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Virginia Tech
1.
Olsen, Jesse Eric Burle.
Flood pulse influences on exploited fish populations of the Central Amazon.
Degree: MS, Fisheries and Wildlife Sciences, 2017, Virginia Tech
URL: http://hdl.handle.net/10919/83864 
► Seasonally fluctuating water levels, known as flood pulses, influence the population dynamics and catches of fishes from river-floodplains. Although different measures of flood pulses, here…
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▼ Seasonally fluctuating water levels, known as flood pulses, influence the population dynamics and catches of fishes from river-floodplains. Although different measures of flood pulses, here called flood pulse variables, have been correlated to changes in catches of river-floodplain fishes, the flood pulse variables that have the strongest relationships to catches have not been identified. Furthermore, it is unclear if flood pulses influence catches of river-floodplain fishes with different life history strategies in different ways. Catches of 21 taxa from approximately 18,000 fishing trips were modeled as a function of fishing effort, gear type, seasonal flood pulse variables, and interannual flood pulse variables. These models were analyzed to understand which flood pulse variables had the strongest relationships to catches, and evaluate different flood pulse influences among taxa with different life history strategies. High water flood pulse variables generally had positive influences on catches in future years, while low water flood pulse variables generally had negative influences on catches in future years. Flood pulses generally had stronger influences on the catches of fishes with high fecundities and smaller eggs than on catches of fishes with low fecundities and larger eggs. Variation was observed in strengths and directions of flood pulse influences on catches of fishes with similar and different life history strategies. While my results were generally consistent with prevailing knowledge of how flood pulses influence catches of fishes, other biological factors of specific fish populations may further explain population responses to flood pulses.
Advisors/Committee Members: Castello, Leandro (committeechair), Jiao, Yan (committee member), Orth, Donald J. (committee member).
Subjects/Keywords: Multispecies fisheries; flood pulse; modeling; floodplain ecology; LASSO
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APA (6th Edition):
Olsen, J. E. B. (2017). Flood pulse influences on exploited fish populations of the Central Amazon. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/83864
Chicago Manual of Style (16th Edition):
Olsen, Jesse Eric Burle. “Flood pulse influences on exploited fish populations of the Central Amazon.” 2017. Masters Thesis, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/83864.
MLA Handbook (7th Edition):
Olsen, Jesse Eric Burle. “Flood pulse influences on exploited fish populations of the Central Amazon.” 2017. Web. 19 Jan 2021.
Vancouver:
Olsen JEB. Flood pulse influences on exploited fish populations of the Central Amazon. [Internet] [Masters thesis]. Virginia Tech; 2017. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/83864.
Council of Science Editors:
Olsen JEB. Flood pulse influences on exploited fish populations of the Central Amazon. [Masters Thesis]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/83864
Virginia Tech
2.
Zhang, Yafei.
Exploring spatial heterogeneity of CPUE year trend and nonstationarity in fisheries stock assessment, an example based on Atlantic Weakfish (Cynoscion regalis).
Degree: MS, Fisheries and Wildlife Sciences, 2016, Virginia Tech
URL: http://hdl.handle.net/10919/78094
► Quantitative population dynamics modeling is needed to evaluate the stock status and fisheries management plans to provide robust model and management strategies. Atlantic Weakfish (Cynoscion…
(more)
▼ Quantitative population dynamics modeling is needed to evaluate the stock status and fisheries management plans to provide robust model and management strategies. Atlantic Weakfish (Cynoscion regalis), one important commercial and recreational fish species along the west coast of Atlantic Ocean that was found to be declining in recent years, was selected as an example species. My study aimed to explore the possible spatial heterogeneity of CPUE (catch per unit effort) year trend based on three fishery independent surveys and explore the influence of nonstationary natural mortality on the fisheries management through a MSE (Management Strategy Evaluation) algorithm based on the Weakfish stock assessment results. Five models for catch rate standardization were constructed based on the NEAMAP (NorthEast Area Monitoring and Assessment Program) survey data and the ‘best' two models were selected based on the ability to capture nonlinearity and spatial autocorrelation. The selected models were then used to fit the other two survey data to compare the CPUE year trend of Weakfish. Obvious differences in distribution pattern of Weakfish along latitude and longitude were detected from these three surveys as well as the CPUE year trend. To test the influence of the model selection on the MSE, five stock-recruitment models and two forms of statistical catch-at-age models were used to evaluate the fishery management strategies. The current biomass-based reference point tends to be high if the true population dynamics have nonstationary natural mortality. A flexible biomass based reference point to match the nonstationary process is recommended for future fisheries management.
Advisors/Committee Members: Jiao, Yan (committeechair), Haas, Carola A. (committee member), Frimpong, Emmanuel A. (committee member).
Subjects/Keywords: Catch rate standardization; population dynamics; Weakfish; risk assessment
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APA (6th Edition):
Zhang, Y. (2016). Exploring spatial heterogeneity of CPUE year trend and nonstationarity in fisheries stock assessment, an example based on Atlantic Weakfish (Cynoscion regalis). (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78094
Chicago Manual of Style (16th Edition):
Zhang, Yafei. “Exploring spatial heterogeneity of CPUE year trend and nonstationarity in fisheries stock assessment, an example based on Atlantic Weakfish (Cynoscion regalis).” 2016. Masters Thesis, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/78094.
MLA Handbook (7th Edition):
Zhang, Yafei. “Exploring spatial heterogeneity of CPUE year trend and nonstationarity in fisheries stock assessment, an example based on Atlantic Weakfish (Cynoscion regalis).” 2016. Web. 19 Jan 2021.
Vancouver:
Zhang Y. Exploring spatial heterogeneity of CPUE year trend and nonstationarity in fisheries stock assessment, an example based on Atlantic Weakfish (Cynoscion regalis). [Internet] [Masters thesis]. Virginia Tech; 2016. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/78094.
Council of Science Editors:
Zhang Y. Exploring spatial heterogeneity of CPUE year trend and nonstationarity in fisheries stock assessment, an example based on Atlantic Weakfish (Cynoscion regalis). [Masters Thesis]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/78094
Virginia Tech
3.
Ballesta Artero, Irene Maria.
Influence of the Estimator Selection in Scalloped Hammerhead Shark Stock Assessment.
Degree: MS, Fisheries and Wildlife Sciences, 2014, Virginia Tech
URL: http://hdl.handle.net/10919/24819
► In natural sciences, frequentist paradigm has led statistical practice; however, Bayesian approach has been gaining strength in the last decades. Our study assessed the scalloped…
(more)
▼ In natural sciences, frequentist paradigm has led statistical practice; however, Bayesian approach has been gaining strength in the last decades. Our study assessed the scalloped hammerhead shark population on the western North Atlantic Ocean using Bayesian methods. This approach allowed incorporate diverse types of errors in the surplus production model and compare the influences of different statistical estimators on the values of the key parameters (r, growth rate; K carrying capacity; depletion, FMSY , fishing levels that would sustain maximum yield; and NMSY, abundance at maximum sustainable yield). Furthermore, we considered multi-levelpriors due to the variety of results on the population growth rate of this species. Our research showed that estimator selection influences the results of the surplus production model and therefore, the value of the target management points. Based on key parameter estimates with uncertainty and Deviance Information Criterion, we suggest that state-space Bayesian models be used for assessing scalloped hammerhead shark or other fish stocks with poor data available. This study found the population was overfished and suffering overfishing. Therefore, based on our research and that there was very low evidence of recovery according with the last data available, we suggest prohibition of fishing for this species because: (1) it is highly depleted (14% of its initial population), (2) the fishery status is very unstable over time, (3) it has a low reproductive rate contributing to a higher risk of overexploitation, and (4) the easiness of misidentification among different hammerhead sharks (smooth, great, scalloped and cryptic species).
Advisors/Committee Members: Jiao, Yan (committeechair), Orth, Donald J. (committee member), Siegried, Kate Andrews (committee member).
Subjects/Keywords: Sphyrna lewini; logistic production model; types of error; likelihood; Bayesian approach
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APA (6th Edition):
Ballesta Artero, I. M. (2014). Influence of the Estimator Selection in Scalloped Hammerhead Shark Stock Assessment. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/24819
Chicago Manual of Style (16th Edition):
Ballesta Artero, Irene Maria. “Influence of the Estimator Selection in Scalloped Hammerhead Shark Stock Assessment.” 2014. Masters Thesis, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/24819.
MLA Handbook (7th Edition):
Ballesta Artero, Irene Maria. “Influence of the Estimator Selection in Scalloped Hammerhead Shark Stock Assessment.” 2014. Web. 19 Jan 2021.
Vancouver:
Ballesta Artero IM. Influence of the Estimator Selection in Scalloped Hammerhead Shark Stock Assessment. [Internet] [Masters thesis]. Virginia Tech; 2014. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/24819.
Council of Science Editors:
Ballesta Artero IM. Influence of the Estimator Selection in Scalloped Hammerhead Shark Stock Assessment. [Masters Thesis]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/24819
Virginia Tech
4.
Brooks, George C.
On the use of demographic models to inform amphibian conservation and management: A case study of the reticulated flatwoods salamander.
