Fig. 1

Conceptual diagram showing competing theories for prairie chub movement. The restricted movement paradigm (RMP) posits that stream fish are largely sedentary and do not move far from their tagging location (a), while the colonization cycle hypothesis (CCH) posits that if downstream drift occurs during early life stages, then upstream bias in movement must occur at adult life stages (d). The drift paradox (DP) describes the situation in which upstream populations persist in spite of little evidence of upstream bias in movement (b, c). Our first hypothesis (H1) was that prairie chub would move more than the RMP predicts, whereas our second hypothesis (H2) was that prairie chub movement was biased in an upstream direction. Acceptance of both hypotheses would be consistent with the CCH (d), whereas rejection of both hypotheses would be consistent with the RMP (a). Acceptance of one hypothesis but not the other results in a paradoxical situation in which upstream movement does not complete the colonization cycle (b) or the upstream bias is greater than the RMP would predict (c)