Movement patterns of fish revealed by otolith microchemistry: a comparison of putative migratory and resident species

We examined movement patterns in two wide ranging species of freshwater fish, a putative resident species the slimy sculpin, Cottus cognatus, and a migratory species the Arctic grayling, Thymallus arcticus. We attempted to trace the extent and patterns of movement over the life history of individual fish using elemental signatures deposited in otoliths of fish that reflect distinctive freshwater chemistries. Patterns of movement were highly variable within both species of fish among the rivers examined. Patterns included movement among major river systems, use of smaller tributaries within a river, but also some individuals exhibited limited movement. Although the diversity of water chemistry signatures varied among watersheds, this was not reflected in a difference between the two species. There was a tendency for less variability in elemental signatures during the older life stages of the fish, particularly for sculpin. The life history information gained in this study demonstrates that both species make extensive movements within a watershed during their life history. Our otolith microchemistry analysis suggests excellent dispersal abilities, and reveals that, despite being referred to as migratory and resident, putative movements by many individuals from both species were extensive.