INDIVIDUAL, POPULATION, AND FOOD-WEB RESPONSES OF FISH TO BIOTIC INTERACTIONS AND ABIOTIC CONDITIONS

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 0223461
• Project Start Date: Oct 1, 2010
• Project End Date: Oct 1, 2015
• Program Code: [(N/A)]- (N/A)

Recipient Organization
NORTH CAROLINA STATE UNIV
(N/A)
RALEIGH,NC 27695

Performing Department
Biology

Non Technical Summary
Abiotic factors such as temperature, dissolved oxygen (DO) concentrations and toxicant exposure, and biotic factors such as prey availability and predator-prey interactions have important consequences for fish at both the individual and population levels. Direct effects and interactions among these factors can influence physiology, energetics, behavior, distribution, growth and survival. Cumulative individual responses can result in changes in population abundance, size structure and growth rate, with consequences for food web and community structure. These interactions are not only important ecologically, but can also have important implications for management, and sometimes significant economic impacts. Many of the abiotic and biotic factors altering aquatic systems are increasingly mediated by anthropogenic influences. For example, In North Carolina and other coastal regions around the world there is serious concern that hypoxia due to anthropogenic eutrophication is having negative effects on fisheries. Nonlethal and indirect effects of hypoxia exposure may be more significant than direct, lethal effects, but these effects are currently poorly understood. Managers and policy makers need information on these impacts to make informed decisions. Similar issues apply to freshwater reservoir systems, where seasonal patterns of hypoxia can interact with summer thermal stratification to cause reduced growth or mortality of some fish. The outcome of these interactions can vary greatly among systems depending on their productivity, depth and other characteristics, so managers need to understand these dynamics to be able to adjust fisheries management strategies accordingly. Introductions of invasive species, both intentionally and unintentionally, are also becoming increasingly common and are perhaps the most significant factor altering biodiversity, food web dynamics and community structure in both freshwater and marine ecosystems. Impacts can range from relatively benign to major changes in energy flow, benthic-pelagic coupling, community composition, and production of sport and commercial fisheries. Understanding what makes a species a particularly good invader or a system particularly vulnerable to invasions are important steps in preventing, eliminating, mitigating or managing the consequences of these introductions. Contaminants, including heavy metals (e.g., mercury), endocrine disrupting compounds are another anthropogenic influence increasingly recognized as having potentially significant impacts on fish, wildlife and human health, ranging from neurological and developmental abnormalities to alterations in reproductive systems (e.g., intersex in fishes). Some of these effects are mediated by interactions with the abiotic environment as well as biological variables. Our ability to respond to each of these issues requires that we consider their impacts at multiple levels from the individual to populations and communities, in the context of their direct and indirect interactions with biotic and abiotic factors, in order to understand their consequences for fish, aquatic ecosystems, and people.

Animal Health Component

(N/A)

Research Effort Categories

Basic

(N/A)

Applied

(N/A)

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
135	0810	1060	20%
135	0810	1070	40%
135	0810	1150	10%
135	0812	1070	10%
135	0812	1150	10%
135	0812	1190	10%

Knowledge Area
135 - Aquatic and Terrestrial Wildlife;

Subject Of Investigation
0810 - Finfish; 0812 - Fish habitats;

Field Of Science
1060 - Biology (whole systems); 1070 - Ecology; 1190 - Limnology; 1150 - Toxicology;

