VTechWorks Repository :: Browsing by Author "Ney, John J."

Browsing by Author "Ney, John J."

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Analysis of a Blue Catfish Population in a Southeastern Reservoir: Lake Norman, North Carolina
Grist, Joseph Daniel (Virginia Tech, 2002-08-14)
This investigation examined the diet, growth, movement, population genetics, and possible consumption demands of an introduced blue catfish Ictalurus furcatus population in Lake Norman, North Carolina. Clupeids, Corbicula fluminea, and Chara were the predominant food items (percent stomach contents by weight) found in blue catfish, and varied by season, lake-region, and fish size-class. Lake Norman blue catfish grow at a slower rate than has been reported for other reservoir populations, with fair to poor body conditions (Wr<85) early in life, but improving with increases in length (Wr>95). Movements and home ranges of blue catfish in Lake Norman were extremely varied, but individual blue catfish did establish specific seasonal home ranges and exhibited site fidelity. A spawning area in the upper region of the lake was identified and data suggested that blue catfish may have segregated populations within Lake Norman. The Lake Norman blue catfish population exhibited relatively little genetic variability, and was genetically differentiated from populations from Santee-Cooper, SC, and Arkansas. Genetic diversity could have been limited by a population bottleneck at the founding of the population or in subsequent generations. A consumption model indicated that 5.0 kg/ha to 8.3 kg/ha of clupeid standing stock could be eaten annually by blue catfish in Lake Norman based on percent stomach contents by weight data, and 21 kg/ha to 42 kg/ha based on percent caloric contribution calculations. This may reduce the possible production of other game fish species, including the put-grow-take striped bass Morone saxatilis fishery.
An analysis of the contamination by and effects of highway- generated heavy metals on roadside stream ecosystems
Mudre, John M. (Virginia Polytechnic Institute and State University, 1985)
This study examined the consequences of the opening and operation of a new highway north of Richmond, Virginia with respect to contamination of the aquatic environment with heavy metals (Zn, Cd, and Pb), and the effects of these metals on the biota of roadside streams. Sixteen sites located on six small, soft-water streams that were crossed by the highway, encompassing six reference sites located upstream of the highway, six sites located directly at the highway, and four sites located downstream of the highway, were sampled over a two and a half year period, allowing both spatial and temporal analyses. Traffic densities on the highway averaged about 12,000 vehicles per day (vpd). Significant increases in the metals concentrations of sediment, benthic invertebrates, fish whole-bodies, and fish tissues (liver, kidney, and bone) were noted over the course of the study, although the increase varied in magnitude, and were not always consistent. Sediment metals concentrations followed a dynamic plateau. Fish whole-body concentrations of Cd and Pb increased steadily over the course of the study. Spot-sampling for the same parameters along another nearby, more heavily traveled highway (50,000 vpd) indicated that increases in metals concentrations in the different ecosystem components at the study streams would have been greater had there been more traffic. A number of biotic parameters were investigated to determine whether metals contamination was affecting the biological integrity of the study sites. These were: benthic macroinvertebrate diversity and density; the percentage of the aquatic insect community that was composed of chironomids; and fish community diversity, density, and biomass. Only benthos density, the percent chironomids, and fish species diversity showed changes that could be related to metals contamination. Indications from spot sampling along the more heavily traveled highway were that if more contamination had been experienced, more biotic parameters would have been disturbed, and to a larger extent. Fish community structure analyses using the Pinkham-Pearson coefficient of similarity indicated that fish community structure became increasingly altered at highway sites, and to a lesser degree downstream sites, over the study period.
Analysis of the impact of flathead catfish predation on the abundance of four centrarchid species
Barr, Brian R. (Virginia Tech, 1994-01-13)
The top piscivore in Byllesby Reservoir, a 98.6 ha hydropower impoundment in southwestern Virginia is the flathead catfish Pylodictis olivaris. The most numerically abundant fish in the reservoir are centrarchids, specifically bluegill Lepomis macrochirus, redbreast sunfish L. auritus, smallmouth bass Micropterus dolomieu, and spotted bass M. punctulatus. A bioenergetics model was used to estimate the number of age-l and older centrarchids consumed annually by the flathead catfish population. These estimates were then compared to estimated abundances of each centrarchid species (age-1 and older) in the impoundment, resulting in an estimate of predation impact.
