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Predation Thirty four bullheads and three rainbow trout were examined for stomach contents during both spring trips. Ten of the bullhead (TL range 154 to 264 mm) possessed fish remains in their stomach; including two HBC (one HBC measured 104 mm; the other was not measured for length), four f1annelmouth suckers, one fathead minnow, one plains killifish, and the remains of several other unidentified fish. The remaining bullheads had either empty stomachs, or had consumed aquatic insects. One rainbow trout (TL = 293 mm) had a 95 mm HBC in its stom.ach. Another rainbow trout had a killifish and a hellgrammite in its stomach. Parasites Percent occurrence of the external parasite (Lemaea cyprinacea) on HBC in April was low, with only five fish (0.4% of total HBC captures) observed carrying the parasite, generally carrying only one parasite per infected fish. One f1annelmouth sucker was captured carrying one of the parasites. During May, only 2 HBC were seen with Lemaea (0.08% of total HBC captures), each carrying one parasite per fish. Occurrence of the Asian tapeworm (Bothriocephalus acheilognathl) was not monitored during these trips. Population Abundance Estimation The following criteria were used to define the sampled population during the spring mark-recapture effort. During April, 273 unique HBC ~ 150 mm were marked [M]. During May, 352 unique HBC ~ 150 mm were captured [C], and 47 unique HBC ~ 150 mm were recaptured [R]. The smallest HBC recaptured had a total length of 164 mm, and the largest recaptured HBC was 385 mm in TL. We defined our sampled population to include all HBC ~ 150 mm in order to provide an estimate comparable to past efforts, and since there is no indication from past efforts that our gear is not efficient at capturing fish between 150 to 164 mm. Length frequency distributions of HBC ~ 150 mm suggested that there may have been violations in the assumption for no emigration or immigration occurring. Figure 10 illustrates some discrepancy in the cumulative length frequencies of HBC between marked [M] fish and captured [C] fish. This discrepancy is interpreted as movement of fish, either into or out of the LCR, or both. Using two-tailed Kolmogorov-Smirnov tests, the cumulative length distribution of marked [M] HBC was significantly different from captured [C] HBC (n1 = 273, n2 = 352, Z = 2.141, P < 0.001). Similarly, the cumulative length distribution of marked [M] HBC was significantly different from recaptured [R] HBC (n1 = 273, n2 = 47, Z = 1.980, P = 0.001; Figure 10). However, we found no significant difference (X2 = 7.72, df = 5, p = 0.172) in the mark rates of HBC within different length strata (Table 5). The typical conclusion drawn from test results as above is that there was significant size selective sampling during both the marking and recapture events (Bernard and Hansen 1992). However, the more likely interpretation is that there was some movement of spawning sized fish either to or from the LCR between the mark and recapture events. Regardless, since the Kolmogorov-Smirnov tests revealed significant differences in length 20