Contrasting patterns of territoriality and foraging mode in two stream-dwelling salmonids, Arctic char ( Salvelinus alpinus ) and brown trout ( Salmo trutta )

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Gunnarsson, Guðmundur Smári, Steingrímsson, Stefán Óli
• Other Authors: Tonn, William
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2011
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Arctic; Iceland; Salvelinus alpinus
• Online Access: http://dx.doi.org/10.1139/f2011-127; http://www.nrcresearchpress.com/doi/full-xml/10.1139/f2011-127; http://www.nrcresearchpress.com/doi/pdf/10.1139/f2011-127

Territoriality and foraging behaviour play major roles in determining the abundance and distribution of mobile animals. To date, territorial behaviour of young-of-the-year (YOY) salmonids is typically described for sit-and-wait individuals that defend territories from one foraging station, but rarely for more mobile fish. We examined the territorial behaviour and foraging mode of 31 YOY Arctic char ( Salvelinus alpinus ) and 30 YOY brown trout ( Salmo trutta ) in relation to ecological factors in six rivers in northern Iceland. Arctic char used larger territories than brown trout, corresponding with high and low mobility prior to attacking prey, respectively. Within species, more mobile fish also used larger territories. Territory size increased with body size and declined with increased food abundance as predicted, but surprisingly increased with rising intruder pressure. Finally, Arctic char territories overlapped more and were less exclusively defended than brown trout territories. This study shows that territories of mobile individuals may not always pertain to the same rules as single central-place territories and highlights that territorial behaviour, and its role in population regulation, may vary between salmonid species.