A potential growth thermal index (PGTI ) for estimating juvenile Atlantic salmon (Salmo salar) size‐at‐age across geographical scales
Sébastien Ouellet‐Proulx, Anik Daigle, André St‐Hilaire, Carole‐Anne Gillis, Tommi Linnansaari, Guillaume Dauphin, Normand Émile Bergeron - Aquatic Science
- Ecology, Evolution, Behavior and Systematics
Abstract
We present a potential growth thermal index (PGTI) and assess its correlation with juvenile Atlantic salmon Salmo salar fork length data collected near the end of the growth season in a range of latitudinal locations and geographic scales (watershed, regional, continental) across the American Northeast. The PGTI is based on two components: a water temperature‐dependent growth curve, and a water temperature time series continuously describing the thermal environment preceding fish sampling. Testing various shapes and characteristics of the temperature‐growth curve against fish length data revealed strong positive correlations for all combinations. PGTI Warming, calculated only from the beginning of the growth season until maximum summer temperature is reached, consistently performed well in explaining fish size‐at‐age across the latitudinal gradient and the three geographic scales that were considered. Varying thermal contrasts created by repeat sub‐sampling of the dataset showed that fish length is better explained by the level of thermal contrast within the dataset than the geographical scale of analysis. A simple Generalized Linear Model (GLM) using a log link function with PGTI Warming, fish density and water discharge as predictors explained 87% of the variance of size‐at‐age of 0+ and 1+ juvenile Atlantic salmon.
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