Do highly anthropized hydrological conditions in marshes influence fish communities according to their life‐history strategies?

AbstractAlterations of natural hydrology in aquatic ecosystems are known
to strongly impact the community composition of different taxa.
Surprisingly, literature on the potential influence of hydrology on fish
community composition is still very scarce in agricultural marshes, where
canals represent one of the few remaining aquatic habitats. This study is
aimed to address this research gap by monitoring fish communities in
independent hydrological units differing in hydrology management over a
6 years period. We predicted variable fish responses to the hydrological
context according to different life‐history strategies (opportunistic,
equilibrium, or periodic species). Periodic and opportunistic species were
the most frequently observed. Despite differences in hydrology between
canals (but little variation over years), we found that hydrology
explained only a very low proportion of variation in the composition of
fish communities. In particular, the flooding duration of meadows in early
spring did not influence the composition of fish communities, not even the
abundance of periodic species expected to rely on such temporary habitats.
Instead, fish communities were more influenced by local habitat variables
(aquatic vegetation cover, turbidity, tree roots, and refuges under the
canal banks). The hydrological management of most hydrological units for
agricultural purposes (i.e., severe flood abatement in spring and shallow
water depth in canals in summer) was found to be incompatible with
conservation goals to promote more diverse fish communities between
hydrological units. Therefore, we call for further investigations in
similar habitats covering a larger range of hydrological conditions.