ISAP Comments on Pallid Sturgeon Condition AssesmentDraft

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t1 sample size of fish used to develop the model, and the potential bias in deriving the model given that it was based largely on fish sampled from the upper basin. Most fish in the size class 600- 1200 mm in the samples used in Randall et al. occur below the curve. As pallid lengths approach 1200 mm, body condition deviates farther from the modeled line, suggesting that as pallid sturgeon grow in length K„declines (Figure 5). However, most fish>1200 mm are above the Shuman et al. line, suggesting higher observed K„ values than those predicted by the model; those fish were excluded from the analyses due to presumed reproductive condition. Thus, it appears that the use of the Shuman et al. model along with the capture of more, larger fish through time could be the cause of the posited range-wide decline in condition in Kn. The discernable decline might be an artifact of pallid sturgeon reaching a length near the inflection point in the Shuman et al. length-weight model (see Figures 4 and 5 in Randall et al.). To determine whether the spatially and temporally dispersed fish with low body condition refect a biotic phenomenon, rather than an artifact of the analytical procedure, it is worth analyzing the data using additional methods. A first approach might be to create a new K„using all lengths of pallid sturgeon in the PSPAP and HAMP databases (and/or separated by upper and lower basins). The K„values could be compared among years to determine if the condition factors for recent years consistently fall below the mean (that is, 1.0). Another approach would be to use Analysis of Covariance (ANCOVA) and compare slopes among years by basin to see if the slopes differ significantly. This approach avoids the comparison of body condition measures against a(perhaps inappropriate)baseline or reference model. The investigators might also consider the ontogenetic switch point of pallid sturgeon to piscivory or to sexual maturity in the analysis of K . Those two ontogenetic changes often have a substantial influence on allocation of resources to growth in length versus weight. Thus, a corresponding statistical comparison might be undertaken as a two-way ANOVA, with year and ontogenetic stage as factors. To avoid ambiguity in the report's conclusions, the ISAP suggests rigorous use of inferential statistics (with p-values)to make comparisons of pallid condition among years. It would also be useful to compute the probability of making a Type II error(i.e., a false finding of no difference)by conducting an appropriate power analysis. The analyses presented in the Randall et al. report potentially mask variation among individual pallid sturgeon, which by ignoring the inherent variability among individuals, can lead to misleading conclusions. An analysis to address variability among individual pallid sturgeon might include quantile regression as described by Cade et al. (2011). This approach explicitly incorporates individual variation, and the resulting analyses of body condition need not rely on comparison to a baseline model. A subset of the Missouri River pallid sturgeon population is well-known as individual fish due to multiple captures of tagged individuals over time and monitoring of telemetered individuals. Apparently, more than 2000 different fish have been captured and measured on multiple occasions. It would be useful to compute body condition for those individuals for comparison among basins, segments, sites, bends, hatchery versus wild individuals, and other attributes that might affect pallid sturgeon body condition. Such detailed analysis of individual pallid sturgeon might better characterize individual body condition that would be obscured in aggregated analyses, and possibly reveal patterns related to fish-stocking origin. Related to this, as Randall et al. point out, a better record of handling of hatchery-reared pallid sturgeon(considering ISAP Comments on Draft Pallid Sturgeon Condition Assessment Page 2 of 4