Flood-Pulse Influences on Fisheries Yields in the Lower Amazon

Seasonally fluctuating water levels, known as ‘flood-pulses,’ drive the generally high productivity of large river fisheries that provide food and income to millions of people globally. Yet, the extent and mechanisms through which flood-pulses influence fisheries yields are poorly understood.  River water levels and fisheries yields and effort data for a total of 41 fish species from the Amazon Basin were analyzed using generalized linear modeling techniques.  Drought intensity two years before fishing took place, fishing effort, and habitat explained most of the variability in fisheries yields encompassing all 41 species (R² = 0.899, p < 0.0001), indicating flood-pulse influences on multispecies fish yields.  More of the variability in annual yields was explained by effort and flood-pulse indexes for species grouped per habitat trait (R² = 0.9) than by feeding trait (R² = 0.78), indicating that habitat traits better explain fish population responses to flood-pulses than feeding traits.  Finally, drought intensity two years before fishing took place explained variability in annual yields in seven out of nine different models across a range of feeding and habitat traits, indicating that droughts have a stronger effect on fish biomass than floods.