Page 47 - Bulletin, Vol.79 No.1, February 2020

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crustaceans cannot cross the ridges , it is possible that there was some kind of
communication between valleys due to other geological movements.

It is also possible that some species were transported by animals – which is apparently
“natural” – or by man. It is known that carp have travelled extensively for millions of
years to stock fish ponds, and many other species, such as the cyprinids, certainly used
the same means … at the time no records of such transfers were made. It is
nevertheless true that carp are considered as a native species when this is obviously
not the case.

th
Since the 19 century the introduction of species has intensified: catfish, silure, perch,
rainbow trout, brook trout, black bass etc. as well as salmon species from North
America but do not seem to have been naturalized. Other species arrived “naturally”,
such as gremille, common nase, as well as pike-perch.

As for the wels catfish …? It should not be forgotten that many connections were
created between rivers by building canals, which opened the way for the passage of
many species, native or not. The network of European canals, a large blue web,
provided a motorway for the circulation of many different species! Thus, the Rhone
valley is connected to the Danube via the Rhine.

Within this area, 62 species of fish have been identified, 45 of which are native – or
thought to be – while 18 have been introduced. Contrary to what is commonly believed,
there is no evidence at all that the introduction of these species caused the
disappearance of the native species. If the number of certain fish has diminished, it is
due mainly to the construction of large dams (diadromous fish), pollution and building
artificial waterways for navigation.

Our fish population is therefore a “melting-pot” of species that survived the ice ages,
species that benefited from hydro-climatic events to repopulate spontaneously rivers
and bodies of water, species that were accidentally or voluntarily introduced for profit or
leisure. Chance and other circumstances played a major role in this haphazard
coexistence of species who found conditions that favoured their development. Climatic
changes that are now being observed will probably modify the ecological characteristics
of our aquatic systems that are robust and adaptable to either the addition or the
disappearance of different species; this is what they have always done.

There is no evidence to suggest that the fauna of today are an intangible group or that
the recolonization of Europe after the ice age is yet complete. We should look carefully
at our waterways: this is not a virgin or static ecological system resulting from a long
history of evolution. This is a system weakened by climatic changes and, frequently, by
human activities for multiple purposes (energy, navigation, sports) or to prevent
flooding, without mentioning all kinds of pollution and a galloping urbanization.

The future must be envisaged on the basis of these facts, not by sustaining the myth
that nature would be beautiful without mankind. To wish to keep things as they are at

1 Fédération des Sociétés de Pêcheurs Genevoises – info-pêche N°80 – février 2018 Région de
Lucerne

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