Keywords

population dynamics

fisheries management

hypoxia

invasive species

mercury

endocrine disruptors

intersex fish

food webs

reservoir fisheries

striped bass

bioenergetics

growth indicators

rna/dna ratios

igf1

Goals / Objectives
The overall goal of this project is to enhance our understanding of the ways in which physical factors, biological interactions and behavior interact to affect the distribution, growth, survival and population dynamics of fishes and their consequences for aquatic ecosystems, people, and management. Specific objectives are as follows: 1. Experimentally determine the sensitivity and response time of three biological indicators of recent growth (RNA/DNA ratios in muscle tissue, plasma levels of insulin-like growth factor-I, and hepatosomatic index) to changes in environmental conditions and assess their feasibility and utility for evaluating the sublethal effects of hypoxia on growth of juvenile estuary-dependent fishes. 2. Determine the physical and biological characteristics that account for variability among years and systems in the occurrence of entrapment and subsequent mortality of striped bass below the metalimnetic oxygen minimum in southeastern reservoirs. 3. Evaluate characteristics of freshwater (e.g., white perch) and marine (e.g., lionfish) invasive species to identify traits that make them particularly successful; evaluate impacts of multiple invasive species on reservoir fish communities, and potential approaches to managing those impacts. 4. Enhance our understanding of factors controlling mercury contamination in fish, the potential impacts of that contamination on the fish, and strategies for using that information to minimize negative human health effects; determine the incidence of intersex fish in relation to sources and concentrations of EDC in NC waterbodies, and evaluate their potential impacts on fish populations.

Project Methods
We will use lab experiments to quantify changes in three biological indicators of recent growth in juvenile spot (a representative estuary-dependent species) as a function of temperature, mean ration level, and temporal variability in ration level. In the field we will collect juvenile spot, measure prey density, and monitor water quality at locations in the mainstem Neuse River estuary and in various nursery creeks differing in severity and duration of hypoxia. Using the relationships we establish in our lab experiments we will apply the appropriate indicator(s) in the field to relate changes in spot growth to the temporal patterns of hypoxia and prey availability within and among these sites. These comparisons will allow us to test the hypothesis that increased severity, frequency and duration of hypoxia will reduce spot growth directly due to suppression of food consumption, and/or indirectly via impacts of hypoxia on prey resources. We will use observations of striped bass habitat selection (via telemetry) and growth coupled with bioenergetics model simulations to evaluate the relative importance of physical habitat and forage availability in determining striped bass growth and survival among southeastern reservoirs. Using data from multiple years and reservoirs on the spatial and temporal patterns of temperature, dissolved oxygen and forage fish distribution and species composition we will identify the combination of physical and biological characteristics that precipitates a striped bass mortality event. Based on these findings we will identify alternative striped bass management strategies for reservoirs depending on their physical properties and biological productivity. We will use field collections and stable isotope analyses to compare the life history characteristics and relative trophic position of white perch in various NC reservoirs varying in size and time since invasion to identify patterns associated with establishment and community impact of this invasive species. Food web simulation modeling will be used to evaluate the individual and combined impacts of multiple invasive species in Lake Norman, NC. A bioenergetics model of lionfish will be combined with field and lab data and population modeling to further elucidate the potential spread of lionfish and its impact on native reef communities. We will continue ongoing field studies to further clarify factors controlling fish tissue mercury concentrations across NC and development of multiple modeling approaches that can be used to inform both fisheries management and efforts to minimize human health risks. We will identify likely point sources of EDCs in the Pee Dee river and other NC waterbodies, use passive sampling devices to measure EDC concentrations, collect fish from multiple trophic levels at impacted and unimpacted sites and perform histological analysis of their gonads to determine the baseline occurrence of intersex at uncontaminated sites and the occurrence and extent of intersex at contaminated sites. Subsequent studies will be designed to evaluate actual effects on the fish, such has changes in reproductive behavior or success.

Progress 10/01/13 to 09/30/14

Outputs
Target Audience: NC Wildlife Resources Commission biologists; Biologists and Staff Scientists in the NC Divisions of Water Quality and Public Health, and Marine Fisheries; Duke Energy Co. Biologists; NC sportfishing groups; NC Marine Fisheries Commission Northern Regional Advisory Committee; NC Cooperative Extension agents; graduate and undergraduate students; K-12 students; general public. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? The project provided numerous professional development opportunities for the PI through conferences and workshops, for graduate students involved in the project through conferences and mentoring by the PI, and training opportunities for undergraduate student employees and volunteers, and non-student employees and volunteers. How have the results been disseminated to communities of interest? Results have been disseminated through publications in the scientific literature, presentations at scientific conferences, discussions with state agency personnel and advisory committees, and presentations to anglers and the public. What do you plan to do during the next reporting period to accomplish the goals? We will continue field and lab data collection and analysis to address project goals.

