Conrad J.L.,500 Industrial Boulevard |
Bibian A.J.,University of California at Davis |
Bibian A.J.,Rice University |
Weinersmith K.L.,University of California at Davis |
And 10 more authors.
Transactions of the American Fisheries Society | Year: 2016
Abstract: Frequent invasions in coastal ecosystems result in novel species interactions that have unknown ecological consequences. Largemouth Bass Micropterus salmoides and Brazilian waterweed Egeria densa are introduced species in the Sacramento–San Joaquin River Delta (the Delta) of California, a highly modified estuary. In this system, Brazilian waterweed and Largemouth Bass have seen marked increases in distribution and abundance in recent decades, but their association has not been specifically studied until now. We conducted a 2-year, bimonthly electrofishing survey with simultaneous sampling of water quality and submerged aquatic vegetation (SAV) biomass at 33 locations throughout the Delta. We used generalized linear mixed models to assess the relative influences of water temperature, conductivity, Secchi depth, and SAV biomass density on the abundance of both juvenile-sized and larger Largemouth Bass. Water temperature had a positive relationship with the abundance of both size-classes, but only juvenile-sized fish had a positive association with SAV biomass density, with highest abundances at intermediate SAV densities. In contrast, larger fish were generally ubiquitous across all sampling conditions, even when SAV was absent or present at low densities. Our results on the Largemouth Bass–SAV relationship are consistent with those of previous studies from lake systems within the Largemouth Bass's native range, where they interact with a different SAV species assemblage. These results are supportive of the hypothesis that the proliferation of Brazilian waterweed has expanded Largemouth Bass rearing habitat in the Delta. Finally, this study has implications for tidal wetland restoration plans for the Delta, suggesting that the larger-sized Largemouth Bass may still inhabit restored areas even if invasive SAV establishment is limited. Received March 30, 2015; accepted October 27, 2015 © 2016 American Fisheries Society.
Schreier B.M.,500 Industrial Boulevard |
Baerwald M.R.,University of California at Davis |
Conrad J.L.,500 Industrial Boulevard |
Schumer G.,Cramer Fish science |
May B.,University of California at Davis
Transactions of the American Fisheries Society | Year: 2016
Abstract: We examined predation by nonnative Mississippi Silversides Menidia audens, other small fishes, and invertebrates on the early life stages of the endangered Delta Smelt Hypomesus transpacificus, which is endemic to the Sacramento–San Joaquin Delta in California. Mississippi Silversides and other putative predators were collected primarily via boat electrofishing in the northern reaches of the upper San Francisco Estuary, an area targeted for substantial tidal wetland restoration to enhance habitat for Delta Smelt and other endangered fishes. Predators’ digestive tracts were removed and analyzed for the presence of Delta Smelt DNA by using quantitative PCR TaqMan assays. Across all sites, 69 of 550 Mississippi Silversides tested positive for Delta Smelt DNA. The number of sampled Mississippi Silversides that were positive for Delta Smelt DNA was significantly greater in offshore habitats than in nearshore habitats. Delta Smelt DNA detection data indicated that a wide variety of other species were also predators of Delta Smelt. Additionally, we used generalized linear modeling to analyze the relationship between Delta Smelt predation detections in Mississippi Silversides and concurrently collected habitat parameters. Turbidity was identified as a significant predictor of predation, as Delta Smelt DNA was detected more often in Mississippi Silverside samples from clearer water. These results suggest that restoration efforts designed to increase turbidity in the estuary may be beneficial in reducing Mississippi Silversides’ predatory impacts on Delta Smelt. Received August 24, 2015; accepted February 3, 2016 Published online June 15, 2016 © American Fisheries Society 2016.
Brooks M.L.,Southern Illinois University Carbondale |
Fleishman E.,University of California at Santa Barbara |
Fleishman E.,University of California at Davis |
Brown L.R.,U.S. Geological Survey |
And 13 more authors.
