Fish farming pollutes

Fish farming pollutes

Volume 19/Number 10/October 1988 continued to kill thousands of seals on the North Sea coasts of the Netherlands, Germany and Scandinavia. The virus i...

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Volume 19/Number 10/October 1988 continued to kill thousands of seals on the North Sea coasts of the Netherlands, Germany and Scandinavia. The virus is now known to have spread to British waters and has been isolated from dead seals from the Wash area where, during August, the Natural Environmental Research Council have recorded 123 seal deaths. However, a relatively large number of seals do tend to die at this time of year from natural causes and part of the apparent increase in seal deaths may be a result of appeals to the public to report findings of dead seals. As yet there is no confirmation that the number of dead seals washed up recently in the Orkney area have succumbed to the virus. Although, to date, the majority of dead animals have been common seals (Phoca vitulina) it appears likely that the grey seal, Halichoerus grypus, will also be susceptible to the virus. British waters support the world's largest population of grey seals (an estimated number of 95 000) with the greatest concentration centred on the Orkney Islands. The grey seal population has been increasing steadily since a ban on culling was introduced and recently has caused some concern to fishing organizations (see Mar. Pollut. Bull 19, 48). Original reports had attributed the seal deaths to an increase in pollution levels although this may still be a contributory factor. As vaccination against the disease seems an impossible task, it seems likely that the epidemic will now have to run its course leaving surviving seals to re-establish populations with resistance to the disease.

chemical reactions on the seabed are methane and hydrogen sulphide, which are toxic to fish. This, if combined with reduced oxygen levels, could cause gill damage resulting in reduced growth and mortalities in the stock. The report concludes that where there is sufficient depth and water exchange, the site is unlikely to become 'soured'. Sites most likely to be adversely affected would be in very sheltered locations, in shallow water and with little water movement. Once the fish farm and its supply of carbon and nitrogen have been moved, the area beneath will gradually revert to its previous state. At one farm, which had been in use for 3 years, it took 8 months for the seabed to revert substantially to its pre-fish farm state, but full recovery of the macrofauna can take up to 3 years.

Pollution from Chinese Shipbreaking

In order to prevent marine environment pollution from the shipbreaking industry, to protect marine ecosystems, to safeguard public health, and to encourage the development of the industry in the Chinese coastal region, a new Regulation on Preventing Pollution from the Tanker Breaking Industry was issued by the State Council on 18 May 1988. In recent years Chinese society has become more open to the outside world. Since 1983 more than 300 tanker breaking yards have been set up with the idea of quickly becoming rich and the industry has to date made large amounts of money for both the State revenue and itself. During the period of 1983 to 1986, A four-year study of aquaculture and the environment 268 tankers were broken up making the industry a has produced the first ever set of scientific indicators profit of £50 million. China is the leading country as far for siting and running marine fish farms. Waste from as the ship-breaking industry is concerned. fish farms can affect the ecological balance within 60 m However, due to a lack of management and environof the sites but shows the effects can be reversed if mental regulations, enormous damage has been done to salmon cages are moved around as in agricultural crop the marine environment and marine organisms. During rotation. the short period January-July 1985 eighteen oil polluThe study, funded mainly by the Highlands and tion incidents occurred and the direct economic losses Islands Development Board, was co-sponsored by the were about £100 000. In recent years oil pollution Nature Conservancy Council, Crown Estates Commis- stemming from the industry has worsened considerably. sioners, Countryside Commission for Scotland and The pollution problem has to be solved if China is to Scottish Salmon Growers Association. It was carried rationally utilize and exploit her coastal resources. It is out by Dr Richard Gowen, of the Scottish Marine Bio- in these circumstances that the new regulation is to be logical Association, and Dr Donald McLusky, from welcomed. Stirling University. The regulation has granted power to the marine enviOn average, 20% of salmon feed is 'missed' by ronmental agencies of local government to be responsfarmed salmon but may be consumed by other fish. ible for supervizing environmental protection work Surplus food and waste products from the fish contain associated with the industry. These agencies will be nitrogen and carbon which, in sufficient quantities, responsible for directly managing and controlling the reduce the level of oxygen available to life on the water areas adjacent to the breaking yards. Shipseabed. Macrofauna then disappears directly below the breaking yards will no longer be allowed to operate farm while, slightly further away, other species move in. near salinas, desalination plants, fishing grounds, scenic At the five sites investigated by the research team, it spots or conservation areas. The new legislation also was found that the effects of the waste were confined to stipulates that any newly planned yard must first submit within 60 m of the farm. The biggest changes were an EIA report to the appropriate environmental noted within 15 m. authority for approval and penalties for any person Some of the possible changes have repercussions on infringing the law have been introduced. the fish themselves. Among the by-products of the FAN ZHIJIE

Fish Farming Pollutes