By Claire Attwood and Sarah Gotheil

The Norwegian research ship, Dr Fridtjof Nansen, will embark on a three to four month voyage in the western Indian Ocean in August, continuing the pioneering research that began in 2008 under the umbrella of the Agulhas and Somali Current Large Marine Ecosystems (ASCLME) Project.

The 2009 voyage of the Nansen will consist of four cruises: an East African Coastal Current cruise (25 days, jointly funded by the ASCLME Project and the South West Indian Ocean Fisheries Project – SWIOFP); a cruise in the Comoros Gyre in the northern part of the Mozambique Channel (25 days); a 15-day cruise to service and deploy oceanographic moorings east of Madagascar; and a cruise to study seamounts and the Agulhas Return Current (41 days).

The ASCLME Project and the FAO’s Ecosystem Approach to Fisheries (EAF)-Nansen Project will fund the 2009 voyage of the Dr Fridtjof Nansen. A partnership with the African Coelacanth Ecosystem Programme (ACEP) will extend the research effort into South African waters. A survey of the Natal Bight, north of Durban, and the inshore edge of the Agulhas Current are planned and will take place from the South African research ship, FRS Algoa.

The 41-day seamounts cruise is likely to be a highlight of the Nansen’s 2009 voyage. Beginning in La Réunion on November 11, it aims to study five seamounts all located in the high seas between 32°00’S and 41°00’S. This expedition, which is the first dedicated survey of seamounts in the Indian Ocean, is made possible through a partnership between the ASCLME Project, the EAF-Nansen Project, the International Union for Conservation of Nature (IUCN) and the Zoological Society of London. There is additional collaboration from the Global Environment Facility, the Norwegian aid agency, Norad, the Food and Agriculture Organization of the United Nations (FAO) and the United Nations Development Programme (UNDP).

A multidisciplinary team of scientists will investigate the chemical, physical and biological oceanography of the seamounts and their surroundings. They will carry out acoustic surveys to identify fish stocks and their distribution and perform acoustic and net studies of zooplankton, micronekton, nekton and fish. The biodiversity of fish, crustaceans and other invertebrates will be assessed through pelagic and bottom trawls and their sampling will help determine the pelagic biodiversity and trophic ecology of the area, as well as provide genetic material for analysis.

Other oceanographic measurements will be taken, including water salinity and temperature, current speed and oxygen. Multibeam bathymetric surveys will be conducted to develop detailed maps of the seafloor. Opportunistic studies of seabirds and marine mammals will also be undertaken.

 

Why seamounts?
Seamounts are underwater mountains that rise from the ocean floor. They are found in all the oceans of the world and are estimated to number as many as 100 000, although only 14 000 seamounts have been located to date. Like other topographic seabed features, they are known to be hotspots of biological diversity and production. Migratory fish and cetaceans rely on seamounts for food. Seamounts also feature concentrations of commercially important fish, such as tuna and orange roughy, and are know to host breeding aggregations of several species. Current knowledge indicates that deep-sea bottom fisheries may cause irreversible depletion of deep-sea fish populations in just a few years and severe damage to slow-growing seabed communities of cold water corals, sponges and other animals found on seamounts; however, due to the limited data and research, neither the level of threats by fishing activities nor appropriate management options have been determined to date.

 

The southern Indian Ocean remains the most significant gap in current knowledge of global seamount ecology and biodiversity. Therefore, the study of five seamounts in the south-western Indian Ocean will make a substantial contribution to scientific knowledge and understanding of seamounts and their relationship with benthic and pelagic fish species.

The results of the seamounts survey will ultimately contribute to providing a baseline for the formulation of sustainable management options for the area and help identify measures to improve the governance framework for high seas resources in the Indian Ocean.