Degree: PhD, Fisheries and Wildlife Science, 2020, Virginia Tech
URL: http://hdl.handle.net/10919/98003
► The southeastern United States is the global salamander hotspot, representing a crucible for diversity. Longleaf pine forests, the predominant ecosystem in the southeast, have been…
(more)
▼ The southeastern United States is the global salamander hotspot, representing a crucible for diversity. Longleaf pine forests, the predominant ecosystem in the southeast, have been reduced to 3% of their former range, with dire consequences for the animals that inhabit them. The Reticulated Flatwoods Salamander, Ambystoma bishopi, is endemic to the region, and currently listed as federally endangered owing to recent population declines. A recovery plan for the species therefore, is required by law, under the Endangered Species Act (ESA). A salient component of modern recovery plans are population forecasts that evaluate future extinction risk. Such forecasts can then be used to assess alternative management strategies proposed to improve the species' long-term prospects. By studying two of the last remaining populations of A. bishopi from 2010-2019, we were able to collect the data required to construct a demographic model that can be used to run population projections. In some regards, A. bishopi is a typical amphibian, in that their populations show dramatic fluctuations in numbers through time, and they exhibit rapid growth in the aquatic larval stage, achieving 60% of their maximum body size in the first three months of life. Flatwoods salamanders breed in ephemeral wetlands, that often dry before successful metamorphosis can occur. The frequency of pond-drying results in a high probability of extinction for a single population, but survival of breeding individuals was equally important when considering long-term persistence. To assure the recovery of A. bishopi, management must consider all elements of the life-history when allocating resources and effort. More generally, both aquatic and terrestrial habitats must be protected for amphibian conservation to be effective, making them ideal candidates for 'umbrella species' status.
Advisors/Committee Members: Haas, Carola A. (committeechair), Jiao, Yan (committee member), Gorman, Thomas Andrew (committee member), House, Leanna L. (committee member).
Subjects/Keywords: Ambystoma bishopi; Conservation; Demography; Endangered Species
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APA (6th Edition):
Brooks, G. C. (2020). On the use of demographic models to inform amphibian conservation and management: A case study of the reticulated flatwoods salamander. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/98003
Chicago Manual of Style (16th Edition):
Brooks, George C. “On the use of demographic models to inform amphibian conservation and management: A case study of the reticulated flatwoods salamander.” 2020. Doctoral Dissertation, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/98003.
MLA Handbook (7th Edition):
Brooks, George C. “On the use of demographic models to inform amphibian conservation and management: A case study of the reticulated flatwoods salamander.” 2020. Web. 19 Jan 2021.
Vancouver:
Brooks GC. On the use of demographic models to inform amphibian conservation and management: A case study of the reticulated flatwoods salamander. [Internet] [Doctoral dissertation]. Virginia Tech; 2020. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/98003.
Council of Science Editors:
Brooks GC. On the use of demographic models to inform amphibian conservation and management: A case study of the reticulated flatwoods salamander. [Doctoral Dissertation]. Virginia Tech; 2020. Available from: http://hdl.handle.net/10919/98003
Virginia Tech
5.
Huang, Jian.
Assessing predictive performance and transferability of species distribution models for freshwater fish in the United States.
Degree: PhD, Fisheries and Wildlife Science, 2015, Virginia Tech
URL: http://hdl.handle.net/10919/73477
► Rigorous modeling of the spatial species distributions is critical in biogeography, conservation, resource management, and assessment of climate change. The goal of chapter 2 of…
(more)
▼ Rigorous modeling of the spatial species distributions is critical in biogeography, conservation, resource management, and assessment of climate change. The goal of chapter 2 of this dissertation was to evaluate the potential of using historical samples to develop high-resolution species distribution models (SDMs) of stream fishes of the United States. I explored the spatial transferability and temporal transferability of stream–fish distribution models in chapter 3 and chapter 4 respectively. Chapter 2 showed that the discrimination power of SDMs for 76 non-game fish species depended on data quality, species' rarity, statistical modeling technique, and incorporation of spatial autocorrelation. The area under the Receiver-Operating-Characteristic curve (AUC) in the cross validation tended to be higher in the logistic regression and boosted regression trees (BRT) than the presence-only MaxEnt models. AUC in the cross validation was also higher for species with large geographic ranges and small local populations. Species prevalence affected discrimination power in the model training but not in the validation. In chapter 3, spatial transferability of SDMs was low for over 70% of the 21 species examined. Only 24% of logistic regression, 12% of BRT, and 16% of MaxEnt had AUC > 0.6 in the spatial transfers. Friedman's rank sum test showed that there was no significant difference in the performance of the three modeling techniques. Spatial transferability could be improved by using spatial logistic regression under Lasso regularization in the training of SDMs and by matching the range and location of predictor variables between training and transfer regions. In chapter 4, testing of temporal SDM transfer on independent samples resulted in discrimination power of the moderate to good range, with AUC > 0.6 for 80% of species in all three types of models. Most cool water species had good temporal transferability. However, biases and misspecified spread occurred frequently in the temporal model transfers. To reduce under- or over-estimation bias, I suggest rescaling the predicted probability of species presence to ordinal ranks. To mitigate inappropriate spread of predictions in the climate change scenarios, I recommended to use large training datasets with good coverage of environmental gradients, and fine-tune predictor variables with regularization and cross validation.
Advisors/Committee Members: Frimpong, Emmanuel A. (committeechair), Orth, Donald J. (committee member), Li, Jie (committee member), Jiao, Yan (committee member).
Subjects/Keywords: Species distribution models; discrimination power; calibration; transferability; climate change; machine learning; New River; stream fish
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APA (6th Edition):
Huang, J. (2015). Assessing predictive performance and transferability of species distribution models for freshwater fish in the United States. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/73477
Chicago Manual of Style (16th Edition):
Huang, Jian. “Assessing predictive performance and transferability of species distribution models for freshwater fish in the United States.” 2015. Doctoral Dissertation, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/73477.
MLA Handbook (7th Edition):
Huang, Jian. “Assessing predictive performance and transferability of species distribution models for freshwater fish in the United States.” 2015. Web. 19 Jan 2021.
Vancouver:
Huang J. Assessing predictive performance and transferability of species distribution models for freshwater fish in the United States. [Internet] [Doctoral dissertation]. Virginia Tech; 2015. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/73477.
Council of Science Editors:
Huang J. Assessing predictive performance and transferability of species distribution models for freshwater fish in the United States. [Doctoral Dissertation]. Virginia Tech; 2015. Available from: http://hdl.handle.net/10919/73477
Virginia Tech
6.
Lin, Laurence Hao-Ran.
Influences of Mountainside Residential Development to Nutrient Dynamics in a Stream Network.
Degree: PhD, Biological Sciences, 2013, Virginia Tech
URL: http://hdl.handle.net/10919/52928
► Forested mountain watersheds provide essential resources and services (e.g., water supply) to downstream ecosystems and human communities. Fast-growing mountainside residential development not only modifies the…
(more)
▼ Forested mountain watersheds provide essential resources and services (e.g., water
supply) to downstream ecosystems and human communities. Fast-growing mountainside residential development not only modifies the terrestrial system but also aquatic systems by changing the nutrient input from the terrestrial to aquatic. However, the impacts of mountainside residential development on stream ecosystems are complex because interactions between in- stream process and hillslope soils control in-stream nutrient dynamics, and it is difficult to experimentally study these interactions at broad spatial scales. In my dissertation research, I first developed models for leaf decomposition in a forested headwater stream by synthesizing several important ecological concepts, including ecological stoichiometry, microbial nutrient mining, and microbe-substrate interaction. I then extended the single stream model to a stream network model and further linked the stream network model with a terrestrial model that simulates nutrient processes and hydrology in hillslope soils. With this complete modeling framework, I conducted a global sensitivity analysis to evaluate the importance of terrestrial nutrient input versus in-stream processes in modifying nitrogen export. I also conducted a simulation to investigate the impacts of housing density, buffer zone protection, and stream travel distance from the residential development to the catchment outlet on nitrogen export at the local and regional scale. The model for leaf decomposition performed better for predicting detritus decay and nutrient patterns when microbial groups were divided into immobilizers and miners and when leaf quality was included as a variable. The importance of terrestrial nutrient input versus in-stream nutrient processes greatly depended on the level of terrestrial nutrient input. When terrestrial nitrate input was low, nitrogen export was more sensitive to in-stream net microbial nitrogen flux (mineralization - immobilization) than nitrate input. However, when terrestrial nitrate input was high, nitrate input was more important than in-stream net nitrogen flux. Greater impacts, i.e., higher nitrogen export at the local scale or greater change in nitrogen export at the regional scale, were associated with higher residential density, a lack of buffer zone protection, and shorter stream travel distance from the residential development to the catchment outlet. Although subject to model assumptions and further validation through field experiments, this research provides a general modeling framework for in-stream processes and aquatic-terrestrial linkages and expands an understanding of interactions between terrestrial and in-stream nitrogen dynamics and the impacts of mountainside development on stream ecosystems, identifies directions for further research, and provides insights for land and river management in mountainous areas.
Advisors/Committee Members: Webster, Jackson R. (committeechair), Barrett, John E. (committee member), Benfield, Ernest F. (committee member), Jiao, Yan (committee member), Claessens, Lodevicus (committee member).
