Juvenile Sturgeon: swimming behavior and physiology Much of the local-scale movement behavior of fishes is shaped by local environmental conditions such as water temperature and velocity. We are evaluating of the swimming capacity and physiology of juvenile Green and White Sturgeon under variable conditions, in order to inform protective screening guidelines at water-diversion points. We will construct endurance curves for multiple size-and age-classes at multiple water temperatures using fine-tuned laboratory swim tunnels. In addition to documenting time-to-fatigue for the juvenile sturgeon, we will use look at physiological indicators in blood samples to quantify and exercise-related stress and recovery. Finally, we are testing the lethal and sub-lethal effects of interactions with current fish protection screens used at west coast water diversion structures. Our goal is to provide a sound understanding of swimming behavior and physiology of juvenile sturgeon in order to support future management and conservation efforts.
Adult Sturgeon: swimming behavior As anadromous fishes, adult sturgeon migrate upstream through riverine environments to access spawning grounds. Yet many potential spawning grounds are inaccessible to sturgeon due to anthropogenic structures. Sturgeon have a unique morphology and swimming behavior that often precludes the use of existing fish ladders, yet little is known about what design features of engineered structures will best facilitate upstream movement of large sturgeon. We are working to quantify the behavioral swimming characteristics of sturgeon, including their response to turbulence flow features and the influence of roughened substrate, intending to provide improved guidance on the design and implementation of sturgeon-specific fishways.
Delta smelt: feasibility of acoustic telemetry methods The Delta smelt are an endangered fish endemic to the San Francisco Estuary. They are small fish, and notoriously sensitive to handling and other stressors, and as such have not been a candidate for acoustic telemetry research. With the ongoing miniaturization of acoustic tags we are exploring the potential of implanting adult smelt with new, smaller JSATS tags that are <2% of the body weight of the fish. We are devising new handling and tagging methodologies to improve post-tagging survival, as well as completing an evaluation of the sub-lethal impacts (behavior and swimming capacity) of the tagging process. We hope that by advancing this technology we will provide the tools necessary to understand habitat selection and movement behaviors of these endangered fish in natural waterways.
PAST PROJECTS Green Sturgeon guidance efficiency Much of the local-scale movement behavior we see in fishes can be related to environmental conditions such as local variation in water velocities. We assessed the movement of juvenile Green Sturgeon near a model fish guidance structure (louver) and its associated hydraulic flow fields. We considered effects of sturgeon size, water temperature, water velocity, and photophase (day or night). Our goal was to quantify the efficiency of the louver for directing this species away from the water-extraction pumps of the California State Water Project under standard operational conditions. We found that in our laboratory model, standard operations were more that 90% effective at guiding large juveniles (>16cm total length), but smaller juveniles were more vulnerable to entrainment under high velocity conditions. ---
Chinook Salmon We examined the potential for LED light to be used to alter behavior of migrating Chinook juveniles around unscreened water diversion pipes. We used a river-scale flume with flows and diversions designed to-scale, and tested the effects of different colors of light during both day and night. The Chinook did not respond to the strobing light cue, at any tested wavelength, during daylight hours. However, entrainment into the diversion pipe increased significantly during night hours when the white and blue light, suggesting potential for strobing lights to be used as an attractant to guide fish towards a bypass structure or fishway. ---
Vulnerability of juvenile sturgeon to common-use pesticides Individual movements are driven, in part, by a fish's past experience and present internal state. We are currently conducting an experiment to understand how exposure to common pesticides at early life stages shapes movement behaviors and their physiological underpinnings. This research focuses on ecologically relevant impacts of pesticide exposure on swimming capacity (aerobic and anaerobic), metabolic rates, basal activity levels, and thermal tolerance. ---
Juvenile sturgeon predation susceptibility Very little is known about susceptibility of juvenile sturgeon to common freshwater predatory fish. We conducted work in simplified laboratory mesocosm to evaluate consumption of sturgeon across early juvenile sizes (5 - 22 cm length). We tested three predator species (Largemouth Bass, Striped Bass, and Channel Catfish). The results indicated that sturgeon reach a size-threshold (around 18-22cm length) where the risk of predation is dramatically decreased. This suggests that management to facilitate rapid growth rates, through fostering abundant food resources and optimal water temperatures (15-19C), may help to increase of recruitment to adult life stages. --- Juvenile sturgeon anti-predator behavior Evolution should favor traits (both morphological and behavioral) that aid an individual in avoiding predation. Sturgeon are a benthically oriented, armored fish that is susceptible to predation by other fishes when small. We experimentally evaluated how juvenile sturgeon balance foraging-activity with predator avoidance. Initial work showed a pronounced reduction in activity in the presence of a predator, regardless of nutritional state. A follow-up study assessed whether that behavior changes across ontogeny, with size-related predation risk. An optimal behavior paradigm suggests that juveniles should decrease predator avoidance behaviors and increase foraging as the individual achieves a size-related predation refuge. ---