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Melnychuk, Michael C.; Welch, David W.

<b>Abstract</b><br/>Behavioral decisions during periods of vulnerability to predation risk, such as migrations during the juvenile life-history stage, may strongly affect the probability of survival. Habitats through which animals migrate are heterogeneous, and risk-reducing behaviors may be more important in some habitats than others. Using biotelemetry data, diurnal and seasonal riverine migration patterns of >3800 juvenile salmon across four species, 12 watersheds, and five years were quantified to evaluate possible effects of migration timing on survival from lower river reaches to coastal waters. In small, clear rivers most salmon avoided migrating during daylight hours, and average survival of fish migrating at night (55%; 95% confidence limits 50–61%) was twice that of fish migrating in daylight (24%; CL 17-31%). Conversely, in the large, heavily silted Fraser River neither preference for nocturnal travel nor effects of diurnal timing on survival were observed. Early ocean survival was also influenced by the timing of ocean entry, but in opposite directions for fish from the Fraser River and smaller rivers. In the Fraser River, average survival for later migrants (69%; CL 60–77%) was nearly twice that of earlier migrants (38%; CL 33–44%), likely related to seasonal increases in river flow. In contrast, in smaller rivers, average survival for earlier migrants (70%; CL 65–74%) was 3-fold greater than survival for later migrants (19%; 95% CL 14–25%). Together these results demonstrate that timing decisions affecting survival of juvenile salmon during their migration are likely mediated by landscape characteristics that plausibly influence the risk of predation.; <b>Usage notes</b><br /><div class="o-metadata__file-usage-entry"><h4 class="o-heading__level3-file-title">Input data for Melnychuk and Welch - Behavioral Ecology</h4><div class="o-metadata__file-description">Contains data describing the date and light level during detection of tagged salmon smolts in British Columbia Rivers, and metadata for individual tagged fish. Detection data are from acoustic transmitters surgically implanted into migrating smolts, and detected on submerged hydrophones with data loggers. csv file is saved with Microsoft Excel 2016. Variables are defined in manuscript.</div><div class="o-metadata__file-name">Melnychuk_Welch_input_data.csv</br></div></div>

British Columbia

Dryad version number: 1</p>

Version status: submitted</p>

Dryad curation status: Published</p>

Sharing link: https://datadryad.org/stash/share/YNkdzZzbD0XIZJFRbO4dfzKiHTnCR4sz5yHs_sbQVO4</p>

Storage size: 216311</p>

Visibility: public</p>

University of British Columbia Library

10.14288/1.0397844

https://doi.org/10.5683/SP2/OTX1CA; https://doi.org/10.5061/dryad.f06k49s

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