Subjects/Keywords: Stream Ecology; Ecosystems; Ecological Modeling; Land Cover Change; Decomposition; Nutrient Spiraling
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APA (6th Edition):
Lin, L. H. (2013). Influences of Mountainside Residential Development to Nutrient Dynamics in a Stream Network. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/52928
Chicago Manual of Style (16th Edition):
Lin, Laurence Hao-Ran. “Influences of Mountainside Residential Development to Nutrient Dynamics in a Stream Network.” 2013. Doctoral Dissertation, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/52928.
MLA Handbook (7th Edition):
Lin, Laurence Hao-Ran. “Influences of Mountainside Residential Development to Nutrient Dynamics in a Stream Network.” 2013. Web. 19 Jan 2021.
Vancouver:
Lin LH. Influences of Mountainside Residential Development to Nutrient Dynamics in a Stream Network. [Internet] [Doctoral dissertation]. Virginia Tech; 2013. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/52928.
Council of Science Editors:
Lin LH. Influences of Mountainside Residential Development to Nutrient Dynamics in a Stream Network. [Doctoral Dissertation]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/52928
Virginia Tech
7.
Vincent, Matthew Timothy.
Estimability of natural mortality within a statistical catch-at-age model: a framework and simulation study based on Gulf of Mexico red snapper.
Degree: MS, Fisheries and Wildlife Sciences, 2013, Virginia Tech
URL: http://hdl.handle.net/10919/52244
► Estimation of natural mortality within statistical catch-at-age models has been relatively unsuccessful and is uncommon within stock assessments. The models I created estimated population-dynamics parameters,…
(more)
▼ Estimation of natural mortality within statistical catch-at-age models has been relatively unsuccessful and is uncommon within stock assessments. The models I created estimated population-dynamics parameters, including natural mortality, through Metropolis-Hastings algorithms from Gulf of Mexico red-snapper Lutjanus campechanus data. I investigated the influences of assumptions regarding model configuration of natural mortality and selectivity-at-age parameters by comparing multiple models. The results of this study are preliminary due to parameter estimates being bounded by uniform priors and thus a potential lack of convergence to the posterior distribution. Estimation of a natural-mortality parameter at age 0 or a Lorenzen natural-mortality parameter could be confounded with selectivity-at-age-1 parameters for bycatch from the shrimp fisheries. The Lorenzen natural-mortality curve was calculated by dividing the parameter by red snapper length at age. An age-1 natural-mortality parameter might not be estimable with the currently available data. Values of the natural-mortality parameter for ages 2 and older appear to be slightly less influenced by assumptions regarding selectivity-at-age parameters. We conducted a simulation study to determine the accuracy and precision of natural-mortality estimation assuming the selectivity-at-age-1 parameter for bycatch from the shrimp fisheries equaled 1.0 and a Lorenzen natural-mortality curve. The simulation study indicated that initial abundance-at-age parameters may be inestimable within the current model and may influence other parameter estimates. The preliminary simulation results showed that the Lorenzen natural-mortality parameter was consistently slightly underestimated and apical-fishing-mortality parameters were considerably underestimated. The estimation of natural mortality within a statistical catch-at-age model for Gulf of Mexico red snapper has many caveats and requires additional investigation.
Advisors/Committee Members: Jiao, Yan (committeechair), Smith, Eric P. (committee member), Murphy, Brian R. (committee member), Walter, John F. (committee member).
Subjects/Keywords: red snapper; Lutjanus campechanus; natural mortality; statistical catch-at-age model; stock assessment; population dynamics
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APA (6th Edition):
Vincent, M. T. (2013). Estimability of natural mortality within a statistical catch-at-age model: a framework and simulation study based on Gulf of Mexico red snapper. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/52244
Chicago Manual of Style (16th Edition):
Vincent, Matthew Timothy. “Estimability of natural mortality within a statistical catch-at-age model: a framework and simulation study based on Gulf of Mexico red snapper.” 2013. Masters Thesis, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/52244.
MLA Handbook (7th Edition):
Vincent, Matthew Timothy. “Estimability of natural mortality within a statistical catch-at-age model: a framework and simulation study based on Gulf of Mexico red snapper.” 2013. Web. 19 Jan 2021.
Vancouver:
Vincent MT. Estimability of natural mortality within a statistical catch-at-age model: a framework and simulation study based on Gulf of Mexico red snapper. [Internet] [Masters thesis]. Virginia Tech; 2013. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/52244.
Council of Science Editors:
Vincent MT. Estimability of natural mortality within a statistical catch-at-age model: a framework and simulation study based on Gulf of Mexico red snapper. [Masters Thesis]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/52244
Virginia Tech
8.
Hua, Dan.
Propagation and monitoring of freshwater mussels released into the Clinch and Powell rivers, Virginia and Tennessee.
Degree: PhD, Fisheries and Wildlife Science, 2015, Virginia Tech
URL: http://hdl.handle.net/10919/51755
► Freshwater mussels (Unionidae) in the United States have experienced dramatic declines, and 25% species are listed as federally endangered. Hence, recovery plans for endangered species…
(more)
▼ Freshwater mussels (Unionidae) in the United States have experienced dramatic declines, and 25% species are listed as federally endangered. Hence, recovery plans for endangered species proposed a strategy of propagation of young mussels for release to natal rivers to augment declining populations. In this study, I conducted laboratory experiments, assessed site suitability for mussel restoration, and evaluated survival and growth rates of released mussels to meet the requirements of recovery plan.
I conducted multiple experiments to develop an improved protocol for juvenile mussel propagation and culture. Significantly greater survival and growth rates were found in newly metamorphosed juveniles of the rainbow mussel (Villosa iris) reared in a substrate of fine sediment and one-month-old juveniles of wavy-rayed lampmussel (Lampsilis fasciola) fed on natural food in pond water. Bio-filter media greatly increased water quality by reducing the concentration of ammonia and nitrite. The negative impacts of flatworm predation and filamentous algae in juvenile culture were controlled, and juvenile escapement was prevented. Juvenile mussels were successfully produced and cultured to stockable size (>15 mm) for release.
I released laboratory-propagated mussels at three historically important sites in Clinch and Powell rivers for the assessment of site suitability. Use of cages was the most effective method to determine site suitability because the free-released mussels (untagged, tagged) had low catchability. Mussels released at Horton Ford, Clinch River, exhibited significantly faster growth. Horton Ford is the most suitable site, while environmental conditions at Fugate Ford, Powell River, are deemed unsuitable for mussel restoration and recovery.
To facilitate the detection of released mussels, I applied Passive Integrated Transponder tags to laboratory-produced juveniles of the endangered Cumberlandian combshell (Epioblasma brevidens) and released them near Brooks Bridge, Powell River. The detection probability increased above 98%. I developed a set of hierarchical Bayesian models incorporating individual variations, seasonal variations, periodic growth stages and growth cessation to estimate survival, detection probability and growth of released mussels in a changing environment. Mussels of E. brevidens exhibited great survival (> 99% per month) and growth, indicating suitable conditions for recovery of this endangered species at this site.
Advisors/Committee Members: Jiao, Yan (committeechair), Neves, Richard J. (committeechair), Orth, Donald J. (committee member), Karpanty, Sarah M. (committee member), Guo, Feng (committee member).
Subjects/Keywords: Freshwater mussel; endangered species; propagation; culture; release; Split-plot design; recirculating system; survival rate; detection probability; growth rate; mark-recapture; PIT tag; hierarchic model; Bayesian
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APA (6th Edition):
Hua, D. (2015). Propagation and monitoring of freshwater mussels released into the Clinch and Powell rivers, Virginia and Tennessee. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/51755
Chicago Manual of Style (16th Edition):
Hua, Dan. “Propagation and monitoring of freshwater mussels released into the Clinch and Powell rivers, Virginia and Tennessee.” 2015. Doctoral Dissertation, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/51755.
MLA Handbook (7th Edition):
Hua, Dan. “Propagation and monitoring of freshwater mussels released into the Clinch and Powell rivers, Virginia and Tennessee.” 2015. Web. 19 Jan 2021.
Vancouver:
Hua D. Propagation and monitoring of freshwater mussels released into the Clinch and Powell rivers, Virginia and Tennessee. [Internet] [Doctoral dissertation]. Virginia Tech; 2015. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/51755.
Council of Science Editors:
Hua D. Propagation and monitoring of freshwater mussels released into the Clinch and Powell rivers, Virginia and Tennessee. [Doctoral Dissertation]. Virginia Tech; 2015. Available from: http://hdl.handle.net/10919/51755
Virginia Tech
9.
Li, Yan.
Spatial dynamics modeling for data-poor species using examples of longline seabird bycatch and endangered white abalone.
