Reproductive ecology of alligator gar, Atractosteus spatula, in a river-floodplain ecosystem of Arkansas

We studied spatial and temporal aspects of alligator gar (Atractosteus spatula) reproduction in the Fourche LaFave River system to provide data pertinent to the conservation of this declining species.  Spawning occurred in floodplain tributaries and generally corresponded with an increase in river stage during late spring/early summer due to flooding from the Arkansas River when water temperatures ranged from 22^oC to 27^oC.  Relative to 2008 and 2009, reproductive success in 2007 was high based on number of estimated spawn events (5), number of larvae/early juveniles observed (> 1,000), and abundance of older juveniles the subsequent fall.  In 2007, river levels were below flood stage preceding the spawning season and then increased to a high magnitude, long duration flood event during and following reproduction.  Reproductive success was absent or low during years when flooding did not correspond with warm temperatures or was of short duration.  Low-order, floodplain tributaries are undervalued elements of river networks, but they appear to be critical to the reproductive success of alligator gar. As predicted by the flood-pulse concept, reproductive success was highest when long- duration flooding was coupled with warm water temperatures during late spring and early summer.