Reduction in growth due to electrofishing and tagging may change interannual movement behavior of stream salmonids: Evidence from Arctic grayling in an interior Alaskan stream
Nf. Hughes, Reduction in growth due to electrofishing and tagging may change interannual movement behavior of stream salmonids: Evidence from Arctic grayling in an interior Alaskan stream, T AM FISH S, 127(6), 1998, pp. 1072-1077
I show that the growth rate of Arctic grayling Thymallus arcticus is reduce
d by electrofishing and tagging (Floy FD-67 internal anchor tags) and prese
nt evidence that this reduction may alter interannual movement behavior. I
demonstrate the reduction in growth by comparing length at age and annual g
rowth 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 w
as 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 < 0.0
001), with a median reduction of 18%. These reductions in growth may change
a fish's movement behavior because fish that move upstream grow more quick
ly 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.