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The four native species of crayfish
in Romania prefer two types of water: the
narrow-clawed crayfish prefer stagnant or slow
flowing waters, whereas the
noble crayfish, the
stone crayfish and the idle crayfish prefer sub-mountainous and mountainous rivers. Their claims
for water quality must be considered in close relation to the species, thus the
narrow-clawed crayfish will tolerate poor water quality as compared to the other
two species (therefore, it is best represented in Romania). Crayfish who prefer
the rivers are the usual victims of outfalls that occur in the river bed.
Basically, the people of almost every village consider the river that is running
through their backyard a "dumping ground" rather than a habitat ...
(unfortunately). As crayfish do not migrate as fast as fish, even if the water
is occasionally affected by pollution, crayfish will suffer. The most dangerous
forms of pollution are the discharges of substances such as detergents,
solvents, insecticides, fuel, cement, lime, ash, sawdust and other similar
substances. In a stream where such substances are discharged, the level of
mortality can reach 100 % in downstream, the hope for recovery remaining in the
river upstream of the source. If we admit that some people, finding easy to
catch crayfish in a stream, can collect almost the entire population, crayfish
extinction is thus very possible. An advice: crayfish were consumed for
thousands of years ... but the wilderness of those days has gone, today it
requires caution DO NOT EAT CRAYFISH FROM THE
BROOKS! (you can see
here
a shocking record of what remains after a "grill"). |
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Non-indigenous species |
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In the late nineteenth century, a few species of crayfish were brought
to Europe in order to be farmed. Obviously, no one anticipated the
time to come, namely crayfish individuals "escaping" from farms and
invading natural territories. Because they are resistant and
prolific species (from North America and Australia) that were
imported, invasion took place quickly, Europe being on the brink of
uncontrollable circumstances for the disappearance of native
species. Actually, a way to stop them has not been found yet. In
some lakes and ponds a powerful insecticide can be applied to kill
every animal, including crayfish, but this is not a widely
applicable solution. At present, Romania is affected by
spiny-cheek crayfish identified in the
Danube. Individuals belonging to the native
narrow-clawed crayfish begin to
lose their populations. Another source of new species is the
Pet-shops which sometimes sell crayfish for aquariums. When crayfish
from their aquarium become too big or too aggressive, some aquarists
(out of ignorance believing that they do a good deed) decide to
release them in the river. This is fatal, because that whole river
is then convicted for medium and long term.
An advice: for no reason DO NOT RELEASE CRAYFISH FROM AQUARIUM IN NATURE, no matter how radical the advice appears, it is better if you euthanize them (one way is by freezing). |
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Crayfish plague |
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Even crayfish can become ill. Several diseases, which are more or less
dangerous, are known, but when the most dangerous ones come back
into focus, the non-indigenous species problems draw our attention
again. Along with the crayfish, it was also the
crayfish plague
(scientific known as
Aphanomyces astaci) that was brought from North America.
European species have no immunity to it and die. It should be added
that for the American species the crayfish plague has no effect,
they are immune to it. Therefore, the recipe for ecological disaster
is complete... there is non-indigenous invasive species that still
bears this plague. Moreover, the plague is spreading with water or
other equipment which may have an effect even where invasive
crayfish has not yet entered (the final effect being the total
mortality of the river). There is no treatment, only prevention.
An advice is too much to say ... (I would like to know what should be done), the only measure is not "helping" the plague, namely: do not enter into brooks with boots or other equipment that was potentially infested (the Danube is one of them), and certainly do not move crayfish from their natural place. |
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