More knowledge about the spawning habits of the invasive silver (Hypophthalmichthys molitrix) and bighead (H. nobilis) carps in the United States could lead to a better understanding of how and where these fish are able to successfully reproduce and continue to expand their range. This study explored the possibility of combining multiple strategies (mobile tracking, catch-per-unit-effort [CPUE] of females, reproductive staging of females, and CPUE of larvae) to determine whether Asian carp were more likely to spawn in specific habitats. Additionally, I explored whether the timing of spawning was size-dependent for female Asian carp, and whether Asian carp larvae overlapped with those of native species in space and time. Adult females and larvae were collected weekly and transmittered adults were tracked generally monthly in Pool 26 of the Mississippi River during optimal spawning temperatures in 2011. Mixed model repeated-measures analyses indicated no effect of habitat on adult female or larvae CPUE. There were significant increases in Asian carp larvae CPUE on June 6 (t77 = 5.65, P < 0.001) and June 20 (t77 = 7.33, P < 0.001), indicating recent spawning bouts. Regression tree analysis found that the highest Asian carp larvae CPUE occurred at temperatures ¡Ý 22.5¡ãC and turbidities ¡Ý 163.5 NTU (0.50 larvae m-3). A multinomial baseline-category logit model suggested that there was a 0.83 probability of relocating a tagged fish in a backwater. Logistic regressions determined that 50% of silver carp females were mature at 688 mm total length and larger silver carp females had a higher probability of being spent earlier in the spawning season than smaller females. Asian carp represented 10% of all collected larvae and made up over half of the total larval catch on June 6, 2011. This study found little evidence suggesting that Asian carp are spawning in specific habitats. However, it is possible that the temporal collection pattern was too coarse to catch their potentially rapid response to spawning cues. Larger females may be contributing disproportionately to the population through early spawning, suggesting that population reduction could be increased by targeting these females.

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 introduction and spread of two Asian Carp species, Bighead carp Hypophthalmichthys nobilis and silver carp Hypophthalmichthys molitrix have caused severe ecological damage throughout North America. Currently, academic institutions, and state and federal agencies are investigating ways of controlling the spread of these species and managing existing populations to minimize further damage. One promising method of control is the commercial harvest of Asian carps for export to China, as both species are highly valued foodfish throughout Asia. Habitat modification and destruction, along with the questionable quality of fish produced in aquaculture facilities throughout China, have caused members of the foodfish industry to search elsewhere for a high quality product destined for middle and upper class consumers in China. At this time, harvest practices are not standardized, and taking market potential into consideration, it is important to optimize aspects of harvest so commercial fishermen and processors can supply consumers with the highest quality product. Therefore, the present studies evaluated the effects of season (summer and fall), geographic origin (Alton and Peoria Reach), and harvest gear type (trammel nets and hoop nets) on commercially caught fresh fish and those subjected to standard processing practices and simulated shipping conditions to China (blast frozen to core temperatures near - 33oC and stored at- 20oC for 6 wk) using quality evaluation methods common in the foodfish industry. Impacts of season, geographical origin, and gear type on fresh Bighead and silver carp were assessed using fillet internal and external pH, color, Torrymeter freshness, and proximate analysis (percent moisture, protein, lipid, and ash). The effects of season, geographical origin, and gear type on fish processed and held under simulated shipping conditions were analyzed using fillet internal and external pH, color, Torrymeter freshness, K value, and peroxide and aldehyde concentrations. Results indicate negligible effects of season of harvest or geographical origin on final quality of Asian carp products, but the optimization of Asian carp products may require only exporting Bighead carp. Hoop nets yielded better quality fish overall, indicating that commercial fishermen should consider using these specifically for the harvest of fish destined for human consumption. Information assembled in this research can be used by commercial fishermen and processors to develop standardized methods for the harvest of Asian carps. Providing a high quality product is vital considering market potential and the resulting economic stimulation provided to fiscally starved areas where these facilities are located. Most importantly, the development of this industry could, in conjunction with continued academic and agency efforts, offer an independent solution to the serious ecological threat posed by these species.

