Browsing by Author "Dr. Thomas J. Kwak, Committee Member"

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Characterizing American Shad Spawning Habitat in the Upper Roanoke River Basin, Virginia
(2005-04-28) Read, Alesia Noelle; Dr. Joseph E. Hightower, Committee Chair; Dr. Kenneth H. Pollock, Committee Member; Dr. Thomas J. Kwak, Committee Member
Populations of American shad (Alosa sapidissima) have declined from historical levels due to overfishing, decreased water quality and habitat losses including those due to dam construction. One approach for restoring these populations is to identify suitable habitat upstream of dams that could be restored through dam removal or by providing fish passage. The goal of this research is to identify and characterize potential spawning habitat for American shad in the upper Roanoke River basin of Virginia, above Kerr Reservoir. Five mainstem rivers that are upstream of the Roanoke Rapids, Gaston, and Kerr dams (Big Otter, Staunton, Banister, Dan, Hyco) were the focus of this research. Roanoke Rapids Dam is the first obstruction to American shad spawning migration in the Roanoke River basin, and just completed the FERC (Federal Energy Regulatory Commission) relicensing process in 2004. One of the provisions of the new license is to evaluate a trap and transport program for spawning American shad. Characterizing the habitat above the dam, in terms of suitability, is an important step in predicting the benefits of fish passage. A detailed physical habitat assessment, including monthly water quality monitoring, indicated that the Banister and Hyco rivers consistently had lower dissolved oxygen concentrations and may provide lower quality habitat for American shad compared to the other rivers. However, according to the current published Habitat Suitability Index (HSI) model, which incorporates surface water temperature and current velocity as criteria for suitable habitat, the five rivers appear to contain suitable habitat with HSI values ranging from 0.83 to 1.00 during May. I constructed a modified HSI model with surface water temperature and current velocity, as well as dissolved oxygen, pH and a component for substrate composition. The modified model suggested that the Big Otter and Staunton rivers would provide the highest quality spawning habitat for American shad because of the presence of gravel, cobble and bedrock substrates. Larger substrates have been suggested to be preferred over smaller substrates by spawning adult American shad in the Neuse River, NC. Egg incubation experiments were conducted during the American shad spawning season, from mid-April to the end of May 2004, throughout the basin. Hatching success from incubation experiments was relatively high (69-94 percent). No significant differences (p<0.05) among incubation sites were found in terms of hatching success, which suggests that water quality throughout the basin is suitable for egg development. The combination of field data and habitat suitability modeling used to predict habitat quality was an efficient approach for assessing habitat and could be used by planners and managers working to restore American shad populations in other river systems. Results from the physical habitat assessment, the habitat suitability modeling and the egg incubation results suggest that a trap and transport program should be successful for spawning American shad in the Roanoke basin.
Live Fast and Die Young: On the Growth and Mortality of Largemouth Bass in Puerto Rico
(2003-02-21) Neal, Jason Wesley; Dr. E. Jacquelin Dietz, Committee Member; Dr. Thomas J. Kwak, Committee Member; Dr. James A. Rice, Committee Member; Dr. Richard L. Noble, Committee Chair
Largemouth bass (Micropterus salmoides) have been widely introduced into freshwater systems around the world. In Puerto Rico, this species presents a management challenge to natural resource agents who wish to promote it as a sportfish because growth and survival are unlike that observed in its native temperate regions. Juvenile growth is linear and rapid (≥1 mm/day), attributed in part to a continuous growing season near optimum temperature year-round. Upon maturation, growth rate slows to near 0 mm/day, and few fish surpassing age 3. This dissertation hypothesized that the slow growth of adult fish results from excessive energy allocation to reproduction. Largemouth bass in Puerto Rico reach sexual maturity in 1 year, spawn over a six-month period, and individual fish spawn multiple times. The diversion of energy from growth to reproduction causes growth rates to decline, and the risk of disease, parasites, predation, or other means of natural mortality increases. I used three approaches to address this hypothesis: (1) empirical assessment of population dynamics, (2) theoretical modeling of bioenergetics processes, and (3) direct experimentation to compare reproductive and non-reproductive largemouth bass. Adult mortality strongly coincided with the reproductive period (January-June), and limited mortality occurred thereafter. Fish condition varied seasonally and with size, and was generally lowest in November just before the reproductive period, making these fish more susceptible to spawning