Eel River Ecology – Wildlife
Influence of river flow and temperature on O. mykiss
Our work has focused on understanding the influence of river flows (magnitude and timing) as well as its temperature on O. mykiss. O. mykiss are partially migratory, with some individuals migrating to the ocean before returning to the river to breed, and other individuals spending their entire lives in freshwater. Our key recent discoveries include that (1) both geomorphology (knick points) and river flows influence the distribution of migratory adults (high river flows at the right time facilitate upriver passage of migrating adults, Kelson et al. 2020 Molecular Ecology). Moreover, we have found that partial migration in O. mykiss (2) is influenced both by sex (females are more likely to migrate) and genotype (individuals with a migratory-genotype are more likely to migrate, Kelson et al. 2019 Canadian Journal of Fisheries and Aquatic Sciences) and (3) that partial migration has ecological consequences (in stream reaches where migratory genotypes dominated, we’ve found higher densities of young fish and lower densities of older fish, resulting in a simpler size structure, compared to when resident genotypes dominated, Kelson et al. 2020 Ecosphere). Finally, we have explored the importance of cold water plumes in warm mainstem rivers, created by cool tributary in-flows, as thermal refugia for cold-water fishes like salmonid fishes (Wang et al. 2020 River Research and Applications). Stephanie is a professor in Environmental Science, Policy, and Management at UC Berkeley.
Ecology and Conservation Biology of river-breeding frogs
California’s river breeding foothill yellow legged frog (Rana boylii), is frequently encountered when visitors to the Angelo Reserve walk along the banks of the South Fork Eel River. These sun-loving frogs bask on rocks and jump into the water at the sound of footfall. The population at the Angelo Reserve is robust, but this species is generally in decline, especially in the southern part of its range and where it occurs near large dams. Field observations and experimental manipulations conducted by Sarah Kupferberg at the Angelo Reserve since 1990 have enhanced our knowledge of this species’ adaptations for survival and its vulnerabilities when humans alter rivers by building dams and reservoirs and diverting stream flows.
During the spring breeding season, adult frogs migrate from the narrow shady tributaries like Fox and Elder Creek where they avoid winter floods, to wide shallow cobble bars on the margins of the sunlit South Fork Eel and Tenmile Creek. Because each female lays one clutch of eggs, the total number of egg masses serves as a proxy for the size of the population. Long term monitoring has revealed that several physically-based factors influenced by variation in streamflow may impair the ability of populations to produce new recruits. By studying the population of Angelo Reserve, Sarah and her colleagues have determined that changes to flow velocity and river stage during egg incubation which result in scour or desiccation influence the number of clutches found three years later, when that cohort of tadpoles would have matured into frogs ready to lay eggs for the first time.
Along with colleague Alessandro Catenazzi, Sarah reared tadpoles in enclosures the various streams on the Angelo Reserve, some warm and some cool, to quantify the extent to which water temperature and quality of algal food resources influence tadpole survival, growth and development. The results of these experiments are being used to inform dam management decision making where hypolimnetic releases from upstream reservoirs occur. Cold water released can slow embryonic development and thus extend the period of desiccation / scour risk; cool summer temperatures also decrease survival, decrease size, and increase time to metamorphosis. To reduce these mortality agents, in association with engineer Scott McBain, Sarah has developed a spreadsheet model to predict the hydrologic and thermal mechanics of breeding timing, embryonic and larval development. The model integrates knowledge of individual ecophysiological and behavioral responses to water temperature with channel morphology and stage discharge relationships. When applied to three different regulated rivers in California (Trinity, Tuolumne, and Alameda Creek) the model predicted that the effects of cooler summer temperatures on tadpoles may have more profound impacts than spring flow fluctuation effects on clutches of eggs.
Spring temp. and upstream migration timing of invasive Pikeminnow in Eel River
Phil Georgakakos studies the distribution of fish and other aquatic vertebrates and their interactions across riverscapes, and how they shift in response to environment conditions, resources, particularly in the context of a changing climate. The historical aquatic vertebrate assemblage of the Eel River has shifted largely in response to overfishing, habitat destruction, and other human-induced activities, and there have been numerous non-native species introductions- notably, the invasive Sacramento Pikeminnow.
