Taken by a fisheries observer on board a NZ bottom trawler NW of New Zealand, this photo shows a giant piece of gorgonian coral being hoisted out of a bottom trawl net. (Note more coral in the net). Coral this size is estimated to be more than 500 years old. © Ministry of Fisheries NZ Related Links •The Evidence, two page summary of the six main reasons why a time-out on high seas bottom trawling is needed now •Why the World Needs a Time Out on High Seas Bottom Trawling, June 2005, full report, English / Spanish (pdf) •Six good reasons for a time-out on high seas bottom trawling, DSCC news, 8 June 2005 •Such a hard case to make? DSCC feature, 7 June 2005 Greenpeace crew member onboard mv Esperanza, holding a large spider crab that caught and killed by EU bottom trawler Playa de Menduiña, fishing in the Hatton Bank, NE Atlantic, 24/10/2004. © Greenpeace/Kate Davison Tasman Sea: A closeup of the bycatch in a bottom trawl net. © Greenpeace / Grace

1. High-seas bottom trawling has spread rapidly but is of minor economic importance.

Globally, the market impact of high seas bottom trawling is tiny; it constituted only a fraction of one percent of the reported total marine fish catch in 2001 by volume and value. In 2001, high seas bottom trawling (HSBT) contributed roughly 200 thousand tons to the worldwide 80-million-ton marine fish catch, negating claims that HSBT contributes to global food security.

Significantly, the majority of the high-seas bottom-trawl catch is destined for markets in the most affluent nations, namely the USA, Europe, and Japan. HSBT fishing is a boutique fishery, temporarily benefiting only wealthy nations and wealthy consumers while trashing the global environment for a very long time (decades to centuries). Restrictions on these fisheries will have no major social impact, and will have very important environmental benefits.

More information: Economics & security – why the carnage doesn't make sense

2. Bottom trawling is the world's most destructive type of fishing.

Weighted with massive bobbins, rollers, or rockhoppers, trawl nets may stretch up to 40 meters in width and are held open by pairs of seven-ton steel trawl doors. Trawler footropes can roll 18-ton seafloor rocks. Trawling trips can last as long as four to six weeks with fishing around the clock. Trawlers sweep a vast area of seafloor, crushing corals, sponges and most of the other living things that they hit. The estimated total area swept annually by trawl nets (the same area is often trawled many times a year) is equivalent to about 50 percent of the world's continental shelf area, or approximately 150 times the area of forest that is annually clearcut worldwide.

Both logic and the large, rapidly growing number of scientific studies documenting trawling impacts lead to the unmistakable conclusion that bottom trawling is the world's most harmful method of fishing. For example, after reviewing available information on the impacts of a variety of fishing gear on deep-water habitats, the International Council for the Exploration of the Seas (ICES) concluded that while all deep-water fishing gear has some impact on the seabed, bottom-trawl fishing is by far the most damaging to deep-water corals and other vulnerable species. ICES advised that "the most effective way of mitigating the effect of trawling on these habitats is to close such areas to [bottom-trawl] fishing."

More information: Bottom trawling

3. Deep-sea fishes are inherently vulnerable to overfishing.

As a result of their slow growth and low reproductive rates, deep-sea fishes are the most vulnerable of all fishes to overfishing. Model simulation studies suggests exploitation rates greater than five percent annually will be unsustainable.

Seamount fisheries have repeatedly devastated fish populations in just a few years. Deep-sea fisheries on the Emperor Seamount chain in the north Pacific, off New Zealand, Australia and Namibia, and in the North Atlantic and Southern Indian Oceans have all experienced rapid depletions of deep-sea fish populations. In its recent review of deep-water fishing, the ICES Advisory Committee on Fisheries Management expressed concern that "deep-sea stocks can be depleted very quickly and that recovery will be slow."

Because of the generally low supply of food in the deep sea, fishes there are normally rather dispersed and come together in large groups only to spawn. High seas bottom trawlers may target these spawning aggregations since they provide the most profitable target. This so severely reduces the chance of recovery that the report describes this tactic as being more like mining than fishing.

Many deep-sea fisheries are also multi-species fisheries or have a large bycatch of unwanted or non-commercial fish species. As a result, these fisheries can be at least as devastating to non-target species as to their intended targets.

