This study describes the parasite communities of juvenile bluegill and examines the development of parasite communities in juvenile bluegill from 2 Michigan lakes. Parasitological examination of 510 juvenile bluegill from 2 Michigan lakes (Three Lakes II [TL] and Gull Lake [GL]) demonstrated that TL bluegill harbored 19 parasite species and GL bluegill harbored 16 parasite species. Parasite communities of juvenile bluegill from both lakes were dominated by larval parasites, particularly larval trematodes. A nonmetric multidimensional scaling analysis showed bluegill of similar lengths to have similar parasite communities. Relative influences of species richness on parasite infracommunities of juvenile bluegill suggest similar patterns of parasite community structure between TL and GL. Patterns in parasite colonization evident in both lakes suggest that the smallest juvenile bluegill are primarily vulnerable to colonization by parasites acquired through direct contact, particularly larval trematodes, while the majority of parasites acquired through ingestion are not acquired until juvenile bluegill are larger and less-gape limited.

A new species of capillariid nematode, Freitascapillaria laticauda n. sp. (Capillariidae), is described from the intestine of the blue ridge sculpin, Cottus caeruleomentum (Cottidae, Scorpaeniformes) from the Blue Lick Run, Maryland, United States. It differs from its congeners mainly in the body length (male 3.1–5.4 mm, female 7.0–11.1 mm), the length of the male esophagus (1.5–2.9 mm) and spicule (42–45 µm), and the size of eggs (60–66 × 27–33 µm). Previous records of Freitascapillaria spp. were from characid, poeciliid, and cyprinid fishes in Brazil, Neotropical Mexico, and China, respectively, so that F. laticauda n. sp. is the first species of this genus reported from Nearctic North America and from a scorpaeniform fish.

Four parasite species ( Crepidostomum cooperi , Cystidicoloides ephemeridarum , Acanthocephalus dirus , Salmincola edwardsii ) infected 215 juvenile brook trout (105 young-of-year; 110, 1-yr-old) from Hunt Creek, Michigan, in 2003, 2004, and 2005. Prevalences of these species in 2004 (main study year) varied from 29 to 37%. Crepidostomum cooperi had the highest mean intensity and mean abundance, followed by C. ephemeridarum . The number of fish infected with each parasite species was significantly higher in 1-yr-old fish than in young-of-year fish. Also, the mean intensities and mean abundances of C. cooperi and C. ephemeridarum and the mean abundance of A. dirus were significantly higher in older fish. The mean intensity of C. cooperi and prevalence of A. dirus were significantly higher in fish between creek sections. Fish length had a significant positive effect on the abundances of C. cooperi and C. ephemeridarum ; parasite species richness, on the abundances of A. dirus and S. edwardsii ; and parasite species richness in the 2003 and 2004 trout cohorts, respectively. Crepidostomum cooperi , C. ephemeridarum , A. dirus , and S. edwardsii commonly infect Michigan brook trout. The small number of parasite species infecting Hunt Creek brook trout is similar to the number of parasite species of brook trout from other Michigan creeks.

One hundred extended growth walleye fingerlings, Sander vitreus (Percidae), collected on 6 October 2004, from 1 rearing pond at the Lake Mills State Fish Hatchery in Lake Mills, Wisconsin, were examined for parasites. Diplostomum sp. (Trematoda: Diplostomatidae), Contracaecum sp. (Nematoda: Anisakidae), Bothriocephalus cuspidatus (Cestoda: Bothriocephalidae), and Proteocephalus sp. (Cestoda: Proteocephalidae) were the only parasites found. The first 3 species occurred as larval stages. Diplostomum sp. and Contracaecum sp. had similar prevalences, mean intensities, and mean abundances (72%, 2.2, and 1.6 and 71%, 2.1, 1.5, respectively) in walleye fingerlings. A headlamp technique used by the Wisconsin Department of Natural Resources personnel generated a prevalence of Diplostomum sp. in the lens that overestimated the prevalence of Diplostomum sp. found in a random subsample of 100 fingerlings examined with a microscope. Proteocephalus sp. and B. cuspidatus infected 14 and 12 fingerlings, respectively.

During 4 consecutive collecting seasons from 1998 through 2001, 77,326 common beach snails ( Stagnicola emarginata , Lymnaeidae) were examined for infections by Trichobilharzia stagnicolae from multiple sites on Walloon Lake, Higgins Lake, and Lake Leelanau, located in the northern region of the lower peninsula of Michigan. Snails were examined for infections using the light-box technique (exposure to bright fluorescent light). The prevalence of infected snails varied significantly among lakes within a year, between years in a lake, at a site from year to year, and at a site over a collecting season. Overall annual prevalence ranged from 0.54% (1999) to 1.32% (2001) on Walloon Lake, from 0.56% (2001) to 1.06% (1998) on Higgins Lake, and 0.30% (2001) to 0.89% (2000) on Lake Leelanau. Generally, the peak in prevalence coincided in July on the lakes. Prevalence was found to increase with snail length in all lakes. A comparison of the light-box technique and crushing snails demonstrated that prevalence varied in magnitude by technique as much as 1.2 and 5.7 times.

