Avila

INVADING SPECIES
They are species that are not native from the place in which they live.
Animals and plants that come from a foreign place and adapt in our
enviroment remaining here.
The causes of the introduction of these species can be involuntary. The
impact caused with the introduction of these species constitutes together with the
destruction of habitat,the principal reason for the disappearance of species.These
have different characteristics concerning mobility, bredding and sexuality.
The introduction of species can have an impact in the comunity of destiny because
of predatory habits, habitat alteration, illnessor parasite introduction and finally
because of the loss of biodiversited due to the hybrid species.
In the 20s a fish from the USA (gambusia) was brought. It was very
voracious for the larvae of the mosquito that caused the malaria.
In the 50s the pike ,so called “shark of sweet water”, appeared in our rivers. It
has teeth on the tongue, he can measure 1.5m and weigh 20kg. They brought the
pike to promote fishing sports.
Half the invading species that threaten the ecological balance are fish.
Other examples are: the black bass, the “percasol”,the “siluro”(river fish)
In the 80s the American crab (cambarus affinis say) that eliminated the
autochthonous crab (potamovius astacus). It has remained in high and low
parts of the rivers bringing a kind of fungus.
The autochthonous crab was a gastronomic and cultural resource that
generated substantial economic benefits.
In the whole thre are 26 invading species (fish) introduced in Spain.
IN AVILA
The vegetation of the Amblés Valley has been modified by diferent habitants.
The flat lands were covered by groves of evergreen but at present the
agrarian landscape predominates. Before, the inhabitants planted hedges,
and they went on changing the landscape. Together with the riversides, in
the high course there are willows, ash-trees and in the middle course the
"bardaguera" (wicker)grows.
The invading animals are the pike and the American crabs.

Soraya Jiménez & Carlos Casillas