February 27, 2023 – Smallmouth bass are an invasive fish species threatening federally protected humpback chub and other native fish, and the Bureau of Reclamation is seeking public comment on dealing with the fish.  Comments are due March 10 on its draft environmental assessment.

The draft Glen Canyon Dam/Smallmouth Bass Flow Options Environmental Assessment presents four potential operational flow options aimed at preventing smallmouth bass from successfully spawning and establishing downstream of Glen Canyon Dam.  Despite recent storms, water levels in Lake Powell continue to decline to historically low levels, which has contributed to water being released at record high temperatures through Glen Canyon Dam. Below the dam, these warm water releases are creating ideal spawning conditions for smallmouth bass, a predatory invasive fish species.

To respond to the threat of smallmouth bass establishment below Glen Canyon Dam, the draft Environmental Assessment identifies various Glen Canyon Dam flow options designed to disrupt and prevent smallmouth bass from spawning in the Colorado River between the dam and confluence of the Little Colorado River. Reductions in water temperature combined with changes in flow velocity would be used to try and prevent smallmouth bass from successfully spawning and establishing downstream of the dam.