Drift net

From Wikipedia, the free encyclopedia

A drift net is a type of fishing net used in oceans, coastal seas and freshwater lakes. They can range in length from 25m to 2.5 miles, although this upper limit is a recent developmets, and nets of up to 50km have been set in recent times^[1]. The term "drift" comes from the way these nets are used. They are essentially unanchored gillnets, with one or more panels of netting suspended in the water column, with floats attached to the "top-rope" of the net, and weights attached to the "foot-rope".

Selectivity properties of a drift net on a hypothetical population.

Drift nets operate by allowing fishes of a particular size to swim through the mesh of the net, as far as their gills but no further. The opercula (gill coverings) then prevent the fish from backing out of the net. The meshes of a drift net are uniform in size and shape, hence highly selective for a particular size of fish. Fish which are smaller than the mesh of the net are able to pass through unhindered, while those which are too large to push their heads through the meshes as far as their gills are not retained. This gives a selectivity ogive which is skewed towards medium sized fishes, unlike active gears such as trawling, in which the proportion of fish entering the net which are retained increases with length^[2].

Controversy around the use of driftnets stems not from their impact on fished populations, which, due to the selectivity parameters of the nets, are well understood, but from their impact on non-target species, particularly dolphins and turtles.

Driftnets have been commonly used by many countries in the coastal waters. However, Japanese driftnet fishing began to draw public attention in the mid-1980s when Japan and other Asian countries began to send large fleets to the North Pacific Ocean to catch mainly tuna and squid. Japan operated about 900 driftnet vessels earning around $300 million a year. Those fishing boats were blamed not only for the indiscriminate destruction of marine life, but also for the poaching of North Pacific salmon, harming the US and Canadian fishing industries, and threatening the jobs of fishermen who did not use such methods. The first Bush administration opposed a U.S. driftnet ban because it would conflict with a treaty with Japan and Canada regarding salmon fishing in the North Pacific^[3].

The UN General Assembly adopted a resolution which bans driftnet fishing in international waters effective December, 1992. The United States still permits drift gillnet fisheries within US waters, and as of March 2007, there are over 1300 vessels fishing with drift nets in European waters ^[4].

[edit] References

1. ↑  Jennings, S. Kaiser, M.J. & Reynolds, J.D. (2005) Marine Fisheries Ecology. Blackwell Science, Oxford, UK. 417pp.
2. ↑  Potter, E.C.E. & Pawson, M.G. (1991) Gill Netting. MAFF Fisheries Leaflet 69. [5]
3. ↑ US Ban on Driftnets - legal case study, accessed 28.3.2007 [6]
4. ↑  European fishing fleet register, accessed 28.3.2007 [7]

This fishing-related article is a stub. You can help Wikipedia by expanding it.