Birds choke to death on migrant fish

Robin McKie, The Observer 17 Feb 08;

Baffled scientists warn of a 'catastrophic' impact as snake pipefish flood into British waters

Britain's sea birds are facing a deadly new threat from a population explosion of strange, seahorse-like creatures in our coastal waters. The snake pipefish, virtually unknown around the UK in 2002, has undergone a massive, baffling and dangerous expansion since then, scientists have discovered.

Divers report seeing hundreds on single dives, while dozens of pipefish - which can grow to more than 18 inches in length - have been found in the nests of puffins, kittiwakes, terns and other sea birds.

The discovery has alarmed biologists because they have found that chicks are choking to death on the rigid, bony bodies of pipefish, while adults are feeding on them despite the fact they have very little nutritional value.

The implications for future generations of sea birds - already badly affected by depletion of Atlantic and North Sea fish stocks - are alarming, scientists warned at a meeting of the Zoological Society in London last week. 'It is an extremely worrying development,' said Professor Sarah Wanless, of the Centre for Ecology and Hydrology (CEH), Edinburgh. 'The spread of pipefish in our waters could have a catastrophic impact on sea bird breeding.'

The explosive growth of the snake pipefish (Entelurus aequoreus) in the past five years has been one of the most mysterious events affecting Britain's coastal waters in recent years. Six years ago they were unknown around the UK. The next year divers and fishermen reported finding occasional specimens.

'Since then the species has increased dramatically in abundance and its spread continues. Indeed it may be accelerating,' states a paper on marine biology by a team led by Professor Mike Harris, another CEH scientist. 'In June last year, 500 were caught in a 15-minute haul off the Farne Islands, while in July and August large catches were recorded in the Norwegian Sea, for example.'

The cause of the pipefish's spread is puzzling. Some scientists suspect that sea warming caused by climate change may be involved, but the link is not obvious. The snake pipefish is a subarctic species unlikely to be attracted directly by our warming coastal waters. Instead, scientists speculate that changes in ocean currents may be driving increasing numbers into our waters, or that their principal foodstuff, various species of plankton, may be becoming more abundant around Britain. Whatever the cause, they say that the impact on sea birds could be disastrous.

Sea bird numbers have been hit by a series of consecutive breeding failures in recent years, affecting skuas, guillemots, shags and others. The problem is starvation. Since 2000 sea birds have not been able to find sufficient food either to sustain their chicks or give them the energy to breed, a problem that is blamed on the dwindling populations of small fish and sand eels that sea birds eat, a phenomenon scientists have been unable to explain.

Now parent guillemots, terns and puffins are scooping pipefish from the sea for their chicks as substitutes for their normal fish food. But the pipefish body is rigid and bony and extremely hard for chicks to eat. Biologists have found dozens left uneaten in single nests while chicks have choked to death on their bodies.

In addition, studies have found that the species is low in fat content and represents poor nutritional value. Nevertheless, sea birds - already affected by poor diet - are turning to pipefish for food, a move that will only further damage their breeding.

'In the longer term, it is going to be very dangerous indeed for the future of sea birds around Britain,' added Wanless. 'Sea birds breed fairly slowly and a number of bad years could have a long-term devastating impact.'