Despite the importance of straying in understanding the ecology of Pacific salmon Oncorhynchus spp. and steelhead O. mykiss, most of what is known about salmon and steelhead straying comes from tagged hatchery fish. We provide estimates of donor straying by natural‐origin spring, summer, and fall Chinook Salmon O. tshawytscha and summer steelhead at three spatial scales in the upper Columbia River watershed by using PIT tags. In total, 823,770 natural‐origin Chinook Salmon and steelhead were PIT‐tagged as juveniles in the Wenatchee, Entiat, Methow, and Okanogan River subbasins and tributaries and the upper Columbia River between 2002 and 2017. Anadromous adults with PIT tags (n = 2,611) were detected at a variety of antenna arrays in the Columbia River basin between 2004 and 2018. Mean donor stray rates of each population were less than 1% at the basin scale (range = 0.0–0.7%), less than 10% at the subbasin scale (range = 0.0–9.8%), and less than 15% at the tributary scale (range = 0.0–14.3%). Many of the populations (11 of 28) that were evaluated across all spatial scales did not have any strays detected, and the mean of means for both species’ stray rates at all spatial scales was generally less than 5% (range = 0.2–4.0%). Chinook Salmon and steelhead strayed at similar rates when originating from the same subbasins and tributaries. Most straying occurred in an upstream direction at the subbasin (84%) and tributary (94%) scales. Variation in stray rates was most consistently associated with spatial scale and location and was less than 15% for both species at all spatial scales.

Trait-selective mortality is of considerable management and conservation interest, especially when trends are similar across multiple species of conservation concern. In the Columbia River basin, thousands of juvenile Pacific salmonids Oncorhynchus spp. are collected each year and are tagged at juvenile bypass system (JBS) facilities located at hydroelectric dams, thus allowing the tracking of population-level performance metrics (e.g., juvenile survival and juvenile-to-adult survival). Several studies have suggested that juvenile salmonid survival is both size dependent and condition dependent, but little is known about trait-selective collection at JBS facilities. Traitselective collection (e.g., length-based or condition-based selectivity) is particularly important, as inferences to population-level performance metrics may be biased if both the survival and collection processes are influenced by similar characteristics. We used a capture-mark-recapture study to investigate length-and condition-selective survival and detection probabilities for two salmonid species in the Columbia River basin. In 2014, juvenile steelhead O. mykiss (n D 11,201) and yearling Chinook Salmon O. tshawytscha (n D 7,943) were PIT-tagged, measured (FL), examined for external condition characteristics (descaling, body injuries, fin damage, or disease symptoms), and released into the Lower Granite Dam JBS facility on the Snake River to continue seaward migration. Results indicated similar trends in both length-and condition-selective juvenile survival and detection probabilities. For both species, survival probability was higher for longer, nondegraded individuals (those without descaling, body injuries, or fin damage). Trends in detection probability were also consistent across species: shorter, degraded individuals were more likely to be detected at downstream JBS facilities than longer, healthier individuals. These results suggest that similar characteristics (FL and external condition) affect survival and detection processes for PIT-tagged steelhead and yearling Chinook Salmon and that JBS facilities may selectively

We quantified the use of habitat patches by brown trout, Salmo trutta, during summer conditions in a plains stream in the western United States. A Global Positioning System was used to map discrete habitat patches (2-420 m 2 ) consisting of macrophytes, wood accumulation, or deep water. Habitat use by brown trout was monitored by radio telemetry. Brown trout used habitat in a nonrandom manner with 99% of all daytime observations and 91% of all nighttime observations occurring in patches that consisted of combinations of deep water, wood accumulations or macrophytes even though such patches constituted only 9.8% of the available habitat. Brown trout used deep water almost exclusively during the day but broadened their habitat use at night. Most fish stayed within a large plunge pool created by a low-head dam. This pool supplemented the deep-water habitat that was naturally rare in our study area and illustrates how human modifications can sometimes create habitat patches important for stream fishes.