Temperature–growth patterns of individually tagged anadromousArctic charrSalvelinus alpinusinUngava andLabrador,Canada

Abstract

Individual measurements of annual, or within‐season growth were determined from tag‐recaptured Arctic charr and examined in relation to summer sea surface temperatures and within‐season capture timing in the Ungava and Labrador regions of Eastern Canada. Differences between two years of growth (2010–2011) were significant for Ungava Bay Arctic charr, with growth being higher in the warmer year. Growth of Labrador Arctic charr did not vary significantly among years (1982–1985). Regional comparisons demonstrated that Ungava Arctic charr had significantly higher annual growth rates and experienced warmer temperatures than Labrador Arctic charr. The higher annual growth of Ungava Bay Arctic charr was attributed to the high sea surface temperatures experienced in 2010–2011 and the localised differences in nearshore productivity as compared to Labrador. Within‐season growth rates of Labrador Arctic charr peaked in June, declined towards August and were negatively correlated with the length of time spent at sea and mean experienced sea surface temperatures. A quadratic model relating growth rate to temperature best explained the pattern of within‐season growth. Collectively, results suggest that increases in water temperature may have profound consequences for Arctic charr growth in the Canadian sub‐Arctic, depending on the responses of local marine productivity to those same temperature increases.

Otolith‐inferred patterns of marine migration frequency in Nunavik Arctic charr

“…The improved growth and associated better reproductive output potential resulting from migrating to a marine environment constitute the most likely reason for the maintenance of the anadromy tactic in salmonids despite the related mortality costs (Dodson et al ., 2013; Hendry et al ., 2004). Comparisons of migratory‐driven growth in Ungava Bay (Nunavik) and along the Labrador coast (Nunatsiavut) have noted a beneficial link between anadromy and nearshore marine productivity in charr (Murdoch et al ., 2015). The findings of this study, therefore, suggest that anadromy is sufficiently fitness‐rewarding under current environmental conditions to be nearly consistently maintained once adopted.…”

Using movement, diet, and genetic analyses to understand Arctic charr responses to ecosystem change

“…Predicting responses of charr to climate change remains challenging. Northward expansion of key prey like capelin could provide an important food source for the low productivity coastal ecosystems found along the north coast of Labrador (Murdoch et al 2015). Comparisons of Ungava and Labrador showed that slightly elevated temperatures coupled with higher local productivity were associated with notably better growth of Ungava charr (Murdoch et al 2015).…”

“…Northward expansion of key prey like capelin could provide an important food source for the low productivity coastal ecosystems found along the north coast of Labrador (Murdoch et al 2015). Comparisons of Ungava and Labrador showed that slightly elevated temperatures coupled with higher local productivity were associated with notably better growth of Ungava charr (Murdoch et al 2015). Conversely, the concomitant ecosystem changes that facilitate the northward expansion of prey may have negative effects on charr.…”

“…Conversely, the concomitant ecosystem changes that facilitate the northward expansion of prey may have negative effects on charr. For example, growth is dependent on interactions between water temperature, prey availability, and seasonal phenologies (Power et al 2012, Murdoch et al 2015. Charr growth is most efficient at lower temperatures when food is limited (Larsson & Berglund 2005).…”