fact sheets - Bottom Trawling
Bottom trawling is an indiscriminate fishing technique that involves dragging weighted nets along the seabed at slow speed. In doing so, it destroys everything in its path, and repeated trawling can irreversibly alter seabed habitats.
Trawling is widely recognised as one of the main threats to benthic communities. It strips the seabed of life, destroying large areas of corals and sponges, and at the same time damaging the nursing and feeding grounds for many fish species.
Trawling also stirs up sediment on the seabed. This can create plumes that travel with currents for tens of kilometres, and can block the penetration of sunlight through the water column, hindering the reproduction of algae and marine plants.
Trawling typically targets slow growing bottom-dwelling species, such as orange roughy and gemfish, that are vulnerable to overfishing, but also kills many species that are caught incidentally. These include seabirds, sharks, sea lions, seals, sea turtles, and sea snakes.
Bottom trawling is largely unregulated in most of the oceanic waters beyond national jurisdictions. Notable exceptions are the waters of the Antarctic, where a number of extensive bottom trawling restrictions are in place and overseen by the Convention for the Conservation of Antarctic Marine Living Resources. The North East Atlantic Fisheries Commission has also closed four seamounts and part of the mid-Atlantic Ridge to bottom trawling for three years.
In a more recent landmark agreement, 20 countries fishing within the waters managed under the South Pacific Regional Fisheries Management Organisation, agreed to exclude bottom trawling on high seas areas where vulnerable ecosystems are likely or known to occur, until an impact assessment has been undertaken and precautionary measures to prevent the destruction of marine life have been implemented.
HSI Action to Mitigate Impacts of Trawling
In an attempt to curb the dire ecological impacts of trawl fishing in Australian waters, HSI first nominated Demersal trawl and Danish seine fishing of the assemblages of sharks (elasmobranches) and fish (teleosts) inhabiting the continental shelf and upper slope of eastern Australia as a Key Threatening Process in 2003. This nomination has since been revised and is currently being assessed by the Federal Government. HSI is expecting a decision on the outcome of this assessment in early 2013.
In 2005, HSI nominated the unique and biologically rich Tasmanian Seamounts for listing as National and Commonwealth Heritage. This area of immense species endemism and diversity was previously in the midst of the trawlers' range, and their subsequent recognition as Commonwealth Heritage in 2006 afforded an extra degree of legal protection to the habitat, invertebrates and fish of 15 of these seamounts. Also home to the chronically over-fished orange roughy, this listing offered protection for populations of the species inhabiting the seamounts covered by the listing.
Protection for this species from trawling was further enhanced later in 2006 when an HSI nomination prompted the listing of orange roughy as a threatened species. This represented the first ever listing of a commercially fished marine species under threatened species laws in the world, bringing an end to the chronic over-exploitation of orange roughy after a 3 year campaign.
In December 2006, HSI mounted a legal challenge against former federal Environment Minister Ian Campbell' s decision in December 2006 to declare the Southern and Eastern Scalefish and Shark Fishery (SESSF), Australia' s largest multi-species trawl fishery, an ecologically sustainable Wildlife Trade Operation. Negotiations with the federal Department of Environment and the Australian Fisheries Management Authority resulted in significant improvements to the fishery, including the investigation and implementation of mitigation measures, such as gear modification and spatial closures, to ameliorate its impact on Australian sea lions, eastern gemfish, albatrosses, petrels and Harrisson' s dogfish.
HSI also continues to engage with the Agreement on the Conservation of Albatrosses and Petrels, to encourage the uptake of mitigation measures to reduce bycatch in trawl fisheries globally.
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