Publications

@article{Rossi2021,

title = {Foraging modes and movements of Oncorhynchus mykiss as flow and invertebrate drift recede in a California stream},

author = {Gabriel J. Rossi and Mary E. Power and Shelley Pneh and Jason R. Neuswanger and Timothy J. Caldwell},

doi = {10.1139/cjfas-2020-0398},

year  = {2021},

date = {2021-02-12},

journal = {Canadian Journal of Fisheries and Aquatic Sciences},

abstract = {Salmonids frequently adapt their feeding and movement strategies to cope with seasonally fluctuating stream environments. Oncorhynchus mykiss tend to drift-forage in higher velocity habitat than other salmonids, yet their presence in streams with seasonally low velocity and drift suggests behavioral flexibility. We combined 3-D videogrammetry with measurements of invertebrate drift and stream hydraulics to investigate the drivers of O. mykiss foraging mode and movement during the seasonal recession in a California stream. From May to July (2016), foraging movement rate increased as prey concentration and velocity declined; however, movement decreased in August as pools became low and still. In May, 80% of O. mykiss were drift-foraging, while by July, over 70% used search or benthic-foraging modes. Velocity and riffle crest depth were significant predictors of foraging mode, while drift concentration was a poor univariate predictor. However top ranked additive models included both hydraulic variables and drift concentration. A drift-foraging bioenergetic model was a poor predictor of foraging mode. We suggest that infall and benthic prey, as well as risk aversion, may influence late-summer foraging decisions.},

keywords = {bioenergetics, ERCZO, foraging behavior, Mediterranean streams, Oncorhynchus mykiss, salmonids, stream hydraulics, video, videogrammetry},

pubstate = {published},

tppubtype = {article}

}

@article{Wang2020,

title = {Tributary confluences are dynamic thermal refuges for a juvenile salmonid in a warming river network},

author = {Terrance Wang and Suzanne J. Kelson and George Greer and Sally E. Thompson and Stephanie M. Carlson.},

doi = {10.1002/rra.3634},

year  = {2020},

date = {2020-04-28},

journal = {River Research and Applications},

abstract = {As rivers warm, cold‐water fish species may alleviate thermal stress by moving into localized thermal refuges such as cold‐water plumes created by cool tributary inflows. We quantified use of two tributary confluence plumes by juvenile steelhead, Oncorhynchus mykiss , throughout the summer, including how trout positioned themselves in relation to temperature within confluence plumes. At two confluences, Cedar and Elder creeks, along the South Fork Eel River, California, USA, we monitored temperatures using in situ logger grids throughout summer 2016. Fish were counted within confluences via snorkel surveys five times a day on 5 days at each site. We found diel and seasonal dependence on confluence use by steelhead, especially at the Cedar Creek confluence, where mainstem temperatures exceeded 28°C. At this site, fish moved into the confluence on the warmest days and warmest times of the day. Fish observed within the Cedar Creek confluence plume were most common in locations between 20–22°C, rather than the coldest locations (14.5°C). At Elder Creek, where mainstem temperatures remained below 24°C, there was little relationship between mainstem temperature and steelhead presence in the confluence plume. At both sites, steelhead distribution within plumes was influenced by spatial variation of temperature and mean temperature in surveyed grid cells. Our results show that cool tributaries flowing into warmer mainstem reaches (over 24°C) likely create important thermal refuges for juvenile steelhead. As mainstem rivers warm with climate change, cool‐water tributary inputs may become more important for sustaining cold‐water salmonids near the southern end of their range.},

keywords = {climate change, Eel river, ERCZO, microhabitat, Oncorhynchus mykiss, stream temperatures, thermal refuges, thermal tolerance},

pubstate = {published},

tppubtype = {article}

}

@article{Kelson2020b,

title = {Partial migration alters population ecology and food chain length: evidence from a salmonid fish},

