That is the view of the Loughs Agency who say that rising fish stocks combined with a lack of natural predators has led to an increase in the number of seals in the river.

An agency spokesman said that seals are nesting closer and closer to population centres.

Seals have been spotted taking up residence close to Prehen Boat House, at the pontoon near Derry City Council's offices and at Greencastle pier.

"We know that there are hundreds of seals in the River Foyle, there could even be thousands, he said."We intend to run a population to determine their exact number.

"Seals in the Foyle are a lot more noticeable due to the population explosion that has occurred. This is due to plentiful food supplies and the fact that seals do not have many natural predators."

The Agency spokesman said that the presence of seals in the river was a good indicator of the Foyle's overall good health.

"The presence of seals is a good sign, he said. "It is an indication that fish stocks are good and points to the fact that the water quality is good.

"Although seals do tend to be good natured there are exceptions and we would encourage people not to go
near them."