. The Canadian field-naturalist. Natural history. ⢠-So ' -^ Si 0£ â o> o â ^^ &£ ^ â â. logjQtotal length (mm) logjototal length (mm) Figure 8. Weight-length relationships (log 10 transformed) from Flathead Chubs collected in the Missouri River, North Dakota, during various periods of 1997 and 1999. The cross-hair markers denote chubs collected in 1997 and the circles represent those collected in 1999. The regression relationship for each set of data is depicted with a solid line. Statistical analyses f
. The Canadian field-naturalist. Natural history. ⢠-So ' -^ Si 0£ â o> o â ^^ &£ ^ â â. logjQtotal length (mm) logjototal length (mm) Figure 8. Weight-length relationships (log 10 transformed) from Flathead Chubs collected in the Missouri River, North Dakota, during various periods of 1997 and 1999. The cross-hair markers denote chubs collected in 1997 and the circles represent those collected in 1999. The regression relationship for each set of data is depicted with a solid line. Statistical analyses for these data are summarized in Table 6. all comparable lengths than in 1997 (Figure 8). The intercept values and slopes of these regression analy- ses were all significantly different between years during each sample period (P< ; Table 6). During some sample periods, the 1999 predicted weights for some Flathead Chub lengths exceeded the 1997 predicted weights by as much as 50%. The weight-length equations reported here were similar to those documented by Gould (1985); how- ever, that study did not identify any significant dif- ferences in slopes or intercepts among sample peri- ods. It would be reasonable to hypothesize that when the environment favors increased growth rates (based on total length), that the habitats would also be favorable for individuals to maintain high body condition (plumpness). Although the logic of this argument seems apparent, our data suggest that Flathead Chubs in 1997 acquired greater total length additions, but did so while they were less plump. Fish condition has been correlated with prey avail- ability in many lentic populations (Wege and Anderson 1978; Liao et al. 1995; Marwitz and Hubert 1997; and Porath and Peters 1997), but we are aware of no such analyses for lotic fish popula- tions. We cannot explain the contradictory condition and growth observations discussed above; however, it could be hypothesized that during a year w
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