Differential Losses of Floy Anchor Tags between Male and Female Brown Trout

Abstract

Abstract Annual loss of floy anchor tags among brown trout Salmo trutta, permanently marked by adipose tin removal, was studied in a population returning to spawn in three successive years (1988–1990) in a tributary of the upper Bow River, Alberta. Significant differences were detected in tag losses between males (44.3%) and females (15.0%). Fork length distributions did not differ between brown trout retaining their tags and fish losing them or between fork length distributions of male and female brown trout that lost their tags. We speculate that higher tag losses among males may be caused by the biting of tags by other males during conflicts on the spawning grounds.