Analysis of the Trophic Support Capacity of Smith Mountain Lake, Virginia, for Piscivorous Fish
Cyterski, Michael John (Virginia Tech, 1999-06-08)
This investigation examined the adequacy of the forage base to meet current demand of piscivores in Smith Mountain Lake, Virginia. Surplus production, or the maximum sustainable supply, of alewife (Alosa pseudoharengus) and gizzard shad (Dorosoma cepedianum) were determined using data on the biomass, growth, and mortality of each species. Mean hydroacoustic alewife biomass from 1993-1998 was 37 kg/ha and mean gizzard shad cove rotenone biomass from 1990-1997 was 112 kg/ha. Mean annual alewife surplus production was determined to be 73 kg/ha and mean annual gizzard shad surplus production totaled 146 kg/ha. Bioenergetics modeling and population density estimates were utilized to derive the annual food consumption (realized demand) of the two most popular sport fish in the system, striped bass (Morone saxatilis) and largemouth bass (Micropterus salmoides). The striped bass population consumed 46 kg/ha of alewife and 27 kg/ha of gizzard shad annually. Largemouth bass ate 9 kg/ha of alewife and 15 kg/ha of gizzard shad annually. Annual consumption by ancillary predators was estimated to be 13 kg/ha of alewife and 35 kg/ha of gizzard shad. Prey supply to predators is limited by morphology, behavior, and distribution. The cumulative effect on prey availability of these three factors, in addition to consumption by other predators, was quantified. For largemouth bass, available supply of alewife and gizzard shad exceeded demand by 20% and 53% respectively. For striped bass, available supply of gizzard shad surpassed demand by 30% but available alewife supply was only 4% greater than demand. Annual demand of all predators was 94% of total available clupeid supply. Striped bass stockings were increased by 50% in 1998 and will remain at this level in the near future. A predator-prey simulation model of alewife and striped bass populations was developed to explore the consequences of increased predator demand. This model incorporated dependencies between alewife abundance and mortality and the mortality, abundance, and growth of striped bass. Model output showed that a 50% stocking increase has a near-zero probability of increasing the mean annual number of legal and citation striped bass in Smith Mountain Lake.
Assessing potential navigation impacts to the Kanawha river ecosystem: a modeling approach
Hershfeld, Donald Christopher (Virginia Tech, 1987-12-05)
An extensive study of the biota of the Kanawha River was integrated to examine the trophic basis of fish production and predict potential impacts of increased tow traffic at two sites in the Winfield Pool. Total standing stock and production of adult fish were estimated as 242 kg/ha and 188 kg/ha/yr, respectively. Sixtyâ one species were categorized into six trophic groups. Trophic generalists (omnivores and herbivore/detritivores) consumed a variety of foods including considerable detritus. These groups accounted for 73 to 83% of total ichthyomass and 81% of total adult production. Total fish consumption at the more riverine upper site was partitioned into 35% l detritus, 28% invertebrates, 20% plant matter, 12% other fish, and 5% crayfish. At the lower, more lentic site the diet consisted of 34% detritus, 25% plant matter, 21% other fish, 17% invertebrates, and 3% crayfish. The overall basis of production relies upon imports of allochthonous materials.
Assessment of the performance of stocked northern and Florida largemouth bass and their progeny in Briery Creek Lake, Virginia
Hoover, Randall S. (Virginia Tech, 1992-02-05)
This study examined the suitability of Florida largemouth bass (Micropterus salmoides floridanus) for introduction into Virginia and other mid-latitude waters by comparing the performance of northern (M. s. salmoides), Florida, and hybrid largemouth bass in a 342 ha south-central Virginia reservoir, Briery Creek Lake (BcL). Fingerling northern and Florida largemouth bass were stocked into Briery Creek Lake in 1986, following impoundment, and in 1987. Largemouth bass were collected for genotypic and performance analyses in the autumn and spring beginning in 1989 and ending spring 1991. Electrophoretic analyses demonstrated that hybrid largemouth bass (F1 and Fx) dominated the 1987-1990 cohorts and indicated that one or both founding stocks were genetically impure. Comparisons of electroshock catch composition showed no survival advantage for Florida largemouth bass (FLMB) age-1 and older and no differential vulnerability to angling among the four presumptive genotypes of largemouth bass in Briery Creek Lake. Age-O FLMB proportions declined over both winters (1989-1990 and 1990-1991) indicating relatively high first-mortality in the thermal regime of Briery Creek Lake (3,875 annual mean of heating degree days). Statistical comparisons of growth revealed no consistent differences among the respective bass genotypes, although survival and growth tended to be slightly higher for PI hybrid bass. The average total length of largemouth bass in BCL was below the state's average by age three. Total lengths of age-O FI and northern largemouth bass (NLMB) were higher than FLMB and Fx bass in October, perhaps as a result of earlier spawning among NLMB and between the subspecies. Relative weights of largemouth bass in BCL were generally below 95; and few significant differences in (Wr) were observed among the presumptive largemouth bass genotypes. The suboptimal condition (Wr) of largemouth bass in BCL coupled with the decline in growth and condition of bass with increasing age suggested inadequate prey abundance in Briery Creek Lake. Overall, Florida subspecific alleles did not increase in BCL over time, but the population genetic composition shifted toward an Fx mixture in the 1990 year class; future generations of largemouth bass should be dominated by Fx individuals. Results of this study did not demonstrate substantial performance differences among northern and Florida largemouth bass, and their hybrids, except for poorer first-year survival of the Florida subspecies. Therefore, this study provides no support for the continued introduction of Florida largemouth bass in Virginia or other mid-latitude regions.