Degree: PhD, Fisheries and Wildlife Science, 2014, Virginia Tech
URL: http://hdl.handle.net/10919/64003
► Spatial analysis of species for which there is limited quantity of data, termed as the data-poor species, has been challenging due to limited information, especially…
(more)
▼ Spatial analysis of species for which there is limited quantity of data, termed as the data-poor species, has been challenging due to limited information, especially lack of spatially explicit information. However, these species are frequently of high ecological, conservation and management interest. In this study, I used two empirical examples to demonstrate spatial analysis for two kinds of data-poor species. One example was seabird bycatch from the U.S. Atlantic pelagic longline fishery, which focused on rare events/species for which data are generally characterized by a high percentage of zero observations. The other example was endangered white abalone off the California coast, which focused on endangered species whose data are very limited. With the seabird bycatch example, I adopted a spatial filtering technique to incorporate spatial patterns and to improve model performance. The model modified with spatial filters showed superior performance over other candidate models. I also applied the geographically weighted approach to explore spatial nonstationarity in seabird bycatch, i.e., spatial variation in the parameters that describe relationships between biological processes and environmental factors. Estimates of parameters exhibited high spatial variation. With the white abalone example, I demonstrated the spatially explicit hierarchical demographic model and conducted a risk assessment to evaluate the efficacy of hypothetical restoration strategies. The model allowed for the Allee effect (i.e., density-dependent fertilization success) by using spatial explicit density estimates. Restoration efforts directed at larger-size individuals may be more effective in increasing population density than efforts focusing on juveniles. I also explored the spatial nonstationarity in white abalone catch data. I estimated the spatially explicit decline rate and linked the decline rate to environmental factors including water depth, distance to California coast, distance to land, sea surface temperature and chlorophyll concentration. The decline rate showed spatial variation. I did not detect any significant associations between decline rate and these five environmental factors. Through such a study, I am hoping to provide insights on applying or adapting existing methods to model spatial dynamics of data-poor species, and on utilizing information from such analyses to aid in their conservation and management.
Advisors/Committee Members: Jiao, Yan (committeechair), Jones, Jess W. (committee member), Haas, Carola A. (committee member), Guo, Feng (committee member), Rogers-Bennett, Laura (committee member).
Subjects/Keywords: spatial nonstationarity; spatial filter; risk assessment; data-poor species; zero-inflated data; demographic model; delta model
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APA (6th Edition):
Li, Y. (2014). Spatial dynamics modeling for data-poor species using examples of longline seabird bycatch and endangered white abalone. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/64003
Chicago Manual of Style (16th Edition):
Li, Yan. “Spatial dynamics modeling for data-poor species using examples of longline seabird bycatch and endangered white abalone.” 2014. Doctoral Dissertation, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/64003.
MLA Handbook (7th Edition):
Li, Yan. “Spatial dynamics modeling for data-poor species using examples of longline seabird bycatch and endangered white abalone.” 2014. Web. 19 Jan 2021.
Vancouver:
Li Y. Spatial dynamics modeling for data-poor species using examples of longline seabird bycatch and endangered white abalone. [Internet] [Doctoral dissertation]. Virginia Tech; 2014. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/64003.
Council of Science Editors:
Li Y. Spatial dynamics modeling for data-poor species using examples of longline seabird bycatch and endangered white abalone. [Doctoral Dissertation]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/64003
Virginia Tech
10.
Stich, Daniel Stephen.
Behavior and population dynamics of grass carp incrementally stocked for biological control.
Degree: MS, Fisheries and Wildlife Sciences, 2011, Virginia Tech
URL: http://hdl.handle.net/10919/34212
► Grass carp Ctenopharyngodon idella have been stocked throughout the world due to their utility as a biological control. In the United States, the species has…
(more)
▼ Grass carp Ctenopharyngodon idella have been stocked throughout the world due to their utility as a biological control. In the United States, the species has been used to successfully control invasive, aquatic weeds such as hydrilla Hydrilla verticillata. Despite the large body of research surrounding the use of grass carp, few studies have demonstrated widely applicable methods for evaluating the success of weed control based on grass carp behavior and population dynamics. Classic methods of biological control using grass carp often rely on a single, large stocking of fish. Few of these studies have demonstrated success in achieving intermediate levels of weed control. Managers would be better equipped to make decisions regarding stocking and maintenance grass carp populations with better information about behavior, survival, and population structure. Improved decision making could result in reduced cost and increased effectiveness of stocking. In order to examine current knowledge gaps for management, I investigated the movements and habitat use of grass carp, post-stocking survival, age-specific survival rates, and population dynamics of grass carp in Lake Gaston, North Carolina and
Virginia.
I characterized relationships between grass carp behavior and environmental factors using radio-telemetry. The average rate of movement for grass carp in Lake Gaston was about 137 m/d. Rapid dispersal after stocking was followed by long periods of no movement. However, when time after stocking was held constant in models of behavior, fish moved about 200 m/d more in the second year after stocking than in the first year, and were found closer to shore. On average, grass carp were found about 40 m from shore in about 2.5-3.5 m of water, although mean depth of water at grass carp locations varied seasonally, being shallowest in summer and deepest in winter. Although depth of water at grass carp locations did not vary by stocking location, Grass carp were found closer to shorelines in the upper reservoir than in the lower reservoir. I found significant relationships between grass carp behavior and hydrological processes such as lake elevation and dam releases in the reservoir, as well as with other environmental factors such as water temperature, photoperiod, and weather conditions. The results of this study should be useful in better understanding how behavior can affect management decisions. Specifically, grass carp behavior appears to change with age and environmental conditions within large reservoir systems. Future research should focus more closely on the effects of large-scale flow dynamics on grass carp behavior.
I estimated age-1 survival of grass carp from mark-recapture models designed for radio-tagged animals, and characterized relationships between age-1 survival and factors under the control of management, such as stocking locations and size at stocking. . According to the most-plausible model developed in this study, survival of age-1 grass carp in Lake Gaston varied throughout the year, and the…
Advisors/Committee Members: Murphy, Brian R. (committeechair), Frimpong, Emmanuel A. (committee member), DiCenzo, Victor J. (committee member), Jiao, Yan (committee member).
Subjects/Keywords: grass carp; hydrilla; biological control; behavior; survival
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APA (6th Edition):
Stich, D. S. (2011). Behavior and population dynamics of grass carp incrementally stocked for biological control. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/34212
Chicago Manual of Style (16th Edition):
Stich, Daniel Stephen. “Behavior and population dynamics of grass carp incrementally stocked for biological control.” 2011. Masters Thesis, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/34212.
MLA Handbook (7th Edition):
Stich, Daniel Stephen. “Behavior and population dynamics of grass carp incrementally stocked for biological control.” 2011. Web. 19 Jan 2021.
Vancouver:
Stich DS. Behavior and population dynamics of grass carp incrementally stocked for biological control. [Internet] [Masters thesis]. Virginia Tech; 2011. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/34212.
Council of Science Editors:
Stich DS. Behavior and population dynamics of grass carp incrementally stocked for biological control. [Masters Thesis]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/34212
11.
Schmitt, Joseph Daniel.
Feeding Ecology of Invasive Catfishes in Chesapeake Bay Subestuaries.
Degree: PhD, Fisheries and Wildlife Science, 2018, Virginia Tech
URL: http://hdl.handle.net/10919/83464
► Blue Catfish Ictalurus furcatus are native to tributaries of the Mississippi River but are now invasive in several Atlantic slope drainages. This includes subestuaries of…
(more)
▼ Blue Catfish Ictalurus furcatus are native to tributaries of the Mississippi River but are now invasive in several Atlantic slope drainages. This includes subestuaries of the Chesapeake Bay, where their feeding ecology and potential impact on native species was largely unknown. We collected stomach contents from 16,110 Blue Catfish at 698 sites in three large subestuaries of the Chesapeake Bay (James, York, Rappahannock rivers). Cumulative prey curves revealed that sample size was sufficient for diet description, though 1,000 – 1500 stomachs were needed per river. Blue Catfish are opportunistic generalists that feed on a broad array of plant and animal material. Logistic regression models reveal that Blue Catfish undergo significant ontogenetic diet shifts to piscivory at larger sizes (P<0.01) though the lengths at which these shifts occur varies by river system (500 – 900 mm total length; TL). Over 60% of Blue Catfish stomachs contained other invasive species, primarily Hydrilla verticillata and Asian clams Corbicula fluminea. Canonical Correspondence Analysis (CCA) revealed that salinity and season explained the most variation in Blue Catfish diet, while Generalized Additive Models (GAMs) demonstrated that there is considerable spatiotemporal and length-based variation in predation of species of concern. Species of concern include American Shad, American Eel, and river herring, which are imperiled, and blue crab, which support valuable fisheries in Chesapeake Bay. Predation of American Shad, American Eel, and river herring was rare (max predicted occurrence in Blue Catfish diets = 8%), while blue crab was much more common in the diet (max predicted occurrence =28%). Predation of American Shad and river herring peaks in freshwater areas in April, while predation of blue crab peaks in brackish areas in October. Predation of all species of concern is highest for large catfish (500 – 1000 mm TL). Field and laboratory-based estimates of consumption rate revealed that Blue Catfish feed at similar rates as Channel Catfish Ictalurus punctatus, and daily ration is estimated to be 2-5% bodyweight per day during warm temperatures, while peak feeding (maximum daily ration) can approach 10% bodyweight per day. While consumption of imperiled species is rare, Blue Catfish could still have negative impacts on these species due to dense catfish populations.
