Changes in the number, size and representativeness of fished species have been
observed for approximately 20 years.
It appears that the proportion of South-living and warm-water fish in French rivers
has increased from 20% and 40%, respectively, to 50% between 1979 and 2004. Whereas
large numbers of these small fish tend to become predominant within the
communities, large fish, more sensitive to the temperature increase, tend to
disappear little by little.