Sensitive and accurate detection methods are critical for monitoring and managing the spread of aquatic invasive species, such as invasive Silver Carp (SC; Hypophthalmichthys molitrix) and Bighead Carp (BH; Hypophthalmichthys nobilis) near the Great Lakes. A new detection tool called environmental DNA (eDNA) sampling, the collection and screening of water samples for the presence of the target species’ DNA, promises improved detection sensitivity compared to conventional surveillance methods. However, the application of eDNA sampling for invasive species management has been challenging due to the potential of false positives, from detecting species’ eDNA in the absence of live organisms. In this dissertation, I study the sources of error and uncertainty in eDNA sampling and develop statistical tools to show how eDNA sampling should be utilized for monitoring and managing invasive SC and BH in the United States. In chapter 2, I investigate the environmental and hydrologic variables, e.g. reverse flow, that may be contributing to positive eDNA sampling results upstream of the electric fish dispersal barrier in the Chicago Area Waterway System (CAWS), where live SC are not expected to be present. I used a beta-binomial regression model, which showed that reverse flow volume across the barrier has a statistically significant positive relationship with the probability of SC eDNA detection upstream of the barrier from 2009 to 2012 while other covariates, such as water temperature, season, chlorophyll concentration, do not. This is a potential alternative explanation for why SC eDNA has been detected upstream of the barrier but intact SC have not. In chapter 3, I develop and parameterize a statistical model to evaluate how changes made to the US Fish and Wildlife Service (USFWS)’s eDNA sampling protocols for invasive BH and SC monitoring from 2013 to 2015 have influenced their sensitivity. The model shows that changes to the protocol have caused the sensitivity to fluctuate. Overall, when assuming that eDNA is randomly distributed, the sensitivity of the current protocol is higher for BH eDNA detection and similar for SC eDNA detection compared to the original protocol used from 2009-2012. When assuming that eDNA is clumped, the sensitivity of the current protocol is slightly higher for BH eDNA detection but worse for SC eDNA detection. In chapter 4, I apply the model developed in chapter 3 to estimate the BH and SC eDNA concentration distributions in two pools of the Illinois River where BH and SC are considered to be present, one pool where they are absent, and upstream of the electric barrier in the CAWS given eDNA sampling data and knowledge of the eDNA sampling protocol used in 2014. The results show that the estimated mean eDNA concentrations in the Illinois River are highest in the invaded pools (La Grange; Marseilles) and are lower in the uninvaded pool (Brandon Road). The estimated eDNA concentrations in the CAWS are much lower compared to the concentrations in the Marseilles pool, which indicates that the few eDNA detections in the CAWS (3% of samples positive for SC and 0.4% samples positive for BH) do not signal the presence of live BH or SC. The model shows that >50% samples positive for BH or SC eDNA are needed to infer AC presence in the CAWS, i.e., that the estimated concentrations are similar to what is found in the Marseilles pool. Finally, in chapter 5, I develop a decision tree model to evaluate the value of information that monitoring provides for making decisions about BH and SC prevention strategies near the Great Lakes. The optimal prevention strategy is dependent on prior beliefs about the expected damage of AC invasion, the probability of invasion, and whether or not BH and SC have already invaded the Great Lakes (which is informed by monitoring). Given no monitoring, the optimal strategy is to stay with the status quo of operating electric barriers in the CAWS for low probabilities of invasion and low expected invasion costs. However, if the probability of invasion is greater than 30% and the cost of invasion is greater than $100 million a year, the optimal strategy changes to installing an additional barrier in the Brandon Road pool. Greater risk-aversion (i.e., aversion to monetary losses) causes less prevention (e.g., status quo instead of additional barriers) to be preferred. Given monitoring, the model shows that monitoring provides value for making this decision, only if the monitoring tool has perfect specificity (false positive rate = 0%).

