Notes: Retention of Adaptive Rheotactic Behavior by F1Fluvial Arctic Grayling

Abstract

Abstract Downstream movements of age-0 Arctic grayling Thymallus arcticus from an indigenous fluvial population (Big Hole River) and two inlet-spawning, lacustrine populations (Upper Red Rock Lake and Ennis Reservoir) were compared in a natural stream. All fish were incubated and reared together in a hatchery and acclimated together in the stream before being released in the stream. All fluvial test fish were F1 progeny of parents originating as gametes from wild fish but reared in a natural lake (1993 trials) or in a hatchery (1994 trials). The F1 fish in four 1993 trials were progeny of parents whose rheotaxis had also been tested as age-0 young. In all four trials of fish with 7–14 d stream acclimation, significantly fewer fluvial than lacustrine fish (P < 0.005) were recovered within 1 d in nets at a weir 1 km downstream from the release site. In two trials of fish with 1 d acclimation, significantly fewer fluvial than lacustrine fish were also recovered in one trial (P < 0.005) but not in the other (...