Inter‐decadal variation in diadromous and potamodromous fish assemblages in a near pristine tropical dryland river

Abstract Freshwater ecosystems are both incredibly biodiverse and highly threatened globally. Variation in environmental parameters including habitat flow can substantially affect many ecological processes within riverine aquatic communities, but the ties between such ecology neither well studied nor understood. In variable tropical dryland river systems, assessing relationships requires data collection over inter‐decadal time scales, which is not typically permitted on development schedules driven short periods (including election funding cycles). Here, we used seine net sampling collected an 18‐year period Fitzroy River, Western Australia, to assess how temporal factors habitat, seasonality, inter‐annual variation wet season magnitude community assemblage structure, recruitment, growth of species rivers. Results demonstrated that macrohabitat (main channel vs floodplain creek) rains resultant flooding had a substantial influence biotic alongside seasonal diel variation. The (measured as discharge volume) greatest impact composition creek habitats was significant driver recruitment rates recruits adults several examined. This study highlights key considerations for conserving systems constituent biota. Specifically, these maintaining (a) rhythmicity each year, (b) diversity volume years, (c) variety types ephemeral, semi‐permanent, permanent shallow deeper main pools, order support diverse array generalist specialist diadromous potamodromous fishes.