Estuaries and Coasts | Year: 2012
Human effects on estuaries are often associated with major decreases in abundance of aquatic species. However, remediation priorities are difficult to identify when declines result from multiple stressors with interacting sublethal effects. The San Francisco Estuary offers a useful case study of the potential role of contaminants in declines of organisms because the waters of its delta chronically violate legal water quality standards; however, direct effects of contaminants on fish species are rarely observed. Lack of direct lethality in the field has prevented consensus that contaminants may be one of the major drivers of coincident but unexplained declines of fishes with differing life histories and habitats (anadromous, brackish, and freshwater). Our review of available evidence indicates that examining the effects of contaminants and other stressors on specific life stages in different seasons and salinity zones of the estuary is critical to identifying how several interacting stressors could contribute to a general syndrome of declines. Moreover, warming water temperatures of the magnitude projected by climate models increase metabolic rates of ectotherms, and can hasten elimination of some contaminants. However, for other pollutants, concurrent increases in respiratory rate or food intake result in higher doses per unit time without changes in the contaminant concentrations in the water. Food limitation and energetic costs of osmoregulating under altered salinities further limit the amount of energy available to fish; this energy must be redirected from growth and reproduction toward pollutant avoidance, enzymatic detoxification, or elimination. Because all of these processes require energy, bioenergetics methods are promising for evaluating effects of sublethal contaminants in the presence of other stressors, and for informing remediation. Predictive models that evaluate the direct and indirect effects of contaminants will be possible when data become available on energetic costs of exposure to contaminants given simultaneous exposure to non-contaminant stressors. © 2011 Coastal and Estuarine Research Federation.
Seesholtz A.M.,500 Industrial Boulevard |
Manuel M.J.,Pacific States Marine Fisheries Commission |
Van Eenennaam J.P.,University of California at Davis
Environmental Biology of Fishes | Year: 2014
California’s Sacramento River mainstem was previously the only known spawning area for the Southern Distinct Population Segment of North American green sturgeon, Acipenser medirostris. Our study provides the first documentation of green sturgeon spawning in the Feather River, a major tributary of the Sacramento River. Egg mats were used to sample two lower Feather River sites from April 12 to July 7, 2011, and we collected 13 green sturgeon eggs at one of those sites. Developmental stages of the eggs ranged from early gastrulation (Stage 15) to post-neurulation (Stage 27), which led us to estimate that four independent spawning events occurred between June 12 and June 19. Spawning occurred after a flow increase while water temperatures were at an optimum (<17.5 °C) for eggs. Results suggest that the area near Thermalito Afterbay Outlet may be important green sturgeon spawning habitat and that the lower Feather River has the potential to provide a second production area of Southern Distinct Population Segment green sturgeon. It should be noted that 2011 was a wet water year and supplemental sampling is needed to understand if water-year type affects green sturgeon usage of the lower Feather River. Given this new information, future management decisions and water management strategies for the Feather River system should take green sturgeon life-history needs into consideration. © 2014, Springer Science+Business Media Dordrecht.
Conrad J.L.,500 Industrial Boulevard |
Holmes E.,University of California at Davis |
Jeffres C.,University of California at Davis |
Takata L.,500 Industrial Boulevard |
And 3 more authors.
North American Journal of Fisheries Management | Year: 2016
Abstract: Passive integrated transponder (PIT) technology allows passive, individual identification of small fish, making it a potentially useful tool to address an information gap of juvenile salmon habitat use in off-channel environments. We investigated the combined use of field enclosures and PIT technology as a method for studying the habitat preference of juvenile Chinook Salmon Oncorhynchus tshawytscha on a flooded rice field, a potential surrogate for lost floodplain habitat. We stocked two field enclosures (182 m2) with 42 juvenile salmon. One enclosure had equal portions of rice stubble, disced, and fallow habitat treatments, and the second contained only the disced treatment. Fish were tagged with 8- or 12-mm-sized PIT tags, and generated approximately 1 million detections in each enclosure over 14 d. We used a condensing procedure to reduce the data volume while preserving habitat use patterns. The smaller 8-mm tags were only detected along antenna edges, and the 12-mm tags had broader but more variable detection fields. Despite this difference, habitat occupancy probabilities showed the same spatial pattern between tag sizes, with increased occupancy in the upstream locations of both field enclosures. Similar results between tag sizes suggest that valuable habitat use data can be obtained with the 8-mm tag. Received January 30, 2015; accepted October 13, 2015 © 2016, American Fisheries Society 2016.
