US Fish & Wildlife Service
Date of this Version
Technical Report 05-02; Prepared for Council on Environmental Quality Washington, DC.
Several biological surveys have been performed at Devils Lake, North Dakota to provide timely information to resource managers to assess the potential for biota transfer from the operation of an outlet designed to carry water to the Sheyenne River. In July, 2005 more than 300 fish were collected from Devils Lake and tested for fish pathogens and parasites using protocols and procedures of the U. S. Fish and Wildlife Service National Wild Fish Health Survey. Eight fish health biologists from the Bozeman and LaCrosse Fish Health Centers worked cooperatively with the Missouri River Fish and Wildlife Management Assistance Office, North Dakota Game and Fish Department, and the Spirit Lake Nation to collect samples from seven different species of fish. Fish were sampled with a variety of gear types from two main areas of the lake over a five day period. The catch was composed of black crappie, fathead minnow, northern pike, walleye, white bass, white sucker, and yellow perch. Testing for fish pathogens and parasites involved four main components. First, immediately upon capture, fish were examined externally and internally for gross signs of disease or other abnormalities. Next, representative samples from each species were examined for external and internal parasites. Then, specific tissues samples were collected using aseptic field techniques and were transferred to the laboratories for pathogens screening using standardized assays. Finally, tissue samples were further tested with highly specific corroborative or confirmatory assays whenever suspect pathogens were detected with screening methods. Results of the pathogen survey were completed within 30 d of sampling. No viral fish pathogens were detected in standard cell culture assays from any species of fish. Two ciliated protozoan parasites, Epistylis sp. and Trichodina sp., were observed in wet mounts of skin scrapings during parasite screening. Additionally, larval forms of the parasitic nematode Contracaecum sp. were recovered from walleye. Three parasitic cestodes were found including Bothriocephalus custpidatus in walleye, Proteocephalus pinguis in northern pike, and Ligula intestinalis in fathead minnow and yellow perch. Major microbial findings included the isolation of six species of bacteria representing both Gram-negative and Gram-positive organisms. Motile aeromonids, such as A. hydrophila, were the most common Gram-negative bacteria and where recovered from six of the seven species of fish sampled. Other less common species included Pleisomonas shigelloides and Pseudomonas putrifaciens. Two Gram-positive bacteria were also cultured including Corynebacterium renale and Streptococcus sobrinus. In addition, antigen of Renibacterium salmoninarum was detected by enzyme-linked immunosorbent assay (ELISA) in very low levels from all species. However, since active infection with R. salmoninarum was not confirmed in these populations by the highly specific polymerase chain reaction (PCR) assay, there was reason to believe the low ELISA optical density values represented false-positive readings. Other than R. salmoninarum, none of the other fish pathogens listed in the National Wild Fish Health Survey were detected in fish from Devils Lake. Likewise, none of the prohibitive fish pathogens found in most state or federal regulations or policies were recovered during the survey. Overall, fish appeared in good general health. Further discussions of major findings from the Devils Lake survey are presented here.
U.S. government work