related mortality. Condition declined with increasing age, suggesting a cumulative effect with no recovery period. Overall, empirical data on largemouth bass population dynamics supported the reproductive energetics hypothesis. Bioenergetics simulation using a conservative mean daily ration of 2% body weight predicted that a non-reproductive, 500-g largemouth bass would grow to 1,140 g in six months (182 d), the maximum spawning season duration. The actual size from tagging studies was 740 g, yielding a 400-g discrepancy between observed and predicted weight. This discrepancy in observed and predicted growth was explained for females using a range of spawning frequency-magnitude combinations, and for males by accounting for lost consumption. To experimentally test the reproductive energetics hypothesis, techniques for artificially propagating largemouth bass and inducing triploidy are discussed. I validated erythrocyte cell length as a ploidy verification technique using known ploidy largemouth bass. Erythrocyte cell length 99% confidence intervals ranged 14.43-16.66 mm for triploids, and 10.23-13.62 mm for diploids. Erythrocyte length correctly distinguished 100% of known-status largemouth bass (n=22) using a sample of 100 erythrocytes per individual. Growth, condition, and reproductive development of diploid and triploid largemouth bass were compared through age 1 in Lucchetti Reservoir. Growth rates up to the size of maturity (275 mm) were similar for both groups, and maturity was not reached until midway into the spawning season, preventing extensive spawning of diploid bass, and resulting in growth rates similar to triploid bass. Diploid largemouth bass exhibited higher GSI values than triploids, and no triploid females had GSI values consistent with maturation, suggesting that the triploids do not invest significant energy into reproductive development. As a result of this study, more comprehensive management of largemouth bass is possible. I refined techniques to produce triploid largemouth bass, and demonstrated the reduced reproductive investment of these sterile fish. Further research using triploids is needed to determine the efficacy of triploidy as a management option, particularly to determine if accelerated adult growth rates are possible. Specific research needs and management recommendations are discussed along with ecological implications of this research.
Spawning Activity and Migratory Characteristics of American Shad and Striped Bass in the Cape Fear River, NC
(2009-08-05) Smith, Joseph Alan; Dr. Kevin Gross, Committee Member; Dr. Thomas J. Kwak, Committee Member; Dr. Joseph E. Hightower, Committee Chair
SMITH, JOSEPH ALAN. Spawning Activity and Migratory Characteristics of American Shad and Striped Bass in the Cape Fear River, NC. (Under the direction of Joseph E. Hightower) Anadromous fish populations within the Cape Fear River, NC have experienced declines since the late 1800s. Three low-head lock and dam structures contributed to this decline by limiting access to upstream habitat. I used egg sampling and sonic telemetry to characterize patterns of migration and spawning activity for American shad and striped bass. Plankton samples were taken below each lock and dam, and at two locations farther upstream. Distribution and stage of development of American shad eggs, as well as observed spawning activity, suggest that most American shad spawning took place below the lowermost lock and dam (river km (rkm) 97). Egg density decreased by an estimated 90% for each successive dam moving upstream. In 2007, 20 American shad and 20 striped bass were captured and transported to a release location upstream of the three locks and dams, where they were tagged with sonic transmitters and released. Sixty percent of American shad in 2007 moved 1 to 33 rkm upstream of the release site, at an average migration rate of 2.30 rkm/hr. All 2007 striped bass moved downstream upon release. However, two striped bass made secondary upstream migrations of 52 and 134 rkm, through two and three dams respectively, and at an average rate of 2.58 rkm/hr. In 2008, 20 American shad and 20 striped bass were captured, tagged with sonic transmitters, and released at their capture locations (all but two striped bass downstream of the first lock and dam). Sixty-five percent of American shad and 77% of striped bass made upstream movements past the lowermost lock and dam in 2008, with average migration speeds of 3.2 rkm/hr for American shad and 3.0 rkm/hr for striped bass. Furthermore, 35% of American shad and 25% of striped bass that made upstream movements were able to migrate upstream of the uppermost lock and dam (rkm 186). Combined results suggest that Lock and Dam #1 had the highest egg collections and a tie for the predicted proportion of the American shad run (35%, tied with the upper river), and Lock and Dam #3 had the highest egg collections and highest predicted proportion of the striped bass run. The locking program established for upstream fish passage provides some access to historical spawning habitat, although spawning of American shad is concentrated in areas below the dams. Further improvements in fish passage should benefit both species.