Physicochemical influences on parasites of age-0 largemouth bass in the Atchafalaya River Basin, Louisiana

We investigated prevalence and intensity patterns of nine parasite taxa in 244 age-0 largemouth bass (Micropterus salmoides) collected from lake (high dissolved oxygen levels), riverine (high current velocities), and swamp (h ypoxic canals and bayous) sites (N=6) in the Atchafalaya River Basin during the 1996 flood pulse. Ectoparasites were dominated by monogenetic trematod es (prevalence=100%; median intensities 27-91 per host) and glochidia (prev alence > 96% at all sites, median intensities 47-148 per host), whereas Pos thodiplastomum minimum (Trematoda), Caecincola spp. (Trematoda; C. parvulus and perhaps C. latostoma), Neoechinorhynchus cylindratus (Acanthocephala), and Proteocephalus ambloplitis (Cestoda) accounted for 94.6% of bass endop arasites. Overall, lake sites supported the highest median parasite intensi ties in bass and most highly parasitized individuals. P. minimum was preval ent in bass collected from all sites, but intensities were highest in bass fi om lake habitats. In contrast, P. ambloplitis exhibited lower than expec ted prevalence in bass from lake sites (P. < 0.05) and higher intensity (P < 0.02) in bass from riverine sites. Patterns of parasite abundance appeare d to be related to habitat effects on intermediate host and parasite life-c ycle dynamics rather than hypoxia-related suppression of bass immune respon ses.