Date of Award

12-1-1981

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

Abstract

From 6 September 1976 to 3 July 1977 a total of 596 fish were collected from the Souris River and Devils Lake, North Dakota. These fish, representing six families and seven species, were examined for evidence of parasitism. Invertebrates and abiotic samples also were collected. Water analyses were completed following standard methods. Parasitic infections were confirmed in 87.3% of the total number examined. The Devils Lake collection included 96 fish from the summer season only, whereas those fish collected from the Souris River contained 20 of each dominant species for all seasons. These samples were structured to examine the seasonality of parasitosis. Twelve percent of the Devils Lake fish were infected with ectoparasites, compared to 35% for the Souris River fish. Six genera of parasites were the most collected from any one host. Twenty-three species of parasites were identified. These include 4 monogeneans, 12 digeneans, 4 cestodes and 1 each of nematode, acanthocephalan and leech. Eight forms could be classified only to genus. Six genera were reported from new hosts, and four parasites were reported from North Dakota fish for the first time. A revised parasite checklist for North Dakota fish is included Chemical levels of nitrates and sulfates and temperature were shown to be statistically significant and possibly related to parasitosis. HosL age was correlated with parasitosis. Pimephales promelas from Devils Lake exhibited a correlation of 1.00 between host age and parasitosis. Stizostedion vitreum demonstrated the opposite relationship in the Souris River and Devils Lake. Significant positive correlation of host age and parasitosis was also noted for Catostomus commersoni and Ictalurus melas from the Souris River. The correlation of the Condition Factor (K) with parasitosis was significant for Perea flavescens from Devils Lake. Esox lucius showed a negative correlation of host condition and parasitosis for Devils Lake, but a positive value for Souris River fish. Comparisons of parasitosis by season were made for Esox lucius, Perea flavescens and Ictalurus melas. Results revealed a general pattern of increase during late summer and fall, followed by a decrease in numbers during the winter season. An increase of parasitosis was followed by a slight decrease during early summer. Spearman Rank Correlation Coefficients were examined for similar species of fish collected from both the Souris River and Devils Lake. In all cases, significant values were found, revealing similarities between the two niscine parasitofaunas.

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