Fish and fish-eating birds at the Salton Sea: a century of boom and bust

We reconstruct historical trends in both fish and fish-eating bird populations at the Salton Sea, California since the Sea's formation in 1905. The fish community has undergone dramatic shifts in composition, from freshwater species present in the initial wash-in to stocked marine species to dominance by an unintentionally introduced cichlid. Historical catch records, creel censuses, and gill-netting studies suggest that total fish biomass in the lake increased dramatically throughout the 1970s, crashed in the late 1980s, recovered in the mid-1990s, and crashed again in the early 2000s. We speculate that crashes in fish populations are primarily due to three physiological stressors—rising salinity, cold winter temperatures, and high sulfide levels and anoxia associated with mixing events. The trends in fish biomass are mirrored in population trends of both breeding and wintering fish-eating birds, as indexed by a number of independent bird surveys. In contrast, most non-piscivorous birds at the Salton Sea show no indication of these temporal dynamics. We discuss possible explanations for the observed trends in fish-eating bird populations, including decline in organochlorine insecticide use and fluctuations in prey abundance at the Salton Sea. Finally, we speculate on the future prospects of both fish and fish-eating birds at the Salton Sea given the environmental challenges the Sea currently faces.