author = {Suzanne J. Kelson and Mary E. Power and Jacques C. Finlay and Stephanie M. Carlson},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/ecs2.3044.pdf},

doi = {10.1002/ecs2.3044},

year  = {2020},

date = {2020-02-21},

journal = {Ecosphere},

volume = {11},

number = {2},

pages = {e03044},

abstract = {Many migratory species, from monarch butterflies to wildebeest, express partial migration, where only a subset of a population migrates. This intraspecific variation is likely to have large ecological consequences. We studied the ecological consequences of partial migration in a salmonid fish, Oncorhynchus mykiss, in coastal streams in California, USA. One ecotype, steelhead trout, migrates to the ocean, whereas the other, rainbow trout, completes its lifecycle in freshwater. Migration has a strong genetic basis in O. mykiss. In one stream, we found differences in the frequency of migration‐linked genotypes below and above a waterfall barrier (migratory allele frequency of 60% below vs. 31% above). Below the waterfall, in the migratory‐dominated region, the density of young fish (<1 yr old) was approximately twice that in the resident‐dominated region above the waterfall (0.46 vs. 0.26 individuals/m2, respectively), presumably reflecting the higher fecundity of migratory females. Additionally, there were half as many older fish (>1 yr old) in pools downstream of the waterfall (0.05 vs. 0.13 individuals/m2). In a second stream, between‐year variation in the dominance of migratory vs. resident fish allowed us to explore differences in fish density and size structure through time, and we found a consistent pattern. In brief, when migratory genotypes dominated, we found higher densities of young fish and lower densities of older fish, resulting in a simpler size structure, compared to when resident genotypes dominated. Moreover, large resident trout had a slightly higher trophic position than young fish (3.92 vs. 3.42 in one creek and 3.77 vs. 3.17 in the other), quantified with stable isotope data. The difference in fish size structure did not generate trophic cascades. Partial migration is widespread among migratory populations, as is phenotypic divergence between resident and migratory forms, suggesting the potential for widespread ecological effects arising from this common form of intraspecific variation.},

keywords = {eco-evolutionary dynamics, ERCZO, extended phenotype, food chain length, intraspecific variation, life history, O. mykiss, Oncorhynchus mykiss, partial migration, population ecology, size structure, steelhead/rainbow trout},

pubstate = {published},

tppubtype = {article}

}

@article{Kelson2020,

title = {Temporal dynamics of migration‐linked genetic variation are driven by streamflows and riverscape permeability},

author = {Suzanne J. Kelson and Michael R. Miller and Tasha Q. Thompson and Sean M. O'Rourke and Stephanie M. Carlson},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/mec.15367-1.pdf},

doi = {10.1111/mec.15367},

year  = {2020},

date = {2020-02-03},

journal = {Molecular Ecology},

volume = {29},

number = {5},

pages = {870-885},

abstract = {Landscape permeability is often explored spatially, but may also vary temporally. Landscape permeability, including partial barriers, influences migratory animals that move across the landscape. Partial barriers are common in rivers where barrier passage varies with streamflow. We explore the influence of partial barriers on the spatial and temporal distribution of migration‐linked genotypes of Oncorhynchus mykiss, a salmonid fish with co‐occurring resident and migratory forms, in tributaries to the South Fork Eel River, California, USA, Elder and Fox Creeks. We genotyped >4,000 individuals using RAD‐capture and classified individuals as resident, heterozygous or migratory genotypes using life history‐associated loci. Across four years of study (2014–2017), the permeability of partial barriers varied across dry and wet years. In Elder Creek, the largest waterfall was passable for adults migrating up‐river 4–39 days each year. In this stream, the overall spatial pattern, with fewer migratory genotypes above the waterfall, remained true across dry and wet years (67%–76% of migratory alleles were downstream of the waterfall). We also observed a strong relationship between distance upstream and proportion of migratory alleles. In Fox Creek, the primary barrier is at the mouth, and we found that the migratory allele frequency varied with the annual timing of high flow events. In years when rain events occurred during the peak breeding season, migratory allele frequency was high (60%–68%), but otherwise it was low (30% in two years). We highlight that partial barriers and landscape permeability can be temporally dynamic, and this effect can be observed through changing genotype frequencies in migratory animals.},

