. The Canadian field-naturalist. Natural history. 2002 Fisher, Willis, Olson, and Krentz: Flathead Chubs in Upper Missouri 37 Table 5. Mean back-calculated total lengths (TL; mm) at age for Flathead Chubs collected in 1997 and 1999 from the Missouri (MO) River in North Dakota. Standard errors are in parentheses. Also noted are total lengths (mm) at age for Flathead Chubs from Perry Creek, Iowa (Martyn and Schmulbach 1978) and from the Peace River, Alberta [Bishop (1975); fork lengths converted to total length using conversion in Martyn and Schmulbach (1978)]. Age MO River (N) MO River (TL) Per
. The Canadian field-naturalist. Natural history. 2002 Fisher, Willis, Olson, and Krentz: Flathead Chubs in Upper Missouri 37 Table 5. Mean back-calculated total lengths (TL; mm) at age for Flathead Chubs collected in 1997 and 1999 from the Missouri (MO) River in North Dakota. Standard errors are in parentheses. Also noted are total lengths (mm) at age for Flathead Chubs from Perry Creek, Iowa (Martyn and Schmulbach 1978) and from the Peace River, Alberta [Bishop (1975); fork lengths converted to total length using conversion in Martyn and Schmulbach (1978)]. Age MO River (N) MO River (TL) Perry Creek Peace River 1 85 () () (NA) 2 37 () () (NA) 3 17 () () (NA) 4 6 () () (NA) 5 1 (NA) NA (NA) The back-calculated lengths at the time of annulus formation for each age group suggested that Flathead Chubs, on average, increase their length by approxi- mately 46% between ages 1 and 2, but then growth slows and plateaus at annual length increases of 19-22% during the remainder of their life (Table 5). Incremental growth analyses for Flathead Chubs col- lected in September of each year indicated that por- tions of the Flathead Chub length range, including those between the total lengths of 95 and 135 mm, significantly increased at a more rapid rate during 1997 than did similar sized fish in 1999 (P<; O u ox c 50 -r 45 â 40 â S 35 30 S 25 20. 1%-^' 96-^^' ^X^Al^* ^^SA^* ^65^1^ ^^%,\9^ .\9^ Total length group (mm) Figure 7. Mean growth increments for Flathead Chubs collected in the Missouri River, North Dakota in September of 1997 and 1999. The increments represent estimated growth from the time of annulus fonnation to the time of capture each year. The letters a and b represent the statistical comparison between years for each total length group noted on the X-axis (vertical comparison). The letters x, y, and z denote the comparison results among total length gr
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