Assessment of the Response of Piscivorous Sportfishes to the Establishment of Gizzard Shad in Claytor Lake, Virginia
Bonds, Charles Craig (Virginia Tech, 2000-02-07)
Gizzard shad were illegally introduced to Claytor Lake in the late 1980s and soon established a thriving population. This study assessed 1) the degree to which gizzard shad were utilized by piscivores (pelagic - striped bass Morone saxatilis, hybrid striped bass M. chrysops x M. saxatilis, and walleye Stizostedion vitreum, and three littoral black basses Micropterus spp.), 2) the availability of gizzard shad as potential prey as determined from age and growth analysis, and 3) the performance (growth rates, relative weight, and relative abundance) of piscivores before versus after gizzard shad establishment. Gizzard shad were more highly utilized by pelagic predators (especially striped bass and their hybrids) than black basses. Rapid growth of gizzard shad (mean back-calculated length at age-1 = 155 mm TL) meant that almost all morphologically available shad were age-0. The reliance on one edible age class of gizzard shad resulted in an unstable food supply as evidenced by much greater striped bass shad consumption in Summer 1998 (63 % by weight) when age-0 shad were more abundant than in Summer 1997 (7 % by weight). Striped bass was the only species to exhibit faster growth rates and mean relative weight (Wr) values in the 1990s versus pre-shad years. Walleye (except age-1) and black bass growth rates declined, and mean Wr values either remained consistent or declined. Largemouth bass and walleye were the only sportfish to show increases in relative abundance. Benefits of gizzard shad as a forage fish appear to be limited to striped bass and its hybrid species. It is possible that gizzard shad have had, directly or indirectly, an adverse impact on the black basses of Claytor Lake, but explanatory analysis of these relationships was beyond the scope of this study.
Assessment of the South Atlantic Red Porgy (Pagrus pagrus) Population Under a Moratorium
Davis, Michelle Leigh (Virginia Tech, 2003-12-10)
Red porgy Pagrus pagrus is a reef fish important to both recreational and commercial fisheries off the coast of the southeastern United States. Stock assessments performed on this species since 1985 have shown a population in decline. As a result, a number of management actions were put in place, including a harvest moratorium in 1999. Stock assessments for many marine species, including red porgy, rely on a combination of fishery-dependent and fishery-independent data. When a moratorium is in place, the flow of fishery-dependent data is interrupted, making assessments more reliant on fishery-independent information. To investigate how loss of fishery-dependent data, as during a moratorium, would affect stock assessment results for red porgy, I conducted model simulations to represent moratoria of various durations. The most recent red porgy stock assessment model developed during a 2002 workshop was used as a tool in these simulations. I found that biological reference points, such as biomass and fishing mortality, and population projections were more variable for longer simulated moratoria. When fishery-dependent data were removed, minor fluctuations in length and age frequencies resulted in larger fluctuations in estimates of biological reference points. The simulated moratoria also resulted in a slight bias toward over-estimating stock productivity. Similar simulations and analyses were conducted to determine the effects of reducing fishery-independent data from the Marine Resources Monitoring, Assessment, and Prediction (MARMAP) program. Length and age data of reduced MARMAP sample sizes were bootstrapped from original data, and used as input for the stock assessment model. Biological reference points and population projections were more variable for small MARMAP sample sizes, due to the incomplete representation of the length and age frequencies of the population. Reduced sample sizes also showed a slight bias toward predicting a more productive population. These types of simulations emphasize the benefits of investigating potential effects of data reduction on assessment results prior to implementing management strategies, such as a moratorium or sampling change, that cause data loss. Although decreasing red porgy data resulted in slight changes in assessment results, there are more data available for this species than other species in the snapper-grouper complex. For these lesser-studied species, reducing data could dramatically affect assessment capabilities. To investigate this, I compiled available data for these species and identified the stock assessment method used. I then predicted assessment capabilities for each species under a moratorium and if the MARMAP survey was eliminated. A moratorium could reduce assessment capabilities for 37 of the 73 species, and 63 species would require management based on key species. Removing MARMAP data would reduce assessment capabilities of eight species, many of which are economically important. There was an overwhelming need for a reliable catch-per-effort index, information that could improve assessment capabilities of 67 species. This index could be obtained by expanding the MARMAP survey, from a fishery observer program, or from commercial logbooks. By linking the red porgy stock assessment, an evaluation of sampling regimes and data loss during a moratorium, and the expansion of this stock assessment strategy to multiple species, managers will ultimately benefit from increased ability to manage stocks experiencing varying regulations and data availability.
