Our study headwater ecosystem is the Lake Victoria basin of East Africa. This ecosystem holds world leading status for freshwater lake size, vertebrate diversity elaboration, species extinctions, exotic species invasions, and freshwater fishery production. It is high in elevation, the source of the Nile River, situated at the centre of the tropics, mostly enclosed by highlands and mountain ranges, and nearly a closed hydrologic system. The ecosystem is old but erratic in persistence on the scale of evolutionary time. Humans may have emerged in the basin, persisted there throughout human history, and recently increased to substantial density. However, the region remains undeveloped with meagre means of transportation, energy production, and industrial activity. Finally, this ecosystem is presently receiving heavy international development assistance including one of the largest and most costly ecosystem study programmes on earth. Lake Victoria has displayed massive ecosystem change in the relatively short three decade period thought to span an original intact system to one still foundering in unanticipated ways (Kaufman, 1992; Goldschmidt et al., 1993; Goldschmidt, 1996; Verschuren et al., 2002).