Not what it seems

According to the Telegraph today, North Sea cod stocks are now so low that they "may never recover". That is the view of Dr Euan Dunn, a fisheries expert working for the Royal Society for the Protection of Birds, who has told The Daily Telegraph that: "I'm not sure that cod will recover, even with no fishing."

His view is based on the annual, official assessment of stocks produced by the International Council for the Exploration of the Sea (ICES), in Copenhagen. This is to be presented to the EU on Friday, and claims there has been no recovery of stocks, the fault being the politicians who "chose to ignore scientists' calls for a ban for the past two years."

The report also claims that a "substantial" amount of cod is caught illegally, even at a time when the stocks are in danger of collapse. European Union "experts" are now calling for a total ban on cod fishing in the North Sea, Irish Sea and west of Scotland.

But, as always, with these issues, nothing is ever quite what is seems. David Griffith, the general secretary of ICES, says: "There is still no clear sign that cod stocks in the North Sea, Irish Sea and west of Scotland are making a recovery", but he adds that, "A further problem that scientists face is substantial under-reporting of catches of cod, which makes it difficult to get a true picture of the state of these stocks."

Therein lies the central problem. Because of this "under-reporting" and the fact that over-quota cod are discarded, without any record being kept, no reliable data of fish stock can actually be obtained. Thus, increasingly, the Commission is relying on results from survey vessels which are totally unreliable.

In the North Sea cod fishery, the information comes from test trawls are made by DEFRA commissioned survey vessels, as part of the International Bottom Trawl Survey (IBTS) series. These are conducted in the spring and autumn, when standardised gear is shot in specific locations, at the same time each year, and trawling is carried out at a standard speed for one half hour. The catch is then measured, and compared year-on-year to determine changes in stocks.

The process has been compared with flying in a hot-air balloon, high over a land completely hidden by a thick layer of cloud, with the occupants seeking to determine what lives on the land, how many of each species there are, how they reproduce, and how the populations might change in the future – all with a basket and a long rope. The surveyors are asked to scrape the basket along the ground for half-an-hour or so, haul it up, and have a look at the contents, from which they are asked to "guesstimate" the population, a process which they then repeat at the same time the following year.

In fact, the problems are even greater than this analogy would indicate. Technically, the result is known as the "catch per unit effort" (CPUE), but it is well known that CPUE can vary over time and can be skewed by uncontrollable variables, giving different yields even when fish stocks are constant.

It may even indicate a decline in fish stocks that are actually increasing, or an increase where they are declining. Some US authorities, therefore, do not consider this to be the most appropriate index, but it is nevertheless being increasingly relied upon by the Commission, on which to base important policy decisions.

Not least of the problems is the choice of gear. In the interests of standardisation, the trawl net used is that designed specifically by the French Research Institute for Exploitation of the Sea (IFREMER) for carrying out fish surveys. It is called a Grande Overture Verticale trawl (GOV trawl), which replaced the Scottish-designed "Granton" trawl previously used.

Described by fishermen as a "semi-pelagic" trawl, this gear does not always make firm bottom contact, espeically when rigged by DEFRA surveyors. However, North Sea cod are bottom feeders and are known to adopt the escape strategy of diving for the bottom, under such nets. Therefore, they are not always caught by this type of gear, and test trawls using it will consistently underestimate the number of cod in this fishery.

Elsewhere, with different food sources, cod may become mid-water feeders and the gear will be more suitable. In other waters, it appears, cod adopt different escape strategies. Thus, as gear designers and fabricators will readily attest, there can be no such thing as a standard gear. Different nets – and techniques – must be adopted in different fisheries, even to catch the same species. Yet the scientists insist on using their standardised gear.

If this was not bad enough, since the survey technique demands that the same area is trawled each year, it can in no way represents either the actual practice of commercial fishing, or the nature of fish distribution. Extending the ‘balloon’ analogy, it is as if the surveyors are trawling a fixed area of a vast prairie in an attempt to estimate the population of a roaming herd of bison.

Fishermen readily report that fish constantly move around – to the extent that one area which has produced fish will not necessarily produce fish again. The whole nature of commercial fishing is that the fishermen still have to hunt for the fish and even trawlers working side-by-side have been known to produce very different catch levels.

Even then, it gets worse. The survey areas were determined many decades ago and are still used, but since they were established, oil production in the North Sea has become a major industry. Many fishermen point out that the industry has transformed the fishery, not least because of the 6,000 k of undersea oil pipelines which criss-cross the area. Their warmth promotes a highly localised increase in food supply, to which the fish gravitate, often deserting less fertile areas. Fishermen have thus taken to trawling along pipeline routes, but the very existence of the pipelines is ignored by the surveyors, who trawl away from these areas.

Other variables include the weather, with higher catches being reported in the turbid water after a storm. Wind direction in certain fisheries will have a considerable impact on the ease with which fish are caught, as will the tide state. Yet another variable is towing speed. Paired trawlers, able to maintain higher towing speeds, catch considerably higher proportions of larger, faster swimming fish than some of the slower, single trawlers. None of these factors are taken into account by DEFRA surveyors.

The situation thus exists where neither the fisheries-dependent data nor the fisheries independent data can give accurate information as to the fish stocks. Nor indeed can the combination of data help. One inadequate measure applied to a general model of fish stocks can result in poor performance of the whole model.

In other words, not only has the commission has no reliable data on which to base determinations of stocks, such data can wildly underestimate fish stocks in the fisheries monitored, or just as equally overstate the numbers of fish available for exploitation.

Nevertheless, the fiction is being maintained that the fisheries in the waters of EU member states are being properly managed on the basis of "scientific" information. Thus, according to The Telegraph, a spokesman for DEFRA said: "The EU will consider this advice in its scientific, technological and economic committee over the next two weeks and then prepare proposals for next year's total allowable catches."

The one thing that can be guaranteed from this is that they will get it wrong. For an analysis of what should be done, click here.