Comparative Ecology of Juvenile Striped Bass and Juvenile Hybrid Striped Bass in Claytor Lake, Virginia
Rash, Jacob Michael (Virginia Tech, 2003-12-08)
Since the introduction of hybrid striped bass M. chrysops x M. saxatilis to Claytor Lake, Virginia in 1993, relative abundance of striped bass Morone saxatilis has dropped disproportionately to stocking density. Potentially deleterious interactions between the two fishes that may limit recruitment to age 1 were considered in terms of trophic relationships, physiological indices of health, overwinter survival, and post-stocking predation. Both fishes preferred habitat types characterized by structure-free sand or gravel substrates, but striped bass and hybrid striped bass did not exhibit significant diet overlap during the growing season. At a total length of approximately 120 mm, the juvenile moronids shifted from a mixed diet of zooplankton and invertebrates to a diet comprised primarily of age-0 fishes. However, after becoming piscivorous striped bass preyed primarily upon age-0 alewife Alosa pseudoharengus, while hybrid striped bass consumed age-0 sunfishes. Striped bass achieved mean total lengths of 229 and 173 mm by the end of the growing season in 2001 and 2002, respectively. Stocked into the reservoir three months later than striped bass, mean hybrid striped bass total lengths reached 133 mm at the end of the 2002 growing season. Condition factor, relative weight, and lipid index values were low, but nearly equivalent for both striped bass and hybrid striped bass throughout this study. Overwinter starvation of smaller (< 150 mm total length) striped bass was observed for the 2001-2002 sampling season. Predation upon stocked fingerlings was not considered significant in limiting juvenile survival; only three fingerling moronids were found in the examination of stomach contents of 200 potential predators captured near stocking sites. It does not appear that resource competition with hybrid striped bass during the growing season resulted in increased overwinter mortality of juvenile striped bass. Delayed stocking of hybrid striped bass lessens the potential for trophic competition between striped bass and hybrid striped bass at this early life-stage.
Compatibility and complementarity of alewife (Alosa pseudoharengus) and gizzard shad (Dorosoma cepedianum) as forage fish in Smith Mountain Lake, Virginia
Tisa, Mark Steven (Virginia Polytechnic Institute and State University, 1988)
The attributes of alewife and gizzard shad as coexistent forage fishes for striped bass (Morone saxatilis), walleye (Stizostedion vitreum vitreum) and largemouth bass (Micropterus salmoides) were evaluated in Smith Mountain Lake, an 8,337 ha hydroelectric impoundment in south-central Virginia. Alewife and gizzard shad larvae exhibited strong spatial segregation which minimized the potential for direct trophic competition and increased feeding opportunities for piscivores. Gizzard shad spawning peaked in June while alewife spawning peaked in July. Daily growth rate of age-0 gizzard shad was 37% greater than for age-0 alewives. Later spawning and slower growth enhanced temporal and morphological availability of alewives to piscivores and reduced the potential for exploitative competition between the clupeids. Distributional analysis indicated that gizzard shad were primarily uplake and littoral while alewives were mostly downlake and pelagic. Alewives co-occurred with striped bass and walleye during the growing season and were crucial in providing forage for these piscivores. Largemouth bass shared a common distribution with gizzard shad and were more trophically dependent than other piscivores on them. Prey supply and predator demand were one year out of phase; gizzard shad and alewife production peaked in the first year of life while their predators' cohort production peaked in the second year. Cohort production analysis indicated that over their lifespan, striped bass prey demand (per 1000 fish) would exceed that of walleye and largemouth bass by 17% and 166%, respectively. Lifespan cohort production patterns and ingestibility limitations on prey assured that most predation pressure in Smith Mountain Lake came from piscivores ages 0-2 and was constrained to alewives ages 0 and 1 and young-of-the-year gizzard shad. Prediction of patterns of consumption of alewife and gizzard shad by piscivores was derived from analyses of morphological and distributional availabilities; these agreed closely with actual diets for most predator-prey location, season and age combinations. The alewife appears to be both compatible with, and complementary to, the gizzard shad as a forage species in Smith Mountain Lake. Suitability of alewives for introductions into other reservoirs will vary with the morphometry and management objectives for those waters.
