THE sea boils with fish frantically trying to escape as eager seabirds circle above. A massive surge of water and a true giant of the deep enters centre stage. At up to 35ft long and weighing ten tonnes, a surfacing minke whale makes an impressive sight.
The west coast of Scotland is one of the best places in Europe to watch the whale - known as muc-mhara-mhionc in Gaelic - and boat trips are laid on for tourists from far and wide.
But in the last few years such spectacles have become markedly le
ss common, with scientists reporting that between 2003 and 2006 sightings fell by two-thirds.
Such glimpses, however, tell us little about the health of the minke whale population; in fact little is known about the health of our sea-mammal populations generally, with the possible exception of seals and harbour porpoises.
The Hebridean Whale and Dolphin Trust, which surveys minke whales off the west coast between Skye and Kintyre, found one minke whale for every eight hours of searching in 2003, but by 2006 this had fallen to one sighting every 23 hours.
Dr Peter Stevick, the trust's science director, says: "We have a very strong signal on the west coast that over the last five years there has been a big decrease in minke whale sightings.
"It could mean there are fewer minke whale. It could mean they have picked up and moved somewhere else. It could be the population is even going up, but they happen to be on the east coast or the Faroes or somewhere else.
"It's difficult to distinguish between these. The likely explanation is a great many of those animals have moved because of changes in conditions that have made it more appealing to be somewhere else."
However, whales would not make such a decision on a whim. Whales are incredibly mobile and swimming a few hundred miles is not a major investment of their time or energy.
"But the surprising thing with a lot of whales is not how mobile they are and how far they can move, but how often we see them staying in or returning to the same place.
"Whales provide a really good indicator for us of how healthy or not the waters around us are. At the moment, the main thing they are telling us is to pay attention to what's going on with fish stocks."
For Professor Ian Boyd, the director of the Sea Mammal Research Unit (SMRU), at St Andrews University, the lack of knowledge about populations of whales, dolphins and others is a cause for concern.
"What we cannot say is what the [population] trends are. It's a mixed picture. I think they are probably doing OK, but because things tend to happen quite slowly, it is easy to get lulled into a false sense of security," he says. "It's possible some populations of marine mammals that we don't know much about could be in decline.
"We could be allowing these animals to decline through ignorance, which is a great danger, especially given the amount of activity in the marine environment."
The prospect of tidal-energy schemes presents a new potential threat from humans to marine mammals on top of existing activity such as shipping, oil exploration, the use of sonar, pollution and plastic litter.
The SMRU is to take part in a study of how marine mammals can cope with underwater turbines when one is installed at Strangford Lough, Northern Ireland, in the next few months.
"I think there are major challenges with tidal turbines in these high- energy areas. What we don't know is whether marine mammals can cope with them."
Prof Boyd emphasises the need for Scottish and UK Marine Bills to include marine spatial planning, effectively a way of zoning areas for suitable uses, alongside protected marine zones for creatures with rare habitats and creatures with less propensity for travel.
"Marine mammals range over vast areas and there's an absolutely desperate need for appropriate marine spatial planning," he says.
Sarah Dolman, of the Whale and Dolphin Conservation Trust, has been campaigning to protect a resident population of about 120 bottlenose dolphins in the Moray Firth, amid the prospect of oil exploration in the area.
"It's obviously a small population and just the loss of a few females could put it in serious trouble," she said.
"There are a number of threats that these animals face. We would certainly advocate that more research is done, but we cannot wait ten or 20 years until that research is done.
"Protection has to come into place now, which is obviously why we are supporting a Marine Bill."
A TALE OF TWO SPECIES AS SEALS SUFFER
FOR Scotland's seals, it is a tale of two species: numbers of grey seal pups soared from the years 1970 to 2000 while harbour seal numbers have slumped alarmingly.
More than 12,600 harbour or common seals were counted in Orkney and Shetland in 2001-2, but by 2005-6 there were just 7,300. It appears juvenile common seals are failing to survive to adulthood but the reasons are unclear.
Professor Ian Boyd, director of the Sea Mammal Research Unit, said: "For the population to be declining at that sort of rate, about 10 per cent a year, I would say it is extremely serious.
"We have got to work out whether there's anything we can do about it and what the cause is. At the moment, we just don't know."
Callan Duck, a senior scientist at the Sea Mammal Research Unit, attacked human attitudes to seals and the idea they should be culled to save fish stocks.
Fish, cetaceans like whales and dolphins, and seabirds "all consume more fish than seals do", he said. "Seals are quite low down on the predation league."
The Scotsman's manifesto to protect the seas
THE Scotsman has launched a campaign for urgent steps to be taken to protect our precious marine life.
We want:
• a network of marine reserves and protected areas to be created to safeguard properly sites such as St Kilda, one of just 30 marine World Heritage Sites, the Sound of Mull, an important area for whales and dolphins, and Loch Sween with its lagoons and tidal rapids;
• a system of marine planning, effectively zoning areas for appropriate use, to safeguard important fishing grounds from offshore wind farms and other developments and allow humans to exploit the seas in the most sustainable way;
• a single marine management organisation for Scottish waters to ensure this system operates as efficiently as possible;
• Scotland should also be given control of conservation to the 200-mile boundary with international waters. At present, the Scottish Government controls out to 12 miles, with the UK government responsible for the waters beyond that.
