Within a few short decades, industrial fishing has expanded from the traditional fishing grounds of the Northern Hemisphere to include all the worlds oceans and seas. Many stocks have been overexploited and are depleted. But the situation is not without hope. Some countries have shown that fish stocks can in fact recover when sustainable fisheries management systems are implemented.

No other group of animals is as difficult to monitor as fish. Spotting scopes and radar equipment are used to locate and count migratory birds along their flight paths. Bats can be monitored by placing ultrasound detectors and photoelectric sensors at the entrance of their caves. But what about fish?

Humans are not capable of looking into the ocean and counting the fish they see. Instead, they must try to estimate the size of fish stocks as accurately as possible. The Food and Agriculture Organization of the United Nations (FAO) uses various sources to estimate global fish stocks and trends as accurately as possible. The results are published every two years in the SOFIA Report (The State of World Fisheries and Aquaculture). The latest report was released in 2012 and reflects the developments to 2009/2010. Fish is the means of subsistence for billions of people around the world. Accordingly, the report is an important document on which UN decisions, international agreements and treaties are based. The data used for the SOFIA Report is taken from the following sources:

Fishermen report their catches to their government authorities, such as the Ministries of Agriculture and Fisheries. The authorities are obliged to send this data to the FAO. The data is also forwarded to scientists in their own country.

Fisheries data is of-ten incomplete or incorrect. For instance, fishermen only report the amounts of those fish which they are officially permitted to catch. They do not include any unwanted bycatch all the fish and marine fauna which are caught inadvertently and until now have mostly been thrown back overboard. An quantitative assessment of bycatch levels would, however, be crucial as this could provide a more realistic estimate of the actual status of fish stocks. In order to improve the flawed basic data, fishery scientists therefore gather their own data.

1. Fishery-dependent data: Fishery scientists regularly accompany fishing vessels. They collect catch samples and detailed data including the age, size, length and number of adult fish. The volume and composition of the catch are of particular interest. They also record the effort expended, such as how long a net is dragged behind the vessel before it is full. This establishes the exact amount of effort involved in catching a certain amount of fish. Researchers call this the catch per unit effort (CPUE). It is the only way of ascertaining the stock density, or the number of fish found in a certain area.

2.  Fishery-independent data: Scientists also conduct research projects using their own vessels. They take nu-merous sample catches not only in the abundant areas highly sought after by the fishermen, but in many different parts of a maritime region. The sampling locations are either chosen randomly or according to a certain pattern. The objective is to obtain a comprehensive overview of the entire maritime region as well as the distribution of fish stocks. During these expeditions it is important that all the marine fauna caught are counted and measured, to enable a reliable assessment of the entire ecosystem to be made. The scientists are also interested in the age of the fish. Using close-meshed nets, therefore, they catch young fish (juveniles) which are not usually taken by the fishermen. The age distribution of the fish is an extremely important aspect of stock predictions. It shows how many of the fish will grow to sexual maturity and thus how populations are likely to develop in future years. How many research expeditions are undertaken differs from country to country. Researchers sample individual fish stocks up to five times a year. Information on the eggs and larvae of some stocks is also recorded. These numbers indicate the parent stock and the numbers of young to be anticipated.

The researchers utilize both the fishery-dependent and the fishery-independent data to adjust and augment the fisheries official catch numbers. For instance, from their own sample catches they can estimate the approximate volume of bycatch in the fishing grounds. In many cases catches from illegal fishing are also shown up. For instance, double logbooks are frequently used one for the authorities showing the official figures, and another for the scientists showing the higher but genuine catch numbers. Comparing these two allows a more accurate estimation of how many fish were actually caught in a maritime region.


Venerable gentlemen of fisheries science: ICES researchers held their statutory meeting at the House of Lords in London in 1929. Upon its foundation in 1902, the ICES had 8 member nations: today it has 20.

ICESThe International Council for the Exploration of the Sea (ICES) was founded in Copenhagen, Denmark, in 1902 and is the worlds oldest intergovernmental organization. At that time there was a growing awareness in some European fishing nations that the long-term management of migratory fish stocks depended on a coordinated approach. Today the ICES acts on behalf of the EU and other fishing nations such as Canada, Iceland and Russia. It is responsible for all the living marine resources in the Northeast Atlantic, a total of 120 species. The ICES recommends the maximum fish catches within a specific maritime region.

The catch data from both the fishermen and the scientists is initially forwarded to higher scientific institutions which utilize it to estimate the current stocks of the various fish species and maritime regions. One objective is to generate a supra-regional overview from the national data. For example, the International Council for the Exploration of the Sea (ICES) in Copenhagen is responsible for the Northeast Atlantic. Its working groups use both the fisheries official catch data and the scientific results to calculate the current stocks of the different species of fish and fauna. The ICES then sends these stock estimates to the FAO. Data about stocks in other maritime regions reaches the FAO in a similar way. For example, the Northwest Atlantic Fisheries Organization (NAFO) is responsible for the Northwest Atlantic. It collates data from Canada, the USA, France (for the Atlantic islands of St. Pierre and Miquelon) and the foreign fleets from Russia and the EU which operate in this region. The NAFO then forwards the data to the FAO. The Canadian and US national fisheries institutes also report directly to the FAO. The FAO does not re-evaluate this information, but merely summarizes, edits and ultimately publishes the data for the various maritime regions of the world.

