Fish structure in channel networks of a large anabranching floodplain: effect of isolation/connection processes

ABRIAL, E.; ESPÍNOLA, L.A.; AMSLER, M.L.; RABUFFETTI, A.P.; LATOSINSKI, F.G.; SZUPIANY, R.N.; EURICH, M.F.; BLETTLER, M.C.M.

WATER RESOURCES RESEARCH

AMER GEOPHYSICAL UNION

Año: 2019

0043-1397

Channel networks of floodplain rivers are the main routes forwater, sediment, organic matter and aquatic organisms between main channels andlakes, playing a substantial role in floodplain dynamics. Despite theirimportance most investigations in large floodplain rivers focus on mainchannels and lentic water bodies. This research deals with fish assemblage variationsin different lotic sites (scour holes and straight reaches) of one of the many channelswhich shape the wide anabranching floodplain of the middle reach of the ParanáRiver. We considered the influence of environmental factors, such ashydro-geomorphological features and water quality of the channel, connections withsurrounding lentic water bodies, seasonality, and interannual flow variations. Theresults showed two main ecological patterns closely related to floodplainconnectivity. In-channel habitat heterogeneity has low influence on fishassemblages when minor channels are connected to significant flooded areas (samplingperiod 2013-2016). Spatial or temporal predictions of fish structure duringthese stages is not easy due to the interaction of several environmental factors.However, during very low water levels (winter of 2018) most lentic areas becomeisolated from the nearby channel network, and floodplain fish are forced to moveinto the numerous scour holes of the floodplain channels where water conditionsresemble those in lentic habitats. Our work highlights the importance ofin-channel characteristics of floodplain river networks and their crucial role forfish conservation, particularly during very low water stages.