They then tend to leave the reserve, allowing vessels to increase their catch rate by fishing just outside the border. Ending fishing in Kiribati’s protected areas, for example, will allow the two highly depleted mainstays of the global sushi market, bigeye and yellowfin tuna, to grow and multiply inside the reserve. Today, the Pacific bigeye population (now the biggest in the world after other stocks were overfished in the other oceans) is down to 16 percent of its estimated unfished population.

“In a well-managed fishery, you’d stop fishing and begin to rebuild the stocks,” said Glenn Hurry, a former executive director of the Western and Central Pacific Fisheries Commission, whose 25 member nations control the region’s $5 billion tuna-dominated fishery.

But today, it’s impossible to shut down a whole fishery to wait for the fish stocks to grow back. And so conservationists have pinned their hopes on these protected areas—which were created as conservation measures, not fisheries management tools—as safe havens for stocks to breed and grow back. Of course, things aren’t quite that simple either. After President Anote Tong of Kiribati created the Phoenix Islands reserve in 2008 (primarily to protect the unusually healthy reef that rings the islands), he went around the world, making speeches and collecting prizes for the closure. But fishing wasn’t restricted in the area. Indeed, data collected by the Global Fishing Watch show the density of fishing vessels inside the reserve is the same as outside it. So when Tong announced in June that it would really be closed to fishing next January 1, he was met with some skepticism.

But fisheries scientists said Global Fishing Watch will make the closure relatively easy to enforce because the vessels that do most of the fishing, industrial purse-seiners, usually exceed 300 tons and are thus required to use the AIS transponders all the time.

There are still a lot of “ifs” floating around the Global Fishing Watch project. It’s still not clear if countries will be able to actually enforce the rules, or if ships will be able to evade detection, or if the technology will be useful in court. There are also questions about the federal government’s role in all this.

Last September, President Barack Obama closed three areas, each also about the size of California, near the Phoenix Islands. While two are only lightly fished and one not at all, they are all candidates for monitoring under the Global Fishing Watch.

Doug McCauley, a marine ecologist at the University of California at Santa Barbara, wondered “why the federal government believes that the burden to develop and test these technologies should be placed on the shoulders of philanthropists in the private sector.” In his mind, creating these mega-reserves is “just a lot of mega-hype until we put some real money into these new enforcement tools.”

While identifying, denouncing, and shaming poachers will bring definite benefits, said Amos of SkyTruth, to reach its full potential, satellite technology is ultimately going to have to marry two key pieces: the AIS signals, which show a vessel’s identity and path with enough precision to indicate whether it’s fishing or transiting, and a sharp satellite picture of the vessel. Without an interception at sea at the very moment the vessel is poaching, “a fishing pattern from AIS isn’t going to hold up in court," Amos said. "You need a satellite picture of the vessel with gear in the water.” That should be possible some day, but with present commercial satellites, a high-resolution picture clear enough to identify a vessel not only costs $3,500, but needs to be requested a week in advance. “So for now you’re not going to bust people with the public tools like AIS and satellite imagery, but you’re going to see some stuff that you can say to your fishery management agency, ‘Were you aware of it?’”

During a year of monitoring the waters around Chile’s Easter Island, a de facto no-take zone, SkyTruth documented the presence of 42 vessels** the Chilean authorities said they knew nothing about. In response, the Chilean government stationed a long-range surveillance airplane in the region and started flying patrols over the area. It was a major upgrade over their earlier surveillance ship, Amos said. “We think this is the way change will happen.”

*An earlier version of this story also suggested that Kiribati's reserve was no more protected than the rest of its waters. Commercial fishing was banned in three percent of the reserve in 2010. We regret the error.

**An earlier version of this story reported that there were hundreds of Chinese vessels in Chilean waters. There were dozens of vessels, not hundreds, though it is not clear how many of them were from China. We regret the error.