Stillwater is attending the 52nd Annual Cal-Neva AFS on February 28-March 2nd!

Stillwater is attending the 52nd Annual Cal-Neva AFS in San Luis Obispo on February 28-March 2nd!  Oral and poster presentations along with abstracts are listed below:

Sessions and oral presentations:


Entrainment Risk for Rainbow Trout at a Hydroelectric Turbine Intake in the South Fork Rubicon River, California Ethan Bell and Ken Jarrett, Stillwater Sciences

Little information exists on the risk of entrainment in hydroelectric turbine intakes for natural populations of riverine trout.  This study focuses on the effects of a turbine intake in Robbs Forebay on a resident Rainbow Trout Oncorhynchus mykiss population in the upper South Fork Rubicon River.  The goal of the study was to determine if entrainment is occurring, and if so, what the overall effect of entrainment is on the population of Rainbow Trout.  Nearly 1,000 Rainbow Trout were tagged with Passive Integrated Transponders (PIT) tags, and monitored for 15 months in 2015 and 2016, using repeated sampling of riverine habitat, and multiple stationary PIT tag arrays positioned throughout the forebay; including antennas on the intake screen.  Most fish that were detected or recaptured remained within the river (154 fish, 15.4% of all tagged fish), while only 33 (3.3%) of the tagged population migrated downstream to the forebay.  The fish detected moving downstream into the forebay were substantially smaller (age-0 based on fork length) than fish that remained in the river.  Of the Rainbow Trout PIT tagged in the South Fork Rubicon River, 9 were observed as entrained in the intake, with an extrapolated annual entrainment rate of 9.5 fish per year; equating to an estimated annual entrainment rate of 0.95%.  Based on the low rate of downstream migration, and a robust population of Rainbow Trout in the South Fork Rubicon River, it does not appear that the measured low annual rate of mortality from entrainment at the Robbs Peak Intake has a substantial effect on the population in the South Fork Rubicon River.


The Effects of Prolonged Drought on Southern Steelhead Trout in a Coastal Creek, Los Angeles, California Ethan Bell, Stillwater Sciences and Rosi Dagit, RCD of the Santa Monica Mountains

Long-term lifecycle monitoring of federally endangered southern steelhead trout Oncorhynchus mykiss in Topanga Creek provides a unique opportunity to examine the health and abundance of a steelhead population before (2008–2011) and during (2012–2016) a prolonged drought. We found that the five-year drought resulted in a substantial and significant decline in available wetted habitat suitable for rearing and upstream migratory access for anadromous adults. The response of the steelhead population has been a significant reduction in anadromous spawning, distribution of rearing, and abundance of all life stages of anadromous and resident steelhead. After five years of drought a population that exceeded 325 individuals in 2008, now numbers fewer than 50 fish, and appears to be at extremely high risk of extirpation. Acknowledging the possibility of increased drought regionally and globally, the need to bolster southern steelhead resiliency to additional disturbance is paramount.


Reintroducing Arroyo Cub to the Arroyo Seco Wendy Katagi, Stillwater Sciences
The Arroyo Seco Watershed, a tributary to the Los Angeles River, has been a hub for utilizing integrated watershed management approaches to address issues of native fish recovery efforts while addressing TMDLs, post-fire recovery, water resource management, and recreation objectives.  Stream restoration efforts in the Central Arroyo Seco provide habitat for native fish and amphibians, including reintroduction of approximately 300 Arroyo Chub Gila orcutti, a California Species of Special Concern, and water quality improvements. Habitat restoration components incorporated vegetation management, such as removal of non-native/invasive plant species in upland and aquatic habitats and revegetation with native plant species; sediment management, including bank stabilization, trail upgrades, and erosion control; and fish and wildlife habitat creation, including scour holes, backwater pools, snags, spawning areas, and riffles. In addition to these ecosystem benefits, the project also provided full capture trash inserts in every storm drain in the City of Pasadena, native plant community/stormwater islands in the Rose Bowl Parking Lot I adjacent to the creek, and education/stewardship opportunities to assist with stream monitoring. Targeted efforts to improve native fish habitat demonstrate that science-based approaches that mimic or restore natural processes and conditions provide the greatest opportunity for restoration and renewal of our urban streams. 

Following reintroduction, Arroyo Chub progeny have been observed in the backwater pools of the southern restoration area.  Fishery biologists were encouraged to see young Arroyo Chub in this stream.  Other native fish, such as trout and stickleback, may be introduced in the future as the stream regains its natural form and function. The restoration project has attracted statewide interest due to the success of this stream restoration within an urban setting.  Native fish, as target species for ecosystem restoration projects in this watershed and nearby southern California watersheds, have become more prevalent in recent years.

Poster Presentations:

2017 McCormack-Williamson Tract Fish Rescue and Relocation Project Eric Sommerauer, Stillwater Sciences
During the morning of February 11, 2017, the Mokelumne River overtopped the McCormack-Williamson Tract (MWT) levee system, creating a failure on the northeast levee and flooding the 1,400-acre farming island. A relief notch was excavated on the opposite side of the island along Snogdrass Slough, however despite this the impounded floodwater overtopped the levee system along Deadhorse Cut. The interior of MWT remained connected to the river system until the Mokelumne River breach was repaired on May 31, 2017. During this time, aquatic species, including several special-status fish species (e.g., Delta Smelt, Longfin Smelt, Green Sturgeon, Central Valley steelhead, Central Valley fall- and late-fall run Chinook Salmon, and Sacramento Splittail), had the potential to enter MWT. Dewatering pumps installed at the southern end of the island began operating on June 8th, 2017 and continued operating until July 6, 2017. In an effort to save fish stranded at MWT, a rescue and relocation effort was conducted from July 6-14, 2017. Approximately 168,000 fish were rescued and relocated during the MWT Fish Rescue and Relocation Project, comprised of five native and 16 non-native species. The rescue and relocation strategies and methods employed during this effort are applicable to future large-scale flooding events at locations comparable to MWT.

Identifying Drivers of Fish Assemblage Dynamics in a Hydrologically Altered Lagoon Henry Baker and Noah Hume, Stillwater Sciences
The Santa Clara River Estuary (SCRE) near Ventura, California has historically supported a variety of native fishes including the federally endangered Tidewater Goby Eucyclogobius newberryi and southern California steelhead (anadromous Rainbow Trout Oncorhynchus mykiss). Based upon long-term monitoring data collected by the City of Ventura, a number of non-native species have been identified in the estuary. Fish assemblage composition in the SCRE, including the relative abundance of native vs. non-native fishes, appears to be highly dynamic. A common sense hypothesis is that this high variability in assemblage composition can be attributed to the variable hydrologic nature of the SCRE. In normal water years (i.e. when annual precipitation approximates long-term average), the SCRE is a closed-mouth lagoon during the summer, with tertiary-treated effluent from the adjacent Ventura Water Reclamation Facility (VWRF) as the predominant input, and little to no input from the Santa Clara River. Depending on upstream dam operations, the Santa Clara River is typically the dominant source of water to the SCRE during winter, with larger precipitation events carrying flows sufficient to breach the beach berm at the mouth of the Santa Clara River. This flashy hydrology results in seasonally variable habitat quantity and water quality in the SCRE due to the interactions between river flows, VWRF flows, and ocean water exchanges. Similarly, annual variations in precipitation can result in interannual variability in habitat conditions. However, univariate analysis of environmental parameters fails to sufficiently explain seasonal and annual variability in fish assemblage composition. Using previously reported and novel data, we performed multivariate analysis of a suite of environmental parameters to identify key drivers of fish assemblage dynamics in the SCRE. Implications for management of native species are discussed.