Advisors/Committee Members: Orth, Donald J. (committeechair), Peoples, Brandon Kevin (committee member), Jiao, Yan (committee member), Castello, Leandro (committee member).
Subjects/Keywords: invasion ecology; food habits; diet; blue catfish; flathead catfish; consumption rates; daily ration; prey selectivity; diet breadth; trophic position; omnivory index
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APA (6th Edition):
Schmitt, J. D. (2018). Feeding Ecology of Invasive Catfishes in Chesapeake Bay Subestuaries. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/83464
Chicago Manual of Style (16th Edition):
Schmitt, Joseph Daniel. “Feeding Ecology of Invasive Catfishes in Chesapeake Bay Subestuaries.” 2018. Doctoral Dissertation, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/83464.
MLA Handbook (7th Edition):
Schmitt, Joseph Daniel. “Feeding Ecology of Invasive Catfishes in Chesapeake Bay Subestuaries.” 2018. Web. 19 Jan 2021.
Vancouver:
Schmitt JD. Feeding Ecology of Invasive Catfishes in Chesapeake Bay Subestuaries. [Internet] [Doctoral dissertation]. Virginia Tech; 2018. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/83464.
Council of Science Editors:
Schmitt JD. Feeding Ecology of Invasive Catfishes in Chesapeake Bay Subestuaries. [Doctoral Dissertation]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/83464
Virginia Tech
12.
Susko, Emily Clare.
The effects of life history strategy and uncertainty on a probability-based approach to managing the risk of overfishing.
Degree: MS, Fisheries and Wildlife Sciences, 2012, Virginia Tech
URL: http://hdl.handle.net/10919/76939
► Recent U.S. legislation applies a precautionary approach to setting catch regulations in federal fisheries management. A transparent approach to complying with federal guidelines involves calculating…
(more)
▼ Recent U.S. legislation applies a precautionary approach to setting catch regulations in federal fisheries management. A transparent approach to complying with federal guidelines involves calculating the catch recommendation that corresponds to a specified probability, P*, of exceeding the "true" overfishing limit (OFL) located within an estimated distribution.
The P* methodology aims to manage the risk of overfishing explicitly, but choice of P* alone does not provide sufficient information on all of the risks associated with a control rule—both the probability of overfishing and the severity of overfishing. Rather, the ramifications of P* choices depend on the amount of uncertainty in the stock assessment and on the life history of the species in question. To evaluate these effects on the risks associated with P* rules, my study simulated fishing three example species under three levels of uncertainty.
Trends identified among example species were consistent with predictions from life history. Periodic strategists, which have highly variable recruitment, experienced probabilities of overfishing which exceeded P* and which increased in time. Equilibrium strategists showed more predictable risks of overfishing but may have less capacity to recover from depleted biomass levels. Differences in the size of the OFL distribution—representing differences in levels of uncertainty—led to mixed results depending on whether the distribution was biased or whether uncertainty was fully characterized. Lastly, because OFL distributions are themselves estimates and subject to uncertainty in their shape and size, lower P* values closer to the tails of the estimated distribution produced more variable resulting risks.
Advisors/Committee Members: Berkson, James M. (committeechair), Jiao, Yan (committee member), Conn, Paul (committee member), Orth, Donald J. (committee member).
Subjects/Keywords: gulf menhaden; simulation model; life history; sandbar shark; uncertainty; risk; fisheries management; vermilion snapper; stock assessment
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APA (6th Edition):
Susko, E. C. (2012). The effects of life history strategy and uncertainty on a probability-based approach to managing the risk of overfishing. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/76939
Chicago Manual of Style (16th Edition):
Susko, Emily Clare. “The effects of life history strategy and uncertainty on a probability-based approach to managing the risk of overfishing.” 2012. Masters Thesis, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/76939.
MLA Handbook (7th Edition):
Susko, Emily Clare. “The effects of life history strategy and uncertainty on a probability-based approach to managing the risk of overfishing.” 2012. Web. 19 Jan 2021.
Vancouver:
Susko EC. The effects of life history strategy and uncertainty on a probability-based approach to managing the risk of overfishing. [Internet] [Masters thesis]. Virginia Tech; 2012. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/76939.
Council of Science Editors:
Susko EC. The effects of life history strategy and uncertainty on a probability-based approach to managing the risk of overfishing. [Masters Thesis]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/76939
13.
White, Allison Lynn.
Spatial and temporal heterogeneity in life history and productivity trends of Atlantic Weakfish (Cynoscion regalis) and implications to fisheries management.
Degree: MS, Fisheries and Wildlife Sciences, 2017, Virginia Tech
URL: http://hdl.handle.net/10919/78707
► The biological characteristics of fisheries stocks that are assessed for management considerations are rarely homogeneous over time or space. However, stock assessment scientists largely ignore…
(more)
▼ The biological characteristics of fisheries stocks that are assessed for management considerations are rarely homogeneous over time or space. However, stock assessment scientists largely ignore this heterogeneity in their models. This thesis addresses the effects of spatial and temporal heterogeneity on stock assessment models using Atlantic Weakfish (Cynoscion regalis) as a case study. First, spatial and temporal variation was incorporated into length-, weight-, and maturity-at-age estimates using mixed-effects models (Chapter Two). The resulting heterogeneous weight and maturity parameters then were applied to per-recruit analyses to examine the sensitivity of biological reference points to spatial and temporal variation in life history attributes (Chapter Three). Mixed-effects life history models incorporating spatial and temporal variation revealed distinct regional and annual trends that were not visible from standard homogeneous models. In several instances, the homogeneous modelling approach produced life history estimates that varied significantly from the spatial and temporal means produced by the heterogeneous models. In some cases, this difference was so great that the homogeneous means were much higher or lower than the heterogeneous means for all regions or years. Minimized AIC statistics revealed that spatially and temporally integrated mixed-effects models were more robust and descriptive of Atlantic Weakfish life history than the standard homogeneous models. Per-recruit and biological reference points derived from these life history estimates in Chapter Three were found to be highly sensitive to spatial and temporal variations in weight parameters. In several cases, reference points used as management targets were so significantly different that ignoring spatial and temporal heterogeneity in Atlantic Weakfish life history would likely cause overfishing and decline of Weakfish in certain regions and years.
Advisors/Committee Members: Jiao, Yan (committeechair), Orth, Donald J. (committee member), Hallerman, Eric M. (committee member).
Subjects/Keywords: Atlantic Weakfish; mixed-effects models; individual variability; spatial heterogeneity; temporal heterogeneity; fish growth; maturity; Yield per-recruit; spawning stock biomass per-recruit; sensitivity analysis
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APA (6th Edition):
White, A. L. (2017). Spatial and temporal heterogeneity in life history and productivity trends of Atlantic Weakfish (Cynoscion regalis) and implications to fisheries management. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78707
Chicago Manual of Style (16th Edition):
White, Allison Lynn. “Spatial and temporal heterogeneity in life history and productivity trends of Atlantic Weakfish (Cynoscion regalis) and implications to fisheries management.” 2017. Masters Thesis, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/78707.
MLA Handbook (7th Edition):
White, Allison Lynn. “Spatial and temporal heterogeneity in life history and productivity trends of Atlantic Weakfish (Cynoscion regalis) and implications to fisheries management.” 2017. Web. 19 Jan 2021.
Vancouver:
White AL. Spatial and temporal heterogeneity in life history and productivity trends of Atlantic Weakfish (Cynoscion regalis) and implications to fisheries management. [Internet] [Masters thesis]. Virginia Tech; 2017. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/78707.
Council of Science Editors:
White AL. Spatial and temporal heterogeneity in life history and productivity trends of Atlantic Weakfish (Cynoscion regalis) and implications to fisheries management. [Masters Thesis]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/78707
14.
Hatch, Joshua M.
The Effects of Ageing Error on Stock Assessment for Weakfish Cynoscion regalis.
Degree: MS, Fisheries and Wildlife Sciences, 2013, Virginia Tech
URL: http://hdl.handle.net/10919/50988
► Inherent uncertainties in the stock assessment for weakfish have precluded accurate and consistent advice concerning the management of commercial and recreational fisheries. Error within ageing…
(more)
▼ Inherent uncertainties in the stock assessment for weakfish have precluded accurate and consistent advice concerning the management of commercial and recreational fisheries. Error within ageing techniques, used to assess relative age frequencies within commercial and recreational harvest, has been cited as a potential source for uncertainty during assessments of the weakfish fishery. The implications for age-reading error on weakfish stock assessment were explored using measurement-error growth models (i.e. Chapter 1), ageing error matrices within a statistical catch-at-age framework (i.e. Chapter 2), and Monte Carlo simulations to gauge robustness of ignoring this type of uncertainty during fisheries stock assessment (i.e. Chapter 3). Measurement-error growth models typically resulted in weakfish that grew to reach larger sizes, but at slower rates, with median length-at-age being overestimated by traditional von Bertalanffy growth curves, at least for the observed age range. Measurement-error growth models allow for incorporation of ageing uncertainty during nonlinear growth curve estimation, as well as the ability to estimate the ageing error variance. Age-reading error was further considered during statistical catch-at-age analysis of the weakfish fishery, mainly through permutations of true catch-at-age via ageing error matrices constructed from estimates of the ageing error variance, thus reflecting changes in relative age compositions as a consequence of ageing uncertainty. As a result, absolute levels of key population parameters were influenced, but general trends in those parameters tended to be similar, with strong congruency across models as to weakfish stock dynamics in most recent years. Finally, Monte Carlo simulations showed that implications for age-reading error on weakfish stock assessment are varied, depending upon the direction and magnitude of the ageing uncertainty. However, relative trends of parameter estimates over time tended to be similar, resulting in proper allocation of weakfish stock status, regardless of the type of ageing error considered. Furthermore, assuming negligible ageing uncertainty within fishery-independent surveys appears reasonable, as simulations incorporating ageing error within indices of relative abundance showed similar patterns to situations that only considered observation noise.