4. Deep-sea ecosystems are severely damaged by bottom trawling.

Myriad living organisms, such as corals, sponges, tube worms, and mussels form complex structures in and on the seafloor, thereby providing crucial food and refuge for marine species and enhancing fish survivorship. Trawling gear removes these complex structures and can strip seamounts bald, greatly altering the composition of the marine community.

Deep-sea corals are especially vulnerable, not only because they are long-lived, but also because their branched physical forms are fragile and easily snagged and cannot, therefore, withstand deep-sea bottom trawling.

Because so many bottom-dwelling deep-sea organisms are extremely slow growing, even a single trawl causes damage that cannot be reversed for decades or centuries.

This is particularly true on seamounts, which have an exceptionally high proportion of endemic species that are not found anywhere else. Endemism on seamounts may range as high as 30 to 50 percent. For endemic species, there are no sources for recolonization after a seamount is trawled, so endemism makes seamounts especially vulnerable.

By any measure, on a worldwide basis bottom trawling is the most harmful fishing method to seafloor habitats.

5. Scientific understanding is inadequate for sustainable deep-sea bottom-trawl fisheries.

Without reliable data, it is impossible for scientists to provide managers with sound advice. The extent of bottom-trawl fishing in international waters is still poorly known. Few data are consistently gathered on high-seas bottom-trawl landings. The FAO states that “it is difficult to assess the development of fishing on the high seas because reports to the FAO of marine catches make no distinction between those taken within EEZs and those taken on the high seas,” nor is gear type distinguished.

Deep-sea bottom-trawl fishing has generally commenced in the absence of basic biological information essential to sustainable fisheries management.

Attempts to regulate the exploitation of seamount species such as orange roughy have failed to prevent fishery collapse, because these species are very different from shallow-water species in longevity, growth rate, and rate of reproduction. Methods of fish stock assessment and fisheries management models developed for shallow-water species are often inappropriate for deep-sea species. In addition, fundamental data about deep-sea fish populations are often lacking or are gathered long after the fish stock has been decimated.

Scientists have almost no understanding of the roles that either target or bycatch species play in deep-sea ecosystems. Most deep-sea food webs are still a scientific mystery. But to judge from what has happened in shallower waters, selective removal of large fish through trawling will have profound, long-term and probably irreversible impacts on the entire ecosystem, especially on productivity and community structure.

We do not even know how many seamounts there are in spite of the fact that they are very large features. The true number is thought to be in the range of 14,000 to 100,000. Only 350 have been biologically explored and only 90 of these have been the subjects of quantitative, taxonomically-broad surveys. We only know enough about them to say that they are biologically very special, that their species are uniquely vulnerable and that seamount ecosystems are rapidly being destroyed by bottom trawling.

6. Management and governance are inadequate for sustainable deep-sea bottom-trawl fisheries.

Existing mechanisms for protecting, recovering, and ensuring the sustainability of high-seas deep-water resources are extremely poor. Unfortunately, the stark reality is that access to high-seas living resources is virtually unimpeded and unregulated.

As deep-sea bottom-trawling fleets have expanded into the high seas, few regional fisheries management organizations (RFMOs) have the competence to regulate deep-sea fisheries, and fewer still have adopted effective regulatory measures.

Vast areas of the oceans lack coverage by an RFMO with the legal competence to manage deep-sea fisheries on the high seas. The entire Indian and Pacific Oceans, as well as the Central and Southwest Atlantic, are without effective regulatory mechanisms to mange deep-water fisheries or protect deep-sea biodiversity beyond national jurisdictions.

There is little evidence that bottom-trawl fisheries on the high seas are operating in a manner consistent with international agreements that provide that fisheries should be managed in a sustainable, precautionary and ecosystem-based manner that protects biodiversity, non-target species and special habitats.

The history of serial depletion of fishes and biodiversity destruction in most high-seas deep-water fisheries indicates an urgent need for action. In areas where a deep-sea fishery requiring regulation commences, the speed with which bottom-trawl fleets deplete these populations is such that they may no longer exist by the time international institutions are operational.

Without a comprehensive governance structure for the management of high-seas deep-sea bottom fishing and the protection of seafloor habitats, commercial extinction of most targeted species and biological extinctions of vast numbers of other marine species are likely in the next 20 years.

More information: RFMOs

Notes:

(1) Why the World Needs a Time Out on High Seas Bottom Trawling, Marine Conservation Biology Institute, USA, British Antarctic Survey, Cambridge, UK, and the Memorial University of Newfoundland, St John’s, Canada. Available in English and Spanish (pdf).