Competition Between Age-0 Largemouth Bass And Juvenile Bluegills In A Virginia Pond
Brenden, 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.
Early life history dynamics of a stocked striped bass (Morone saxatilis) population and assessment of strategies for improving stocking success in Smith Mountain Lake, Virginia
Sutton, Trent M. (Virginia Tech, 1997)
The early life history dynamics of stocked, fingerling striped bass (Morone saxatilis) were evaluated in Smith Mountain Lake, Virginia, from 1994-96 and incorporated into an individual-based model to assess various stocking strategies in terms of their largest percent increases in first-year growth, overwinter survival, and recruitment to age 1. Age-0 striped bass exhibited dissimilar patterns of dispersion and size-dependent spatial distribution as a result of differences in habitat availability between stocking sites and water temperature preferences. Although size increased over the growing season, a bimodal length distribution developed by fall during both 1994 and 1995; this distribution consisted of large-mode juveniles (> 180 mm TL) that weighed several times more than small-mode fish (<140 mm TL). Differential growth was attributed primarily to size-dependent differences in food habits and diet quality: small-mode striped bass maintained a mixed, low quality diet of invertebrates and small, age-0 cyprinids, while large-mode juveniles consumed only larger, energetically more profitable age-0 alewives. This disparity in food habits, largely due to the inability of small-mode striped bass to consume distributionally- and morphologically-invulnerable age-0 alewives, resulted in size-dependent differences in physiological well-being as large-mode juveniles had amassed greater absolute energy stores than small-mode fish by the end of the growing season. Spring sampling revealed that the bimodal length distribution had become unimodal and was comprised almost entirely of large-mode juveniles. Because the few surviving small-mode striped bass collected during spring were extremely emaciated, it appears that this size group exhausted their energy stores and, consequently, starved over the winter. Individual-based model simulation results indicated that stocking juvenile striped bass at a median total length of 52 mm on 08 June, while maintaining the current stocking density at 300,000 fingerlings, would result in the largest percent increases in first-year growth, survival, and number of age-1 recruits. This strategy was also less sensitive to perturbations in alewife population parameters and water temperature regime, and was more robust to these variations than the existing stocking scheme (300,000 fingerling striped bass with a median total length = 42 mm introduced on 15 June).
The effects of coal mining on sedimentation and fish assemblages in the Powell River, Virginia
Temple, Alan J. (Virginia Tech, 1997)
An ecological study was undertaken on the Powell River system in Virginia from 1988 - 1990 to evaluate the effects of land uses on hydrology, water quality, sedimentation (particle size < 2 mm), and fish assemblages and to derive ecological indicators for monitoring. The hydrologic (disturbance) regime of the sixth order reach was Classified. Although surface coal mining appears to have reduced flow variance, the changes were not sufficient to alter the hydrologic classification. Tributaries draining coal-mined lands had elevated specific conductivity, iron, manganese, sulphate, and turbidity relative to tributaries in unmined watersheds or in the sixth order mainstem (p ≤ 0.05). The fifth order reach, which had a greater proportion of watershed area surface-mined, exhibited higher specific conductivity, iron, sulphate, turbidity, and total solids than the sixth order (p ≤ 0.05). Despite the upstream-to-downstream, lower-to-higher water quality gradient, there was no compelling evidence from the use of state water quality standards and a nine-variable water quality index that water quality differentially affected fish assemblages. The primary physical habitat gradient in the lower river was sedimentation. Upstream, embeddedness increased in shallow-water habitats (p ≤ 0.001) and sediment depth increased in pools (p ≤ 0.001). Stepwise multiple regression analysis indicated that variation in sediment level was explained primarily by the proportion of the watershed surface-mined (R² = 0.75). Index of Biotic Integrity scores for fish assemblages were not correlated with sedimentation in shallow-water or in pool habitats (p > 0.066). Functional metrics, as opposed to taxonomic metrics, however, varied with sedimentation (p ≤ 0.002). In shallow-water habitats, omnivore relative abundance increased and specialized insectivore abundance decreased in higher sedimented sites. Top carnivore abundance decreased in pools with higher sedimentation levels. Abundance of lithophilous benthic spawners, postulated as the most sediment-sensitive reproductive guild, was not consistently correlated with sedimentation. Nine fish species were classified as sediment-intolerant and eight were classified as sediment-tolerant. The sediment-intolerant group was composed mostly of benthic insectivores. Habitat analyses indicated that sediment-intolerant species, as a category, utilized microhabitats with low sedimentation levels relative to the sediment-tolerant species group (p ≤ 0.0001). Species not classified as either sediment-intolerant or sediment-tolerant utilized microhabitats intermediate in sedimentation level (p ≤ 0.0001).
