Commercial sea fishing has been taking place for centuries. The first analysis of historic data from the UK has indicated that, over the past 118 years, the commercial productivity of UK fisheries has decreased by 94 per cent.
In 2009 the European Commission estimated that 88 per cent of marine fish stocks were overfished based on statistics dating from 20 to 40 years ago. However, statistics on fish landings (the part of the fish catch that is put ashore) of 'demersal' species (bottom living species, such as cod, haddock and plaice) in the UK have been collected since 1889.
The study analysed these previously neglected statistics and corrected them for shifts in the proportion of fish landed abroad and increases in fishing power over the years. Fishing power is a measure of how fishers increase their ability to catch fish over time, for example, using larger boats and engines, tougher nets and electronic detection equipment. This so-called 'technological creep' must be considered for the study to produce a reliable index of change in productivity in terms of landings of demersal species and is reported as landings per unit of fishing power (LPUP). The number of boats in a fleet was also incorporated into the measure of LPUP to account for the decline in their number.
Over the 118 years, LPUP fell by 94 per cent. The decline is significant even if changes in fishing power are not considered. In 1889 a largely sail-powered fleet landed twice as many fish in the UK as the present-day fleet of technologically sophisticated vessels. Peak catches were observed in 1938 when landings were 5.4 times more than today. A more detailed analysis revealed that losses of some individual species were greater. Catch rates of haddock have declined by over 100 times and halibut by 500 times since records began.
The researchers identified four phases in UK fisheries in terms of trends in LPUP. The first was from 1889 to the onset of the First World War when the fleet was converted from sail to steam power. This sharp increase in fishing power saw the LPUP fall despite increases in landings. The second phase covered the inter-war years and saw a wave of expansion due to exploitation of previously unfished areas in the Arctic and West Africa. This increase in LPUP continued until the late 1950s when catches started to collapse because fish stocks in these distant waters were fully exploited and countries such as Iceland were limiting fishing opportunities. The final phase began in 1983 when the EU's Common Fisheries Policy1 was formally created. Since 1983 the LPUP has remained at a constant low level.
One complication with using LPUP data as an index is that they do not incorporate estimates of discarding, where fish are returned to the sea if the Common Fisheries Policy quota is reached. The data do not provide a direct estimate of fish stock decline but do illustrate how the rewards of fishing have fallen since the 1880s. It is clear that seabed ecosystems have undergone reorganisation and commercial stocks of bottom-living species have collapsed. This indicates the need for action to eliminate further overexploitation of European seas and rebuild fish stocks.
Source: European Commission
(28/06/10)
