The Lower Putah Creek Coordinating Committee discussed the high fatality rate of salmon at their regular meeting on Dec. 9.
When the salmon reached the bottom of apuran Creek, low water quality killed the majority of the salmon.
“The fish die off is unprecedented to our knowledge,” said streamkeeper Rich Marovich.
Alix Rabidoux, Principal Water Resource Engineer at Solano County Water Agency, presented a timeline of the salmon’s migration path and changes to the water quality.
Rabidoux described the work that they had done to clear the pass of salmon leading to their arrival in early November; however, salmon mortalities cropped up in Lower Putah Creek.
After noticing the fatalities, local agencies began analyzing the water quality. They noticed low levels of dissolved oxygen in the Yolo Bypass Toe Drain. The Toe Drain serves to manage the wetlands as the main supply source for fall flood up from October to December. Water from the Toe Drain is used until March or April to maintain the appropriate water levels.
Likely, the rain storm on Oct. 26 flooded the water system with plants and other debris. The presence of additional organic matter in the water caused oxygen levels to drop to near-zero level.
“No mortalities (occurred) higher up in the system,” said Rabidoux. “Really only in the Yolo Bypass.”
A variety of agencies are collaborating to try and increase water quality for any remaining salmon making the run.
“We hope to save the salmon run this year, but the longer term (benefit) is this is the practice run so that we’re ready for next time” said Max Stevenson, who will replace Marovich as streamkeeper.
At the meeting, Marovich gave his final streamkeepr’s report after 21 years in the position. He highlighted the LPCC’s successes in his years on the job including efforts to ensure that the salmon population could be self-sustaining, controlling invasive Himalayan blackberries, and removing large, flammable eucalyptus trees.
Marovich thanked the committee members, “for all you’ve done and all you continue to do for Putah Creek.”
The committee directed Stevenson to pursue new grants. One offers $6 million to support efforts to reduce the effects of drought on wildlife and fish. Stevenson suggested that the funds could help create longer-term solutions to prevent further salmon fatalities. The second, a FEMA-grant, is aimed towards wildfire relief.