Effects of seasonal habitat limitations on the distribution and energetics of stocked salmonids in Lake Moomaw, Virginia
Hampton, Thomas M. (Virginia Tech, 1993-07-15)
Lake Moomaw, a 1024 ha flood control reservoir in western Virginia, retains sufficient cold, oxygenated water (< 21°C, ≥ 5.0 mg/L) to allow trout survival throughout most of the summer. However, trout habitat declines to an annual minimum in September. vertical gillnets and ultrasonic telemetry were used to determine the horizontal and vertical distribution of two cohorts of brown trout, Salmo trutta, and rainbow trout, Oncorhynchus mykiss, relative to ambient temperature and dissolved oxygen. Capture of trout in gillnets afforded the assessment of condition (K), relative liver weight (HSI), and daily consumption (CD) of age 1+ brown and rainbow trout in relation to habitat dynamics. Most age 1+ brown and rainbow trout were distributed in the metalimnion (12 - 21°C) from July to October, even when dissolved oxygen declined below 5.0 mg/L. Location in the metalimnion placed young trout near optimum temperatures and maximum prey abundance. The growth, condition, relative liver weight, and daily consumption of age 1+ brown and rainbow trout were apparently unaffected by habitat limitations. Age 1+ brown trout preyed almost exclusively on alewives, Alosa pseudoharenqus, whereas aquatic and terrestrial insects constituted a substantial portion of young rainbow trout diet. Age 2+ rainbow trout were distributed in the metalimnion from July to September, but were located in the hypolimnion (<12°C) in October. Adult brown trout were located in the metalimnion during July, but were distributed in the hypolimnion from August to October. Adult trout in the hypolimnion were at low temperature (10°C) and diminished dissolved oxygen concentrations (<5.0 mg/L). Distribution in the hypolimnion also resulted in isolation from primary forage alewives. Age 2+ brown trout effectively were not feeding, as only one of 16 adult brown trout collected in two years of sampling contained food. Adult rainbow trout consumed primarily alewives in August and aquatic insects in September, but were apparently not feeding in October. Small sample size precluded the direct measurement of the effects of this isolation on the growth of age 2+ trout in Lake Moomaw. A bioenergetics model predicted that even brief durations of isolation from prey could severely limit the growth of age 2+ brown and rainbow trout.