keywords = {ecology, ERCZO, genetic variation, landscape genetics, life history, O. mykiss, Oncorhynchus mykiss, partial barrier, partial migration, river networks},

pubstate = {published},

tppubtype = {article}

}

@article{Kelson2019,

title = {Do precipitation extremes drive growth and migration timing of a Pacific salmonid fish in Mediterranean‐climate streams?},

author = {Suzanne J. Kelson and Stephanie M. Carlson},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/ecs2.2618.pdf},

doi = {10.1002/ecs2.2618},

year  = {2019},

date = {2019-03-20},

journal = {Ecosphere},

volume = {10},

number = {3},

pages = {e02618},

abstract = {Climate change is expected to increase weather extremes and variability, including more frequent weather whiplashes or extreme swings between severe drought and extraordinarily wet years. Shifts in precipitation patterns will alter stream flow regimes, affecting critical life history stages of sensitive aquatic organisms. Understanding how threatened fish species, such as steelhead/rainbow trout (Oncorhynchus mykiss), are affected by stream flows in years with contrasting environmental conditions is important for their conservation. Here, we report how extreme wet and dry years, from 2015 to 2018, affected stream flow patterns in two tributaries to the South Fork Eel River, California, USA, and aspects of O. mykiss ecology, including over‐summer fish growth and body condition as well as spring out‐migration timing. We found that stream flow patterns differed across years in the timing and magnitude of large winter–spring flow events and in summer low‐flow levels. We were surprised to find that differences in stream flows did not impact growth, body condition, or timing of out‐migration of O. mykiss. Fish growth was limited in the late summer in these streams (average of 0.02 ± 0.05 mm/d), but was similar across dry and wet years, and so was end‐of‐summer body condition and pool‐specific biomass loss from the beginning to the end of the summer. Similarly, O. mykiss migrated out of tributaries during the last week of March/first week of April regardless of the timing of spring flow events. We suggest that the muted response to inter‐annual hydrologic variability is due to the high quality of habitat provided by these unimpaired, groundwater‐fed tributaries. Similar streams that are likely to maintain cool temperatures and sufficient base flows, even in the driest years, should be a high priority for conservation and restoration efforts.},

keywords = {Drought, ERCZO, growth, headwaters, migration, Oncorhynchus mykiss, salmonids, stream flows},

pubstate = {published},

tppubtype = {article}

}

@article{Power2008,

title = {Seasonal Reassembly of a River Food Web: Floods, Droughts, and Impacts of Fish},

author = {Mary E. Power and Michael S. Parker and William E. Dietrich},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Power_2008_EcoMono.pdf 

https://angelo.berkeley.edu/wp-content/uploads/sites/59/Power_FoodWebDrouFloodFish_EcoMono2008.pdf 

https://angelo.berkeley.edu/wp-content/uploads/sites/59/Power_AppA_EcoMono2008.pdf 

https://angelo.berkeley.edu/wp-content/uploads/sites/59/Power_AppB_EcoMono2008.pdf},

