The Eel River Recovery Project (ERRP) has successfully estimated the Eel River fall Chinook run since 2012, and each year is unique and has different challenges. The 2015-2016 citizen assisted monitoring project was the most difficult, however, because early rains failed and dives were not able to be scheduled, and then rainfall was so high after December 1 that observations of migrating and spawning Chinook salmon were limited for protracted periods.
Despite the El Nino conditions in the ocean that are usually linked to increased precipitation, rains from September through November were extremely sparse. Lower Eel River flows as measured by the U.S. Geologic Survey at Scotia did not exceed 100 cfs until November 11, which limited fish passage and prevented normal fall flushing of algae beds. Algae impairs visibility and harbors swimmers itch organisms. Consequently, dive surveys were restricted to the 12th Street Pool that is deeper and mixed by winds and other pools were surveyed by kayak.
Early run Eel River fall Chinook were confined to the estuary during late August and early September as flows at Scotia were only just over 30 cubic feet per second (cfs). ERRP documented movement of fish upstream as far as the 12th Street Pool by September 21 after light rains, but the major influx into lower river pools was with extremely high tides from October 22-24. Hundreds of Chinook salmon sat in shallow, algae infested pools and about 10% of early run fish went blind as a result of a fluke attacking their eyes.
Dives on October 31, November 7 and November 14 estimated that 920, 1000, and 1200 Chinook salmon were holding, respectively, with approximately 25% of the fish comprised of smaller jack salmon. This suggests good survival of juveniles from 2014-2015. ERRP estimated 5,000 Chinook salmon were holding in the lower Eel River from the 12th Street Pool downstream on November 14. Extensive Chinook salmon spawning in the main Eel River downstream of Dyerville was documented by ERRP from November 11 through December 1.
Before December 1, Chinook salmon access to headwaters was limited, with spawning on the main Eel below Dos Rios, the South Fork below Leggett, and the Van Duzen River downstream of Goat Rock Falls. After December 1, flows were adequate for access and spawners were seen in low numbers throughout the basin, including upper Outlet Creek, Ten Mile Creek, the Middle Fork and Black Butte River, and the upper South Fork near Branscomb. Lower South Fork Eel River tributaries showed a late fall Chinook run peak in mid-December. Chinook arrived at the Van Arsdale Fish Station on December 6, and only 102 fish passed upstream to spawn during the entire season. Spawners were noted in Ten Mile Creek and upper Outlet Creek, but none were seen in Tomki Creek (SEC 2016). ERRP once again found that sediment impairment limited spawning use of a number of other Eel River tributaries.