Advisors/Committee Members: Jiao, Yan (committeechair), Orth, Donald J. (committee member), O'Reilly, Robert Laux (committee member), Smith, Eric P. (committee member).
Subjects/Keywords: Ageing error; Weakfish; Bayesian; Statistical catch-at-age; Simulation
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APA (6th Edition):
Hatch, J. M. (2013). The Effects of Ageing Error on Stock Assessment for Weakfish Cynoscion regalis. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/50988
Chicago Manual of Style (16th Edition):
Hatch, Joshua M. “The Effects of Ageing Error on Stock Assessment for Weakfish Cynoscion regalis.” 2013. Masters Thesis, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/50988.
MLA Handbook (7th Edition):
Hatch, Joshua M. “The Effects of Ageing Error on Stock Assessment for Weakfish Cynoscion regalis.” 2013. Web. 19 Jan 2021.
Vancouver:
Hatch JM. The Effects of Ageing Error on Stock Assessment for Weakfish Cynoscion regalis. [Internet] [Masters thesis]. Virginia Tech; 2013. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/50988.
Council of Science Editors:
Hatch JM. The Effects of Ageing Error on Stock Assessment for Weakfish Cynoscion regalis. [Masters Thesis]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/50988
Virginia Tech
15.
Hayes, Christopher Glenn.
Investigating single and multiple species fisheries management: stock status evaluation of hammerhead (Sphyrna spp.) sharks in the western North Atlantic Ocean and Gulf of Mexico.
Degree: MS, Fisheries and Wildlife Sciences, 2007, Virginia Tech
URL: http://hdl.handle.net/10919/30989
► Three hammerhead sharks (Sphyrna spp.) are currently managed as part of the large coastal shark complex in the United States. Including multiple species in an…
(more)
▼ Three hammerhead sharks (Sphyrna spp.) are currently managed as part of the large coastal shark complex in the United States. Including multiple species in an assessment ignores the different stock dynamics of each individual species within the complex due to different life histories. This study completed individual assessments of scalloped (S. lewini), great (S. mokarran), and smooth (S. zygaena) hammerhead sharks in the U.S. Atlantic Ocean and Gulf of Mexico. Combined data for all three species and unclassified hammerhead sharks were also used to produce a stock assessment of the hammerhead shark complex. Depletions of 83%, 96%, and 91% were estimated for scalloped, great, and smooth hammerhead sharks, respectively, between 1981 and 2005. When modeled as a single stock, the hammerhead shark complex experienced a 90% decline over the same time period. All three stocks, and the complex were overfished (below population size associated with maximum sustainable yield (MSY)), and overfishing (fishing level above that associated with MSY) occurred in 2005. We found that scalloped hammerhead shark population recovery is likely to occur within 10 years if catch remains at or below 2005 levels. Great and smooth hammerhead sharks will likely still be overfished in 30 years unless catches are reduced.
It appears that the species composition could be changing in this hammerhead shark complex. The faster-growing scalloped hammerhead sharks are able to withstand fishing pressure better than great or smooth hammerhead sharks. However, it is difficult to target any single large coastal shark species while fishing; hence they are subject to similar fishing pressure. The result is a greater decline in great and smooth hammerhead sharks than experienced by scalloped hammerhead sharks. Therefore, the proportion of scalloped hammerhead sharks increased between 1981 and 2005. Species-specific stock assessments, such as those presented here, allow managers to more closely monitor populations of slower-growing species and reduce the risk of overexploitation of those species.
Advisors/Committee Members: Jiao, Yan (committeechair), Berkson, James M. (committee member), Corttes, Enric (committee member).
Subjects/Keywords: hammerhead sharks; Sphyrna; stock assessment; multi-species; production model; population dynamics
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APA (6th Edition):
Hayes, C. G. (2007). Investigating single and multiple species fisheries management: stock status evaluation of hammerhead (Sphyrna spp.) sharks in the western North Atlantic Ocean and Gulf of Mexico. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/30989
Chicago Manual of Style (16th Edition):
Hayes, Christopher Glenn. “Investigating single and multiple species fisheries management: stock status evaluation of hammerhead (Sphyrna spp.) sharks in the western North Atlantic Ocean and Gulf of Mexico.” 2007. Masters Thesis, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/30989.
MLA Handbook (7th Edition):
Hayes, Christopher Glenn. “Investigating single and multiple species fisheries management: stock status evaluation of hammerhead (Sphyrna spp.) sharks in the western North Atlantic Ocean and Gulf of Mexico.” 2007. Web. 19 Jan 2021.
Vancouver:
Hayes CG. Investigating single and multiple species fisheries management: stock status evaluation of hammerhead (Sphyrna spp.) sharks in the western North Atlantic Ocean and Gulf of Mexico. [Internet] [Masters thesis]. Virginia Tech; 2007. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/30989.
Council of Science Editors:
Hayes CG. Investigating single and multiple species fisheries management: stock status evaluation of hammerhead (Sphyrna spp.) sharks in the western North Atlantic Ocean and Gulf of Mexico. [Masters Thesis]. Virginia Tech; 2007. Available from: http://hdl.handle.net/10919/30989
Virginia Tech
16.
Li, Yan.
Investigating ecosystem-level effects of gillnet bycatch in Lake Erie: implications for commercial fisheries management.
Degree: MS, Fisheries and Wildlife Sciences, 2010, Virginia Tech
URL: http://hdl.handle.net/10919/76836
► Lake Erie supports one of the world's largest freshwater commercial fisheries. Bycatch has become a concern in current fisheries management. This study focused on four…
(more)
▼ Lake Erie supports one of the world's largest freshwater commercial fisheries. Bycatch has become a concern in current fisheries management. This study focused on four species in Lake Erie that include two major commercial and recreational species, walleye (Sander vitreus) and yellow perch (Perca flavescens); an invasive species, white perch (Morone americana); and an endangered species, lake sturgeon (Acipenser fulvescens). The analyses were based on two datasets, the Partnership Index Fishing Survey (PIS) data and the commercial gillnet logbook data. The bycatch of walleye, yellow perch and white perch was predicted by a delta model developed on the PIS data. Discards were estimated as the difference between predicted bycatch and landed bycatch. Results highlighted bycatch and discard hotspots for these three species that have great management implications. Three classification tree models, a conditional inference tree and two exhaustive search-based trees, were constructed using the PIS data to estimate the probability of obtaining lake sturgeon bycach under specific environmental and gillnet fishing conditions. Lake sturgeon bycatch was most likely to be observed in the west basin of Lake Erie. The AdaBoost algorithm was applied in conjunction with the generalized linear/additive models to analyze catch rates of walleye, yellow perch and white perch. Three- and five-fold cross-validations were conducted to evaluate the performance of each candidate model. Results indicated that the Delta-AdaBoost model yielded the smallest training error and test error on average. I recommend the Delta-AdaBoost model for catch and bycatch analyses when data contain a high percentage of zeros.
Advisors/Committee Members: Jiao, Yan (committeechair), Guo, Feng (committee member), Hallerman, Eric M. (committee member).
Subjects/Keywords: model analysis; gillnet; Lake Erie; commercial fisheries; bycatch
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APA (6th Edition):
Li, Y. (2010). Investigating ecosystem-level effects of gillnet bycatch in Lake Erie: implications for commercial fisheries management. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/76836
Chicago Manual of Style (16th Edition):
Li, Yan. “Investigating ecosystem-level effects of gillnet bycatch in Lake Erie: implications for commercial fisheries management.” 2010. Masters Thesis, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/76836.
MLA Handbook (7th Edition):
Li, Yan. “Investigating ecosystem-level effects of gillnet bycatch in Lake Erie: implications for commercial fisheries management.” 2010. Web. 19 Jan 2021.
Vancouver:
Li Y. Investigating ecosystem-level effects of gillnet bycatch in Lake Erie: implications for commercial fisheries management. [Internet] [Masters thesis]. Virginia Tech; 2010. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/76836.
Council of Science Editors:
Li Y. Investigating ecosystem-level effects of gillnet bycatch in Lake Erie: implications for commercial fisheries management. [Masters Thesis]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/76836
Virginia Tech
17.
He, Qing.
Investigating the performance of process-observation-error-estimator and robust estimators in surplus production model: a simulation study.
