Stuart Coles, The Telegraph 14 Feb 08;
It may come as a surprise to most people that there are any seahorses at all in British coastal waters, and more surprising still that numbers appear to be increasing.
Seahorse experts met in London this month to discuss the apparent population surge in seahorses and their close relative, the pipefish.
The reasons for this increase, described as "rapid and dramatic" is not yet clear and a number of theories have been put forward including a natural population boom or warmer waters.
As with any shift in population, it is also having a knock-on effect upon other species, including sea birds.
Pipefish form a distinct family with seahorses (syngnathids) and as the name would suggest, look like straight-bodied seahorses with tiny mouths.
Numbers of the snake pipefish, once rarely seen in northern British waters, now often end up in the region's trawler nets in vast numbers, say scientists.
Once associated with deep northern waters, they have even been found recently further south by fishermen in the Thames Estuary.
A European team led by the Centre for Ecology & Hydrology (CEH) says that the numbers of snake pipefish in British waters has increased more than one hundredfold since 2003.
They say although there have been changes in water temperature in the North Sea since around 1988, the large numbers of snake pipefish have only appeared in the last four or five years - putting a global warming theory in doubt.
"There is no doubt that numbers of snake pipefish have increased. In the last few years they are just everywhere," said Professor Mike P Harris of CEH.
"Although climate change may well have had an effect, the jury is, we think, still out on this matter."
Cindy van Damme of the Netherlands' Wageningen IMARES - the Institute for Marine Resources and Ecosystem Studies, believes she may be nearer an answer.
She says recent shifts in ocean currents have led to a change in the composition of plankton - it has shrunk.
"Plankton is the major food item of pipefish and sea horses. The mouth opening of this group of fishes restricts the prey size they can handle. We think this mechanism explains the huge increase of snake pipefish. Hence this outbreak may very well last for only a limited number of years."
However long it lasts, it is impacting startlingly upon pipefish predators - which include everything from mackerel, dolphins, otters and sharks to seabirds.
Although they are eaten by birds such as gannets, kittiwakes and puffins, their spiny, 'armoured' forms, like seahorses make them difficult for young birds to swallow and digest - some young birds even choke to death on them.
In fact, their nutritional value for birds is in doubt - and their explosion in numbers seems to be linked with poor breeding seasons.
Scientists are also recording birds with large numbers of uneaten pipefish, with nests actually made of the fish. They say the pipefish appear to be a poor substitute for their normal food such as sand eels.
The explanation for increased sightings of seahorses in many place on Britain's coastline, and at vastly varying depths, may be a little more straightforward.
Neil Garrick-Maidment, Director of the UK's Seahorse Trust, doubts global warming has anything to do with it. "There's no evidence at all, as far as I can see. It's just people jumping on the bandwagon."
He says seahorses were first recorded in British waters in the 1880s and even appear in early Pictish art.
The increase is sightings is due to the Trust's British Seahorse Survey, better awareness, shifting currents and the role of the internet, says Mr Garrick-Maidment.
"There are simply more people out there looking, that's the reason we have so many sightings," he says, adding that better relationships with fishermen have added to data coming in to the Survey which was started in 1994.
"They were reluctant at first, as they didn't always want to reveal where they were fishing, but we've cracked that."
The survey has eight co-ordinators and receives frequent emailed sightings, reports and photographs from members of the public, agencies and even power stations - whose warm waters and filters are thought to attract seahorses.
Britain's changing Gulf Stream also plays a role, he says. "It's hard trying to even convince people that there are seahorses in our waters - they usually think they are tropical creatures. But the Gulf Stream is a major influence on species, we have basking sharks, turtles and all manner of jellyfish - lots of creatures people think are tropical."
Besides, he says, half of the world's seahorse species live in cold or temperate waters. If global warming does turn out to playing a role he says he "will be the first to admit I'm wrong - but I just don't see it."
Mr Garrick-Maidmen, who founded the world's first seahorse aquarium (in Exeter) and has spent 28 years studying and breeding them, clearly has not lost his great enthusiasm.
"They are fascinating, magical creatures. We have only just scratched the surface of what we know, there's an awful lot of work to do. Hence the Survey will be going on for a long time yet."