Impacts
What was accomplished under these goals? My research in 2014 used a combination of field telemetry, stable isotope analysis and ecotoxicology to address questions concerning how biological interactions and anthropogenic impacts affect survival and distribution of fishes. We completed our acoustic telemetry study of White Bass in Jordan Lake, NC evaluating potential mechanisms driving declines in reservoir white bass populations. We found that total annual mortality of White Bass was high (71%). Both fishing and natural mortality were concentrated during the spring with fishing mortality accounting for most of the mortality (54% vs. 17%), suggesting that reducing current liberal harvest limits may help sustain reservoir White Bass populations. Our acoustic telemetry study of Largemouth Bass in coastal river systems found that they exhibited avoidance behavior in response to dissolved oxygen concentrations below 1.8 mg/L and fed less during these hypoxic events but did not suffer mortality. Bass displaced 16.5-40 km (simulating an angling tournament) dispersed quickly from their release point (87% within 21 days); 40% of the fish displaced 16.5 km returned to their capture location, but none of the fish displaced 35-40 km did so. Stress levels (measured by plasma cortisol concentrations) were similar in bass from simulated and actual tournaments and were unrelated to survival, post-release survival, or return. Endocrine-disrupting compounds (EDCs) can disrupt the reproductive biology of aquatic organisms, cause intersex condition in fish (female oocytes in the gonads of male fish), and affect humans as well. Using a GIS approach combined with field sampling we mapped point and nonpoint sources of EDCs across North Carolina and showed that sites associated with point and nonpoint sources had higher levels of estrogenicity than reference sites. However, there only a weak relationship between source type and concentrations of common endocrine active contaminants and no relationship between source type and frequency of intersex. Using radio telemetry we are evaluating dispersal and survival of juvenile Muskellunge in western NC rivers to address questions about variable success of stocking programs in establishing Muskellunge fisheries. High downstream dispersal and very high mortality in the first three months after stocking may explain poor success in the New River. Preliminary results from the French Broad River, where stocking has resulted in a viable fishery, suggest lower rates of dispersal and mortality. Despite two decades of stocking, efforts to rebuild the Neuse River Striped Bass population have not been successful. We are exploring potential reasons for this failure by using acoustic telemetry to determine spatial distribution and natural mortality of juvenile Striped Bass over the first year of life as well as movement and fishing, catch-and-release and natural mortality of adult striped bass. Tilapia are potentially invasive species that may have negative effects on other fishes, but typically do not survive winter temperatures in North Carolina. We are using a combination of field sampling, diet and stable isotope analyses to evaluate their effects on sport fish, and laboratory thermal tolerance experiments to provide a risk assessment of their potential to become established in non-heated waterbodies in the state. All of this work simultaneously contributes to our basic ecological knowledge and informs management of ecologically and economically important aquatic resources.

Publications

• Type: Journal Articles Status: Published Year Published: 2014 Citation: Bethke, B.J., J.A. Rice, and D.D. Aday. 2014. White Perch in Small North Carolina Reservoirs: What Explains Variation in Population Structure? Transactions of the American Fisheries Society 143: 77-84. DOI: 10.1080/00028487.2013.830989.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Campbell, L.A. and J.A. Rice. 2014. Effects of hypoxia-induced habitat compression on growth of juvenile fish in the Neuse River Estuary, North Carolina. Marine Ecology Progress Series 497: 199213. DOI: 10.3354/meps10607.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Sackett, D.K., C. Lee Pow, M.J. Rubino, D.D. Aday, W.G. Cope, S. Kullman, J.A. Rice, T.J. Kwak and M. Law. 2014. Sources of Endocrine Disrupting Compounds in North Carolina Waterways: A Geographic Information Systems Approach. Environmental Toxicology and Chemistry. Published online (print to come), DOI 10.1002/etc.2797.

