Continued Gizzard Shad (Dorosoma cepedianum) Range Expansion in the Colorado River Basin

Gizzard shad (Dorosoma cepedianum) was introduced to the Colorado River basin in 1996 as a result of unintentional stocking. It then rapidly spread into lakes and rivers in both the upper and lower Colorado River basins. We captured adult gizzard shad in the Yampa and White rivers in Colorado in 2012 during boat electrofishing surveys not specifically targeting gizzard shad. These captures document the range expansion of gizzard shad into these Green River tributaries. We also collected larval and young-of-year gizzard shad during seining surveys in backwaters of the middle Green River in 2012, thereby confirming that this species successfully reproduces and recruits in the Green River. The introduction and expansion of gizzard shad has the potential to negatively affect sport fisheries and native fish communities in the Colorado River basin.