Search Results (3)

The Wildlife Services—National Wildlife Research Center Mississippi Field Station, working in conjunction with Mississippi State University, conducted a study to evaluate the effectiveness of several non-lethal, commercial, physical bird deterrents. Deterrents were available on the open market to reduce double-crested cormorant (Nannopterum auritus) (DCCO) roosting time on floating oyster cages. We hypothesized that reducing bird loafing time on floating oyster cages would reduce the potential for bird defecation. Double-crested cormorant defecation can increase coliform counts in both the water and oysters, which could result in oyster farm closure. Shellfish farms often differ from one another due to environmental factors and farm locations. Six deterrent devices were selected as options for farmers, and the amount of time DCCOs occupied floats with deterrents was compared to the time they occupied those without deterrents (i.e., on a control pond). All deterrents except the Scarem Kite significantly reduced or halted DCCO use of floats compared to the control. Of note, the Scarem Kite is the only deterrent that requires consistent wind to operate effectively. The research facility is open-air, but we did not have sufficient wind for proper Scarem Kite function. Thus, it is possible that all deterrents would have produced significant reductions in DCCO use. Our results are encouraging and show that minimal deterrent applications to oyster cage floats can help farms achieve their operational plans’ goals and reduce the potential for pathogen transfer by birds. The data presented here should be considered a starting point for developing an efficient deterrent plan that meets state and federal standards. Full article

Seasonal movements of Double-crested Cormorants (Nannopterum auritum) have been studied at breeding and wintering sites in the southeastern United States, but little information exists on the movements of these birds within and from their southern breeding sites in lacustrine systems. Since 2001, cormorants have established nesting colonies on islands in Guntersville Reservoir in Alabama, USA. Following the movements of tagged cormorants using satellite telemetry, we found that the mean home range during the 2017 breeding season (May–August) was 41.76 km², with a core use area of 6.36 km². The mean home range used by these birds was largest during the period coinciding with incubation: 9–30 May: (98.86 ± 80.64 km²) compared with the chick-rearing 31 May–4 July: 18.30 ± 22.56 km²), and the post-fledge periods (5 July–15 August: 42.04 ± 30.95 km²). There was no significant difference in the metrics of movement and space use between male and female cormorants assessed in this study. Differences in space used by cormorants breeding in Alabama relative to their northern breeding grounds may be explained by landscape characteristics and availability of prey. Full article

Mass mortality events of common carp (Cyprinus carpio, carp) associated with carp edema virus (CEV) alone or in coinfections with koi herpesvirus (KHV), is an emerging issue. Despite recent outbreaks of CEV in wild carp populations, the host range of North American species has not been well studied. To that end, we intensively sampled carp (n = 106) and co-habiting native fish species (n = 5 species; n = 156 total fish) from a CEV-suspect mass-mortality event of carp in a small Minnesota lake (Lake Swartout). Additionally, fecal and regurgitant samples (n = 73 each) from double-crested cormorants (Phalacrocorax auritus, DCCO) were sampled to test the potential of DCCO to act as a vector for virus transmission. CEV was confirmed to be widespread in the Lake Swartout carp population during the outbreak with high viral loads and histological confirmation, suggesting that CEV was the cause of the mortality event. There were no detections of CEV in any native fish species; however, DCCO regurgitant and fecal samples were positive for CEV DNA. In addition, three CEV-positive and one CEV + KHV-positive mortality events were confirmed with no observed mortality or morbidity of non-carp species in other lakes. This study provides evidence that CEV infection and disease may be specific to carp during mortality events with mixed-species populations, identifies DCCO as a potential vector for CEV, and further expands the known range of CEV, as well as coinfections with KHV, in North America. Full article