Browsing by Author "Dr. Thomas J. Kwak, Committee Chair"
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- Behavior and Habitat Use of Introduced Flathead Catfish in a North Carolina Piedmont River(2006-06-19) Malindzak, Edward George; Dr. Wayne C. Starnes, Committee Member; Dr. Kenneth H. Pollock, Committee Member; Dr. Thomas J. Kwak, Committee ChairThe 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.
- High-Density Grass Carp Stocking Effects on a Reservoir Invasive Plant, Water Quality, and Native Fishes(2008-11-14) Garner, Alan Brad; Dr. Kenneth H. Pollock, Committee Member; Dr. Thomas J. Kwak, Committee Chair; Dr. Joseph E. Hightower, Committee MemberStocking grass carp Ctenopharyngodon idella is a commonly applied technique used to control nuisance aquatic vegetation in reservoirs. Factors that influence the degree of aquatic vegetation control are stocking density, regional climate, abundance and species composition of the aquatic plant community, and relative grass carp feeding preferences for the plant species. We evaluated high-density grass carp stocking in a reservoir for control of parrot-feather (Myriophyllum aquaticum, an invasive aquatic plant that is not preferentially consumed by grass carp) and the associated effects on water quality and native fishes. Lookout Shoals Lake, a piedmont North Carolina reservoir, was stocked with triploid grass carp at a density of 100 fish per vegetated hectare. Parrot-feather biomass in the lake was significantly reduced three months after grass carp stocking, compared to biomass in in-situ exclosures. During the second year after grass carp stocking, parrot-feather biomass in the lake compared to biomass in in-situ exclosures indicated continued control, but unexplained lack of growth within most experimental exclosures precluded biomass analyses. Increases in ambient water chlorophyll a, reactive phosphorus, and nitrate-nitrite concentrations were measured after grass carp stocking. We evaluated the native fish community using seasonal shoreline electrofishing before and after grass carp stocking. Total catch for all fish species in aggregate at shoreline transects was not significantly different after grass carp stocking by number or biomass. Catch rates of largemouth bass Micropterus salmoides, bluegill Lepomis macrochirus, and redbreast sunfish Lepomis auritus were not significantly different after grass carp stocking, but yellow perch Perca flavescens catch rates were significantly lower. The biological significance of fish distribution changes and long-term effects on lake biota remain undetermined. Our results demonstrate that intensive grass carp stocking can control an invasive aquatic plant that is not preferentially consumed by grass carp, and reveal associated changes in water quality and fish distributions.
- Sicklefin Redhorse Reproductive and Habitat Ecology in the Upper Hiwassee River Basin of the Southern Appalachian Mountains(2009-04-23) Favrot, Scott Douglas; Dr. Thomas J. Kwak, Committee Chair; Dr. Wayne C. Starnes, Committee Member; Dr. Kenneth H. Pollock, Committee MemberHiwassee River tributaries were frequently occupied by adult sicklefin redhorse Moxostoma sp. during the spawning season; lower reaches of tributaries and Hiwassee River were primarily occupied during the postspawning season; and lower reaches of Hiwassee River were most heavily used during winter. Sicklefin redhorse selected annual, seasonal, and spawning microhabitat non-randomly. Sicklefin redhorse generally were associated with swift thalweg currents, shallow depths, and coarse substrates (e.g., boulder and bedrock) supporting river weed Podostemum ceratophyllum. However, different microhabitats were selected seasonally and during spawning. During 2007, mean daily water temperature for observed sicklefin redhorse spawning was 17.5 °C (11.0–21.1 °C). Male and female sicklefin redhorse conducted spawning migrations simultaneously; however, males tended to occupy spawning tributaries longer than females. All sicklefin redhorse that conducted spawning migrations in both 2006 and 2007 demonstrated spawning tributary fidelity. Foraging was the most common behavior observed for adult sicklefin redhorse with bedrock being the dominant foraging substrate annually. Sicklefin redhorse reproductive behavior was atypical for the genus Moxostoma. An undescribed repetitious post-spawning digging behavior was observed for spawning females. Spawning substrate samples reveal that very coarse gravel and small cobble were dominant spawning substrates. My results increase knowledge pertaining to reproductive ecology, seasonal behavior, and suggest critical management issues important to the life history of the sicklefin redhorse. The spawning migration of black redhorse Moxostoma duquesnei, golden redhorse Moxostoma erythrurum, river redhorse Moxostoma carinatum, sicklefin redhorse and silver redhorse Moxostoma anisurum was sampled with resistance board weirs and prepositioned areal electrofishers (PAEs) during the spring of 2006 and 2007 in Valley River, North Carolina. Spawning was observed for all five redhorse species in 2007 at water temperatures generally ranging from 8–21 °C and mean daily Valley River flows ranging from 1.7–4.5 m3/s. Silver redhorse migrated and spawned first followed by black redhorse, sicklefin redhorse, golden redhorse, and river redhorse with considerable overlap occurring. Male golden redhorse and river redhorse displayed agonistic behavior and spawning site fidelity, while female sicklefin redhorse displayed site fidelity. Silver redhorse and river redhorse were not significantly different (P > 0.05) in size (i.e., total length and weight), while the other redhorse species exhibited a morphological interspecific significant difference (P < 0.05). The spawning migration chronology between males and females was significantly different (P < 0.05) for black redhorse and sicklefin