Effects of freshwater input on nektonic community of a temperate Estuary. Management implications

Trabajo presentado en la Aquatic Biodiversity and Ecosystems Conference, celebrada en Liverpool del 30 de agosto al 4 de septiembre de 2015.A long term ecological research program is developed monthly at the Guadalquivirsince 1997 to date in order to assess the nekton (fish, decapod crustaceans)response to freshwater inputs (dam discharges) in a temperate estuary withregulated riverine inflow. River discharges are regulated mainly for economicpurposes. Such water management usually causes a decrease in the fresh-water input to estuaries and an increase in the residence time of suspendedmatter and organisms within estuaries altering estuarine natural hydrologi-cal regime. In other cases, whether discharges occur in summer for crop riceirrigation may also result in negative (osmotic stress due to salinity fluctua-tions) effects on larval and juvenile survival of marine species, especially forthose with a stronger salinity-related distribution. An additional negativeeffect of freshwater discharge was an unusually high and persistent turbidityevent which may negatively impact the nursery function of estuaries eitherby decreasing prey availability or by decreasing survival/arrival of marine re-cruits. The anthropogenic pressures that may stimulate unusual decreasingof salinity in the warmer season and the occurrence of high and persistentturbidity events (HPTEs) should be avoided in order to preserve the nurseryfunction of temperate estuaries.N