D.Litt et Phil. / Please refer to full text to view abstract

Since their introduction to the United States in the 1970s, the invasive silver carp (Hypothalmichthys molitrix) has migrated into the native waters of 16 states with populations in the Mississippi, Missouri, Ohio and Illinois River systems expanding at exponential rates in the past decade. As this species advances towards Lake Michigan, the threat of their invasion into the Laurentian Great Lakes is becoming very real. Silver carp are opportunistic, capable of rapid and extensive dispersal. They have the potential to compete with native species for critical habitat and food, which are very important limiting resources in all freshwater systems. Understanding their diet and habitat selection could be helpful for predicting their expansion and impacts in systems they invade. In order to fully understand habitat selection, 77 silver carp were implanted with ultrasonic transmitters during Spring 2008 and Spring 2009 in Pools 26 (N=24) and 27 (N=53) of the Mississippi River. Fish were located monthly to assess macrohabitat use. To determine if phytoplankton availability was influencing habitat selection, environmental chlorophyll a (used as a surrogate for phytoplankton abundance) was quantified monthly at silver carp detection sites and at randomly generated points from all macrohabitats. 240 silver carp were sacrificed to analyze foregut chlorophyll a concentrations (Pool 26 N=141; Pool 27 N=99); chlorophyll a concentrations in the river at fish locations were measured. This allows us to determine utilization of available phytoplankton resources. Silver carp were detected mostly in channel border wing dike areas with island side channel also being a popular macrohabitat. Chlorophyll a concentrations in the river were higher in areas where carp were detected compared to random sites across all macrohabitat types (Ksa=1.28 p=0.080). There was no significant relationship between foregut chlorophyll a concentrations and what was available in the environment, suggesting silver carp are using resources similarly across all habitats. Given that this species accumulated high concentrations of phytoplankton in their guts even in areas of low phytoplankton concentrations, they may be able to successfully invade areas with scarce phytoplankton resources.

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract, appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on October 9, 2009) Thesis advisor: Dr. Andrew D. Clarke. Includes bibliographical references.

Knowledge of natal environments and dispersal of Silver Carp (Hypophthalmichthys molitrix) inhabiting the Ohio River, and Kentucky and Barkley lakes would inform development of strategies to control established and emerging populations. However, the principal natal environments supporting the emerging bigheaded carp population in the Ohio River basin are unknown. There is also a need to assess the role of tributaries as nursery sites to increase understanding of dispersal patterns and better target young fish. The goal of this study was to identify recruitment sources and determine dispersal patterns of Silver Carp in the Ohio River basin using evidence from otolith core trace element compositions relative to ambient water elemental measurements. Fish were collected from the Ohio River, and Kentucky and Barkley lakes from 2014-2017 and water samples were taken during summer 2012-2017. Water samples maintained temporal stability and spatial differentiation for the Ohio River and tributaries during the sampling period. Results suggest that most Silver Carp in the Ohio River are utilizing tributaries during early life. Results also suggest there is passage of carp through the locks into the lakes from the Ohio River and natural reproduction is occurring in or above Kentucky and Barkley lakes. Results will inform development of efforts to target and remove spawning and young bigheaded carps as well as direct management efforts in the Tennessee and Cumberland River systems.

No description available.

Ph.D. (Zoology) / Please refer to full text to view abstract

When a species is introduced outside their native range, the genetic diversity of the introduced population is generally decreased due to the founder effect, and the fitness of individuals in the introduced population may decrease due to inbreeding depression. Invasive species are a paradox to this paradigm because while the initial population size of an invasive species may be small in their non-native range, the individuals are able to survive, eat, and reproduce so successfully, that they have deleterious effects on native species. One mechanism that invasive species use to overcome a lack of genetic diversity and adapt to their new environment is CpG methylation, a heritable and environmentally influenced epigenetic modification that regulates the expression of certain genes to alter phenotypes without altering an organism’s DNA sequence.Bighead and silver carps, two species of bigheaded carp native to eastern Asia, are believed to have been introduced to the United States in the 1970s. Since that time, populations of both bighead and silver carp have surged, particularly in the Mississippi River drainage, where they compete with native planktivores for food, injure boaters, and threaten the multi-million dollar fisheries industry in the Great Lakes. In this study, methylation-sensitive amplified fragment length polymorphisms (MS-AFLPs) were used to analyze the genetic and epigenetic diversity of bighead and silver carp from the Gan, Pearl, and Yangtze rivers in their native China and from the Illinois River in the United States. While the heterozygosity of silver carp in Illinois was not found to be significantly lower than that of silver carp in China, the silver carp in Illinois did show a significantly higher level of methylation compared to Chinese silver carp. There is evidence that CpG methylation may play a significant role in allowing silver carp to adapt and thrive in an introduced environment.

