http://www.theargus.co.uk/archive/2...6707641.US_fish_is_a_threat_to_our_ecosystem/
A dangerous American goldfish could wipe out whole species of its weaker English cousins.
Scientists are studying the aggressive pumpkinseed fish, which sometimes kills and eats its own kind, to learn how to stop it attacking the natural habitat of English fish and devouring their young.
The fish, named because of the colour of its fins, has already escaped into the wild and is spreading across Sussex.
It is known for its ability to eat anything and for its cannibalistic tendencies.
A pumpkinseed fish which started off in a tank of nine and is the only survivor of a long battle involving group bullying and physical attacks, is being kept in the Worthing office of the Environment Agency, a partner in the study to track the fish's habits and work out whether steps need to be taken to eradicate it from English waterways.
Working with the Centre for Environment, Fisheries and Aquaculture Science (Cefas), the agency is tagging selected fish in the River Ouse with miniature radios to track their progress. The team is also monitoring diet, breeding habits and ability to survive in colder rivers.
The pumpkinseed fish, which grows to 20cm, was first brought to the UK as an ornamental fish about 100 years ago.
Since then it has been escaping from ponds and lakes during flooding or because owners, fed up with it eating its own kind, have released it into the wild. Its sale and purchase are now banned without a licence.
The fish's progress across the country has been slow - it is believed to be mainly present in East and West Sussex - but some have also been spotted in Cambridgeshire and London.
The fish are omnivores and will eat the eggs and young of other fish.
Richard Horsfield, leader of the Sussex Environment Agency's ecological team, said: "They are present in such huge numbers.
"Because they are so wide-spread they virtually clear out the native species.
"We are talking thousands of fish out there now. We have got studies to look at their mechanism for survival and ways of eradicating them."
One group of fish tested in a primary school pond in Pease Pottage were found to have traces of the scales of other pumpkinseed fish in their stomachs.
The remaining fish kept by the agency is the winner of a programme of intimidation to kill off its tankmates.
Mr Horsfield said: "There were nine and gradually they picked on the less dominant fish and hounded them into the corner. They died one by one.
"Eventually the surviving fish did spawn with one of the others. It then pushed all the others up behind the pump.
"Then there were two of them, until one morning we came in and one was dead."
It is feared that as England's climate gets warmer, pumpkinseed fish could thrive in places they have not before.
Dr Gordon Copp, of Cefas, said: "They have been here for a long time. What we don't know is whether they have been having an effect on native species.
"If a fish like that is put in a situation and becomes very abundant they will eat all the available food around them.
"It is an aggressive fish, primarily around nesting time."
RSPCA spokeswoman Klare Kennett said there were often problems with people releasing unwanted pets into the wild.
She said: "We have got quite a delicate ecosystem. Any animal that isn't native to this country that is introduced to the wild will cause problems."
The agency would like anyone who sees a pumpkinseed fish in the wild to call them on 08708 506506.
A dangerous American goldfish could wipe out whole species of its weaker English cousins.
Scientists are studying the aggressive pumpkinseed fish, which sometimes kills and eats its own kind, to learn how to stop it attacking the natural habitat of English fish and devouring their young.
The fish, named because of the colour of its fins, has already escaped into the wild and is spreading across Sussex.
It is known for its ability to eat anything and for its cannibalistic tendencies.
A pumpkinseed fish which started off in a tank of nine and is the only survivor of a long battle involving group bullying and physical attacks, is being kept in the Worthing office of the Environment Agency, a partner in the study to track the fish's habits and work out whether steps need to be taken to eradicate it from English waterways.
Working with the Centre for Environment, Fisheries and Aquaculture Science (Cefas), the agency is tagging selected fish in the River Ouse with miniature radios to track their progress. The team is also monitoring diet, breeding habits and ability to survive in colder rivers.
The pumpkinseed fish, which grows to 20cm, was first brought to the UK as an ornamental fish about 100 years ago.
Since then it has been escaping from ponds and lakes during flooding or because owners, fed up with it eating its own kind, have released it into the wild. Its sale and purchase are now banned without a licence.
The fish's progress across the country has been slow - it is believed to be mainly present in East and West Sussex - but some have also been spotted in Cambridgeshire and London.
The fish are omnivores and will eat the eggs and young of other fish.
Richard Horsfield, leader of the Sussex Environment Agency's ecological team, said: "They are present in such huge numbers.
"Because they are so wide-spread they virtually clear out the native species.
"We are talking thousands of fish out there now. We have got studies to look at their mechanism for survival and ways of eradicating them."
One group of fish tested in a primary school pond in Pease Pottage were found to have traces of the scales of other pumpkinseed fish in their stomachs.
The remaining fish kept by the agency is the winner of a programme of intimidation to kill off its tankmates.
Mr Horsfield said: "There were nine and gradually they picked on the less dominant fish and hounded them into the corner. They died one by one.
"Eventually the surviving fish did spawn with one of the others. It then pushed all the others up behind the pump.
"Then there were two of them, until one morning we came in and one was dead."
It is feared that as England's climate gets warmer, pumpkinseed fish could thrive in places they have not before.
Dr Gordon Copp, of Cefas, said: "They have been here for a long time. What we don't know is whether they have been having an effect on native species.
"If a fish like that is put in a situation and becomes very abundant they will eat all the available food around them.
"It is an aggressive fish, primarily around nesting time."
RSPCA spokeswoman Klare Kennett said there were often problems with people releasing unwanted pets into the wild.
She said: "We have got quite a delicate ecosystem. Any animal that isn't native to this country that is introduced to the wild will cause problems."
The agency would like anyone who sees a pumpkinseed fish in the wild to call them on 08708 506506.
