Marine Pollution Bulletin
shelter and a conservation area to protect fish and crustaceans? Should it be designed to attract and accumulate fish for ease of harvesting? Is it to provide feeding and a permanent home for a continuous cornmercial supply? There are also basic questions about its functioning and how it should be operated. Will it generate its own fish populations and contribute to a net increase in productivity or will it simply concentrate existing stocks? Will a reef of scrap steel remain intact long enough to be worthwhile and might the substance of the reef introduce toxic material to the food chains or create tainting or discoloration problems in the associated fish? Will it break up and cause debris problems that are at present of so much concern to fishermen? Does suitable gear exist or can it be developed to fish the species that will be available? Economic issues would finally need to be considered. Would any enhancement be merely at a very local level and if so how could the fishery be most effectively managed? Would it pay? Such questions must be asked and answered, Answers could come from experimental and observational work at sea, but the necessary studies would take several years and would not be cheap. However, in view of their relevance to major oil industry problems and current national concerns, it would seem that the cost of the work should be borne by the oil industry encouraged by central government, and, given the possibility of generating new employment, significant support from regional agencies and local authorities might be expected. The role of the fishing industry in this may be somewhat ambivalent. Their fear of debris has already
been noted. In addition, if the major enhancement is on the bottom, benefits to pelagic fishermen will not be obvious, while offshore demersal men may feel less than enthusiastic if the focus is on specific inshore sites. It should therefore be recognized that the fishing industry may not be of one mind on this issue. However, they must be consulted on the projects and kept closely involved. Ground work for the required studies has already been well laid. A number of recent conferences have discussed the subject and others are planned for 1987. Some observations have been made round working platforms and a few non-operational installations are present in the North Sea that could usefully be a focus for further studies. The Heriot-Watt Institute of Offshore Engineering addressed the topic in a recent report to the Science and Engineering Research Council, and Aberdeen University Marine Studies Ltd have produced a detailed proposal on rig sections placed at inshore sites. There is of course no suggestion that a 'rigs to reefs' policy is the answer to all decommissioning problems. Offshore installations come in a wide range of structures and situations. Each case should be treated on its merits and only some will be amenable to reef conversion, but the option is there and its assessment requires appropriate studies at sea. If the essential facts are to be available in time to assist with the decisions which must be taken by the end of the decade, funds should be made available and the work should start now.
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In the Greenpeace study, flatfish from the inner Thames Estuary were taken from the cooling water intake screen at the West Thurrock Power Station over a four month period. Just over 360 flounder were exan~ned of which 30% had abnormalities. 22% of the sample were affected by fin rot, skin lesions, petechial bleeding, surface nodules, and the viral disease, lymGreenpeace have just published a report on work phocystis. The Report questions the Ministry of Agricarried out on their behalf by the University of London culture, Fisheries and Food's interpretation of a on the incidence of diseased fish in the inner Thames Government study carried out in 1983 in which they Estuary (The Greenpeace Great Rivers Campaign, were unable to establish a link between fish disease and Aquatic Environment Monitoring Research Report, the sewage sludge dumping operation conducted by the Interim Report RR5). Thames Water Authority. The work was commissioned as a result of the The theory presently under consideration by a Joint mounting concern of Dutch and German scientists at Working Group from the University of London and the high levels of diseased fish in coastal and estuarine Greenpeace is that a great number of abnormalities waters in the southern part of the North Sea. Appar- found in some flatfish populations can be attributed to ently almost 50% of all the dab caught in the Southern increasing levels of marine pollution. The habits of the North Sea in 1984 were diseased; 20-30% of all fish flounder are different from other flatfish in that they caught in the German Bight, once a dumping ground tend to remain in estuaries for most of the year. Greenfor chemical waste, are now diseased. In addition 40% peace maintain that for this reason they are more likely of flounders and dab examined in Dutch coastal waters to be immediately and consistently exposed to pollutin 1985 had liver cancer and 50% of eels studied near ants at a higher concentration than other species which Stade on the River Elbe suffered from a viral infection spend more time in deeper coastal water.
Fish Disease in the Thames 1Estuary