Survey of Specific Fish Pathogens and Parasites in Free-Ranging Fish from Devils Lake and the Sheyenne and Red Rivers in North Dakota

Field: Agricultural and Biological Sciences (Life Sciences)

We present results of a th ird fish pathogen and parasite survey at Devils Lake and a second survey of the Sheyenne and Red rivers in North Dakota. Surveys were performed to provide information to resource managers to assess the potential for biota transfer from operation of an outlet on Devils Lake to the Sheyenne River. Fish health biologists from Bozeman, Dexter, Idaho, and Lacrosse Fish Health Centers (FHC) worked cooperatively with the Missouri River Fish and Wildlife Management Assistance Office, Valley City National Fish Hatchery, North Dakota Game and Fish Department, and the Spirit Lake Nation to collect samples from the three bodies of water. In September 2006, 387 fish were collected from two sampling areas on Devils Lake. During October 2006, we collected 78 fish from the Sheyenne River near the southern boundary of the Spirit Lake Nation and 72 fish from the Red River south of Fargo, North Dakota. The catch on Devils Lake was composed of black crappie, fathead minnow, northern pike, walleye, white bass, white sucker, and yellow perch. We collected black bullhead, northern pike, tadpole madtom, walleye, and white sucker from the Sheyenne River, and channel catfish, freshwater drum, goldeye, sauger, stonecat, and walleye from the Red River. Fish were tested for the presence or absence of pathogens and parasites using protocols and procedures of the U.S. Fish and Wildlife Service National Wild Fish Health Survey. Five main components of the survey included: I) record catch results and weigh and measure fish; 2) perform external and internal examination for gross signs of disease or other abnormalities, 3) aseptic collection of specific tissues samples; 4) external and internal parasites survey; and 5) application of standardized screening and confirmatory assays for specific fish pathogens. Overall, fish appeared in good general health. We did not detect any fish virus in standard cell culture assays from the three bodies of water. Major microbial findings included the isolation several Gram-negative motile bacteria from the Families Aeromonadaceae, Enterobacteriaceae, and Pseudomonadaceae. Many of the bacteria within these families are normal constituents of aquatic ecosystems or are considered normal flora of animal gastrointestinal tracts. Aeromonas hydrophila, Hafnia alvei, Pseudomonas fluorescens and Pseudomonas sp. were the most commonly isolated species from these groups. No Grampositive bacteria were found during the surveys although antigen of Renibacterium salmoninarum was detected by enzyme-linked immunosorbent assay (ELISA) in very low levels from several species collected from all three bodies of water. Active infection with R. salmoninarum was not confirmed in these populations by the highly specific polymerase chain reaction (PCR) assay and there was reason to believe low ELISA optical density values may have represented false-positive readings. Other than R. salmoninarum, none of the fish pathogens listed in the National Wild Fish Health Survey were detected in fish from Devils Lake or the Red and Sheyenne rivers. Likewise, none of the regulated or prohibited fish pathogens indicated in federal fish health inspection policies were detected. At Devils Lake, we observed or recovered parasites from all species offish surveyed except white sucker. One ciliated protozoan parasite, Trichodina sp., was observed in wet mounts of gill filaments of yellow perch and skin scrapings from walleye and yellow perch. Five species of parasites from the Class Trematoda were found. At Devils Lake, Gyrodactylus hoffmani was observed on the fins of fathead minnow. Neascus of Posthodiplotomum sp. was found in fathead minnow and black crappie. Diplostomum spathaceum was observed in the lens of eyes from fathead minnow. We found Paurorhynchus hiodontis encysted in mesenteric tissues of goldeye collected from the Red River. Three parasites of the Class Cestoidea were found including adult Bothriocephalus cuspidatus in walleye, metacestodes of Bothriocephalus sp. in black crappie, fathead minnow, and walleye. In addition, Proteocephalus pinguis was observed in northern pike, and Ligula intestinalis in fathead minnow. Larval forms of the parasitic nematode Contracaecum sp. were recovered from black crappie, white bass, and walleye at Devils Lake, and from black bullhead, tadpole madtom, and walleye from the Sheyenne River. A presumptive finding of a second or third larval stage of Raphidascaris acus was made from a nematode found in mesenteric tissues of yellow perch at Devils Lake.