Food consumption and growth of Atlantic salmonSalmo salarparr in sub‐Arctic rivers: empirical support for food limitation and competition

The quantitative food consumption and somatic growth of Atlantic salmonSalmo salarparr were compared between three sub‐Arctic rivers in northern Norway and Finland, addressing the potential occurrence of resource limitation and interspecific competition. In one of the rivers, previous resource partitioning studies have suggested severe dietary competition between juvenileS. salarand a dense population of alpine bullheadsCottus poecilopus. It was hypothesized thatS. salarparr in this river would have restricted food consumption and growth rates compared to theS. salarpopulations in the other two rivers where interspecific competition was less likely to occur. The feeding and growth performance differed significantly between theS. salarpopulations. The lowest food acquisition and growth rates were in theS. salarparr population living in sympatry withC. poecilopus, confirming a restricted food supply for theS. salarparr and providing empirical support for the presence of resource limitation and interspecific food competition in this river system. The study reveals thatS. salarparr in sub‐Arctic rivers may experience food limitations resulting in diminished growth rates.