Offshore petroleum installations in the North Sea used as fish aggregating devices – potential and suggestions for preparation, management and monitoring.

Abstract

There are approximately 70 working and planned structures in the Norwegian sector of the North Sea. The majority are steel-legged installations (oil and gas jackets) placed in depths ranging from 70 to 200 m. Several oil fields and structures are soon to be abandoned. Production from the North-east Frigg and Odin fields, was stopped in 1993 and 1994 respectively

From a technical and safety viewpoint, most of the structures are probably removable. Economically, concern has been expressed as to whether it is necessary to remove to shore all the installations. A positive environmental impact may be achieved by using some of the structures as fish aggregating devices.

The implications of creating an artificial reef from a steel jacket by toppling in-place are discussed. A typical steel jacket in the Norwegian sector of the North Sea weighs 5,000 - 10,000 tonnes (excluding piles) and has a volume of 100,000-150,000 m3. It may also be possible to utilise some of the deck modules. Technical and biological aspects relating to artificial reef establishment are reviewed, including the identification of the chemicals and materials that need to be removed prior to toppling. Suggestions for further management and monitoring for documentation purposes, are reviewed. A 5 year monitoring programme protocol is proposed.

The creation of a test reef from a steel jacket would present an ideal opportunity to obtain essential data, hitherto lacking in the North Sea, on the usefulness of high profile steel reefs as fisheries management tools. Data obtained would also be used to propose effective North Sea reef management and exploitation strategies. The suitability of using material arising from the petroleum industry, as components for artificial reefs, seeks to be determined.