RESEARCH is being carried out into why the population of seals is so low at the Teesmouth estuary on the North-East coast.

Seals were driven away by industrial development and human disturbance early in the 19th Century. They returned more than 150 years later, the first European example of seals re-establishing themselves in an industrial area.

The colony has been increasing ever since and this year there are 73 adult common or harbour seals and more than 20 grey seals.

The common seals have produced five pups, all of which survived, the most they have produced in a year.

However, the number is still low and Rebecca Turner, research officer with the Industry Nature Conservation Association (Inca) at Billingham, Teesside, has been investigating the seals' diet as part of attempts to discover a reason for the poor breeding performance.

By discovering what they eat, she will know which species to concentrate on when trying to find out if pollution is a factor.

Ms Turner said: "We are delighted there have been five healthy pups born this year, which is the most we have seen since the seals returned to Teesmouth. However, we would expect the number of pups born each year to be about 20 per cent of the seal colony so it is still low.

"There could be several reasons - the colony is still young so it may have taken time to settle, there might have been a shortage of breeding females or it could have been pollution.

"My research has set out to find what the seals are eating and has confirmed they are opportunistic and there is healthy fish in the estuary.

"Having knowledge of the diet of seals enables pollutant analysis to be conducted on the prey species."