Degree: MS, Fisheries and Wildlife Sciences, 2010, Virginia Tech
URL: http://hdl.handle.net/10919/76859
► This study investigated the performance of the three estimators of surplus production model including process-observation-error-estimator with normal distribution (POE_N), observation-error-estimator with normal distribution (OE_N), and…
(more)
▼ This study investigated the performance of the three estimators of surplus production model including process-observation-error-estimator with normal distribution (POE_N), observation-error-estimator with normal distribution (OE_N), and process-error-estimator with normal distribution (PE_N). The estimators with fat-tailed distributions including Student's t distribution and Cauchy distribution were also proposed and their performances were compared with the estimators with normal distribution. This study used Bayesian method, revised Metropolis Hastings within Gibbs sampling algorithm (MHGS) that was previously used to solve POE_N (Millar and Meyer, 2000), developed the MHGS for the other estimators, and developed the methodologies which enabled all the estimators to deal with data containing multiple indices based on catch-per-unit-effort (CPUE). Simulation study was conducted based on parameter estimation from two example fisheries: the Atlantic weakfish (Cynoscion regalis) and the black sea bass (Centropristis striata) southern stock.
Our results indicated that POE_N is the estimator with best performance among all six estimators with regard to both accuracy and precision for most of the cases. POE_N is also the robust estimator to outliers, atypical values, and autocorrelated errors. OE_N is the second best estimator. PE_N is often imprecise. Estimators with fat-tailed distribution usually result in some estimates more biased than estimators with normal distribution. The performance of POE_N and OE_N can be improved by fitting multiple indices. Our study suggested that POE_N be used for population dynamic models in future stock assessment. Multiple indices from valid surveys should be incorporated into stock assessment models. OE_N can be considered when multiple indices are available.
Advisors/Committee Members: Jiao, Yan (committeechair), Du, Pang (committee member), Prager, Michael H. (committee member), Haas, Carola A. (committee member).
Subjects/Keywords: surplus production model; robust estimators; process-observation-error-estimator; Bayesian estimation
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APA (6th Edition):
He, Q. (2010). Investigating the performance of process-observation-error-estimator and robust estimators in surplus production model: a simulation study. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/76859
Chicago Manual of Style (16th Edition):
He, Qing. “Investigating the performance of process-observation-error-estimator and robust estimators in surplus production model: a simulation study.” 2010. Masters Thesis, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/76859.
MLA Handbook (7th Edition):
He, Qing. “Investigating the performance of process-observation-error-estimator and robust estimators in surplus production model: a simulation study.” 2010. Web. 19 Jan 2021.
Vancouver:
He Q. Investigating the performance of process-observation-error-estimator and robust estimators in surplus production model: a simulation study. [Internet] [Masters thesis]. Virginia Tech; 2010. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/76859.
Council of Science Editors:
He Q. Investigating the performance of process-observation-error-estimator and robust estimators in surplus production model: a simulation study. [Masters Thesis]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/76859
Virginia Tech
18.
Rijal, Staci Faye.
Informing U.S. Caribbean fisheries management through simulation modeling: a case of length-based mortality estimation models.
Degree: MS, Fisheries and Wildlife Sciences, 2010, Virginia Tech
URL: http://hdl.handle.net/10919/36379
► Length-based stock assessment models estimating mortality rates are attractive choices for assessing fisheries with data deficiencies. The U.S. Caribbean is exploring using these models and…
(more)
▼ Length-based stock assessment models estimating mortality rates are attractive choices for assessing fisheries with data deficiencies. The U.S. Caribbean is exploring using these models and trying to optimize their commercial sampling program for such a model.
A simulation model was constructed to compare two length-based mortality estimators, the Beverton-Holt and Gedamke-Hoenig models. The simulations also tested aspects of the Gedamke-Hoenig model previously not thoroughly addressed, such as the effects of varied life history parameters, violating the assumptions of constant growth and recruitment, sample sizes (n), and sampling program length (Ys) on total mortality rate estimates (Z).
Given the scenarios investigated, the Beverton-Holt model produced consistently biased, but more stable results when n was low, variation was high for both growth and recruitment, and sampling began after the change in Z took place. The Gedamke-Hoenig model was generally less biased and detected changes in Z, but produced variable results of the current Z, especially with low sample sizes and high variability. In those situations, both models can be carefully interpreted together for management advice.
In the Gedamke-Hoenig model results, a clear pattern emerged in the mean accuracy and precision of the model where after an asymptote was reached, increasing n did not improve the means. The variance of the model improved with both increasing n and increasing Ys. Outliers were predictable and could be accounted for on a case-by-case basis.
The model developed here can be a tool for guiding future stock assessment model choice and sample design in the U.S. Caribbean and other regions.
Advisors/Committee Members: Berkson, James M. (committeechair), Gedamke, Todd (committee member), McMullin, Steve L. (committee member), Jiao, Yan (committee member).
Subjects/Keywords: fisheries; stock assessment; Caribbean; simulations; model
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APA (6th Edition):
Rijal, S. F. (2010). Informing U.S. Caribbean fisheries management through simulation modeling: a case of length-based mortality estimation models. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/36379
Chicago Manual of Style (16th Edition):
Rijal, Staci Faye. “Informing U.S. Caribbean fisheries management through simulation modeling: a case of length-based mortality estimation models.” 2010. Masters Thesis, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/36379.
MLA Handbook (7th Edition):
Rijal, Staci Faye. “Informing U.S. Caribbean fisheries management through simulation modeling: a case of length-based mortality estimation models.” 2010. Web. 19 Jan 2021.
Vancouver:
Rijal SF. Informing U.S. Caribbean fisheries management through simulation modeling: a case of length-based mortality estimation models. [Internet] [Masters thesis]. Virginia Tech; 2010. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/36379.
Council of Science Editors:
Rijal SF. Informing U.S. Caribbean fisheries management through simulation modeling: a case of length-based mortality estimation models. [Masters Thesis]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/36379
Virginia Tech
19.
Jones, Jess W.
Genetics, demography and modeling of freshwater mussel (Bivalvia: Unionidae) populations in the Clinch River, U.S.A.
Degree: PhD, Fisheries and Wildlife Sciences, 2009, Virginia Tech
URL: http://hdl.handle.net/10919/26288
► Genetic variation was examined in two endangered mussel species, Epioblasma brevidens and E. capsaeformis, and a common species Lampsilis fasciola, in the Clinch River, TN,…
(more)
▼ Genetic variation was examined in two endangered mussel species, Epioblasma brevidens and E. capsaeformis, and a common species Lampsilis fasciola, in the Clinch River, TN, by screening mitochondrial DNA (mtDNA) sequences and nuclear DNA microsatellites. These species use fish hosts with varying dispersal capabilities, ranging from low, moderate, and high, respectively. Patterns of mtDNA polymorphism exhibited different trends for long-term population sizes for each species during the Holocene (~10,000 ya to present); namely, E. brevidens has declined over time, E. capsaeformis has remained stable, and L. fasciola has expanded. Long-term effective population size (Ne) was smallest in E. brevidens, intermediate in E. capsaeformis, and highest in L. fasciola. Moderately diverged mtDNA lineages, perhaps indicative of secondary contact, were observed in E. brevidens and E. capsaeformis. High levels of gene flow (Nm) were estimated among demes of L. fasciola using traditional F-statistics and likelihood estimates of Nm, whereas such metrics were lower in E. brevidens and E. capsaeformis. Data are consistent with population dynamics and life history traits of each species and their fish hosts.
Age, shell growth, and population demography of Epioblasma brevidens, E. capsaeformis, and Lampsilis fasciola were studied from 2004-2007 in a 32-km reach of the Clinch River, TN. Observed maximum age and length of E. brevidens was 28 y and 71.5 mm for males and 11 y and 56.6 mm for females; of E. capsaeformis, 12 y and 54.6 mm for males and 9 y and 48.6 mm for females; and of L. fasciola, 45 y and 91.3 mm for males and 13 y and 62.6 mm for females. For all three species, observed maximum age and length was greater among males than females. Estimated population size in this river reach was approximately 43,000 individuals for E. brevidens, 579,000 individuals for E. capsaeformis, and 30,000 individuals for L. fasciola. Mean recruitment y-1 of 1 y-old E. brevidens ranged from 7.1% to 20%, of E. capsaeformis from 4.0% to 32.4%, and of L. fasciola from 5.8% to 25.6%. Population growth rate y-1 was 24.9% for E. brevidens, 34.6% for E. capsaeformis, and -22.4% for L. fasciola. Mortality rates of females were higher than for males of E. capsaeformis and L. fasciola, but not E. brevidens. Juvenile mussels were collected but temporally and spatially variable in occurrence, and a significant component of the age-class structure of all three species. Recruitment was very high during 2006-2007 for E. capsaeformis and other species, likely due to low river discharges in the spring-summer of 2005-2007. Surplus individuals of E. brevidens and E. capsaeformis are currently available to conduct translocations for restoration purposes.
Population modeling of Epioblasma brevidens and E. capsaeformis in the Clinch River was conducted to determine suitable harvest levels for translocation of sub-adults and adults, and to determine quantitative criteria for evaluating performance and recovery of extant and reintroduced populations. For both…
Advisors/Committee Members: Neves, Richard J. (committeechair), Orth, Donald J. (committee member), Jiao, Yan (committee member), Walters, Jeffrey R. (committee member), Hallerman, Eric M. (committeecochair).
