5 Changes in Local Communities Since the Nineteenth
Century
Several studies have analysed changes in composition of fish communities in
different localities of the Seine River basin since the late nineteenth and early
twentieth century. Such studies relied on historical sources and more recent scientific
sampling data [7, 26, 27], and, overall, they examined community changes in about
30 river stretches with varying environmental characteristics (i.e. from small rural
rivers to the lower Seine River). Although the data and methods used in these studies
were not always similar (e.g. analysis on taxonomic structure or consideration of
functional traits, species presence/absence or integration of relative abundance data),
a number of general trends can nevertheless be highlighted regarding the long-term
trajectories of fish communities (Fig. 4).
These studies concluded that long-term changes vary greatly depending on the
local natural and anthropogenic conditions. However, they also suggest that the most
significant changes have been observed in both streams and larger rivers, while
communities in mid-size rivers have remained much more stable.
?
?
?
Current situation
?
2007
2011
2016
2011
2004
***
***
***
Confirmed presence
?
Possible presence
To be confirmed
Occasional observation
Occasional observation
evidence of reproduction
***
N
0
60 km
Fig. 3 (continued)
Changes in Fish Communities of the Seine Basin over a Long-Term Perspective
309
Century
Several studies have analysed changes in composition of fish communities in
different localities of the Seine River basin since the late nineteenth and early
twentieth century. Such studies relied on historical sources and more recent scientific
sampling data [7, 26, 27], and, overall, they examined community changes in about
30 river stretches with varying environmental characteristics (i.e. from small rural
rivers to the lower Seine River). Although the data and methods used in these studies
were not always similar (e.g. analysis on taxonomic structure or consideration of
functional traits, species presence/absence or integration of relative abundance data),
a number of general trends can nevertheless be highlighted regarding the long-term
trajectories of fish communities (Fig. 4).
These studies concluded that long-term changes vary greatly depending on the
local natural and anthropogenic conditions. However, they also suggest that the most
significant changes have been observed in both streams and larger rivers, while
communities in mid-size rivers have remained much more stable.
?
?
?
Current situation
?
2007
2011
2016
2011
2004
***
***
***
Confirmed presence
?
Possible presence
To be confirmed
Occasional observation
Occasional observation
evidence of reproduction
***
N
0
60 km
Fig. 3 (continued)
Changes in Fish Communities of the Seine Basin over a Long-Term Perspective
309