Behavior and Habitat Use of Introduced Flathead Catfish in a North Carolina Piedmont River

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Title: Behavior and Habitat Use of Introduced Flathead Catfish in a North Carolina Piedmont River
Author: Malindzak, Edward George
Advisors: Dr. Wayne C. Starnes, Committee Member
Dr. Kenneth H. Pollock, Committee Member
Dr. Thomas J. Kwak, Committee Chair
Abstract: The flathead catfish Pylodictis olivaris is a large piscivorous carnivore that has been widely introduced beyond its native range. I studied the behavior of a flathead catfish population that has recently inhabited a section of the Deep River, North Carolina (in the upper Cape Fear River basin), and currently coexists with the federally endangered Cape Fear shiner Notropis mekistocholas. This coexistence raises concerns of predation risks of the flathead catfish on the Cape Fear shiner. I radio-tagged 24 adult flathead catfish in the Deep River between Carbonton and Highfalls dams and monitored their behavior from June 2004 to August 2005. Fish were tracked weekly to determine seasonal patterns, and subsets of those were tracked once per hour for a 24-hour period to determine diel patterns. Eight of the fish were captured, tagged, and released in the upstream, shallow section of the river, and 16 in the deep, downstream, impounded section. A majority of the tagged fish either quickly moved into or stayed in the downstream, impounded section for the entire study period. Flathead catfish selected microhabitats non-randomly annually and within three functional seasons (spawning, growth, and winter). Flathead catfish were usually associated with habitats that were relatively deep (3-6 m), slow in velocity, over bedrock substrates, and nearly always in or adjacent to coarse woody debris or associated with no cover. Among seasons, these fish utilized different habitats, with faster bottom velocities during the spawning season, silt/clay substrates and faster mean column velocities in the growth season, and in the winter season, they occupied the deepest water available and most frequently, not associated with any cover type. I calculated estimates of seasonal home range as linear home range and kernel density estimates (99%, 95%, 90% and 50%). Flathead catfish mean linear home ranges were greater than 16 km annually, and mean seasonal ranges were 13.1 km during spawning, 10.1 km during growth, and 3.8 km in winter. Mean kernel density estimates of home range at 95% level were approximately half the linear estimate of home range annually and for each season. Mean kernel density estimates of home range at 50% (or core use) level were one-tenth of respective linear home ranges. On a diel scale, flathead catfish were generally more active and occupied deeper water at night. My findings on habitat use of adult flathead catfish at multiple spatial and temporal scales suggest the predation risk to Cape Fear shiners may be minimal, based on limited overlap. Furthermore, my results support other recent research describing flathead catfish as a highly mobile fish. These results add to our ecological understanding of this species in its introduced range and offer implications for improved management.
Date: 2006-06-19
Degree: MS
Discipline: Fisheries and Wildlife Sciences

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