Deep-sea trawling blamed for death of fish species

Species of fish and the ecosystems that sustain them are being destroyed by deep-sea trawling, a new report warns.

Fish species, some new to science, are being "decimated", according to the report by the Zoological Society of London (ZSL).

Many species, including the orange roughy, a brick-red fish famed for its longevity, the large-eyed alfonsino and the roundnose grenadier, part of a family which makes up 15 per cent of the deep-sea fish population, are at the mercy of deep-sea trawlers because they exist outside areas covered by legally binding international agreements, established to preserve species from overfishing.

The ZSL report provides one of the strongest pieces of evidence yet on the detrimental effect of trawling on deep-sea corals and seamounts (underwater mountains whose summits do not reach the surface).

The report supplements a recent scientific analysis by the wildlife charity WWF which revealed the dangers to fish species caused by deep-sea trawling and some of its practices - primarily "bottom trawling", by which heavy rollers are dragged over the ocean floor, trapping fish and mammals and destroying entire ecosystems. The WWF warned that fish stocks in international waters were being plundered to the point of extinction because governments are failing to protect them. It listed tuna and the orange roughy among those under threat.

"Our research actively demonstrates the vulnerability of deep-sea corals and their associated biodiversity to trawling across seamounts," Alex Rogers, ZSL's senior research fellow, said. "Some of the corals destroyed are thousands of years old and will not be replaced."

The ZSL report analysed the most favourable areas in the world's oceans for corals and compared them with areas where fish are commercially trawled. The results showed that a broad band of the South Atlantic, Pacific and Indian oceans, between 20°S and 60°S, are at risk of "extremely significant" damage to ecosystems. Further commercial exploration for alfonsino and orange roughy fisheries on large seamounts in the central-eastern Indian Ocean, the southern portions of the underwater Mid-Atlantic Ridge in the South Atlantic, and some regions of the southern-central Pacific Ocean are likely to impact profoundly on seamount ecosystems.

The report also showed that 52 per cent of the world's seamounts are located beyond areas controlled by the regional fisheries management organisations (RFMOs), whose task it is to ensure waters are not overfished. The South Atlantic and Indian oceans are not covered by an RFMO at all. The WWF found that even some of those oceans which were covered lacked protection because individual countries did not have the "political will" to enforce fishing limits.

The ZSL called for research on where seamounts are located, better studies to assess the impact of trawling and more action from governments to stop unsustainable deep-sea fishing. "It is essential that the burden of proof shifts to governments and fisheries when deciding whether it is appropriate to exploit these irreplaceable ecosystems," Dr Rogers said.