redhorse and not significantly different (P > 0.05) for the other three species; however, spawning migration bounds for both sexes of all five species were similar. All five species typically selected spawning microhabitat non-randomly. Interspecific redhorse spawning site microhabitats were generally significantly different (P < 0.05) due to deviation of one or two species. My findings suggest that seasonal, habitat, and ethological reproductive isolating are functioning within Hiwassee Basin; however, indicate that anthropogenic activities and alterations have the ability to diminish or remove these reproductive barriers. I compared resistance board weirs and prepositioned areal electrofishers to determine gear efficiency for migrating potamodromous fishes. Fish species richness and diversity were higher for PAE total catch, while weir catch had higher species dominance. Total PAE catch by number was much higher than total weir catch; however, PAE total biomass was lower than weir total biomass. Weirs generally did not demonstrate a velocity bias, while PAEs did. On average, PAE mortality was five times higher than weir mortality. My results will assist fisheries managers in selecting the most appropriate gear to address research and management objectives when sampling medium-sized rivers.
- Trophic Relations of Introduced Flathead Catfish in a North Carolina Piedmont River(2007-10-15) Brewster, Jessica Robin; Dr. Thomas J. Kwak, Committee ChairThe flathead catfish Pylodictis olivaris is a large piscivious ictalurid that is native to the Mississippi and Rio Grande river drainages, but has been widely introduced across the United States. I studied the trophic relations of introduced flathead catfish in the upper Cape Fear River basin, located in the piedmont region of North Carolina. My specific objectives for this study were to (1) quantify the diet of the flathead catfish and determine an ontogentic shift in diet; (2) determine selectivity for different prey fishes based on their occurrence in the flathead catfish diet and abundance in the river system; (3) determine diel chronology in feeding; (4) calculate daily ration and gastric evacuation rate to quantify the rate of food consumption; and (5) conduct field experiments to elucidate the mechanisms of the predator-prey relationship by determining preferences in introduced flathead catfish and channel catfish feeding between prey species, prey location in the water column, and accessibility to cover. River ecologists and fisheries managers are concerned with introductions of flathead catfish because of negative impacts to native fish communities associated with direct predation and indirect competition from these apex predators. There are also concerns with introductions that result in co-occurrence with imperiled species, and within my study site, introduced flathead catfish occur with the federally endangered Cape Fear shiner Notropis mekistocholas and the Carolina redhorse Moxostoma sp., a federal species of concern. I sampled a section of the Deep River in North Carolina that was hydrologically divided into unimpounded and impounded reach, to quantify diet and determine diet selectivity. A second study site, located at the confluence of the Deep and Haw rivers where the Cape Fear River is formed, was sampled in conjunction with the first field site to determine diel feeding chronology, daily ration, and gastric evacuation rate. Flathead catfish were collected using non-lethal, low-frequency, pulsed-DC electrofishing, and diets were sampled using non-lethal, pulsed gastric lavage. A randomized prey curve determined that the number of stomachs sampled was sufficient to accurately describe flathead catfish diet. The prey taxon with the greatest occurrence in the diet was crayfish, while sunfish composed the greatest percent of the diet by weight; neither imperiled fish species was found in any stomach sampled. An ontogenetic shift in diet was evident when flathead catfish reached about 300 mm in total length, and flathead catfish length significantly explained variation in percent-composition-by-weight of crayfish, sunfish, and darters. Flathead catfish showed positive prey selectivity for taxa that occupied similar benthic microhabitat as this predator, highlighting the importance of prey encounter rates to the predatory behavior of flathead catfish. Flathead catfish fed throughout the 24-h period and displayed a highly variable diel feeding chronology for July with a mean stomach fullness of 0.32%, but showed a single mid-day peak in feeding during August (mean fullness = 0.52%). The gastric evacuation rate for flathead catfish increased between July (0.40⁄h) and August (0.59⁄h), as did daily ration, which more than doubled between the two months (3.06% in July, 7.37% in August). A tethering experimental approach proved effective in determining prey selection dynamics for two contrasting large catfish species in the field, when they were presented choices among prey differing in species, location in the water column, and access to shelter from the predator. The flathead catfish, an obligate carnivore, showed no preference among all three treatment effects, whereas channel catfish, a feeding generalist, showed strong specificity for prey species and location of that prey item in the water column. These research findings under controlled conditions in a field setting offer additional insight into prey selection dynamics of these introduced catfish predators as it occurs in a natural setting that could not be gained by traditional sampling and observational approaches. Understanding the trophic relations of introduced flathead catfish and the degree of vulnerability among prey taxa will allow resource managers to make science-based decisions that may decrease the impacts of introduced flathead catfish on native fish populations and allow enhanced protection for imperiled species.