Effects of Watershed and Habitat Conditions on Stream Fishes in the Upper Roanoke River Watershed, Virginia
Stancil, Vann Franklin (Virginia Tech, 2000-06-22)
I collected fish samples and habitat data at 43 sites throughout the upper Roanoke River watershed, Virginia. Sites were separated into three watershed areas size classes: 10 - 15, 20 - 30, and 70 - 80 km². I correlated physical in-stream conditions with proportions of forest, disturbed, and herbaceous/agricultural land at various watershed-scales to determine factors affecting stream habitat. I grouped fishes into metrics commonly used in indexes of biotic integrity and created a multimetric index called the mean metric score to represent fish communities at sites. Fish variables and metric values were compared with stream habitat and watershed variables to determine primary influences on fish communities. I correlated land use at 24 spatial scales, which differed by buffer width and stream network area, with mean metric scores to determine zones of greatest influence on fish communities. In-stream habitat conditions and amounts of forest, herbaceous/agricultural, and disturbed land varied greatly among sites. Habitat varied due to natural differences among sites, such as elevation and watershed area, and due to land use. Disturbed land use was greatest at lower elevations while forests were more abundant at higher elevations. Substrate size distribution was highly correlated with all three land use types at several spatial scales. Correlations between land use within various buffers and median particle size became stronger as larger proportions of watersheds were included in analysis. Fish species richness increased from small to large sites by species addition. Species collected at small sites were also collected at large sites, but several species collected at large sites were absent elsewhere. For example, orangefin madtoms and bigeye jumprocks were only collected at three large sites. Fish distribution was a result of several factors such as watershed area, elevation, proportions of pools and of riffles, particle size, and land use within buffers and entire watersheds. Sites with high mean metric scores were primarily limited to tributaries of the North and South Forks of the Roanoke River. Most sites with low mean metric scores were located near the cities of Roanoke and Salem. Forest and disturbed land use were highly correlated with mean metric scores. Elevation was also highly correlated with mean metric scores but herbaceous/agricultural land use was not. Correlations between percent forest within 24 buffers and mean metric scores were highest for small stream network areas and declined as more land farther from sites was included for analysis. Correlations between disturbed land use and mean metric scores were strong regardless of the area considered. Mean metric scores declined precipitously as disturbed land use within watersheds and buffers increased from 0 to 10 %, but reached a plateau at 10 to 20 % after which increases in disturbed land use did not result in lower mean metric scores. My results suggest that species addition and ecological shifts from more generalized to more specialized species occur with increased stream size. Forested buffers are important for maintaining ecological integrity, and buffers along sites with adequate integrity should be candidates for riparian restoration. Future development should be concentrated in watersheds that are already developed and reforestation of riparian areas in developed watersheds may reduce the impacts of watershed-level disturbance.
Evaluating the effects of angler behavior on the efficacy of harvest regulations in recreational fisheries
Creamer, Allan E. (Virginia Tech, 1993-01-05)
A computer-implemented simulation model was modified to compare various regulation schemes and determine how they are affected by angler non-compliance and voluntary catch-and release fishing. Combinations of three creel limits and five length limits were simulated. Scenarios for no regulations and catch-and-release were also simulated. Angler noncompliance varied from 0% to 50% and voluntary release included rates of 20%, 50%, and 80%. Based on catch, harvest, yield, and PSD, the ranking of specific regulations changed little among levels of angler non-compliance and voluntary release. All four decision variables were most influenced by regulations when angler compliance was high and voluntary release was low. Further, for a fishery with a high degree of voluntary release, and relatively high angler compliance, regulations did not produce any discernible benefits in the fishery. The model was demonstrated with data on a smallmouth bass, Micropterus dolomieu, fishery for the upper and lower James River, Virginia. Simulated regulations were assessed based on adjustments to angler non-compliance, which averaged based on adjustments to angler non-compliance, which averaged 17 percent, and voluntary release, which averaged 90 percent. Model results indicate that more restrictive regulations improved PSD and catch, whereas numerical harvest and yield in weight benefitted from liberal regulations. Variability among the 81 regulations was low, suggesting that voluntary release (90% average) is a dominant control in the James River smallmouth bass fishery. From a management standpoint, these findings also suggest that, where appropriate, management strategies should focus on increasing voluntary release and rely on regulations only in certain fisheries.
An Evaluation of Relative Weight as an Indicator of Body Composition and Nutritional Status in Wild Fish
Copeland, Timothy (Virginia Tech, 2004-11-02)
Condition indices are widely used to generate biological insight. However, purported relationships to indices are imprecise or inconsistent in the wild. I investigated factors influencing relative weight (Wr), a condition index commonly applied to fish. I first examined the relationship of Wr to physiology in two bluegill Lepomis macrochirus populations over a year. I regressed tissue composition (percentages of lipid, protein and water) and organ indices (liver-, gonad-, and viscerosomatic indices) on Wr. The regression model had little explanatory power (adjusted R2 = 0.14). Lipid was most influential (partial R2 = 0.11), but correlation strength fluctuated by season and population. To test the generality of these results, I performed a similar regression on a bluegill population with higher average Wr. Again, variables were not well correlated to Wr (adjusted R2 = 0.13). Combining comparable data sets increased Wr range 64% but explanatory power was low (adjusted R2 = 0.41) Both studies showed that expected correlations of physiological variables to Wr can be confounded in natural environments. To examine differences between natural and laboratory environments, I manipulated initial Wr and ration of juvenile bluegills. Although organ indices and tissue composition of all groups changed in time ((Wilks' Δ > 0.387, P > 0.03), no temporal pattern matched to Wr. At termination, all variables showed high correlations to Wr (r2 > 0.64). Correlation strength increased with time in the laboratory. Both ration and environment influenced correlations. Lastly, I examined differences in interpretation of Wr for chain pickerels Esox niger, largemouth bass Micropterus salmoides, and black crappies Pomoxis nigromaculatus. Regression models were compared to concurrent bluegill models. Piscivore models fit well (adjusted R2 > 0.50), whereas bluegill models had the lowest explanatory power (adjusted R2 = 0.13 and 0.14). Ecological specialization affected correlations to Wr. Theoretically, condition index values are determined by resource acquisition versus expenditure. Exact physiological expression is determined by life history and performance. Condition indices are imprecise predictors but track net somatic investment with great generality. Ancillary data, such as growth or length-at-maturity, may clarify interpretation. Condition indices should be used as qualitative monitoring tools, not omnibus physiological predictors.
