Oil drilling 'has a damaging effect' on sea fish stocks

The North Sea oil industry may be disrupting the ability of fish such as cod to reproduce because of the "gender-bender" chemicals released when oil is extracted from the seabed, new research suggests.

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Bad news: it's boom time for fish

The North Sea oil industry may be disrupting the ability of fish such as cod to reproduce because of the "gender-bender" chemicals released when oil is extracted from the seabed, new research suggests.

Male cod take on female characteristics, and female fish produce smaller eggs and spawn when exposed to the alkynated phenols, which occur naturally in underground oil reservoirs and are released during production.

The endocrine system of the fish is upset by amounts of the chemicals as low as 0.02 parts per million, studies by Norway's Institute of Marine Research have shown.

The findings, released yesterday at the North Sea Conference in Bergen, have profound implications for the oil industry because they are believed to represent the first indication that offshore oil drilling, now practised in many parts of the world, may seriously damage fish stocks. Although gender-alteration has been found before in freshwater fish – attributed to chemicals in detergents – this is the first evidence that sea fish can be affected.

Trisha O'Reilly, of the UK Offshore Operators Association, which represents British oil companies in the North Sea, recognised the concern over the release of chemicals into the marine environment. She refused to comment on the findings, but promised: "We will be actively participating in cross-boundary research work with the Norwegian oil industry, and co-ordinating our research effort with them to ensure that these concerns are properly addressed."

The Norwegian research team exposed young cod in the laboratory to concentrations of alkynated phenols that the oil industry itself said they might encounter in the vicinity of oil installations. They found the male fish produced a chemical normally associated with females, and their sperm was weaker. Female fish produced smaller roe and spawned about three weeks later – potentially a hazard to young cod,

Dr Ole Arve Misund, director of the Institute of Marine Research, said: "Apart from the obvious problem that smaller eggs produce smaller larvae and so reduce the chances of the cod surviving, they also produced at the wrong time, so that the spring plankton bloom which is the baby cod's main food source, would have disappeared. The three-week delay could produce a mismatch with the environment that could be important for the young cod's survival."

The research had been done only on cod, but other marine species might be similarly affected, from haddock to plankton, Dr Misund said.

Sub-seabed oil reservoirs consist of oil and gas as well as water, which contains the alkynated phenols. This "produced water" is a substantial by- product of the industry – oilfields in the British sector of the North Sea account for about 260 million tons of it a year, while those in the Norwegian sector produce another 120 million tons. Most of it is dumped straight out into the sea, although some is pumped back into the reservoir to force out the remaining oil.

"Many of the oilfield platforms are so close that you may get an 'additive effect', where the release from one platform adds to the effect of the release from a neighbouring one," Dr Misund said.

Further research would attempt to model the potential effect of the chemicals across the North Sea as a whole. The recent decline in cod stocks was attributable to over-fishing, he said, but he added that reproductive difficulties could make it harder for depleted stocks to recover.

The British Government would examine the research, the Environment minister Michael Meacher promised.