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Auburn Lake Trails, CA, United States

Miller J.A.,Oregon State University | Gray A.,Cramer Fish science | Merz J.,University of California at Santa Cruz
Marine Ecology Progress Series | Year: 2010

Chinook salmon is an anadromous species that varies in size at freshwater emigration, which is hypothesized to increase population resiliency under variable environmental regimes. In California's Central Valley (USA), the majority of naturally spawned juveniles emigrate in 2 pulses: small juveniles (referred to as fry), typically ≤55 mm fork length (FL), emigrate from natal streams in February-March, whereas larger juveniles (smolts), typically >75 mm FL, emigrate in mid-April-May. In some river systems, there is a smaller pulse of emigrants of intermediate size (parr), typically 56 to 75 mm FL. Although the relative contribution of these migratory phenotypes to the adult population is unknown, management activities focus on survival of larger emigrants and most artificially produced fish (98%) are released from hatcheries at parr and smolt sizes. We reconstructed individual length at freshwater emigration for a sample of adult Central Valley Chinook salmon from 2 emigration years using chemical (Sr:Ca and Ba:Ca) and structural otolith analyses. The adult sample was comprised of individuals that emigrated as parr (mean ≤ 48%), followed by smolts (32%) and fry (20%). Fry-sized emigrants likely represent natural production because fish ≤55 mm FL comprise<2% of the hatchery production. The distribution of migratory phenotypes represented in the adult sample was similar in both years despite apparent interannual variation in juvenile production, providing evidence for the contribution of diverse migratory phenotypes to the adult population. The contribution of all 3 migratory phenotypes to the adult population indicates that management and recovery efforts should focus on maintenance of life-history variation rather than the promotion of a particular phenotype. © Inter-Research 2010 · www.int-res.com. Source

Del Real S.C.,East Bay Municipal Utility District | Workman M.,U.S. Fish and Wildlife Service | Merz J.,Cramer Fish science
Environmental Biology of Fishes | Year: 2012

The lower Mokelumne River (LMR), located in the California Central Valley, supports a population of natural-origin Oncorhynchus mykiss. In addition, the Mokelumne River Fish Hatchery (Hatchery) contributes hatchery produced O. mykiss to the system annually. We conducted a 3 year acoustic tagging study to evaluate the migratory characteristics of LMR hatchery and natural-origin O. mykiss to the Pacific Ocean. Specifically, we analyzed downstream movement and migration rates, routes, and success of acoustically tagged O. mykiss of hatchery and natural origin under variable release locations in non-tidal and tidal habitats. Results from our study suggest there are significant differences in the proportion of hatchery and natural O. mykiss that demonstrate downstream movement. Fish origin, size, and release location all had a significant effect on whether an individual demonstrated downstream movement. Mokelumne origin O. mykiss that initiated downstream movement utilized numerous migration routes throughout the Delta during their migration towards the Pacific Ocean. We identified four primary migration pathways from the lower Mokelumne River through the Sacramento-San Joaquin Delta while the Delta Cross Channel was closed. However, several other pathways were utilized. Origin had a significant effect on O. mykiss success in reaching key points in the Delta and through the Estuary. Fish size had a significant effect on whether an individual reached the marine environment. Of the 467 O. mykiss tagged, 34 successfully reached the Pacific Ocean (Golden Gate Bridge), and of these, 33 were hatchery-origin and 1 was natural-origin. A higher proportion of hatchery-origin fish (10% of tagged) migrated to the ocean compared to natural-origin fish (<1%). Our study provides valuable information on the differences between hatchery and natural-origin O. mykiss migration characteristics as well as unique insight into the migratory behavior of little studied non-Sacramento River origin salmonids. © 2011 Springer Science+Business Media B.V. Source