- Trout Population and Production Dynamics in North Carolina State Park Streams(2010-03-29) Wallace, Benjamin Craig; Dr. Thomas J. Kwak, Committee Chair; Dr. James A. Rice, Committee Member; Dr. Kenneth H Pollock, Committee MemberABSTRACT WALLACE, BENJAMIN CRAIG. Trout Population and Production Dynamics in North Carolina State Park Streams. (Under the direction of Thomas J. Kwak.) Stream trout (Salmonidae) fisheries provide popular recreational fishing opportunities in North Carolina and nationwide. These fisheries may be managed under historical practices with limited information available to evaluate or plan management alternatives. The use of dynamic rates of population functions can serve as a superior method to quantify trout populations and provide a scientific basis from which to guide management decisions. Three trout species, brook trout Salvelinus fontinalis, brown trout Salmo trutta, and rainbow trout Oncorhynchus mykiss, inhabit streams under a variety of management regulations and stocking regimes in Stone Mountain State Park, North Carolina. To investigate trout population and production dynamics in intensively utilized southern Appalachian Mountain streams, we studied six stream reaches to (1) intensively sample and quantify critical population parameters of stream trout in a State Park, (2) develop empirical estimates of stream trout production rate based on population parameters, (3) sample and quantify nongame fish assemblages associated with trout fisheries, (4) measure and quantify water quality and instream habitat characteristics associated with trout and nongame fish assemblages, and (5) present the results of this study in an applied context toward guiding management strategies for stream trout fisheries in North Carolina State Parks, as well as other coldwater streams across North America. Of the three unstocked streams sampled, brook trout were present in two and brown trout were present in all three. Wild trout are short-lived with a maximum age of two years among fish sampled in Stone Mountain State Park streams. Mean annual brook trout density in unstocked waters ranged from 195.09 to 234.13 fish/ha and that for brown trout was 169.87 to 2,038.69 fish/ha. Annual brook trout production ranged from 5.91 to 8.81 kg/ha and annual brown trout production ranged from 14.07 to 64.16 kg/ha in unstocked waters. Age-0 and age-1 fish contributed the most production in the unstocked waters. Allopatric brook trout were found in the uppermost headwaters of two unstocked streams. Brook trout, brown trout, and rainbow trout were present in all three sampled reaches of the East Prong Roaring River. Trout densities in delayed harvest managed waters fluctuated widely over time and could not be explained by the frequency and density of stocking alone. Few trout remained in the sampling reaches for long periods of time after stocking into delayed harvest waters. Trout density in hatchery supported waters declined rapidly after being opened to harvest. Nongame fish were collected in four of the six sampling reaches, and species richness ranged from 2 to 13. Nongame fish density was highest in a portion of the East Prong Roaring River where instream and riparian habitat rehabilitation previously occurred. Instream habitat, stream gradient, and overhead cover were similar within unstocked waters and within stocked waters but were different between the two stream groups. Stream temperatures in the East Prong Roaring River are marginally suitable for trout. Other water quality measurements were similar among all reaches that were studied. Salmonid production can be used to monitor success of stream trout populations and, in conjunction with the ecotrophic coefficient, guide management decisions in coldwater streams nationwide. P/B ratios developed from our empirical estimates of production can be used to estimate production in the future with reduced sampling effort. Based on our findings, management options for streams in Stone Mountain State Park are presented. My results, in addition to future research and monitoring, can improve understanding of trout population dynamics, native trout distribution, habitat modifications, and management effects.