A total of 65 largemouth bass, Micropterus salmoides , and 27 smallmouth bass, M. dolomieu , collected in April–September 2000 and April–July 2001 from Gull Lake, Michigan, were examined for acanthocephalans. Leptorhynchoides thecatus and Neoechinorhynchus cylindratus infected all the bass examined. Leptorhynchoides thecatus had the highest mean intensity (258.2 ± 185.4 in 2000 and 145.0 ± 61.0 in 2001) of the species infecting smallmouth bass. Although N. cylindratus had higher mean intensities (42.1 ± 37.9 in 2000 and 68.9 ± 70.5 in 2001) than did L. thecatus in largemouth bass, the values were not significantly different between bass species. The prevalence, mean intensity, and mean abundance of Pomphorhynchus bulbocolli in the bass species were below the values for the other acanthocephalan species. Leptorhynchoides thecatus and N. cylindratus are the most abundant intestinal helminths in bass from Gull Lake.

Ergasilus megaceros (Copepoda: Ergasilidae) was recovered from the nasal fossae (lamellae) of the olfactory sac in 1 (1.8%) of 56 sea lampreys, Petromyzon marinus Linne, 1758, collected in May 2002 from the Cheboygan River, Michigan. Although the sea lamprey is a new host record for E. megaceros , this fish species may not be a preferred host because of its low prevalence. Ergasilus megaceros is the second ergasilid species reported from the sea lamprey in North America. This is the third report of an ergasilid species infecting the nasal fossae of fishes in North America, with E. rhinos being the only other species reported from this site.

Bunodera sacculata (Trematoda: Allocreadiidae) infected 65 (54%) of 120 yellow perch collected in 1997 and 40 (50%) of 80 perch from Silver Creek in 1998, and 17 (30%) of 56 perch in 2000 from Silver Lake in lower Michigan. Gravid B. sacculata occurred in the pyloric ceca and anterior intestine. There were differences in monthly trends (July through August) in prevalences, mean intensities, and mean abundances of B. sacculata in Silver Creek between 1997 and 1998. The mean intensity ± SD (8.2 + 9.1) and mean abundance (4.1 ± 7.8) of B. sacculata were significantly higher in 1998 than in 1997 and 2000. An additional 20 perch (0+ in age) collected from the creek in July 1998 were all infected and had the highest mean intensity of 21.3 ± 14.1.

A total of 239 green frogs Rana clamitans , collected between June 3 and August 27, 1998 from 6 locations in southwestern Michigan, was examined for helminths. Of the 26 helminth taxa found, the larval cestode Mesocestoides sp. had the highest mean intensity, followed by the larval trematode Fibricola sp. Of the helminths that mature in frogs, Haematoloechus varioplexus had the highest prevalence and Gorgodera amplicava had the highest mean intensity. Frogs from 118th Pond had the highest species richness (20), mean helminth species richness (5.2), and mean helminth abundance (153.7). Frogs from Constantine East had the highest mean helminth species diversity (0.8778) and evenness (0.6033), followed by frogs from 118th Pond. In all comparisons of mean helminth community species richness, abundance, diversity, and evenness, adult frogs had significantly higher or higher values than did juveniles at each location. Jaccard's coefficients of similarity for the helminth communities for location pairs ranged from 0.545 to 0.823. Nine and 2 core helminth taxa occurred at the local and regional levels, respectively. The differences in several helminth community measures in green frogs among locations stress the importance of local ecological conditions on helminth community structure.

Sanguinicola occidentalis (Trematoda: Sanguinicolidae) infected 58 (48%) of 120 yellow perch collected in 1997 and 40 (50%) of 80 yellow perch collected in 1998 from Silver Creek in lower Michigan. The mean intensity and mean abundance of this blood fluke were higher in 1998 than in 1997. The fluke was found in the bulbous arteriosus of the perch heart, free in the petri dishes when the gill filaments were teased apart, and in the body cavity washings, and 1 individual was associated with an eye. Of the 269 S. occidentalis examined from perch, none had eggs. Most perch examined and infected were only 1+ yr in age. Spearman's correlation coefficients between S. occidentalis intensity and host length in 1997 and 1998 were not significant. An additional 25 yellow perch (0+ yr in age) collected in 1998 were not infected. Thirty-seven (33%) of 113 snails ( Campeloma decisum ) examined in July and August 1999 from Silver Creek were infected with S. occidentalis.

Eighty stocked lake trout Salvelinus namaycush (Salmonidae), collected from 2 locations in Lake Huron in May 1995, were examined for parasites. The parasite fauna of this top predator in Lake Huron was characterized by only 6 helminth species. Echinorhynchus salmonis infected all lake trout with a mean intensity of 163.9. The intensity of this acanthocephalan species significantly increased with host length and weight. Eubothrium salvelini infected 78 lake trout with a maximum number of 81 scoleces counted. Diplostomum sp., Cyathocephalus truncatus, Capillaria salvelini, and Neoechinorhynchus sp. infrequently infected lake trout. The low parasite species richness in these lake trout is believed to be due to their large size at stocking and to the loss of historical enzootic host–parasite relationships that followed the absence of this fish species in Lake Huron for 26 yr.