Wanted dead or alive: a state-space mark–recapture–recovery model incorporating multiple recovery types and state uncertainty

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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“…; Hostetter et al. ). Therefore, a beta‐binomial distribution was used to facilitate an “informed partitioning” method.…”

Section: Methodsmentioning

confidence: 98%

“…; Hostetter et al. ), which required predation rates to be partitioned by river reach (Figure ). A benefit of this partitioning was that predation rates delineated by river reach could be summed to evaluate colony‐specific and cumulative predation rates (Figure ).…”

Section: Methodsmentioning

confidence: 99%

Cumulative Effects of Avian Predation on Upper Columbia River Steelhead

et al. 2019

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“…This is especially true of SCR‐based studies which frequently target rare and elusive species and often deal with sparse datasets (Blanc et al 2013, Satter et al 2019, Tourani et al 2020). Dead‐recovery data, on the other hand, are often readily available for a wide array of taxa studied with CR methods (Catchpole et al 2004, Kendall et al 2006, Besnard et al 2007, Sidhu et al 2007, Hostetter et al 2018). Leveraging the demographic and spatial information contained in such data in an open‐population spatial capture–recapture framework has the potential to improve population parameter estimation with little to no additional cost of sampling.…”

Section: Discussionmentioning

confidence: 99%

Integrating dead recoveries in open‐population spatial capture–recapture models

et al. 2021

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“…The low recapture rates (inherent to juvenile bypass detection of PIT tagged smolts) inhibits precision in this partitioning. Previous research indicates that consumption impacts from individual colonies were spatially proportionate amongst river reaches across years [ 25 , 26 ]. We therefore implemented an “informed partitioning” method to share information among years and increase precision in estimates of reach-specific predation probabilities.…”

Section: Methodsmentioning

confidence: 99%

Cumulative effects of piscivorous colonial waterbirds on juvenile salmonids: A multi predator-prey species evaluation

et al. 2022

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We investigated the cumulative effects of predation by piscivorous colonial waterbirds on the survival of multiple salmonid (Oncorhynchus spp.) populations listed under the U.S. Endangered Species Act (ESA) and determined what proportion of all sources of fish mortality (1 –survival) were due to birds in the Columbia River basin, USA. Anadromous juvenile salmonids (smolts) were exposed to predation by Caspian terns (Hydroprogne caspia), double-crested cormorants (Nannopterum auritum), California gulls (Larus californicus), and ring-billed gulls (L. delawarensis), birds known to consume both live and dead fish. Avian consumption and survival probabilities (proportion of available fish consumed or alive) were estimated for steelhead trout (O. mykiss), yearling Chinook salmon (O. tshawytscha), sub-yearling Chinook salmon, and sockeye salmon (O. nerka) during out-migration from the lower Snake River to the Pacific Ocean during an 11-year study period (2008–2018). Results indicated that probabilities of avian consumption varied greatly across salmonid populations, bird species, colony location, river reach, and year. Cumulative consumption probabilities (consumption by birds from all colonies combined) were consistently the highest for steelhead, with annual estimates ranging from 0.22 (95% credible interval = 0.20–0.26) to 0.51 (0.43–0.60) of available smolts. The cumulative effects of avian consumption were significantly lower for yearling and sub-yearling Chinook salmon, with consumption probabilities ranging annually from 0.04 (0.02–0.07) to 0.10 (0.07–0.15) and from 0.06 (0.3–0.09) to 0.15 (0.10–0.23), respectively. Avian consumption probabilities for sockeye salmon smolts was generally higher than for Chinook salmon smolts, but lower than for steelhead smolts, ranging annually from 0.08 (0.03–0.22) to 0.25 (0.14–0.44). Although annual consumption probabilities for birds from certain colonies were more than 0.20 of available smolts, probabilities from other colonies were less than 0.01 of available smolts, indicating that not all colonies of birds posed a substantial risk to smolt mortality. Consumption probabilities were lowest for small colonies and for colonies located a considerable distance from the Snake and Columbia rivers. Total mortality attributed to avian consumption was relatively small for Chinook salmon (less than 10%) but was the single greatest source of mortality for steelhead (greater than 50%) in all years evaluated. Results suggest that the potential benefits to salmonid populations of managing birds to reduce smolt mortality would vary widely depending on the salmonid population, the species of bird, and the size and location of the breeding colony.

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Wanted dead or alive: a state-space mark–recapture–recovery model incorporating multiple recovery types and state uncertainty

Cited by 8 publications

References 47 publications

Cumulative Effects of Avian Predation on Upper Columbia River Steelhead

Cumulative Effects of Avian Predation on Upper Columbia River Steelhead

Integrating dead recoveries in open‐population spatial capture–recapture models

Cumulative effects of piscivorous colonial waterbirds on juvenile salmonids: A multi predator-prey species evaluation

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