04 May 2010

What does 'overfishing' mean?

In case 'overfishing' was still an obscure concept, a recent study makes it clearer.

The study is focused on the dramatic fish stock decline (cod, haddock, ling, halibut etc.) occurred in British Isles waters across 118 years, 1889-2007.

Researchers analysed landings per unit power and found that the availability of bottom-living fish for the fleet fell by 94%.

Modern high-tech fishing fleets of today require 17 times more effort to catch the same amount of fish as compared with the late 1800s.

According to Callum Roberts, one of the authors of this study, "This research shows that the state of UK bottom fisheries, and by implication European fisheries since the fishing grounds are shared, is far worse than we had thought."

With these findings, researchers underlined the need for urgent action to eliminate overexploitation of European fisheries and rebuild fish stocks to much higher levels of abundance than those that exist today.


Figure: Landings of bottom-living fish per unit of fishing power of large British trawlers from England, Wales and Scotland. Closed circles show landings per unit of fishing power into England and Wales, open circles show those into Scotland (from Thurstan et al. 2010).

The article:
Thurstan R.H., Brockington S., Roberts C.M. 2010. The effects of 118 years of industrial fishing on UK bottom trawl fisheries. Nature Communications 1, Article #:15 - doi:10.1038/ncomms1013
Abstract -- In 2009, the European Commission estimated that 88% of monitored marine fish stocks were overfished, on the basis of data that go back 20 to 40 years and depending on the species investigated. However, commercial sea fishing goes back centuries, calling into question the validity of management conclusions drawn from recent data. We compiled statistics of annual demersal fish landings from bottom trawl catches landing in England and Wales dating back to 1889, using previously neglected UK Government data. We then corrected the figures for increases in fishing power over time and a recent shift in the proportion of fish landed abroad to estimate the change in landings per unit of fishing power (LPUP), a measure of the commercial productivity of fisheries. LPUP reduced by 94%—17-fold—over the past 118 years. This implies an extraordinary decline in the availability of bottom-living fish and a profound reorganization of seabed ecosystems since the nineteenth century industrialization of fishing.

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