Friday, 30 September 2011

The fish making offshore oil platforms their home

Could these man-made structures be used as reef habitat too?
September 2011: Oil and gas platforms could be serving as beneficial habitats for commercially important fish populations such as cod and haddock, a marine ecologist has told the World Conference on Marine Biodiversity being held in Aberdeen.

If adequate knowledge is to be gained from the existing offshore platforms, there may also be potential for man-made structures like offshore platforms and installations for renewable energy to be used as reef habitat, Dr Toyonobu Fujii of the University of Aberdeen's Ocean Lab said.

The researcher has been analysing long-term bottom trawl survey data of fish distributions in relation to the installation history of offshore oil and gas platforms in the North Sea.

Commercially important species gather in numbers‘There are currently no fewer than 500 offshore installations extracting oil and gas primarily from the continental shelf in the North Sea and, since the first installation, more and more researchers have been aware that a variety of commercially important fish species such as cod, haddock and saithe gather in substantial numbers around these artificial structures,' said Dr Fujji.

‘Currently, all the offshore platforms and the safety zones around these platforms, combined, account for only 0.08 per cent of the surface area of the North Sea. However, the proportion of fish abundance estimated to aggregate around these structures was much higher than the surface area alone would suggest.

‘We still don't know exactly why they are gathering there. It could be because there are more feeding opportunities or possibly because they provide places for them to shelter or hide.

Could be used as a nursery or breeding ground‘But if they are using these habitats as nursery or spawning grounds then the implications of the physical presence of these structures could be important since such biological mechanisms strongly drive the future population dynamics of the fish.'

Dr Fujii says more research is needed into the causes and seasonal nature of such phenomena in association with artificial structures. He also wants to explore whether other fish species such as flatfish or pelagic fish such as mackerel show similar trends and are attracted to these sites.

‘Given the magnitude of scales at which fish movement could be influenced by the offshore platforms, such knowledge will be of critical importance for future spatial management of seafloor as well as sustainable fisheries management, perhaps this is even more pertinent now with the expected expansion of offshore renewable energy developments.'

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