Date of Award
Master of Science
Eichholz, Dr. Michael
The long-tailed duck (Clangula hyemalis; hereafter LTDU) breeds on the arctic tundra across Alaska and Canada and winters south of the ice edge along the Pacific and Atlantic coasts, as well as on the Great Lakes. Data suggest that LTDU populations are in decline and, as a result, efforts have been made to better understand their population distributions through satellite telemetry studies. Radio-marked LTDUs from previous studies have shown very little use of Lake Michigan, even though aerial surveys indicate that large concentrations of this species overwinter there. LTDUs using Lake Michigan face a host of conservation issues, such as risk of exposure to type E botulism, bycatch in fishing gear, wind energy development, and a changing ecosystem. Using satellite telemetry, I documented migratory routes and habitat use of LTDUs wintering on Lake Michigan. LTDUs on Lake Michigan were captured via night-lighting and 10 LTDUs were surgically implanted with Telonics platform transmitter terminals (PTTs). Six (60%) radio-marked LTDUs provided information on Lake Michigan habitat use, while only 3 (30%) provided information on migratory routes. The average distance from shore of individual radio-marked LTDUs on Lake Michigan varied from 1.4-7.8 km and average water depths at these locations varied from 16.8-27.7 m during daylight hours. At night, radio-marked LTDUs were located further offshore (averaging 7.3-16.5 km) and at deeper water depths (averaging 59.6-74.8 m). LTDUs tended to move south on Lake Michigan as winter progressed, and then relocated to the north basin before spring migration. James Bay and Hudson Bay were the primary stopover sites during spring and fall migration, and the province of Nunavut, Canada was used during the breeding season. After breeding, radio-marked LTDUs traveled north to waters near Adelaide Peninsula, Nunavut, Canada. Only one radio-marked LTDU provided information for a full migration cycle and it returned to winter on Lake Michigan. Two methods, ocular and molecular examination of the alimentary canal, were used to determine the diets of LTDUs on Lake Michigan. A total of 16 LTDU carcasses were donated by hunters for diet determination. An esophageal, small intestine, and cloacal swab were collected from each carcass for molecular determination of prey species through qPCR analysis. The esophagus of each carcass was then removed and prey items determined to lowest taxonomic level using a dissection microscope (10X Ocular). Molecular methods detected more prey species (4) than ocular methods (1), so molecular methods show promise as a non-lethal means to determine LTDU diets. Quagga mussel (Dreissena rostriformis bugensis) was the primary prey item with 100% occurrence. Diporeia spp., yellow perch (Perca flavescens), and alewife (Alosa pseudoharengus) were also detected, suggesting that LTDUs are opportunistic feeders. An in-person hunter harvest survey was conducted at Two Rivers, Wisconsin, to determine how environmental variables influenced harvest, to estimate harvest rates, and to gather hunter input regarding hunting regulations on Lake Michigan. Results indicate that LTDUs made up 97% of the total harvest, and that hunters averaged 3.8 LTDUs per day. Harvest of LTDUs was positively correlated with hunter numbers, and wave height was the most influential environmental variable affecting hunter numbers. Results suggest that few hunters go out when wave heights exceed 1.5 m. Hunters indicated that they would prefer a later or longer season on Lake Michigan, and that they were concerned about LTDU populations. Information from this study aids resource managers and scientists as they seek to determine basic information regarding LTDUs that winter on Lake Michigan. Migratory data is important in determining if the eastern population of North American LTDUs should be managed based on wintering and/or breeding distribution, while habitat use information will aid in mitigating impacts from fishing bycatch and future wind energy development. Habitat use and diet data will benefit resource managers and scientists seeking to determine where and how LTDUs may become exposed to avian botulism type E. Diet data will also aid in determining how LTDU diets are changing due to the altered ecosystem in Lake Michigan from introduced and invasive species. Moreover, results from the diet portion of this study suggest that molecular methods, that can be used non-lethally or in combination with lethal methods, show promise for determining LTDU prey items. Information on harvest rates can be used in determining harvest impacts, while hunter perceptions may aid resource managers as they make decisions regarding season structure and limits for LTDUs on Lake Michigan.
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