As part of his PhD work, Phil conducted repeated snorkel surveys over a five year period at the Eel River in order to investigate patterns of variation in the aquatic vertebrate community through time and space. This study constitutes one of the most extensive survey efforts in space, time, and species of animal counted in a coastal California river. Generally, Phil has found that invasive animals were more abundant in downstream reaches and slower water habitats. Populations of native species tended to be denser upstream, especially in late summer, when invasive numbers are high downstream.
Identifying the drivers that favor native species expansion downstream can help guide restoration efforts hoping to shift assemblages towards more desirable historical states. Phil’s particular observations of the invasive Sacramento Pikeminnow migrating upstream during Spring and early Summer led him and collaborator David Dralle to develop a statistical model to forecast the timing and extent of upstream migration by pikeminnow in response to discharge and air temperature. In years with low flow and high air temperature, the model predicts that pikeminnow will move upstream earlier, overlapping (and competing) with native fishes for a longer period of time. This suggests a potential management technique of decreasing water withdrawals in years of high temperature/low flow in order to keep river temperatures cool, limiting the co-occurrence of pikeminnow and rearing salmonids.
In addition to understanding the negative impacts for native animals that occur in the novel communities created by species introductions , Phil is interested in understanding how altered species interactions, particularly reduced positive interactions influence native species. In Northern California, Pacific Lamprey seasonally enter the coastal rivers in order to spawn. As part of his dissertation, Phil investigated how bioturbation during lamprey redd (spawning nest) construction influences invertebrate drift, juvenile Steelhead foraging behavior and growth potential, and the effects of built lamprey redds on local water velocity.
Phil and his collaborators Gabe Rossi and Sarah Kupferberg have found that drifting invertebrates are more numerous and more concentrated downstream of redd building lamprey, increasing the foraging profitability of juvenile steelhead. He also found that lampreys’ redds can create velocity refugia for aquatic species, as the flow velocity is lower in the bottom of the redd depression. Phil’s observations suggest that this lower flow velocity (as well as other properties of Lamprey redds) may be exploited by foothill yellow-legged frogs who the use the redds as egg mass deposition sites. Overall, Phil’s observations suggest a number of positive interactions that may alter the population dynamics of species interacting with spawning lamprey in the Eel River.
Phil is a former PhD student in the Integrative Biology Department at University of California, Berkeley, and recently started a Postdoc position with Prof. Ted Grantham in the Dept. of Environmental Science, Policy, and Management at UCB.
In his current position, Phil and Ted Grantham are investigating how water withdrawals for cannabis cultivation in the South Fork Eel River influence river flow, temperature, and aquatic organisms. They plan to model the impacts of withdrawals on flow and use these calculations to determine when and where river temperatures might be impacted. Using the results of their modeling work they will also study how changes in these physical characteristics will alter species distributions of aquatic organisms and key ecological interactions. Phil will also continue working with Dr. Mary Power to monitor the movement and distribution of invasive fish and frogs in the upper South Fork Eel River. This monitoring builds on the work he started during his PhD, and aims to determine what factors encourage the spread of native species and inhibit non-natives.
Phenology and photo-documentation of common aquatic insects in the Eel River
Aquatic insects are some of the most abundant organisms in a freshwater river community. Most aquatic insects live under water as larvae (eating, growing and maturing), then metamorphose as flying adults,whose jobs are to disperse and reproduce. Many aquatic insects emerge synchronously, in large numbers over a short period of time.
Shelley studied emergence patterns of several common mayfly (Ephemeroptera), caddisfly (Trichoptera), moth (Lepidoptera), and true flies (Diptera) found along an eight kilometer reach of the South Fork Eel River at the Angelo Coast Range Reserve (Mendocino Co., CA). Notable synchronous emergence peaks were observed for Gumaga spp. (Sericostomatidae: Trichoptera) and a mayfly, Ephemerella excrucians (Ephemerellidae: Ephemeroptera) with a downstream to upstream emergence pattern. Interspecific temporal segregation was also observed between two mayfly species of Procloeon (Baetidae: Ephemeroptera). Habitat preference was also observed among sampling sites: Petrophila confusalis (Crambidae: Lepidoptera) only emerged over large stones and boulders; Heptageniid mayflies preferred emerging from flowing water and Gumaga and midges (Chironomidae) emerged in highest numbers from slow flowing water. Shelley also compared the efficiency of two different emergence traps.