Around 1500 fish stocks around the world are commercially fished, with the various stocks being exploited to different extents. Comprehensive estimations of abundance currently exist for only around 500 of these stocks. In most cases these are the stocks which have been commercially fished for many decades. For many years, exact records have been kept of what and how much is caught: the tonnages and also the age and size of the fish. Datasets for cod off the coast of Norway, for example, go back as far as the 1920s. Very little is known about other fish species and maritime regions particularly the Exclusive Economic Zones of some developing countries. Many developing countries provide catch data alone, without any scientific assessment. The FAO makes limited use of such data. There are also some maritime regions for which not even simple catch data is available. The FAO believes that it is impossible to make any reliable estimation of such stocks. Therefore no reliable data exists for many of the worlds fish stocks. Moreover, fisheries biologists are even unable to confirm how many fish stocks there actually are. If any data is available, it applies only to commercially exploited species. Naturally an overall survey of all the worlds fish would be desirable but the cost would be exorbitant. Hundreds of research expeditions would be required, making the exercise unaffordable.


Global estimation of fish abundance: Data on the status of fish stocks is provided by the fisheries and scientists. The FAO collates this information and then attempts to draw up a picture of the worldwide situation. The problem is that reliable data exists for only about 500 stocks. Experts do not agree on the status of other fish stocks.

Critics point out, therefore, that the FAO statistics do not take a large proportion of stocks into account. A joint American-German research group has therefore developed its own mathematical model to estimate the status of all populations from the catch amounts reported by the fisheries alone, without the fishery-independent data from the scientists. These researchers are also investigating how stock catches have developed over time. According to this model, a fish stock is depleted when the catch decreases conspicuously within a few years. Attempts are being made to circumvent the lack of stock calculations by simply interpreting catches over the course of time. The researchers have meticulously requested information from the authorities of the countries responsible for regions with no catch data at all. Based on the model, which takes 1500 commercially exploited stocks and around 500 other stocks into account, the fish are in even worse shape than assumed by the FAO: 56.4 per cent of the stocks are overexploited or depleted, not 29.9 per cent as claimed by the FAO. But the work of this American-German research group is itself under fire, with claims that its data is inconsistent and still unreliable. It presents a distorted picture of the reality, say other researchers. Which of the methods better illustrates the state of the worlds fisheries is currently a subject of heated debate. Despite the uncertainties, the researchers and the FAO agree on one thing: over the years the situation has deteriorated. Recovery will only be possible if the endangered stocks are fished less intensely for a number of years.

The results are alarming, because the pressure on fish populations has been escalating for years. According to the current SOFIA Report, the proportion of overexploited or depleted stocks has increased from 10 per cent in 1974 to 29.9 per cent in 2009. After temporary fluctuations, the proportion of fully exploited stocks rose during the same period of time, from 51 per cent to 57 per cent. The proportion of non-fully exploited stocks, in contrast, has declined since 1974 from almost 40 per cent to only 12.7 per cent in 2009. A clear trend is therefore emerging: as far as overfishing and the intensive exploitation of the oceans are concerned, the situation is not improving; it is slowly but steadily deteriorating. It is interesting that the total annual fish catch has been fluctuating for about 20 years between a good 50 and 60 million tonnes. It peaked in 1994 at 63.3 million tonnes. In 2011 a total of 53.1 million tonnes was landed about four times more than in 1950 (12.8 million tonnes). The FAO, however, records the catches of not only fish but also other marine species such as prawns, mussels and squid. If these numbers are added to those for fish, total catches are much greater. Accordingly, for the past 20 years the total marine catch has been a steady 80 million tonnes annually. The peak was reached in 1996 with 86.4 million tonnes. In 2011 it was 78.9 million tonnes.

Fig. left 3.3>

The number of overexploited stocks has soared since the 1970s, while the number of non-fully exploited stocks has decreased. Fully-exploited stocks are not, in principle, problematic. It is important to manage them sustainably, however.

fig. right 3.4>

The development of catch volumes of world marine capture fisheries since 1950. Catches in China might have been adjusted upwards for many years, in order to comply with the governments official output targets.

The reason why fish catches have remained fairly stable is because over time the coastal maritime regions were fished out, prompting the fisheries to spread out into new areas. They have expanded in geographical terms, from the traditional fishing grounds of the North Atlantic and North Pacific further and further south. They have also penetrated into ever-deeper waters. Only a few decades ago it was virtually impossible in technical terms to drop nets deeper than 500 metres. Today the fisheries are operating at depths of up to 2000 metres. Moreover, once the stocks of the traditional species had been exhausted, the fishing industry turned to other species. Some of these were given new names in an effort to promote sales and make them more attractive to consumers. For instance the slimehead went on sale as orange roughy. It is still possible to remove virtually the same amounts of fish from the oceans, therefore, but the composition of the global catch and the stocks themselves have changed. Consistent catches are no indication that fish stocks have remained stable.


Taking catch volumes as the benchmark, China has been the most important fishing nation for years now. However, the data available is extremely unreliable. A large number of experts believe that catches have been adjusted upwards for many years, in order to comply with the governments official output targets. Therefore the figures have presumably been too high for some time. Only recently has this practice begun to change in China. Peru, until 2009 the second most important fishing nation, has slipped to fourth place. This is due to the low catches of anchovies which can be ascribed to climate change in particular, but also to a complete closure of the fishery designed to protect future anchovy stocks. Indonesia is currently the second and the USA the third most important fishing nation. Developments in Russia are interesting. Since 2004, its catches have increased by about 1 million tonnes. According to the Russian authorities, this growth is a result of changes to the comprehensive documentation of catches. Until now some local catches were registered in the home port as imports and not as domestic catches. Russia plans to further expand its fishing industry in the coming years, the goal being to land 6 million tonnes by the year 2020. This would amount to slightly more than the combined catches of all EU nations, which totalled 5.2 million tonnes in 2010.

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