Unique seamount ecosystems destroyed by trawling

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A scientific report on the severity of the situation was outlined by Dr Alex D Rogers, ZSL Senior Research Fellow, at a Scientific Meeting on Deep-Sea Biology. Significant areas that have a high likelihood of harbouring vulnerable marine ecosystems have been identified and will now be communicated to Governments, fisheries managers and the fishing industry in an effort to stop the destruction and devastation caused by deep-sea trawling in these areas.

Dr Rogers stated: “Our research actively demonstrates the vulnerability of deep-sea corals and their associated biodiversity to trawling across seamounts. Some of the corals destroyed are thousands of years old and will not be replaced. Fish hundreds of years old are also being decimated as a result of the trawling.

“Our results show that oceanic areas not covered by the Regional Fisheries Management Organisations (RFMOs) and other binding regional agreements are home to significant unique aquatic biodiversity. In the case of deep-sea trawling it is, therefore, essential that the burden of proof shifts to Governments and fisheries when deciding whether it is appropriate to exploit these irreplaceable ecosystems.”

Speaking at ZSL’s Scientific Meeting on Deep-Sea Biology, Dr Rogers brought together the key points illustrated in the UNEP report*. In particular, the report demonstrated that:

Just over half (52%) of the worlds seamounts are located beyond areas of national jurisdiction and the majority of these have summits shallower than 3,000m water depth.

Stony corals are prominent on sampled seamounts and form a significant component of the species diversity on them, additionally creating and maintaining habitat for other organisms. Consequently, impact of trawling on these corals also gives an indication of the impact on all associated species.
An “environmental niche factor analysis” (ENFA) was used to model the potential global distribution of deep-sea stony corals on seamounts. The most favourable areas for corals were found to be located in the North Atlantic Ocean, and in a band between 20°S and 60°S in the Southern Hemisphere.

Deep-water trawl fisheries occur in areas beyond national jurisdiction for around 20 major fish species, including orange roughy, alfonsino, roundnose grenadier and Patagonian toothfish. The areas found to be suitable for fishing for these commercial species are, broadly speaking, the southern Indian Ocean, South Atlantic, North Atlantic and South Pacific Ocean.

Comparing the distributions of the commercially trawled fish, fishing effort and coral habitat on seamounts, reveals a broad band of the southern Atlantic, Pacific and Indian Oceans between 20°S and 60°S where likely ecosystem damage could be extremely significant. This suggests that further commercial exploration for alfonsino and orange roughy fisheries on large seamounts in the central-eastern Southern Indian Ocean, the southern portions of the Mid-Atlantic Ridge in the South Atlantic, and some regions of the southern-central Pacific Oceans are likely to impact negatively on diverse seamount ecosystems.

Notes to editors:

Seamounts are elevations of the seabed, effectively underwater mountains, where the summit does not reach the surface. They occur in chains or clusters along mid-oceanic ridges, near islands arcs or as single elevations in the seafloor. Seamounts often form biological hotspots, as a result of the presence of hard substrata and strong currents, which lead to numerous species of permanently-attached, filter-feeding animals residing on them. Of these species, corals are some of the most common, and many other species are dependent on their presence to create an appropriate niche environment.

*Seamounts, Deep-sea corals and Fisheries: vulnerability of deep-sea corals to fishing on seamounts beyond areas of national jurisdiction – UNEP WCMC Report.

Joint Lead Authors: Malcolm R Clark, National Institute of Water and Atmospheric Research, New Zealand; Derek Tittensor, Dalhousie University, Nova Scotia, Canada; Alex D Rogers, Institute of Zoology, Zoological Society of London, UK.

Photo - Crown Copyright, all rights reserved. Data provided by the UK Department of Trade and Industry as part of the Strategic Environmental Assessment programme.