They are species that are introduced by an artificial way in an ecosystem. This species can cause some problems like the extinction of species from their own place and also can cause several plagues. We can see the following examples:
It is found in some parts of Spain. It comes from southeast Russia. Its name is because a stripped pattern on its shell. It has the shape of a fingernail, but sometimes can grow to 5 cm. It’s usually attached to rocks or others solid objects.
They are found in river Ebro but they are more diverse in South America, Asia and Africa and they live in freshwater environments and coastal waters. Their name come from the barbells which have the cat’s whiskers. Some of them have an armour-plated and they haven’t got scales. Catfishes are of considerable commercial importance because many of them are farmed or fished for food.
We have got this information from wikipedia.
SILVIA VINUES, JARA VILLAR, BEATRIZ AZNAR