Subjects/Keywords: Freshwater mussels; quantitative recovery criteria; fish hosts; Ne; and Nm; Epioblasma brevidens; E. capsaeformis; Lampsilis fasciola; age; growth; population demography; juvenile recruitment; population modeling; harvest; reintroduction; historical population trends
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APA ·
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APA (6th Edition):
Jones, J. W. (2009). Genetics, demography and modeling of freshwater mussel (Bivalvia: Unionidae) populations in the Clinch River, U.S.A. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/26288
Chicago Manual of Style (16th Edition):
Jones, Jess W. “Genetics, demography and modeling of freshwater mussel (Bivalvia: Unionidae) populations in the Clinch River, U.S.A.” 2009. Doctoral Dissertation, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/26288.
MLA Handbook (7th Edition):
Jones, Jess W. “Genetics, demography and modeling of freshwater mussel (Bivalvia: Unionidae) populations in the Clinch River, U.S.A.” 2009. Web. 19 Jan 2021.
Vancouver:
Jones JW. Genetics, demography and modeling of freshwater mussel (Bivalvia: Unionidae) populations in the Clinch River, U.S.A. [Internet] [Doctoral dissertation]. Virginia Tech; 2009. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/26288.
Council of Science Editors:
Jones JW. Genetics, demography and modeling of freshwater mussel (Bivalvia: Unionidae) populations in the Clinch River, U.S.A. [Doctoral Dissertation]. Virginia Tech; 2009. Available from: http://hdl.handle.net/10919/26288
Virginia Tech
20.
Leaf, Robert Thomas.
The Evolutionary Effects of Fishing: Implications for Stock Management and Rebuilding.
Degree: PhD, Fisheries and Wildlife Sciences, 2010, Virginia Tech
URL: http://hdl.handle.net/10919/28636
► Recent empirical studies have demonstrated inter-generational morphological and life-history changes in fish stocks that have been impacted by size-selective harvest. Evolutionary processes in biological populations…
(more)
▼ Recent empirical studies have demonstrated inter-generational morphological and life-history
changes in fish stocks that have been impacted by size-selective harvest. Evolutionary processes
in biological populations occur through differential survival and reproductive success based, in
part, upon individual phenotypic variability. Fishing is a source of directional selection resulting
in the directed removal of some phenotypes; however, many aspects of the evolutionary effects
of fishing remain have yet to be described. In order to better understand the life-history and
morphological changes that occur as a result of size-selective fishing, and their effect on fishery
dynamics, I first determined the suitability of Japanese medaka (Oryzias latipes) for selection
experiments. I performed selection experiments using Japanese medaka and report how
morphology and life-history characteristics changed over multiple generations of selection. I
then used these patterns of change in life-history and morphology to validate individual-based
simulation candidate models to test general mechanisms of life-history relationships. Finally, I
applied the individual-based simulation modeling approach in order to describe how biological
and fishery characteristics change in a large, age-structured population exposed to size-selective
fishing over multiple generations. I found that the Japanese medaka has attractive characteristics
for biological investigation. The selection experiments indicated large changes in the age-atmaturity,
including a nearly 50% decrease over four generations in the most intense sizeselective
removal regimes. However, I did not observe significant changes in length-at-age or
weight-at-age over the course of the experiment. Candidate simulation models were poor at
predicting some aspects of the life-history characteristics of Japanese medaka. The simulation
model to determine fishery characteristics predicted large decreases in yield and egg production
as a result of decreases in length-at-age. Understanding the relationships of life-history
characteristics and their role in determining population resilience is a step toward understanding
the importance of evolutionary processes in fishery management.
Advisors/Committee Members: Jiao, Yan (committeechair), Hallerman, Eric M. (committee member), Murphy, Brian R. (committee member), Berkson, James M. (committee member), Prager, Michael H. (committee member).
Subjects/Keywords: Keywords: Japanese medaka; Oryzias latipes; aquaculture; life-history evolution; quantitative genetics; heritability; individual-based model; fishery-induced evolution
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APA (6th Edition):
Leaf, R. T. (2010). The Evolutionary Effects of Fishing: Implications for Stock Management and Rebuilding. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/28636
Chicago Manual of Style (16th Edition):
Leaf, Robert Thomas. “The Evolutionary Effects of Fishing: Implications for Stock Management and Rebuilding.” 2010. Doctoral Dissertation, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/28636.
MLA Handbook (7th Edition):
Leaf, Robert Thomas. “The Evolutionary Effects of Fishing: Implications for Stock Management and Rebuilding.” 2010. Web. 19 Jan 2021.
Vancouver:
Leaf RT. The Evolutionary Effects of Fishing: Implications for Stock Management and Rebuilding. [Internet] [Doctoral dissertation]. Virginia Tech; 2010. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/28636.
Council of Science Editors:
Leaf RT. The Evolutionary Effects of Fishing: Implications for Stock Management and Rebuilding. [Doctoral Dissertation]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/28636
Virginia Tech
21.
Yu, Hao.
Spatial and temporal population dynamics of yellow perch (Perca flavescens) in Lake Erie.
Degree: PhD, Fisheries and Wildlife Sciences, 2010, Virginia Tech
URL: http://hdl.handle.net/10919/28586
► Yellow perch (Perca flavescens) in Lake Erie support valuable commercial and recreational fisheries critical to the local economy and society. The study of yellow perch's…
(more)
▼ Yellow perch (Perca flavescens) in Lake Erie support valuable commercial and recreational fisheries critical to the local economy and society. The study of yellow perch's temporal and spatial population dynamics is important for both stock assessment and fisheries management. I explore the spatial and temporal variation of the yellow perch population by analyzing the fishery-independent surveys in Lake Erie. Model-based approaches were developed to estimate the relative abundance index, which reflected the temporal variation of the population. I also used design-based approaches to deal with the situation in which population density varied both spatially and temporally.
I first used model-based approaches to explore the spatial and temporal variation of the yellow perch population and to develop the relative abundance index needed. Generalized linear models (GLM), spatial generalized linear models (s-GLM), and generalized additive models (GAM) were compared by examining the goodness-of-fit, reduction of spatial autocorrelation, and prediction errors from cross-validation. The relationship between yellow perch density distribution and spatial and environmental factors was also studied. I found that GAM showed the best goodness-of-fit shown as AIC and lowest prediction errors but s-GLM resulted in the best reduction of spatial autocorrelation. Both performed better than GLM for yellow perch relative abundance index estimation. I then applied design-based approaches to study the spatial and temporal population dynamics of yellow perch through both practical data analysis and simulation. The currently used approach in Lake Erie is stratified random sampling (StRS). Traditional sampling designs (simple random sampling (SRS) and StRS) and adaptive sampling designs (adaptive two-phase sampling (ATS), adaptive cluster sampling (ACS), and adaptive two-stage sequential sampling (ATSS)) for fishery-independent surveys were compared. From accuracy and precision aspect, ATS performed better than the SRS, StRS, ACS and ATSS for yellow perch fishery-independent survey data in Lake Erie. Model-based approaches were further studied by including geostatistical models. The performance of the GLM and GAM models and geostatistical models (spatial interpolation) were compared when they are used to analyze the temporal and spatial variation of the yellow perch population through a simulation study. This is the first time that these two types of model- based approaches have been compared in fisheries. I found that arithmetic mean (AM) method was only preferred when neither environment factors nor spatial information of sampling locations were available. If the survey can not cover the distribution area of the population due to biased design or lack of sampling locations, GLMs and GAMs are preferable to spatial interpolation (SI). Otherwise, SI is a good alternative model to estimate relative abundance index. SI has rarely been realized in fisheries.
Different models may be recommended for different species/fisheries when we estimate…
Advisors/Committee Members: Jiao, Yan (committeechair), Frimpong, Emmanuel A. (committee member), Carstensen, Laurence William Jr. (committee member), Guo, Feng (committee member), Orth, Donald J. (committee member).
Subjects/Keywords: fishery-independent survey; spatial generalized linear model; generalized additive model; generalized linear model; catch rate; Lake Erie; Yellow perch; spatial interpolation; sampling design
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APA ·
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Export
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APA (6th Edition):
Yu, H. (2010). Spatial and temporal population dynamics of yellow perch (Perca flavescens) in Lake Erie. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/28586
Chicago Manual of Style (16th Edition):
Yu, Hao. “Spatial and temporal population dynamics of yellow perch (Perca flavescens) in Lake Erie.” 2010. Doctoral Dissertation, Virginia Tech. Accessed January 19, 2021.
http://hdl.handle.net/10919/28586.
MLA Handbook (7th Edition):
Yu, Hao. “Spatial and temporal population dynamics of yellow perch (Perca flavescens) in Lake Erie.” 2010. Web. 19 Jan 2021.
Vancouver:
Yu H. Spatial and temporal population dynamics of yellow perch (Perca flavescens) in Lake Erie. [Internet] [Doctoral dissertation]. Virginia Tech; 2010. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/10919/28586.
Council of Science Editors:
Yu H. Spatial and temporal population dynamics of yellow perch (Perca flavescens) in Lake Erie. [Doctoral Dissertation]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/28586
. 
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