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The warnings from the scientific community about the state of the world's fisheries are becoming increasingly apocalyptic.

As ministers arrive in Japan this week for the closing stage of the , they're being urged to place a monetary value on the world's resources, in the hope that this might spur more action.

Over exploitation of global fisheries apparently equates to an annual loss to the world of $50 billion, according to a .

Sustainable fishing is what the UN auditors prefer, but what does that mean? How much do we really know about the numbers of fish out there, and the ability of the oceans to keep replenishing that stock?

And in practical terms, how can governments balance the needs of consumers, the fishing industry and those who want to protect biodiversity and conserve fish stocks?

There are two places where delegates hope to make a start. One is in dealing with illegal fishing, which one expert told me represents about 20 per cent of the global catch. This week there will be a call for a radical new approach to policing the seas.

And the second place where talks are focused is on making sure that those agreements on managing fisheries that have already been signed, actually happen.

Dr Alex Rogers, a scientist from Oxford University and London's Institute of Zoology, campaigns to help draw attention to the state of the oceans. He told me about a recent study of his on fishing on the "High Seas" - waters outside of territorial claims.

He found that surprisingly few fish stocks are actually managed at all, and that in some cases, even those covered by international agreements are being fished as if they weren't.

In many cases, he says, fish stocks have been decimated - reduced to ten per cent or less of their original stock levels - so we are fishing only the remnants of these fisheries.

Here's what he said when .

"There's evidence of systematic misreporting of catches in many cases, and in many other cases we simply do not know what is being taken in these fisheries. These fisheries have to be brought into a situation where they are managed sustainably or they have to be closed. If you can't manage a fishery then it should not be taking place."

He was also surprised to find that in the main area in the world for deep water fishing, the north Atlantic, most of the vessels are European.

"So it's us here in Europe that are responsible for these unsustainable fisheries on the High Seas... Despite the fact that Europe has signed up to many of these international agreements on fishing they are failing to meet their commitments. It's a real shock that this kind of free-for-all is still going on on the High Seas with respect to deep water fish resources, and I just find it appalling that this can be allowed to go on."

His point is that despite the fact that many of the states and the regional fisheries management organisations involved took part in negotiated agreements, they simply aren't implementing those rules.

Dr Rogers is at the Japan biodiversity meeting. He says talks over extending marine protected zones have already run into trouble, with moves to try to divert attention to coastal regions, and not to deal with the high seas at all - even though these represent about half of the world's oceans.

Fishing groups don't quite see things Dr Rogers' way.

Newsnight spoke to Dale Redmell, chief executive of the .

He thinks have been brought in in a state of moral panic.

"They think fish stocks are on a fast trajectory to destruction, we don't agree with that at all. We're beginning to see an upturn of low stocks - we've seen that since the early part of the century, which shows were going in the right direction."

He says that MPAs are based on a set of untested scientific principles, defined too narrowly.

"They haven't accounted at all for the inter-relation between human use of marine resources and their protection. It has potential economic, social impacts that we need to consider too."

And on policing, he thinks that from the UK perspective at least, regulation has improved and our fleet is performing well.

"Whether there is a broader, global issue that may be the case. It's about getting the right governance arrangements in place. That applies in Europe and elsewhere. It's not just about enforcement, it's about getting governance to work properly. We'd like to see management responsibilities devolved to countries, as opposed to from Brussels. They need to listen to industry better, also."

In Vancouver in British Columbia, a micro version of the bigger global fisheries debate is currently underway. We went to hear more about the fierce discussions taking place over how best to ensure the returning Sockeye Salmon run each year. Click here to read more about that and to see our interactive map with video which illustrates the salmon life cycle.

Watch my film from British Columbia on Newsnight on Tuesday 26 October 2010 at 2230 BST on ´óÏó´«Ã½ Two and then afterwards on the ´óÏó´«Ã½ iPlayer.