Relationship between Juvenile Fish Condition and Survival to Adulthood in Steelhead

Evans, Allen F.; Hostetter, Nathan J.; Collis, Ken; Roby, Daniel D.; Loge, Frank J.

doi:10.1080/00028487.2014.901248

Cited by 38 publications

(49 citation statements)

References 26 publications

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“…Evans et al. () found that juvenile length and condition were strong predictors of adult survival in steelhead from the Columbia and Snake rivers. In a study of Chinook Salmon from the Willamette River (a tributary of the Columbia River that enters downstream of the hydropower system) based on scale analysis, Claiborne et al.…”

Section: Discussionmentioning

confidence: 99%

“…Evans et al. () found that steelhead with general bodily injuries had higher susceptibility to avian predation but that the level of descaling was not influential. Gadomski et al.…”

Section: Discussionmentioning

confidence: 99%

“…), and smaller fish and fish in poorer condition also have a lower return probability (Ward and Slaney ; Zabel and Williams ; Evans et al. ). This suggests that the apparent effects of bypass on return probability could be at least partly due to a correlation between bypass probability and fish size and condition and not due to bypass passage itself.…”

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confidence: 99%

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Associations among Fish Length, Dam Passage History, and Survival to Adulthood in Two At‐Risk Species of Pacific Salmon

et al. 2019

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Threatened or endangered salmon and steelhead originating in the Snake River basin must pass through a series of eight major hydroelectric dams during their seaward migration. Understanding the effects of specific dam passage routes on lifetime survival for these stocks is essential for successful management. Juvenile fish may pass these dams via three primary routes: (1) spillways, (2) turbines, or (3) juvenile bypass systems, which divert fish away from turbines and route them downstream. Bypass systems may expose fish to trauma, increased stress, or disease. However, numerous studies have indicated that direct survival through bypass systems is comparable to and often higher than that through spillways. Some researchers have suggested that the route of dam passage affects mortality in the estuary or ocean, but this is complicated by studies finding that fish size affects the route of passage. We tested whether passage through bypass systems was associated with the probability of adult return after accounting for fish length and other covariates for two species of concern. We also investigated the association between fish length and the probability of bypass at dams and how this relationship could lead to spurious conclusions regarding effects of bypass systems on survival if length is ignored. We found that (1) larger fish had lower bypass probabilities at six of seven dams; (2) larger fish had a higher probability of surviving to adulthood; (3) bypass history had little association with adult return after accounting for fish length; and (4) simulations indicated that spurious effects of bypass on survival may arise when no true bypass effect exists, especially in models without length. Our results suggest that after fish leave the hydropower system, bypass passage history has little effect on mortality. Our findings underscore the importance of accounting for fish size in studies of dam passage or survival.

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Section: Discussionmentioning

confidence: 99%

“…Evans et al. () found that steelhead with general bodily injuries had higher susceptibility to avian predation but that the level of descaling was not influential. Gadomski et al.…”

Section: Discussionmentioning

confidence: 99%

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Associations among Fish Length, Dam Passage History, and Survival to Adulthood in Two At‐Risk Species of Pacific Salmon

et al. 2019

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“…, Evans et al. ) and downstream life history decisions (Satterthwaite et al. ), which may influence their motivation to feed during late summer despite the increased effort required to acquire food in low‐drift and low‐flow conditions (Caldwell et al.…”

Section: Discussionmentioning

confidence: 99%

Do precipitation extremes drive growth and migration timing of a Pacific salmonid fish in Mediterranean‐climate streams?

Kelson

Carlson

2019

Ecosphere

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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.

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“…The methods of Evans et al. () were used to capture, tag, and release steelhead smolts at Rock Island Dam (Figure ). Steelhead smolts were captured at the Rock Island Dam juvenile fish trap, anesthetized (with tricaine methanesulfonate), and PIT‐tagged (12‐ × 2‐mm tags [length × width]; 134.2 kHz) annually during 2008–2018.…”

Section: Methodsmentioning

confidence: 99%

Cumulative Effects of Avian Predation on Upper Columbia River Steelhead

et al. 2019

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To investigate the cumulative effects of colonial waterbird predation on fish mortality and to determine what proportion of all sources of fish mortality (1 − survival) was due to bird predation, we conducted a mark–recapture–recovery study with upper Columbia River steelhead Oncorhynchus mykiss that were PIT‐tagged and released (N = 78,409) at Rock Island Dam on the Columbia River, USA. We used a state–space Bayesian model that incorporated live detections and dead recoveries of tagged fish to jointly estimate predation and survival probabilities during smolt out‐migration to the Pacific Ocean over an 11‐year study period. Estimated cumulative (all colonies combined) avian predation probabilities ranged from 0.31 (95% credible interval [CRI] = 0.27–0.38) to 0.53 (95% CRI = 0.42–0.64) annually, indicating that avian predation was a substantial source of mortality. Of the predator species evaluated, predation by Caspian terns Hydroprogne caspia was often the highest, with predation probabilities ranging from 0.11 (95% CRI = 0.09–0.14) to 0.38 (95% CRI = 0.29–0.47). Probabilities of predation by double‐crested cormorants Phalacrocorax auritus and mixed colonies of California gulls Larus californicus and ring‐billed gulls L. delawarensis were generally lower than the probabilities for terns but were also substantial, with upwards of 0.04 (95% CRI = 0.03–0.07; cormorants) and 0.31 (95% CRI = 0.25–0.39; gulls) of steelhead consumed. Comparisons of total smolt mortality with mortality due to avian predation indicated that avian predation accounted for 42% (95% CRI = 30–56%) to 70% (95% CRI = 53–87%) of total mortality, suggesting that more steelhead were consumed by avian predators than died from all other mortality sources combined. Results indicate that avian predation, although not the original cause of steelhead declines in the basin, is now a factor limiting the survival of upper Columbia River steelhead. Using the analytical framework developed in this study, future studies can consider the cumulative impact of multiple mortality sources across large spatial and temporal scales to more fully understand the extent to which they limit fish survival.

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Relationship between Juvenile Fish Condition and Survival to Adulthood in Steelhead

Cited by 38 publications

References 26 publications

Associations among Fish Length, Dam Passage History, and Survival to Adulthood in Two At‐Risk Species of Pacific Salmon

Associations among Fish Length, Dam Passage History, and Survival to Adulthood in Two At‐Risk Species of Pacific Salmon

Do precipitation extremes drive growth and migration timing of a Pacific salmonid fish in Mediterranean‐climate streams?

Cumulative Effects of Avian Predation on Upper Columbia River Steelhead

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