A MAJOR pollution scare was sparked off in York after dead fish were found floating in the River Foss.

The Environment Agency sent officers to investigate after people called in worried that they could have been killed by pollution.

Around 20 dead fish of several varieties including roach, chub and pike were found in the river at Skelton but thor-ough tests showed they had been killed by naturally occurring low oxygen levels, and not pollution.

Darren Starkey, environmental protection officer for the Environment Agency, based at York, said: "We got a report of some dead fish and sent an officer out there to take various samples.

"He took readings for dissolved oxygen in the water and it was extremely low.

"There were around 20 dead fish so we're not talking about a major ecological disaster and there were also large numbers of live fish.

"The Foss is a river which is rich in nutrients with quite prolific weed and algae growth.

"The weeds photosynthesise by releasing oxygen into the water during the day and taking it back in at night.

"When we have a few bright days followed by a dull day the amount of oxygen the weeds take in during the night is more than that which is made during the day and some of the weaker fish suffer.

"The fish are also spawning at the moment which makes them weaker."

Mr Starkey said the problem was nowhere near as bad as in other years such as the drought of 1995 when several thousands fish died in the River Foss.

But he was keen to urge people to continue reporting dead fish sightings as they do not always have a natural cause.

He said: "Although this is a natural occurrence and all part of the river's ecosystem we still want people to phone in if they see dead fish.

"We don't want people to assume that lack of oxygen is the cause as it may not be and we'd rather have ten calls like this than miss something we should be dealing with."

The 24-hour freephone number for the Environment Agency is 0800 807060.