Parasite Community Structure in 3 Types of Sunfish By Emily Fischbach and Michael Sukhdeo

Department of Ecology and Natural Resources

Introduction Results

Discussion

Bluegill Sunfish (Lepomis macrochirus), Pumpkinseed Sunfish (Lepomis gibbosus), and Green Sunfish (Lepomis cyanellus) are all common freshwater Sunfishes in North America of the family Centrarchidae. All of the young cohabit the shallow littoral zones of lakes or ponds. As adults, they begin to dominate different sections of the water. Pumpkinseed and Green Sunfish dominate the shallow portion of the littoral zone which pushes Bluegill Sunfish to deeper water through competition (Werner and Hall, 1977). Pumpkinseed Sunfish have special jaw apparatus that allows them to crush and consume snails more effectively than the other two fish (Keast, 1978). Trematodes, or parasitic flatworms, commonly infect fish and have been known to be in all 3 fishes. A key stage in parasitic flatworms includes snails, who are intermediate hosts responsible for infecting fish. Snails are primarily found in the shallow littoral zone.

Fish SamplingFish were sampled twice a month for the summer, spring, and fall seasons at Weston Mills Pond, New Jersey. Small fish were caught using a seining net; Larger fish using a fishing reel. Fish were transported in 2 five gallon buckets with oxygen, and stored live for no longer than 5 days in 2 fifty gallon tanks with oxygen and filters.

ReferencesParasite Identification:Identification was done using the text, “Parasites of North American Freshwater Fishes” by Glenn L.Hoffman . More specific identification used dichotomous keys from this text.

Hypothesis I hypothesize there will be a significant difference in trematode prevalence and

mean intensity between fishes, with the highest prevalence and intensity being in Pumpkinseed fishes, due to their feeding behavior and close proximity to snails.

Fish Identification: Fish were indentified using Minnesota’s Department of Natural Resource’s guide on Sunfish Biology and Identification. Fish DissectionFish were euthanized via pithing, using a thin scalpel inserted into the brain. Fish were then placed on a dissecting tray for dissection. Fish species, weight, and standard length were measured. Parasites from each organ were counted.

Methods

86%

14%Pumpkinseed

P.minimum centrarchi

Other

EH = 0.2396%

4%Bluegill

P.minimum centrarchi

Other

EH = 0.59

85%

15%Green Sunfish

Posthodiplo-stomum spp.

Other

EH = 0.66

The most common parasite in Pumpkinseeds was the larval trematode (metac-ercarie) of P. minimum centrarchi.

Shannon Diversity Index (EH = 0.23) calculations show that Pumpkinseeds had the lowest community evenness

The most common parasite in Bluegills was the larval trematode (metacercarie) of P. minimum centrarchi.

Shannon Diversity Index (EH = 0.59) calculations show that Bluegills had medium community evenness compared to the other 2 fishes

The most common parasite in Green Sunfish was the larval trematode (metacercarie) of Posthodiplostomum spp.

Shannon Diversity Index (EH = 0.66) calculations show that Green Sunfsih had the highest community evenness

Larval Trematode ( or Metacercarie) intensity is correlated with host size for Bluegills and Pumpkinseeds but not Greensunfish.

There is no significant difference in larval trematode intensities of P.minimum centrarchi between Pumpkinseed and Bluegill Sunfish in all organs. There is a significant difference in larval trematode intensities of Posthodiplostomum spp. in Green Sunfish and larval trematode P.minimum centrarchi in both Bluegill and Pumpkinseed Sunfish, with lower intensities in all organs except the Gonads, where the intensity of Posthodiplostomum spp is higher than that of P.minimum centrarchi.

I reject the hypothesis that Pumpkinseed Sunfish have higher intensities and prevalence of larval trematodes, as larval trematode prevalence in all 3 fish are similar and there is no significant difference in total larval trematode levels between Pumpkinseed and Bluegill sunfish.

There is however, a significant difference in total larval trematode levels between Green and Pumpkinseed Sunfish, and Green and Bluegill Sunfish. This may be due to small size of Green Sunfish captured.

1. Hoffman, Glenn L. Parasites of North American Freshwater Fishes. Berkeley: Univ. of California, 1967. 2. Keast, Allen. "Feeding Interrelations between Age-groups of Pumpkinseed (Lepomis Gibbosus) and Comparisons with Bluegill (Lepomis Macrochirus)." Journal of the Fisheries Research Board of Canada 35.1 (1978): 12-27. 3. Mittelbach, Gary G. "Predation and Resource Partitioning in Two Sunfishes (Centrarchidae)." Ecology 65.2 (1984): 449-513. 4. Osenberg, Craig W., and Gary G. Mittlebach. "Effects of Body Size on the Predator-Prey Interaction Between Pumpkinseed Sunfish and Gastropods." Ecological Monographs 59.4 (1989): 405-325.  "Sunfish Biology and Identification." Minnesota DNR. N.p., n.d. 6. Werner, Earl E., Dennis R. Laughlin, Donald J. Wagner, Leni A. Wilsmann, and Frederick C. Funk. "Habitat Partitioning in a Freshwater Fish Community Habitat Partitioning in a Freshwater Fish Community." Journal of the Fisheries Research Board

of Canada 34.3 (1977): 360-70.

3 3.5 4 4.5 5 5.5 6 6.5 70

100

200

300

400

500

R² = 0.243572889167635

R² = NaNR² = NaN

L.Trematode Intensity vs. Fish Length

Fish Length (cm)

# La

rval

Tre

mat

ode

N=26 N=25N=28