4.2 | Colorado Pikeminnow diet composition
Isotopic biplots between Colorado Pikeminnow and potential prey items
corrected for trophic discrimination suggested our analysis incorporated
most potential prey items (Figure 3). The mixing models resulted in
substantial predicted overlap in the proportion each diet item was
consumed within periods (Figure 4). However, Colorado Pikeminnow
demonstrated a predicted increase in invertebrate consumption
(probability = 0.94) from a historical median of 2.4% (95% CI = 0.0 –
30.5%) to a contemporary median of 24.9% (18.1 – 33.2%). The diet
mixing models predicted Red Shiner (median = 28.4%, 95% CI = 10.6 –
41.6%) took the place of Fathead Minnow (29.0%, 2.7 – 68.6%) as the
mostly highly consumed fish prey. Consumption of Flannelmouth Sucker and
Speckled Dace, which was difficult to distinguish due to similar isotope
values, averaged ~ 18% for each species and consumption
by Colorado Pikeminnow may not have changed between periods
(probabilities of 0.68 and 0.73, respectively). Prior to its extirpation
and similar to other native potential prey, Roundtail Chub was predicted
to have contributed ~18% (median = 17.9%, 1.5 –
53.7%) to Colorado Pikeminnow’s diet.