Risk to Porpoises

[Guest guest]

Increasing numbers of harbour porpoises are starving to death in the

North Sea around Scotland because of climate change, it has been

claimed.

Evidence suggests warmer waters are affecting supplies of sand eels,

which are the preferred prey of porpoises.

 

Experts say the mammals are not switching diet, so risk starvation.

 

The study has been conducted by a team of scientists from Aberdeen

University and the Scottish Agricultural College (SAC) in Inverness.

 

The porpoises themselves do not mind warmer waters, but the sand eel

is becoming less abundant.

 

It makes you wonder how many more hidden impacts of climate change

there are for whales and dolphins

 

Dr Colin MacLeod

Aberdeen University

 

Porpoises are affected by humans in a number of ways including by-

catch in fisheries, pollution and noise in the ocean.

 

The new study, published this week in the Royal Society journal

Biology Letters, has found the animal could also be affected by

climate change.

 

Research on seabirds has shown there is a strong link between

breeding success, survival and the abundance of sand eels.

 

However, unlike seabirds that only eat sand eels, it had been assumed

that harbour porpoises would simply switch to eating other fish

species when sand eel numbers fell, without suffering any ill

effects.

 

Bad news

 

By examining the stomach contents of stranded porpoises from the east

coast of Scotland collected each spring between 1992 and 2001,

researchers found that at this time of year, harbour porpoises rely

heavily on sand eels for food.

 

When they looked at stomachs from animals that died in the springs of

2002 and 2003, they found they contained many fewer sand eels and

much less food overall.

 

To work out whether this was affecting the porpoises' well-being, the

information was compared to the results on stranded porpoises

conducted by staff from SAC in Inverness.

 

 

Scientists say the implications spread beyond the North Sea

 

The results showed that while only 5% of stranded porpoises had died

because of starvation in the late 1990s, 33% of stranded porpoises

had starved to death in the springs of 2002 and 2003.

 

Researchers say it is bad news as if, as predicted, the waters of the

North Sea continue to warm, the numbers of sand eels are expected to

continue to decline.

 

Colin MacLeod, the scientist at Aberdeen University who led the

research, said: " Harbour porpoises are already affected by humans,

and this latest research shows that we have yet another thing to

worry about when trying to conserve them.

 

" The problem is that climate change is not like by-catch or chemical

pollution that can be solved at a local or regional level, it's a

global issue that is affecting porpoises at a local level.

 

" This was not an effect of climate change we expected for harbour

porpoises. It makes you wonder how many more hidden impacts of

climate change there are for whales and dolphins. "

 

'Difficult task'

 

The scientists say the implications of their research spread well

beyond harbour porpoises in the North Sea.

 

Dr MacLeod explained: " Climate change is altering sea temperatures

throughout the world and so many species of whales, dolphins and

porpoises are being exposed to similar changes in local temperatures.

 

" However, in many cases we do not know what prey the animals are

eating or whether these prey are as sensitive to changes in water

temperature as sand eels.

 

" This makes the already difficult task of conserving the many

threatened populations and species of whales, dolphins and porpoises

even more so.

 

He added: " It also makes it very clear that to save the whales, you

also need to save the fish, squid and other animals they rely on for

food. "