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

Abstract

Faulkner et al. (2019) presented data and analyses to support a hypothesis that bypass encounters by juvenile Chinook Salmon Oncorhynchus tshawytscha and steelhead O. mykiss at hydropower dams are not harmful (e.g.,

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

“…In their comment, Storch et al (2021) take issue with several aspects of the Faulkner et al (2019) study. We welcome the criticisms raised by Storch et al (2021) since we believe it is constructive to debate the merits of scientific analyses, especially when the outcomes are used to support management decisions. However, we believe that Storch et al (2021) mischaracterized some of our results and conclusions.…”

“…We welcome the criticisms raised by Storch et al (2021) since we believe it is constructive to debate the merits of scientific analyses, especially when the outcomes are used to support management decisions. However, we believe that Storch et al (2021) mischaracterized some of our results and conclusions. In particular, Storch et al (2021) state in their first sentence that " Faulkner et al (2019) presented data and analyses to support a hypothesis that bypass encounters by juvenile Chinook Salmon … and steelhead … at hydropower dams are not harmful…" This choice of wording seems to imply that the motivation of our investigation was "to support" a preconceived position.…”

“…Furthermore, in reporting results we never stated that bypass encounters are not harmful in general, only that the evidence for an effect of bypass passage on adult return probability was not strong after accounting for fish length. Storch et al (2021) also state that " Faulkner et al (2019) fitted a suite of mixed-effects models to assess their hypothesis that fish length largely explains variation in bypass probability." This is another mischaracterization of "our hypothesis," and this time it is not even defensible as a loose statement of a classic null hypothesis.…”

“…Moreover, our results simply showed that there was strong evidence for length effects on bypass probability after accounting for other sources of variation, and we made no such claim that fish length "largely explains variation." Storch et al (2021) go on to make statements like "If the assertion of Faulkner et al (2019) -that variation in adult returns can be best explained by Transactions of the American Fisheries Society 150:196-206, 2021 Published 2020. This article is a U.S. Government work and is in the public domain in the USA ISSN: 0002-8487 print / 1548-8659 online DOI: 10.1002/tafs.10280 fish size-is credible…" and "This brings into question the veracity of an argument, as in Faulkner et al (2019), suggesting that size upon ocean entry is the principal driver of differential survival."…”

“…Instead, we showed that there was strong evidence for an association between length and adult return probability after accounting for other sources of variation, but we never made the assertion that length was the primary factor affecting survival. Storch et al (2021) put forth several concerns with the data, methods, and conclusions of Faulkner et al (2019) and provide some additional analyses meant to support their arguments. Although we agree with some of their concerns, we find weaknesses in their arguments and shortcomings in their supporting analyses that undermine many of their conclusions.…”