Evaluation of stream improvement practices in southeastern trout streams
Maughan, O. Eugene; Nelson, Kent L.; Ney, John J. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1978)
Factors affecting largemouth bass recruitment in a trophy bass reservoir of Virginia, Briery Creek Lake
Ray, Bradley A. (Virginia Tech, 2008-07-28)
Briery Creek Lake (BCL) has low abundance of young largemouth bass (LMB) compared to Sandy River Reservoir (SRR), which could jeopardize the trophy-LMB management goal in BCL. I assessed factors that may limit recruitment of LMB in BCL: angling, predation, competition, growth, and food availability. Age-0 LMB were monitored from nesting through their first summer with nest surveys, light traps, and electrofishing. Nesting success was higher in BCL (53%) than SRR (31%). Initial light trap catch-per-unit-effort (CPUE) was higher in BCL than SRR but, by July, light trap and electrofishing CPUE was higher in SRR than BCL. LMB nest success, growth, and CPUE did not differ between areas in BCL that were experimentally closed and areas left open to angling. Predation on age-0 LMB did occur in BCL, but was not higher than predation in SRR. Diet overlap between age-0 LMB and bluegill in BCL was >60% during June, indicating potential for competition. Zooplankton samples indicated that density of copepods was similar between reservoirs (2.3/liter); however, the average size of copepods was smaller in BCL (0.42 mm) than SRR (0.71 mm). I examined the activity of trypsin, which digests and converts protein. Trypsin activity was lower in BCL than SRR on 23 and 27 June, indicating that a nutritional deficiency exists for age-0 LMB in BCL. This deficiency was likely caused by the reduced zooplankton size in BCL and led to slower growth of age-0 LMB during June in BCL (0.8 mm/day) than SRR (1.2 mm/day). The fact that age-0 LMB CPUE in BCL dropped lower than SRR by July, despite BCL having a greater nesting success and higher CPUE in early June, indicates that a recruitment bottleneck for LMB occurred in June. Maintaining the trophy LMB fishery in BCL requires management options that consider the factors in June that affect recruitment. I recommend decreasing the presently overabundant aquatic macrophytes in BCL, thus allowing for increased nutrient availability for phytoplankton, the primary food source of zooplankton. This could increase the density and size structure of zooplankton, and thereby increase food availability for age-0 LMB.
Fine sediment effects on brook trout egg and alevin survival in Virginia
Argent, David G. (Virginia Tech, 1995-02-05)
Detailed information about negative effects of fine sediments on early life stages of brook trout (Salvelinus fontinalis) in southern Appalachian streams is lacking. Information on survival to different stages of egg and alevin development could indicate critical timing of sediment impacts. This study was designed to determine the effects of fine sediments (0.43-0.85 rom in diameter) on survival of brook trout eggs through early development stages under controlled laboratory and field conditions. Recently fertilized eggs were loaded into Whitlock-Vibert (W-V) boxes lined with 0.4 rom Nitex netting that contained mixtures of gravel and fine sediments. Survival to eyed, hatched, and emerged stages of development was determined for six amounts of fine sediment (0-25% by weight) in the laboratory study and for three amounts of fine sediment (0-20% by weight) in the field study. Survival in laboratory systems to each stage of development was inversely related to the percentage of fine sediment; even at low levels of fine sediment survival was reduced. In the field study, fine sediment may have played a role in the survival success of developing embryos, but determining a definitive relationship was confounded by effects of scouring flows and fungal infestations. The fungus Saprolegnia spp., may have increased the mortality rate of viable eggs and facilitated the disintegration of nonviable embryos, especially in the field study. Brook trout are sensitive to increasing levels of fine sediment through early development. However under field conditions such an effect may be difficult detect.

Browsing by Author "Ney, John J."

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