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Davis, CA, United States

Hammock B.G.,University of California at Davis | Johnson M.L.,Michael L. Johnson LLC

Climate change is likely to increase the metabolisms of ectothermic animals living below their thermal optimum. While ectothermic top predators may compensate by increasing foraging, ectothermic prey may be unable to increase foraging because of increased predation risk from ectothermic predators. We examined how the diurnal drift behavior (i.e., the downstream movement associated with foraging) of the mayfly Baetis, an ectothermic herbivore, responds to changing temperature in the implied presence and absence of trout, an ectothermic predator. In an experiment replicated at the catchment scale, water temperature and trout presence strongly interacted to affect the diurnal drift of Baetis from artificial channels lacking periphyton over a water temperature range of 4.2-14.8 °C. In fishless streams, daytime drift increased with increasing water temperature, likely because of increased metabolic demand for food. However, in trout-bearing streams, daytime drift decreased with increasing water temperature. Our interpretation is that the perceived threat of trout rose with increasing water temperature, causing mayflies to reduce foraging despite heightened metabolic demand. These results suggest that anticipated increases in stream temperature due to climate change may further escalate divergence in structure and process between fishless and trout-bearing streams. Similar dynamics may occur in other ecosystems with ectothermic predators and prey living below their thermal optima. © 2014 Springer-Verlag Berlin Heidelberg. Source

Innes R.J.,University of California at Davis | Innes R.J.,U.S. Department of Agriculture | McEachern M.B.,University of California at Davis | Van Vuren D.H.,University of California at Davis | And 4 more authors.
Journal of Mammalogy

We studied the association between space sharing and kinship in a solitary rodent, the dusky-footed woodrat (Neotoma fuscipes). Genetic relatedness was inversely correlated with geographic distance for female woodrats but not for males, a pattern consistent with female philopatry and male dispersal. However, some female neighbors were unrelated, suggesting the possibility of female dispersal. Relatedness of female dyads was positively correlated with overlap of their home ranges and core areas, indicating that females were more likely to share space with relatives, whereas males showed no correlation between relatedness and the sharing of either home ranges or core areas. However, some females that shared space were not close relatives, and some closely related males shared space. House sharing was exhibited both by close relatives and by distantly related or unrelated woodrats, and was not correlated with relatedness. The kin structuring we describe likely resulted from a pattern of female philopatry and male dispersal, but also may have resulted from kin-directed behaviors by females. © 2012 American Society of Mammalogists. Source

Quinones R.M.,University of California at Davis | Holyoak M.,University of California at Davis | Johnson M.L.,University of California at Davis | Johnson M.L.,Michael L. Johnson LLC | Moyle P.B.,University of California at Davis

Understanding factors influencing survival of Pacific salmonids (Oncorhynchus spp.) is essential to species conservation, because drivers of mortality can vary over multiple spatial and temporal scales. Although recent studies have evaluated the effects of climate, habitat quality, or resource management (e.g., hatchery operations) on salmonid recruitment and survival, a failure to look at multiple factors simultaneously leaves open questions about the relative importance of different factors. We analyzed the relationship between ten factors and survival (1980-2007) of four populations of salmonids with distinct life histories from two adjacent watersheds (Salmon and Scott rivers) in the Klamath River basin, California. The factors were ocean abundance, ocean harvest, hatchery releases, hatchery returns, Pacific Decadal Oscillation, North Pacific Gyre Oscillation, El Niño Southern Oscillation, snow depth, flow, and watershed disturbance. Permutation tests and linear mixed-effects models tested effects of factors on survival of each taxon. Potential factors affecting survival differed among taxa and between locations. Fall Chinook salmon O. tshawytscha survival trends appeared to be driven partially or entirely by hatchery practices. Trends in three taxa (Salmon River spring Chinook salmon, Scott River fall Chinook salmon; Salmon River summer steelhead trout O. mykiss) were also likely driven by factors subject to climatic forcing (ocean abundance, summer flow). Our findings underscore the importance of multiple factors in simultaneously driving population trends in widespread species such as anadromous salmonids. They also show that the suite of factors may differ among different taxa in the same location as well as among populations of the same taxa in different watersheds. In the Klamath basin, hatchery practices need to be reevaluated to protect wild salmonids. © 2014 Quinones et al. Source

Quinones R.M.,University of California at Davis | Johnson M.L.,University of California at Davis | Johnson M.L.,Michael L. Johnson LLC | Moyle P.B.,University of California at Davis
Environmental Biology of Fishes

Appraisal of hatchery-related effects on Pacific salmonids (Oncorhynchus spp.) is a necessary component of species conservation. For example, hatchery supplementation can influence species viability by changing genetic, phenotypic and life-history diversity. We analyzed time series data for seven salmonid taxa from the Klamath River basin, California, to investigate trajectories of wild and hatchery adult populations. Linear regression coupled with randomized permutations (n = 99,999), two- tailed t tests, and Bayesian change point analysis were used to detect trends over time. Cross correlation was also used to evaluate relationships between wild and hatchery populations. The taxa of interest were spring, fall, and late-fall Chinook Salmon (O. tshawytscha); Coho Salmon (O. kisutch); Coastal Cutthroat Trout (O. clarki clarki); and summer and hybrid Steelhead Trout (O. mykiss). Significant decreases were detected for summer and hybrid Steelhead Trout. The proportion of wild fall Chinook has also significantly decreased concurrently with increases in hatchery returns. In comparison, returns of most Chinook and coho runs to the hatcheries, and fall Chinook strays to wild spawning areas from Iron Gate Hatchery have significantly increased since the 1970s. Increases were also detected for wild late-fall Chinook and spring Chinook adults. However, both of these were significantly correlated with Chinook Salmon returns to Trinity River Hatchery, suggesting augmentation by hatchery strays. Changes in abundances appeared related to changing ocean habitat conditions and hatchery practices. Our results suggest that anadromous salmonid populations in the Klamath River basin are becoming increasingly dependent on hatchery propagation, a pattern that can threaten population persistence. © 2013 Springer Science+Business Media Dordrecht. Source

Klassen P.,East San Joaquin Water Quality Coalition | Johnson M.L.,Michael L. Johnson LLC
ACS Symposium Series

Surface water quality in the San Joaquin River watershed in the Central Valley of California is impacted by multiple stressors. To address water quality issues attributed to agricultural activities, the Central Valley Regional Water Quality Control (Water Board) enacted a regulatory program called the Irrigated Lands Regulatory Program (ILRP). The ILRP requires agricultural dischargers to identify if wastewater discharges are impacting downstream beneficial uses and impairing water quality. To comply with the requirement of the ILRP, agricultural interests in five northern San Joaquin Valley counties formed the East San Joaquin Water Quality Coalition (ESJWQC or Coalition). Coalition membership in 2010 stood at more than 2,400 landowners/operators responsible for over 559,000 irrigated acres on over 9,000 parcels. In 2004, the Coalition put in place a surface water monitoring program to determine compliance with state water quality criteria protective of beneficial uses. As a result of finding numerous exceedances of criteria, the Coalition developed in 2007 its initial Management Plan to address exceedances of those criteria. A modified approach was implemented in 2009 that targeted high risk lands identified through GIS mapping of pesticide use, downstream exceedances, cropping patterns, and proximity to water. The development of a grower-led program to monitor water quality, develop and implement management plans and use of a targeted approach for selecting and implementing Best Management Practices resulted in improvements in water quality. © 2011 American Chemical Society. Source

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