Development of an accurate model to predict the phenology of Atlantic salmon smolt spring migration

Abstract

1. Changes in migration timing, resulting from the alteration in river continuity or the effect of climate change, can have major consequences on the population dynamics of diadromous fish. Forecasting the phenology of fish migration is thus critically important to implement management actions aimed at protecting fish during their migration. 2. In this study, an 11-year monitoring survey of Atlantic salmon smolts (Salmo salar) from the Ourthe River, Belgium, was analysed within a European Special Area of Conservation to improve the understanding of environment-induced spring migration. A logistic model was fitted to forecast smolt migration and to calculate phenological indicators for management, i.e. the onset, end, and duration of migration, while accounting for the influence of photoperiod, water temperature, and hydrological conditions. 3. The results indicated that the photo-thermal units accumulated by smolts above a 7 C temperature threshold was a relevant proxy to reflect the synergistic effect between temperature and photoperiod on smolt migration. After integrating the effect of river flow pulses, the model accurately explained the inter-annual changes in migration timing (R 2 = 0.95). The model predictions provide decisive management information to identify sensitive periods during which mitigation measures (e.g. hydropower turbine shutdown, river discharge management) should be conducted to promote smolt survival. 4. The model was used to predict phenological characteristics under future scenarios of climate change. The results suggest a joint effect of hydrological alterations and water warming. Temperature increases of 1-4 C were associated with earlier initiation of migration, 6-51 days earlier, and spring flood events greatly influenced the duration of the migration period. Accordingly, the combined effects of human-induced modifications of the hydrological regimes and increasing temperatures could result in a mismatch between the smolt and favourable survival conditions in the marine environment.

Improving bypass performance and passage success of Atlantic salmon smolts at an old fish-hostile hydroelectric power station: a challenging task

“…Eflows); (v) increase of the functioning flow of the bypass; and vi) shutdown of the microturbine and the main turbines during the night period. This last management measure could be facilitated by the existence of a predictive model of smolts' downstream migration in the Meuse River basin at the spring season scale, which will enable effective targeting of this measure (Teichert et al, 2020). The Lorcé Dam has been equipped with an operational upstream fish pass since 2007 (Benitez et al, 2015), and thus we hope that in the future this site will go from a fish-hostile to a fish-friendly ecological status.…”

Trying to choose the less bad route: Individual migratory behaviour of Atlantic salmon smolts (Salmo salar L.) approaching a bifurcation between a hydropower station and a navigation canal

“…Upstream of the Kaplan turbines, the bar screen should be combined with a downstream bypass, which would favour successful passage of migrating smolts (Larinier and Travade, 2002;Fjeldstad et al, 2018). In addition, a combination of real-time smolt monitoring and the recently developed predictive model of smolt downstream migration (Teichert et al, 2020) may be useful when mitigation measures need to be implemented, such as the opening of the spillway gates or turbines shutdown. In some instances, spillway gates may be the preferred migration route (Calles et al, 2012;Katopodis and Williams, 2012).…”

Biological and environmental influences on the migration phenology of Atlantic salmon Salmo salar smolts in a chalk stream in southern England

“…These releasing factors predominantly involve water temperature and river discharge, although other factors might also contribute to migratory release (Aldvén et al, 2015;Antonsson & Gudjonsson, 2002;McCormick et al, 1998). The cumulative water temperature and the relative changes in daily water temperature experienced by smolts have both been found to influence the timing of smolt migration (Teichert et al, 2020;Zydlewski et al, 2005).…”

“…These releasing factors predominantly involve water temperature and river discharge, although other factors might also contribute to migratory release (Aldvén et al., 2015; Antonsson & Gudjonsson, 2002; McCormick et al., 1998). The cumulative water temperature and the relative changes in daily water temperature experienced by smolts have both been found to influence the timing of smolt migration (Teichert et al., 2020; Zydlewski et al., 2005). Increased river discharge has also been reported as an important releasing factor, although whether it is more important than water temperature appears river‐specific (Aldvén et al., 2015; Jonsson & Ruud‐Hansen, 1985).…”