Occurrences of Steelhead Trout (Oncorhynchus mykiss) in southern California, 1994-2018

Dagit, Rosi; Booth, Michael T.; Gómez, Mauricio; Hovey, Timothy; Howard, Steve; Lewis, Scott; Jacobson, Sandra A.; Larson, Mary Jo; McCanne, Dan; Robinson, T. H.

doi:10.51492/cfwj.106.4

Cited by 3 publications

(3 citation statements)

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“…The only fish species found in the foothill and montane reaches of our study streams is native O. mykiss , which is near its southern range limits in this study region (Dressler et al., 2023). Although anadromous adult steelhead have been observed in the lower reaches of some of our study streams (Dagit et al., 2020), we believe that most O. mykiss in our study reaches are resident trout because the anadromous form is extremely rare in southern California (Dagit et al., 2020), barriers (dams, railroad and road crossings, bridge footings, culverts, or concrete channels) impede adult steelhead access to our montane and foothill study reaches, adult steelhead have almost never been observed recently in our study reaches, and the size, morphology, behaviour, and colour patterns of the observed fish are consonant with a resident trout classification (Moyle, 2002; Quinn, 2018). In our study reaches, trout may re‐distribute themselves among pools during the wet season when water levels are high; however, most trout are trapped in home pools during the summer when flows between pools are very low or non‐existent (Cooper, 1984b; Wiseman et al., 1993).…”

Section: Methodsmentioning

confidence: 70%

“…Further, the resiliency of sensitive species and stream communities to disturbances is inhibited by the construction and maintenance of barriers (e.g., dams and road crossings) that block salmonid migrations and intercept the downstream drift of stream organisms, impeding the recolonisation of disturbed habitats (Kukuła & Bylak, 2022). Human alterations of landscapes and waterscapes, then, can enhance the negative impacts of climate change on native stream species and ecosystems (Dagit et al., 2020; Monaghan et al., 2016; National Marine Fisheries Service, 2012). In the case of southern California, changes in climate, and patterns in land and water use, are combining to extirpate many native steelhead and resident trout populations (National Marine Fisheries Service, 2023).…”

Section: Discussionmentioning

confidence: 99%

“…Historically, the top aquatic predators in most southern California coastal streams were native O. mykiss , including both the endangered anadromous steelhead form and the resident rainbow trout form (Cooper et al., 1986; Dagit et al., 2020; National Marine Fisheries Service, 2012, 2016, 2023). Although steelhead or rainbow trout can move across stream reaches during the wet season when flows are adequate, they often are relegated to pools with adequate habitat, resources, and refuge space during the dry season (Cooper et al., 2015; Grantham et al., 2012; Hwan et al., 2018).…”

Section: Introductionmentioning

confidence: 99%

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Trout and invertebrate assemblages in stream pools through wildfire and drought

