| Summary: | I show that the growth rate of Arctic grayling Thymallus arcticus is reduced by electrofishing and tagging (Floy FD-67 internal anchor tags) and present evidence that this reduction may alter interannual movement behavior. I demonstrate the reduction in growth by comparing length at age and annual growth of fish that either were or were not electrofished and tagged 1 year previously. For six of the seven ages compared (ages 3-9), the mean length of electrofished and tagged fish was reduced; in four cases the reduction was significant (P < 0.05 or P < 0.001). Annual growth of electrofished and tagged fish was also significantly less than that of untagged fish (P < 0.0001), with a median reduction of 18%. These reductions in growth may change a fish's movement behavior because fish that move upstream grow more quickly than fish that stay put or move downstream. If differences in growth are responsible for differences in movement, the effects of electrofishing and tagging are large enough to turn a fish destined to move upstream into one that stays put or moves downstream. [References: 30]
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