doi = {10.1890/06-0902.1},

issn = {0012-9615},

year  = {2008},

date = {2008-05-01},

journal = {Ecological Monographs},

volume = {78},

number = {2},

pages = {263–282},

abstract = {Eighteen years of field observations and five summer field experiments in a coastal California river suggest that hydrologic regimes influence algal blooms and the impacts of fish on algae, cyanobacteria, invertebrates, and small vertebrates. In this Mediterranean climate, rainy winters precede the biologically active summer low-flow season. Cladophora glomerata, the filamentous green alga that dominates primary producer biomass during summer, reaches peak biomass during late spring or early summer. Cladophora blooms are larger if floods during the preceding winter attained or exceeded ‘‘bankfull discharge’’ (sufficient to mobilize much of the river bed, estimated at 120 m3/s). In 9 out of 12 summers preceded by large bed-scouring floods, the average peak height of attached Cladophora turfs equaled or exceeded 50 cm. In five out of six years when flows remained below bankfull, Cladophora biomass peaked at lower levels. Flood effects on algae were partially mediated through impacts on consumers in food webs. In three experiments that followed scouring winter floods, juvenile steelhead (Oncorhynchus mykiss) and roach (Lavinia (Hesperoleucas) symmetricus) suppressed certain insects and young-of-the-year fish fry, affecting persistence or accrual of algae positively or negatively, depending on the predator-specific vulnerabilities of primary consumers capable of suppressing algae during a given year. During two post-flood years, these grazers were more vulnerable to small predators (odonates and fish fry, which stocked steelhead always suppressed) than to experimentally manipulated, larger fish, which had adverse effects on algae in those years. During one post-flood year, all enclosed grazers capable of suppressing algae were consumed by steelhead, which therefore had positive effects on algae. During drought years, when no bed-scouring winter flows occurred, large armored caddisflies (Dicosmoecus gilvipes) were more abundant during the subsequent summer. In drought-year experiments, stocked fish had little or no influence on algal standing crops, which increased only when Dicosmoecus were removed from enclosures. Flood scour, by suppressing invulnerable grazers, set the stage for fish mediated effects on algae in this river food web. Whether these effects were positive or negative depended on the predator-specific vulnerabilities of primary consumers that dominated during a given summer.},

keywords = {Cladophora glomerata, context dependency, effect sizes, flood scour, food chain length, interaction strength, Lavinia (Hesperoleucas) symmetricus, long-term studies, Mediterranean hydrologic regimes, Oncorhynchus mykiss, population, predator impacts},

pubstate = {published},

tppubtype = {article}

}

@article{Suttle2004,

title = {How Fine Sediment in Riverbeds Impairs Growth and Survival of Juvenile Salmonids},

author = {Kenwyn B. Suttle and Mary E. Power and Jonathan M. Levine and Camille McNeely},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/How-Fine-Sediment-in-Riverbeds-Impairs-Growth-and-Survival-of-Juvenile-Salmonids_Suttle_Power_Levine_McNeely.pdf},

doi = {http://dx.doi.org/10.1890/03-5190},

year  = {2004},

date = {2004-08-01},

journal = {Ecological Applications},

volume = {14},

number = {4},

pages = {969-974},

abstract = {Although excessive loading of fine sediments into rivers is well known to degrade salmonid spawning habitat, its effects on rearing juveniles have been unclear. We experimentally manipulated fine bed sediment in a northern California river and examined responses of juvenile salmonids and the food webs supporting them. Increasing concentrations of deposited fine sediment decreased growth and survival of juvenile steelhead trout. These declines were associated with a shift in invertebrates toward burrowing taxa unavailable as prey and with increased steelhead activity and injury at higher levels of fine sediment. The linear relationship between deposited fine sediment and juvenile steelhead growth suggests that there is no threshold below which exacerbation of fine-sediment delivery and storage in gravel bedded rivers will be harmless, but also that any reduction could produce immediate benefits for salmonid restoration.},

keywords = {fine sediment, Oncorhynchus mykiss, Pacific salmonids, parr, river food web, sedimentation, steelhead trout},

pubstate = {published},

tppubtype = {article}

}

@article{Finlay2002,

title = {Spatial scales of carbon flow in a river food web},

author = {Jacques C. Finlay and Sapna Khandwala and Mary E. Power},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Spatial-scales-of-energy-flow-in-food-webs-of-the-South-Fork-Eel-River_Finlay_2002.pdf},

