WWF-Eastern Africa Regional Programme Office (WWF-EARPO), through its freshwater programme, began the task of establishing the Reserve flows for Mara River in 2006. The first two site assessments covering three sites were conducted in March and July 2007 by a team of specialists comprising a geomorphologist, hydrologist, hydraulic engineer, aquatic ecologist, riparian ecologist, water quality specialists, and socioeconomist. The first Reserve flows for the river were prescribed in October 2007 during the EFA workshop held in Narok, Kenya. At this workshop it was also agreed that continued monitoring of the river’s flow levels and ecological status is critical to improve the accuracy of the prescribed flows. The present work reports on the results of a fish sampling exercise conducted in February 2009 during the third assessment for the Mara River. The assessment covered one additional site in the Nyangores River and coincided with the period of low flows in the Mara River.