Smolt outmigration timing in Norway ...

• Main Authors: Lennox, Robert, Vollset, Knut, Ugedal, Ola, Lamberg, Anders, Skaala, Øystein, Sandvik, Anne, Saegrov, Harald, Kristiensen, Torstein, Jensen, Arne, Haraldstad, Tormond, Barlaup, Bjørn
• Format: Dataset
• Language: English
• Published: Dryad 2021
• Subjects: FOS Biological sciences; Atlantic salmon; Salmo salar
• Online Access: https://dx.doi.org/10.5061/dryad.p2ngf1vq9; https://datadryad.org/stash/dataset/doi:10.5061/dryad.p2ngf1vq9

Aim - Accurate predictions about transition timing of salmon smolts between freshwater and marine environments are key to effective management. We aimed to use available data on Atlantic salmon smolt migration to predict the emigration timing in rivers throughout Norway. Location - In this study, we used data outmigration timing data of Atlantic salmon (Salmo salar) smolts from 41 rivers collected from 1984-2018 to make a predictive model for the timing of out-migrating salmon smolts along 12 degrees latitude. Methods - Smolt migration data were collated from rivers where smolts are monitored with traps, video, and tagging and matched to river-specific metadata. Using a mixed effect generalized additive model, we tested for effects of spatial location, air temperature, river flow, and counting methods on the timing of 25% smolt emigration from rivers. Results - After accounting for spatial effects and repeated measurements (across years and among rivers), air temperature and counting method were significant ... : Data Collection Smolt migration data The goal of our study was to collate available smolt migration data from Norway, in an attempt to make a predictive model of the timing of smolt migration in this area. Data were extracted from three sources. (1) published scientific articles, (2) Norwegian reports, and (3) unpublished data available from the authors’ research institutions. Data were updated from previous compilations using the same methodology (Ugedal et al. 2014). The database does not contain daily counts but summarizes the timing of smolt emigration by percentiles, recording the dates of 25% passage, 50% passage, and 75% passage (Table 1). Smolt migration was monitored in 348 river years, comprising 47 rivers between 58.02 and 70.50 degrees latitude from 1984-2018 (Figure 1). Monitoring was conducted using different methods of observation: traps (N = 252 river years), video counting (N = 84 river years), and tagging (N = 12 river years). Note Eio and Vigda are the only two rivers that had multiple ...