Browsing by Author "Brenden, Travis Owen"
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- Competition Between Age-0 Largemouth Bass And Juvenile Bluegills In A Virginia PondBrenden, Travis Owen (Virginia Tech, 1999-09-23)I assessed the potential for trophic competition between age-0 largemouth bass and juvenile bluegills by quantifying food resource use similarity in a Virginia recreational small impoundment and by experimentally stocking the species sympatrically and allopatrically in 1.0 m cages and monitoring mortality, growth, and resource use. Niche breadth of bluegills in the small impoundment was greater than that of largemouth bass for eight out of nine sampling dates during the summer and fall of 1997. Virtually every type of item consumed by largemouth bass also was consumed by bluegills. In spite of this, diet overlap between the species was low. Largemouth bass fed primarily on Calanoida, Ephemeroptera, and fish, while bluegills consumed Diptera and Cyclopoida. The fishery of the impoundment consisted of relatively high and moderate densities of slow- and average-growing largemouth bass and panfish, respectively. If the fishery was managed to provide a high density of small bluegill, largemouth bass and bluegill might compete considering the number of prey items shared. Manipulative cage experimentation, which consisted of stocking 5 largemouth bass alone, 10 bluegill alone, 5 largemouth bass and 10 bluegill, 5 largemouth bass and 30 bluegill, and 15 largemouth bass and 10 bluegill in cages, indicated that largemouth bass and bluegills can compete and that there exists a strong asymmetry in their competitive relationship. Bluegills had a much stronger impact on largemouth bass than the reverse. When stocked alone, largemouth bass grew significantly larger than when stocked with either 10 or 30 bluegills. There were no significant differences in bluegill growth rates except between bluegills stocked alone and bluegills stocked with 15 largemouth bass. The analysis of food resource use indicates that Copepoda and Diptera larvae may be the limiting resources catalyzing the competitive interaction. This research suggests that a competitive juvenile bottleneck could occur, depending largely on whether overwinter survival of largemouth bass is size related. Competition between largemouth bass and bluegills may explain why enhancement stocking of fingerling largemouth bass typically is not successful. Further research is needed on the appropriate timing and length at stocking of introductory largemouth bass stockings. Additionally, I recommend that resource partitioning and competition between largemouth bass and bluegills be explored in connection with studies concerning overwinter survival and angling opportunities in small impoundments. Competition between the species may impose an ecological constraint that restricts achievable options in certain systems.
- Evaluation of Current Management Strategies for the New River, Virginia, Muskellunge Fishery: Modeling the Effect of Alternative Harvest Regulations and Habitat SelectionBrenden, Travis Owen (Virginia Tech, 2005-04-01)The purpose of this research was to evaluate current management strategies for the New River, Virginia, muskellunge Esox masquinongy fishery, which is the premier muskellunge fishery in the state. The primary objectives were to evaluate potential benefits and angler support for more restrictive harvest regulations and to quantify habitat selection at multiple spatial scales. A secondary objective was to develop an alternative procedure for testing differences in muskellunge condition from relative weight Wr data that incorporates uncertainty regarding the accuracy of the standard weight equation and that is based on derived statistical properties of the Wr index. Abundance of memorable-length (³1,070 mm) muskellunge was predicted to increase with minimum length limits of 914, 1,016, and 1,143 mm. Although yield per recruit would decline under a 1,143-mm minimum length limit, it was predicted to remain fairly stable at length limits of 914 and 1,016 mm due to fast growth rates of young fish. Even though most anglers defined trophy muskellunge to be in excess of 1,016 mm, angler support for length limits in excess of 1,000 mm was low. Habitat variables that were most strongly related to muskellunge habitat selection were measures of patch shape complexity and water depth. Increased river discharge was found to significantly affect muskellunge habitat use and selection, with fish abandoning deeper open-water habitats and moving to shallower areas closer to the shoreline during periods of high discharge. As for the secondary objective, a new statistical test (R-test) was developed that can be used to test for differences in Wr between and within fish stocks. Comparison with other statistical tests indicated that the R test provides more conservative results than traditional statistic procedures, and that substantial variability in standard weight equations will make it more difficult to detect statistical differences. Management recommendations for the New River muskellunge fishery include increasing the minimum length limit to approximately 965 to 1,067 mm and limiting the stocking of muskellunge only to those areas with sufficient juxtaposition of shallow- and deep-water habitat patches.