Progress 10/01/12 to 09/30/13

Outputs
Target Audience: Target audiences:NC Wildlife Resources Commission biologists; Biologists and Staff Scientists in the NC Divisions of Water Quality and Public Health, and Marine Fisheries; Duke Energy Co. Biologists; National Marine Fisheries Service and National Ocean Service scientists; NC sportfishing groups; Lake Norman Advisory Committee; NC Marine Fisheries Commission Northern Regional Advisory Committee; NC Cooperative Extension agents; graduate and undergraduate students; K-12 students; general public. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? The project provided numerous professional development opportunities for the PI through conferences and workshops, for graduate students involved in the project through conferences and mentoring by the PI, and training opportunities for undergraduate student employees and volunteers, and non-student employees and volunteers. How have the results been disseminated to communities of interest? Results have been disseminated through publications in the scientific literature, presentations at scientific conferences, discussions with state agency personnel and advisory committees, and presentations to anglers and the public. What do you plan to do during the next reporting period to accomplish the goals? We will continue field and lab data collection and analysis to address project goals.

Impacts
What was accomplished under these goals? The PI co-edited a 34-chapter, peer-reviewed book published by the American Fisheries Society in 2013, that is the first comprehensive reference text on biology and management of inland striped bass and hybrid striped bass populations. Research in this reporting period used a combination of field telemetry, stable isotope analysis and ecotoxicology to address questions concerning how biological interactions and anthropogenic impacts affect survival and distribution of fishes. We identified strong, seasonal peaks in fishing and natural mortality of white bass, along with competitive interactions with invasive white perch, as potential mechanisms driving declines in reservoir white bass populations. We documented that largemouth bass in coastal rivers are more tolerant of hypoxia (low dissolved oxygen) than anticipated, and temporarily move to refuge areas to avoid severe hypoxia. We also determined that largemouth bass displaced long distances by tournament anglers in coastal systems disperse quickly from release points and often return to original capture locations 20 km away, and that the level of stress incurred due to tournament catch, handling and displacement does not affect their survival or redistribution after release. Endocrine-disrupting compounds (EDCs) can disrupt the reproductive biology of aquatic organisms, cause intersex condition in fish (female oocytes in the gonads of male fish), and affect humans as well. We quantified the extent of anthropogenic EDC contamination in representative streams across NC in relation to potential sources and were surprised to find relatively high EDC concentrations in many streams with no known point- or non-point sources, as well as in streams with obvious EDC sources. We are currently quantifying the effects of these exposures on fish populations.

Publications

• Type: Books Status: Published Year Published: 2013 Citation: Biology and management of inland striped bass and hybrid striped bass. 2013. J.S. Bulak, C.C. Coutant and J.A. Rice (eds.). American Fisheries Society, Symposium 80, Bethesda, Maryland.
• Type: Book Chapters Status: Published Year Published: 2013 Citation: Rice, J. A., J. S. Thompson, J. A. Sykes, and C. T. Waters. 2013. The role of metalimnetic hypoxia in striped bass summer kills: consequences and management implications. Pages 121-145 in J. S. Bulak, C. C. Coutant, and J. A. Rice, editors. Biology and management of inland striped bass and hybrid striped bass. American Fisheries Society, Symposium 80, Bethesda, Maryland.
• Type: Book Chapters Status: Published Year Published: 2013 Citation: Thompson, J.S. and J.A. Rice. 2013. The relative influence of temperature and forage availability on growth of age 1-5 striped bass in two southeastern reservoirs. Pages 93-120 in J. S. Bulak, C. C. Coutant, and J. A. Rice, editors. Biology and management of inland striped bass and hybrid striped bass. American Fisheries Society, Symposium 80, Bethesda, Maryland.
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Cerino, D., A.S. Overton, J.A. Rice, and J.A. Morris Jr. 2013. Bioenergetics and Trophic Impacts of the Invasive Indo-Pacific Lionfish. Transactions of the American Fisheries Society 142:1522-1534.
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Sackett, D.K, D.D. Aday and J.A. Rice and W.G. Cope. 2013. Maternally transferred mercury in wild largemouth bass, Micropterus salmoides. Environmental Pollution 178:493-497.
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Feiner, Z.S., J.A. Rice, A.J. Bunch, and D.D. Aday. 2013. Trophic niche and diet overlap between invasive white perch and resident white bass in a southeastern reservoir. Transactions of the American Fisheries Society 142:628641.
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Feiner, Z.S., J.A. Rice, and D.D. Aday. 2013. Trophic niche of invasive white perch and potential interactions with established reservoir species. Transactions of the American Fisheries Society 142:628641.
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Sackett, D.K, W.G. Cope, J.A. Rice and D.D. Aday. 2013. The influence of fish length on tissue mercury dynamics: implications for natural resource management and human health risk. International Journal of Environmental Research and Public Health 10: 638-659.
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Sackett, D.K, D.D. Aday, J.A. Rice and W.G. Cope. 2013. Validation of a predictive model for fish tissue mercury concentrations. Transactions of the American Fisheries Society 142:380-387.

