Aquaculture for all

Unmodified Water Releases Impact Spawning Areas

Salmonids Sustainability +2 more

US - Despite repeated warnings, a government agency failed to modify water releases from a California reservoir, resulting in the loss of fall-run Chinook salmon, which are a "species of concern" under the Endangered Species Act.

The United States Bureau of Reclamation (USBR) did not modify water releases from the New Melones Reservoir in Tuolumne County, resulting in salmon spawning in side channels that were inundated with high flows, according to work conducted by FISHBIO, a research fishery team of scientists, based in Oakdale, California.

Water releases throughout the year did not create enough space in the reservoir to avoid high fall flow conditions. As a result, at least 23 redds (areas where salmon nest and spawn) between Knights Ferry and Orange Blossom Bridge on the Stanislaus River have been dewatered and the salmon eggs lost. These 23 redds appear to account for more than 10 per cent of the total number in the area on the river, and that number may grow as evaluation continues.

"This loss is unfortunate and could have been prevented," said Kevin Kauffman, General Manager of the Stockton East Water District. "The USBR refused to modify releases from New Melones despite repeated warnings," he said.

Fall-run Chinook salmon represent the only race of salmon that spawn in the Stanislaus River. Fall-run Chinook salmon need flow rates of approximately 300 to 500 cubic feet per second of water flow beginning in early October each year, to maximise spawning success.

"This year, the USBR maintained flows in excess of 2,000 cfs until November 2nd," stated Jeff Shields, General Manager of the South San Joaquin Irrigation District. "These salmon spawned in areas where the high flows covered the redds," he added. "When the USBR reduced the river flows, the redds became dewatered."

The three water districts – OID, SSJID and SEWD – have asked the USBR to provide an explanation for the reasoning behind the flow changes that destroyed the redds. "To date, the Bureau has not responded," noted Mr Shields.

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