Pipefish population explosion will not save starving seabirds

In a paper submitted to the journal Marine Biology, an international team of scientists led by Professor Mike Harris from the Centre for Ecology & Hydrology in Banchory, reports a dramatic increase in pipefish numbers over the past few years. Pipefish were once rarely seen in British waters but are now frequently caught in trawler nets, with numbers rising 100 fold since 2002, according to some trawl surveys. Even regular divers have reported unusually large numbers along some stretches of coastline.

Dr Doug Beare from the European Commission’s Joint Research Centre in Italy, said that climate change is unlikely to be the primary cause of the dramatic increase. He commented, “There have been changes in water temperature in the North Sea since about 1988 but large numbers of snake pipefish have only appeared during the last three or four years. These major outbreaks of previously rare species do occasionally ‘just happen’ in marine ecosystems and they can have a startling effect on marine food webs. Interestingly, they are often associated with very poor breeding seasons in seabirds.”

Professor Harris said, “ Only in the last 3 years or so have snake pipefish been recorded in the diet of many species of seabird, including puffins, terns and kittiwakes breeding in colonies around UK coastlines, and in Norway, Iceland and the Faeroe Islands. 2006 seems to have been a bumper year, at least in northern Britain, and there is evidence that these birds are turning to the pipefish when their normal prey are in short supply.”

Breeding failures at seabird colonies off the east coast of Britain are becoming common and are thought to be due to low availability of sandeels, their usual and preferred food source. The reasons behind this reduced availability are complex but include effects due to the presence of the North Sea sandeel fishery and climate change.

Professor Harris is pessimistic that the availability of snake pipefish will provide an alternative source of nutrition for the birds during their breeding season. “The nutrient value of the snake pipefish is unknown but their rigid, bony structure makes them difficult for the birds to swallow. There have been numerous sightings of seabirds flying around with these fish protruding from their beaks and chicks, in particular, have great difficulty swallowing them. Many young puffins and kittiwakes have been found starving even when their nests were littered with uneaten pipefish, and tern chicks have been seen choking to death, apparently unable to regurgitate fish stuck in their throats.”

Most pipefish are small and live among seaweed and other marine vegetation close to the coast. The snake pipefish is much larger and can grow to more than 50cm in length and it is these fish that live in the open sea. They are normally found in Atlantic waters spreading from Norway and Iceland in the north to the Azores in the south and eastwards to the Baltic. Close relatives of the seahorse, pipefish are long and thin with segmented and usually hard, armour-cased bodies. Like the seahorse, it is the male that cares for the developing eggs, keeping them in a brood pouch or attached to the underside of his body.