Fishermen who rake giant nets across the ocean floor to maximize their catch are destroying unique and unexplored ecological systems, according to the summary of a UN draft environmental report made public yesterday.
Most of the underwater volcanic mountains, or seamounts, which contain deep-sea corals and are home to thousands of marine species, are in unregulated areas.
Over-exploitation of traditional fish such as cod and hake has prompted fleets to trawl the high seas for deep-dwelling species such as orange roughy, alfonsino and roundnose grenadier, but they are harming biodiversity in vulnerable regions of the Pacific, Atlantic and Indian Oceans.
"There is an urgency, first of all, to deal with regulating those fisheries and secondly to get out there and look at those habitats before they are gone," said Alex Rogers, of the Zoological Society of London and a co-author of the report.
"Some of the corals being destroyed are thousands of years old and will not be replaced. Fish hundreds of years old are being decimated as a result of this trawling," he told a news briefing.
The report will be presented at the UN, which is debating a plan to ban deep sea bottom-trawling in unregulated areas.
It reveals new findings about the underwater mountains, some of which rise above 1,000m from the sea floor, and the sea creatures that thrive on them.
The precise number of large seamounts worldwide is unknown. It is estimated to be around 100,000 but Rogers said scientific information exists on only about 40.
The report used coral records on seamounts and global data sets on environmental factors and computer modelling to plot the potential global distribution of stony corals on seamounts and areas particularly vulnerable to deep sea trawling.
It says more commercial fishing for alfonsino and orange roughy in the central-eastern Southern Indian Ocean, in the South Atlantic and in some regions of the southern-central Pacific Ocean are likely to have a negative impact on seamount ecosystems.
Matthew Gianni, a fisheries expert and author of a report on the impact of trawl fisheries and their impact, told the briefing that 11 countries are responsible for 95 percent of high seas bottom-trawling.
Spain, which has the largest trawling fleet, had about 40 percent of the bottom trawl catch in 2001, followed by Russia with 14 percent, Portugal, Estonia and Norway with 7 percent each.
The bottom-trawl catch in 2001 was valued at US$280 million to US$320 million, or about 0.5 percent of world marine catch.