Teply M.,Cramer Fish science
Western Journal of Applied Forestry | Year: 2013

Uneven-aged stands with multistory, diverse canopies are common throughout the forests of the Inland Northwest, and both current regulations and prescriptions under consideration often promote further diversification. Understanding the potential effects of alternative riparian management prescriptions on stream shade is important, and effects may vary with even-aged versus uneven-aged conditions. For a range of riparian stand conditions in Central Idaho, in this article, we compare shade predictions from two approaches using a widely used model introduced by Chen et al. in 1998, one that accounts for multiple canopies ("canopy-explicit approach") and another that accounts for a single-layer canopy ("canopy-average approach"). We found slight improvements using the canopy-explicit approach when there were distinct overstory and understory canopies. However, we found that both approaches underpredicted shade levels observed in the field. The underestimate is influenced by the Forest Vegetation Simulator (FVS) canopy cover metric that we used to inform the model; this metric underestimates vertical nonoverlapping cover, an important input to the shade model. We used the canopy-explicit approach to evaluate effects of the Idaho Forestry Program (IFP), a major conservation agreement that the State of Idaho is currently pursing with federal agencies, on stream shade. For this evaluation, we compared shade predicted to occur through implementation of the IFP with that from passive (no harvest) management. For the IFP, we found that shade reduction would be approximately 5%, on average, largely because of the effect of the 25-ft stream-adjacent no-harvest zone that this alternative requires. We also compared shade produced under the IFP with shade targets developed by the Idaho Department of Environmental Quality. Predicted IFP shade levels were lower than target levels, in large part because of the effect of the FVS cover metric. Overall, these comparisons highlight the usefulness of the approach in comparing the effects of different management alternatives on shade, despite the bias introduced by using the FVS cover metric and problems inherent in comparing results developed through simulation to targets based on different methods. Copyright © 2013 by the Society of American Foresters. Source

Cavallo B.,Cramer Fish science | Merz J.,University of California at Santa Cruz | Setka J.,East Bay Municipal Utility District
Environmental Biology of Fishes | Year: 2013

We evaluated the effects of non-native, piscivorous fish removal and artificial flow manipulation on survival and migration speed of juvenile Chinook salmon, Oncorhynchus tshawytscha, emigrating through the eastern Sacramento-San Joaquin Delta of California (Delta) using a Before-After-Control-Impact study design. Acoustically-tagged salmon survival increased significantly after the first predator reduction in the impact reach. However, survival estimates returned to pre-impact levels after the second predator removal. When an upstream control gate opened (increasing flow and decreasing tidal effect) juvenile salmon emigration time decreased and survival increased significantly through the impact reach. Though a short-term, single season experiment, our results demonstrate that predator control and habitat manipulation in the Delta tidal transition zone can be effective management strategies to enhance salmon survival in this highly altered system. © 2012 Springer Science+Business Media B.V. Source

Cordell J.R.,University of Washington | Toft J.D.,University of Washington | Gray A.,Cramer Fish science | Ruggerone G.T.,Natural Resources Consultants Inc. | Cooksey M.,University of Washington
Ecological Engineering | Year: 2011

The Duwamish estuary is an industrialized waterway located in Seattle, WA, USA. Despite a history of habitat loss, naturally produced juvenile Chinook salmon use the estuary. In addition to experiencing degraded habitat in the estuary, wild salmon growth may be affected by competition with more than three million hatchery fish released yearly into the river. Restoring habitat to benefit salmon in the Duwamish River is a priority for trustees of public resources, and a number of wetland restoration sites have been created there. We tested the function of restored sites in the Duwamish estuary for juvenile Chinook salmon by comparing fish densities from enclosure nets or beach seines at three paired restored/un-restored sites and by applying environmental and diet data to a bioenergetics model. We also examined temporal and diet overlap of wild juvenile Chinook salmon with other salmon species and with hatchery-reared Chinook salmon using non-metric multidimensional scaling (NMDS). At a brackish upstream site with a relatively large opening to the river, we found higher densities of juvenile Chinook salmon at the restored site. NMDS results indicated that juvenile Chinook salmon fed on different taxa at the restored sites than at the reference sites. However, modeled growth was similar at restored and reference sites. Co-occurring juvenile chum and Chinook salmon fed differently, with chum eating smaller prey, and Chinook salmon eating larger prey. Co-occurring hatchery and wild juvenile Chinook salmon had similar diets, indicating that they may compete for prey. However, modeled growth was positive and did not differ between hatchery and wild fish, suggesting that food was not limiting. Bioenergetics models indicated that overall juvenile Chinook salmon growth potential at the brackish water site was consistently higher than at more saline sites. Our results suggest that restoration sites in the Duwamish estuary that have larger access openings and are located in brackish water may have increased function over other configurations. © 2010 Elsevier B.V. Source

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