Seismic waterguns produce acoustic energy that has the potential to affect aquatic organisms. This study examined the effects of exposure to a 1,966.4 cm³ watergun array (two units) on the abundance, behavior, and spatial distribution of Asian carp (Hypophthalmichthys spp.) and native fish species (i.e., bigmouth buffalo, Ictiobus cyprinellus; black buffalo, Ictiobus niger; channel catfish, Ictalurus punctatus; flathead catfish, Pylodictis olivaris; freshwater drum, Aplodinotus grunniens; gizzard shad, Dorosoma cepedianum; smallmouth buffalo, Ictiobus bubalus). Waterguns were deployed, approximately centered and perpendicular to the shoreline, in a channel that connects the Illinois River to a set of backwater gravel pits. To evaluate the effect of waterguns, six mobile side-looking split-beam hydroacoustic surveys were conducted at fixed times over a period of 12 days, during and between replicated watergun firing periods. Acoustic data collected over a five day period before placement of the waterguns were used as a control. Proximity to the waterguns of the first detected Asian carp while the watergun array was operational (52.95 ± 7.41 m, mean ± SE) was not different relative to when turned off (36.53 ± 6.08). In contrast, the closest detected native fish were farther from the waterguns while firing (32.38 ± 3.32 m) compared to when they were off (15.04 ± 1.6 m). The waterguns did not affect the abundance of acoustically detected Asian carp within the survey area, but the abundance of native fish was reduced during the firing treatment (115.82 ± 10.19) compared to both the control (203.46 ± 12.12) and off treatment (175.84 ± 12.16). The cumulative abundance of Asian carp relative to distance from the waterguns, examined at 50 m intervals up to 480 m bi-directionally away from the waterguns, was sporadically different (i.e., reduced abundance while the waterguns were firing) between treatments (i.e., at the 250, 300, 350, and 480 m intervals). In contrast, there was a significantly lower cumulative abundance of native fish during the firing treatment at every distance interval tested. The spatial distributions, relative to distance away from the waterguns, of both fish groups were affected by the firing of the waterguns. During active operation of the waterguns, there were proportionally less targets of both fish groups detected within a 50 m radius. While firing, there were proportionally more native fish farther than 400 m away on either side of the waterguns, and a larger proportion of Asian carp farther than 400 m from the waterguns on the northern side of the channel (i.e., closer to the Illinois River main channel). Asian carp and native fish were both more likely to be detected closer to the HMS pits when the waterguns were turned off. The watergun array did not influence the directional movement of detected Asian carp. In contrast, native fish were less likely to swim towards the IL River while the waterguns were firing versus not firing. The size distributions of both Asian carp and native fish species that remained in the survey area did not change across watergun treatments. It is concluded that the seismic watergun array examined in this study had a greater impact on native fish species than on Asian carp. Due to the lowered abundance, but not complete suppression of fish, it is suggested that the watergun array (as tested) is not suitable as a barrier for areas where absolute exclusion of fish is desired. The results from the spatial distribution analyses suggest the tested watergun array could be more suitable as a herding tool to facilitate removals of large fish aggregations. Caution should be taken to the extrapolation to other fish species and to fish exposed to seismic waterguns in different environments (i.e., deeper water, reduced shoreline interaction) or exposure to a larger array of waterguns.

Broad-scale niche models are good for examining the potential for invasive species occurrences, but can fall short in providing managers with site-specific locations for monitoring. Using Oklahoma as an example, where invasive bighead carp (Hypophthalmichthys nobilis) are established in certain reservoirs, but predicted to be widely distributed based on broad-scale niche models, we cast bighead carp reproductive ecology in a site-specific geospatial framework to determine their potential establishment in additional reservoirs. Because bighead carp require large, long free-flowing rivers with suitable hydrology for reproduction but can persist in reservoirs, we considered reservoir tributaries with mean annual daily discharge ≥8.5 cubic meters per second (m3/s) and quantified the length of their unimpeded portions. In contrast to published broad-scale niche models that identified nearly the entire state as susceptible to invasion, our site-specific models showed that few reservoirs in Oklahoma (N = 9) were suitable for bighead carp establishment. Moreover, this method was rapid and identified sites that could be prioritized for increased study or scrutiny. Our results highlight the importance of considering the environmental characteristics of individual sites, which is often the level at which management efforts are implemented when assessing susceptibility to invasion.