Miles A.K.,U.S. Geological Survey |
Van Vuren D.H.,University of California at Davis |
Tsao D.C.,500 Industrial Boulevard |
Yee J.L.,U.S. Geological Survey
California Fish and Game | Year: 2015
As mitigation for habitat impacted by the expansion of a pier on Suisun Bay, California, two vehicle parking lots (0.36 ha and 0.13 ha) were restored by being excavated, graded, and contoured using dredged sediments to the topography or elevation of nearby wetlands. We asked if pickleweed (Sarcocornia pacifica L, [Amaranthaceae]) colonization could be enhanced by experimental manipulation on these new wetlands. Pickleweed dominates ecologically important communities at adjacent San Francisco Bay, but is not typically dominant at Suisun Bay probably because of widely fluctuating water salinity and is outcompeted by other brackish water plants. Experimental treatments (1.0-m2 plots) included mulching with pickleweed cuttings in either the fall or the spring, tilling in the fall, or applying organic enrichments in the fall. Control plots received no treatment. Pickleweed colonization was most enhanced at treatment plots that were mulched with pickleweed in the fall. Since exotic vegetation can colonize bare sites within the early phases of restoration and reduce habitat quality, we concluded that mulching was most effective in the fall by reducing invasive plant cover while facilitating native plant colonization.
Sustaita D.,Silverado |
Sustaita D.,University of Connecticut |
Quickert P.F.,SAFE , LLC |
Patterson L.,500 Industrial Boulevard |
And 2 more authors.
Journal of Wildlife Management | Year: 2011
We undertook a 2-year (2002-2004) mark-recapture study to investigate demographic performance and habitat use of salt marsh harvest mice (Reithrodontomys raviventris halicoetes) in the Suisun Marsh. We examined the effects of different wetland types and microhabitats on 3 demographic variables: density, reproductive potential, and persistence. Our results indicate that microhabitats dominated by mixed vegetation or pickleweed (Salicornia spp.) supported similar salt marsh harvest mouse densities, reproductive potential, and persistence throughout much of the year, whereas few salt marsh harvest mice inhabited upland grass-dominated microhabitats. We found that densities were higher in diked wetlands, whereas post-winter persistence was higher in tidal wetlands, and reproductive potential did not differ statistically between wetland types. Our results emphasize the importance of mixed vegetation for providing adequate salt marsh harvest mouse habitat and suggest that, despite their physiognomic and hydrological differences, both diked and tidal wetlands support salt marsh harvest mouse populations by promoting different demographic attributes. We recommend that habitat management, restoration, and enhancement efforts include areas containing mixed vegetation in addition to pickleweed in both diked and tidal wetlands. Copyright © 2011 The Wildlife Society.
Maier K.L.,U.S. Geological Survey |
Gatti E.,U.S. Geological Survey |
Gatti E.,Jet Propulsion Laboratory |
Wan E.,U.S. Geological Survey |
And 5 more authors.
Quaternary Research (United States) | Year: 2015
We document characteristics of tephra, including facies and geochemistry, from 27 subsurface sites in the Sacramento-San Joaquin Delta, California, to obtain stratigraphic constraints in a complex setting. Analyzed tephra deposits correlate with: 1) an unnamed tephra from the Carlotta Formation near Ferndale, California, herein informally named the ash of Wildcat Grade (<~1.450 to >~. 0.780. Ma), 2) the Rockland ash bed (~. 0.575. Ma), 3) the Loleta ash bed (~. 0.390. Ma), and 4) middle Pleistocene volcanic ash deposits at Tulelake, California, and Pringle Falls, Bend, and Summer Lake, Oregon, herein informally named the dacitic ash of Hood (<~0.211 to >~. 0.180. Ma). All four tephra are derived from Cascades volcanic sources. The Rockland ash bed erupted from the southern Cascades and occurs in up to >. 7-m-thick deposits in cores from ~. 40. m subsurface in the Sacramento-San Joaquin Delta. Tephra facies and tephra age constraints suggest rapid tephra deposition within fluvial channel and overbank settings, likely related to flood events shortly following volcanic eruption. Such rapidly deposited tephra are important chronostratigraphic markers that suggest varying sediment accumulation rates in Quaternary deposits below the modern Sacramento-San Joaquin Delta. This study provides the first steps in a subsurface Quaternary stratigraphic framework necessary for future hazard assessment. © 2015.