Cooper,

Wiseman,

DiFiore

et al. 2024

Freshwater Biology

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Climate change is increasing the frequency, severity, and extent of wildfires and drought in many parts of the world, with numerous repercussions for the physical, chemical, and biological characteristics of streams. However, information on how these perturbations affect top predators and their impacts on lower trophic levels in streams is limited. The top aquatic predator in southern California streams is native Oncorhynchus mykiss, the endangered southern California steelhead trout (trout). To examine relationships among the distribution of trout, environmental factors, and stream invertebrate resources and assemblages, we sampled pools in 25 stream reaches that differed in the presence (nine reaches) or absence (16 reaches) of trout over 12 years, including eight reaches where trout were extirpated during the study period by drought or post‐fire flood disturbances. Trout were present in deep pools with high water and habitat quality. Invertebrate communities in trout pools were dominated by a variety of medium‐sized collector–gatherer and shredder invertebrate taxa with non‐seasonal life cycles, whereas tadpoles and large, predatory invertebrates (Odonata, Coleoptera, Hemiptera [OCH]), often with atmospheric breather traits, were more abundant in troutless than trout pools. Structural equation modelling of the algal‐based food web indicated a trophic cascade from trout to predatory invertebrates to collector–gatherer taxa and weaker direct negative trout effects on grazers; however, both grazers and collector–gatherers also were positively related to macroalgal biomass. Structural equation modelling also suggested that bottom‐up interactions and abiotic factors drove the detritus‐based food web, with shredder abundance being positively related to leaf litter (coarse particulate organic matter) levels, which, in turn, were positively related to canopy cover and negatively related to flow. These results emphasise the context dependency of trout effects on prey communities and of the relative importance of top‐down versus bottom‐up interactions on food webs, contingent on environmental conditions (flow, light, nutrients, disturbances) and the abundances and traits of component taxa. Invertebrate assemblage structure changed from a trout to a troutless configuration within a year or two after trout were lost owing to post‐fire scouring flows or drought. Increases in OCH abundance after trout were lost were much more variable after drought than after fire. The reappearance of trout in one stream resulted in quick, severe reductions in OCH abundance. These results indicate that climate‐change induced disturbances can result in the extirpation of a top predator, with cascading repercussions for stream communities and food webs. This study also emphasises the importance of preserving or restoring refuge habitats, such as deep, shaded, perennial, cool stream pools with high habitat and water quality, to prevent the extirpation of sensitive species and preserve native biodiversity during a time of climate change.

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Section: Methodsmentioning

confidence: 70%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Trout and invertebrate assemblages in stream pools through wildfire and drought

Cooper,

Wiseman,

DiFiore

et al. 2024

Freshwater Biology

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Cybaeus (Araneae: Cybaeidae) in the Nearctic: the devius and tardatus species groups of the Californian clade

Bennett

Copley

2021

Zootaxa

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Species of North American Cybaeus L. Koch (Araneae: RTA clade: Cybaeidae) are moist-forest spiders classified in Holarctic and Californian clades. Here, in the fourth paper in a planned series reviewing the six Californian clade species groups, we review the species of the devius and tardatus groups. We recognize five species in the devius group (Cybaeus bilectus Bennett spec. nov., C. bryoncavus Bennett spec. nov., C. devius Chamberlin & Ivie, C. echo Bennett spec. nov., and C. wilsonia Bennett spec. nov.) and four in the tardatus group (C. orarius Bennett spec. nov., C. piazzai Bennett spec. nov., C. tardatus Chamberlin, and C. topanga Bennett spec. nov.). All of these species are rarely encountered and have restricted distributions either in the central and southern Sierra Nevada Mountains of eastern California, U.S.A (devius group) or the southern coast of western California (tardatus group). Some of these species are likely endangered or already extinct; most have not been seen in many decades and none have been collected more recently than 1995. Descriptions, illustrations, distribution maps, and identification keys are provided as well as a discussion of conservation issues of relevance to the group.

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Checklist of marine and estuarine fishes from the Alaska–Yukon Border, Beaufort Sea, to Cabo San Lucas, Mexico

Love

Bizzarro

Cornthwaite

et al. 2021

Zootaxa

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This paper is a checklist of the fishes that have been documented, through both published and unpublished sources, in marine and estuarine waters, and out 200 miles, from the United States-Canadian border on the Beaufort Sea to Cabo San Lucas, Mexico. A minimum of 241 families and 1,644 species are known within this range, including both native and nonnative species. For each of these species, we include maximum size, geographic and depth ranges, whether it is native or nonnative, as well as a brief mention of any taxonomic issues.

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Occurrences of Steelhead Trout (Oncorhynchus mykiss) in southern California, 1994-2018

Cited by 3 publications

References 39 publications

Trout and invertebrate assemblages in stream pools through wildfire and drought

Trout and invertebrate assemblages in stream pools through wildfire and drought

Cybaeus (Araneae: Cybaeidae) in the Nearctic: the devius and tardatus species groups of the Californian clade

Checklist of marine and estuarine fishes from the Alaska–Yukon Border, Beaufort Sea, to Cabo San Lucas, Mexico

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