Pima County, Sonoran Institute Plan Fish Survey for Lower Santa Cruz River

On November 9, staff from Pima County’s Regional Flood Control District, Regional Wastewater Reclamation Department and Office of Sustainability and Conservation and the Sonoran Institute will take part in a “Fish Survey” at four locations along the Lower Santa Cruz to determine which species are now found in the river. They will be joined by experts from the Arizona Game and Fish Department, University of Arizona, United States Geological Survey and United States Fish and Wildlife Service.

Improved water quality from Pima County’s wastewater treatment facilities has created conditions that now allow the Santa Cruz north of downtown Tucson to have a steadily increasing fish community — with four different fish species found in November 2015.

The team will start the survey in the riverbed near the Cortaro Road Bridge, then move along the course of the Santa Cruz to a site farther north in Marana. The process will involve delivering mild electrical shocks then gathering the fish in nets to be identified, counted and returned to the water unharmed. The survey team will repeat the process at several spots in each section of the river in order to account for the varying environmental conditions along the river, and because different species of fish prefer the faster-moving, open water in the middle of the river while others keep to the lush, more sedate vegetated banks. Though all species counted in the last three years have been non-native species, hopes are high for counting one or more native species that would have washed down from the upstream areas of the Santa Cruz River.

The existence of so many fish is almost entirely due to upgrades to Pima County’s two metropolitan wastewater treatment facilities, the Tres Rios Water Reclamation Facility (WRF) and the Agua Nueva WRF. The County began operations of the expanded and upgraded Tres Rios WRF and the new state-of-the-art Agua Nueva WRF in 2013 following a $605 million dollar project that came in substantially under budget. The Santa Cruz River downstream of the two facilities flows year-round through northwest Tucson and Marana, making it the longest stretch of river dominated by effluent in the state.

The media is invited to observe the process of the survey and will be given full access to the team with proper safety precautions observed. The team will gather at the Cortaro Road site at 8:30 a.m. on November 9. Additionally, photos and video of previous counts can be made available in advance of that effort.


Brian Powell, Office of Sustainability and Conservation, brian.powell@pima.gov, 520-724-6555

Claire Zugmeyer, Sonoran Institute, czugmeyer@sonoraninstitute.org, 520-290-0828 x 1143