Oxbow lakes are highly productive waterbodies that host multiple life stages of many freshwater aquatic species. Oxbow lakes also provide habitat to Silver Carp (Hypophthalmichthys molitrix), which has enabled populations to grow and expand within the United States. Silver Carp are undesirable because they can compete for resources with native fishes. My goal was to identify patterns of distribution and dispersion of Silver Carp in Moon Lake, Mississippi, to assist and inform precise harvesting of fish. I implanted thirty-five adult Silver Carp with acoustic tags that I released into Moon Lake. I observed that Silver Carp were disproportionately found in locations where water depths ranged from 2.0-5.9 m during all seasons, despite the availability of locations with shallower and deeper water. Silver Carp did aggregate in the wintertime (December-February) in comparison to all other seasons. This information about depth distributions and seasonal aggregations can inform removal programs.

Invasive species are often both ecologically and economically detrimental, particularly in freshwater ecosystems where direct and indirect impacts of invasion interact with pre-existing anthropogenic stressors to magnify consequences for native communities and habitats. Planktivorous silver carp (Hypophthalmichthys molitrix) are invasive in the Mississippi River watershed, where their daily consumption of detrital seston can total more than half their body mass, and where they outnumber all native species combined in some river reaches. Because of these astonishing abilities, silver carp can cause basal resource changes, altering the body sizes and abundances of native plankton communities upon invasion. Much research has focused on this outcome of silver carp proliferation, but investigation into other effects of their presence in invaded systems has not received the same attention. Despite the unique tendency of silver carp to experience species-specific mass-mortality events, for example, there is a dearth of peer-reviewed evaluation of the possible ecological consequences of these occurrences. To elucidate the effects of these events which can comprise hundreds of thousands of individuals, we determined how the decomposition of silver carp carcasses following mass-mortality events affected benthic invertebrate community composition and productivity using a mesocosm approach. Each mesocosm was subjected to either the presence or absence of a silver carp carcass over the length of an eight-week experiment. Carcass presence created anoxic conditions in the mesocosms and acutely increased benthic invertebrate biomass and benthic periphyton growth. While acute, changes to benthic conditions following silver carp mass-mortality events are likely to have long-term effects in both invaded freshwater systems and their surrounding terrestrial landscapes. Given the magnitude of die-offs, it is possible that these events could cause ecosystem-level alterations. Further research, therefore, is needed into the additional impacts that may follow carcass decomposition to quantify and predict outcomes associated with continued silver carp invasion.

<p>Silver carp (<i>Hypophthalmichthys molitrix</i>)<b> </b>are an underutilized, invasive fish threatening native species throughout major water systems in the United States. The goal of this research was to use silver carp meat to create a value-added product, to analyze the changes in physicochemical structure and consumer liking over time, and to evaluate the benefits of adding soy, pea, and a combination of soy and pea protein isolates to the formulations. Fish nuggets were prepared from minced meat in four treatments consisting of 3% soy protein isolate (SPI), 3% pea protein isolate (PPI), a combination of 1.5% SPI and 1.5% PPI, and a control without plant protein isolate. Nuggets from each treatment were stored frozen for 1.5, 8.5, and 13.5 weeks. Proximate composition, pH, cook loss, textural hardness, expressible moisture, color, microbial counts and lipid oxidation were evaluated. Sensory acceptability was also evaluated for each frozen storage time period and treatment. A descriptive (QDA^™) trained sensory panel was also conducted on all treatments independent of the storage testing. Results showed that lipid oxidation and textural hardness significantly (P < 0.05) increased with frozen storage time. PPI had significantly lower expressible moisture compared to the control at week 1.5, but there were no statistically significant differences between treatments at weeks 8.5 and 13.5. Similarly, formulations with PPI improved (p<0.05) cook loss for week 1.5, but not week 8.5 or 13.5. Overall, sensory acceptability did not change (P > 0.05), with the exception of decreased degree of liking scores for SPI aroma (p=0.03) and flavor (p=0.03)) during the frozen storage period; all degree of liking scores remained above 6.5 throughout analysis, indicating that consumers’ acceptability of the sample treatments over time despite the changes in physicochemical structure. The descriptive panel created an attribute lexicon for the aroma, flavor, and mouthfeel of the fish nuggets and did not find significant differences in intensities for those attributes between the treatments. Although there were measurable changes in oxidation, texture, expressible moisture, and cook loss over 13.5 weeks, these changes did not impact sensory acceptance. The addition of protein isolates improved water holding capacity initially but did not maintain those benefits over extended shelf life and had little impact on consumer liking during any time period. Overall, this study demonstrated that value-added products such as silver carp nuggets can be created using an otherwise under-utilized fish. The fish nuggets had high sensory acceptability, and the addition of protein isolates did not significantly improve their sensory characteristics; therefore, silver carp nuggets can be formulated without the need of additional protein additives .</p>