doi = {10.2307/3071769},

year  = {2002},

date = {2002-00-00},

journal = {Ecology},

volume = {83},

number = {7},

pages = {1845-1859},

abstract = {Spatial extents of food webs that support stream and river consumers are largely unknown, but such information is essential for basic understanding and management of lotic ecosystems. We used predictable variation in algal δ13C with water velocity, and measurements of consumer δ13C and δ15N to examine carbon flow and trophic structure in food webs of the South Fork Eel River in Northern California. Analyses of δ13C showed that the most abundant macroinvertebrate groups (collector-gatherers and scrapers) relied on algae from local sources within their riffle or shallow pool habitats. In contrast, filter-feeding invertebrates in riffles relied in part on algal production derived from upstream shallow pools. Riffle invertebrate predators also relied in part on consumers of pool-derived algal carbon. One abundant taxon drifting from shallow pools and riffles (baetid mayflies) relied on algal production derived from the habitats from which they dispersed. The trophic linkage from pool algae to riffle invertebrate predators was thus mediated through either predation on pool herbivores dispersing into riffles, or on filter feeders. Algal production in shallow pool habitats dominated the resource base of vertebrate predators in all habitats at the end of the summer. We could not distinguish between the trophic roles of riffle algae and terrestrial detritus, but both carbon sources appeared to play minor roles for vertebrate consumers. In shallow pools, small vertebrates, including three-spined stickleback (Gasterosteus aculeatus), roach (Hesperoleucas symmetricus), and rough-skinned newts (Taricha granulosa), relied on invertebrate prey derived from local pool habitats. During the most productive summer period, growth of all size classes of steelhead and resident rainbow trout (Oncorhynchus mykiss) in all habitats (shallow pools, riffles, and deep unproductive pools) was largely derived from algal production in shallow pools. Preliminary data suggest that the strong role of shallow pool algae in riffle steelhead growth during summer periods was due to drift of pool invertebrates to riffles, rather than movement of riffle trout. Data for δ15N showed that resident rainbow trout (25-33 cm standard length) in deep pools preyed upon small size classes of juvenile steelhead that were most often found in riffles or shallow pools. While many invertebrate consumers relied primarily on algal production derived from local habitats, our study shows that growth of top predators in the river is strongly linked to food webs in adjacent habitats. These results suggest a key role for emigration of aquatic prey in determining carbon flow to top predators.},

keywords = {cannibalism, carbon and nitrogen stable-isotope ratios, carbon flow, Oncorhynchus mykiss, river food webs, scraper and collector-gatherer (SCG) taxa, spatial scale, steelhead trout, terrestrial detritus, trophic structure},

pubstate = {published},

tppubtype = {article}

}

@article{Power2001,

title = {Carbon isotope signatures and spatial scales of energy flow in food webs supporting salmonids in food webs supporting salmonids in Northern California rivers},

author = {Jacques C. Finlay and Mary E. Power},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/eScholarship-UC-item-79t2s4f8.pdf},

year  = {2001},

date = {2001-05-01},

journal = {Technical Completion Report},

volume = {UCAL-WRC-W-906},

abstract = {Spatial scales of the food webs that support the growth of juvenile salmonids in California rivers are largely unknown, but such information is essential for management of flows, species, and other ecosystem factors influencing salmonid production. Our project objectives were: 

1. to determine whether predictable variation in algal d13C with water velocity, and measurements of consumer d13C and d15N could be used to examine energy flow and trophic structure in food webs of the South Fork Eel River, and other salmon-bearing streams in Northern California, and 

2. to provide this information as a basis for examining how changes in access to energy sources following river regulation or invasions of exotic species might influence the access of various web members, including salmonids, to these sources.},

keywords = {cannibalism, Carbon and nitrogen stable isotope ratios, energy flow, Oncorhynchus mykiss, river food webs, river-watershed exchange, spatial scale, steelhead trout, terrestrial detritus, trophic structure},

pubstate = {published},

tppubtype = {article}

}