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.

Mercury (Hg) is a global pollutant, yet Hg biomagnification, the increase in Hg with trophic level, remains poorly characterized in many regions, especially at subtropical latitudes. The present study assessed subtropical reservoirs of eastern China, which provided an opportunity to quantify Hg biomagnification under highly altered conditions that included high atmospheric Hg deposition, use of reservoirs for fisheries, manipulation of food webs through stocking and high fishing pressure, and increasing eutrophication. Despite China’s Hg emission and deposition rates that are among the highest worldwide, low fish Hg concentrations and Hg biomagnification rates were found; this was explained by food web structure and fish species characteristics. Stocked species occupied lower trophic levels and had significantly lower Hg concentrations relative to wild fishes. Evidence of decreased Hg concentrations with eutrophication (as indicated by chlorophyll-a) was observed, suggesting algal biodilution and/or somatic growth dilution. Relative to temperate lakes, zooplankton density dilution may also be causing reduced Hg concentrations in subtropical biota. Hydrogeomorphic features, such as water retention time and percent crop cover, explained Hg bioaccumulation factors and Hg concentrations at the base of the food web. Eutrophication and hydrogeomorphic features also influenced the bioavailability of selenium, which can protect against the toxicity of Hg at adequate concentrations, and the concentration of eicosapentaenoic acid, a beneficial fatty acid, in the planktivorous Bighead Carp (Hypophthalmichthys nobilis). This may indicate that the risk of exposure to the neurotoxicant methylmercury relative to benefits of fish consumption may increase with eutrophication in some fish species. Overall, the findings of this study suggest food web structure, eutrophication, and hydrogeomorphic features together explain low Hg concentrations in anthropogenically modified subtropical reservoirs in eastern China. / Thesis (Ph.D, Biology) -- Queen's University, 2014-07-01 11:35:12.637

Asian carp have rapidly expanded their range through much of the Mississippi River Drainage over the past 10 to 15 years. Silver and bighead carp are now the dominant fish species present along several reaches of the Illinois River. The upper Illinois River and shipping canals entering Lake Michigan are of great concern as pathways for Asian carp to enter the Great Lakes. Knowledge of reproductive habitats and dispersal pathways for these species may be valuable for ongoing and future efforts to control these exotic invasives. Previous studies have successfully identified spawning areas of native riverine species via otolith microchemistry, but this technique has not yet been applied to Asian carps. Both stable isotope and trace element ratios have been found to differ significantly among the large rivers of the Mississippi River drainage, enabling identification of natal environment for individual fish. The primary objective of this study was to identify differences in natal river origin and floodplain habitat use through the incorporation of trace elements (Sr:Ca) and stable isotopes (δ18O and δ13C). Silver and bighead carp were collected via electrofishing and trammel netting along four reaches of the Illinois River from the Mississippi-Illinois River confluence at Grafton, IL to the upper segment of the Illinois River upstream of Starved Rock State Park. Sagittal otoliths were removed from both silver and bighead carp collected from each of the four reaches of the Illinois River for analysis of stable isotope ratios and trace element concentrations. Water samples were collected seasonally from the four reaches of the Illinois River and several of its associated floodplain lakes in addition to the Missouri, Upper Mississippi and Middle Mississippi Rivers to validate water signatures of the various river reaches. Results indicated the majority of adult Asian carp caught in the Illinois River originated from the Illinois. However, there was strong evidence indicating roughly twenty percent of captured adults were in fact immigrants from other sources; primarily the Middle Mississippi river and, to a lesser extent, the Missouri River. Stable isotope results indicated that Asian carps primarily used river channel rather than floodplain lake habitats during early life. The findings of this study suggest current Asian carp removal efforts should continue to be primarily directed within the Illinois River, however, the evidence of immigrant silver carp indicate expanding the control efforts into other rivers (Middle Mississippi River and Missouri River) will further support the control of Asian carp within the Illinois River.

No description available.