Progress 10/01/11 to 09/30/12

Outputs
OUTPUTS: Invasive species and anthropogenic habitat modifications pose a substantial threat to established freshwater fish communities. We initiated a study to explore potential causes of declines in white bass Morone chrysops populations in NC reservoirs, with particular emphasis on the impact of invasive white perch Morone Americana. Using hydroacoustic telemetry we are evaluating the spatial and temporal distribution of white bass and white perch in Jordan Lake, NC, and estimating natural and fishing mortality rates of white bass. Diet and Stable Isotope Analyses are being used to determine diet and trophic level of each species at various sizes, to evaluate the potential for resource competition. Hypoxia, or low dissolved oxygen concentrations, can have major effects on distribution, growth and survival of fishes. Using hydroacoustic telemetry we are evaluating the effects of seasonal and episodic hypoxia on movement and survival of largemouth bass Micropterus salmoides in a large coastal river system. We are also using similar techniques to evaluate the survival and movement of largemouth bass displaced by tournament angling in the NC Albemarle Sound system. We evaluated the cause of major striped bass summer mortality events in Lake Norman in relation to hypoxia and introduction of invasive alewife Alosa pseudoharengus, using a combination of historical water quality data, fish sampling, and hydroacoustic surveys of fish spatial and temporal distributions in the lake in relation to water quality conditions. We evaluated the effects of episodic hypoxia on distribution and growth of juvenile spot Leiostomus xanthurus in the Neuse River Estuary, NC, using a combination of molecular and physiological indicators of recent growth in relation to recent water quality conditions. Laboratory experiments were used to calibrate measures of various bioindicators to growth over the previous week. Water quality was monitored and fish collected from the estuary under a wide range of conditions. Results from the lab experiments were used to estimate recent growth of field fish in relation to recent water quality conditions in the field. Mercury bioaccumulation in fish is a major source of contamination for humans and wildlife, with significant health impacts. Mercury concentrations in fish vary widely across NC, among fish species, and with fish size. We evaluated the relationship between methylmercury (MeHg, the toxic form) concentration in muscle tissue of several commonly harvested fish species in relation to length-based harvest regulations for these species, and determined the extent to which MeHG concentration increased with fish length independent of fish age and trophic level within each species. Because MeHg can have negative effects on development we also evaluated the relationship between MeHg concentration in the tissue of female largemouth bass to MeHg concentration in their eggs. PARTICIPANTS: Individuals: J.A. Rice, D.D. Aday, W.G. Cope, R.J. Borski (PIs); D. Sackett (Post-Doc), M. Brey, L. Glass-Campbell (PhD students), Z. Feiner, B. Galster-Bethke, D. Brown, K. Lincoln (MS students), D. Owensby (technician), M. Beckmann, P. Begue (volunteers). Partner Organizations: NC Wildlife Resources Commission, NC Division of Water Quality, NC Division of Air Quality, NC Division of Marine Fisheries, Duke Energy Co., Duke University, U.S. Army Corps of Engineers, Christopher Newport University. Collaborators and Contacts: D. Aday, R. Borski, J. Hightower, J. Buckel, T. Kwak, NCSU Biology; C. Harms, M. Stoskopf, M. Law, NCSU College of Veterinary Medicine; G. Cope, S. Kullman, NCSU Env. and Molecular Toxicology; K Gross, NCSU Statistics; M. Hale, J. Deberardinis, NC Division of Water Quality; M. Loeffler, NC Division of Marine Fisheries; R.L. Noble, H.C. Edwards, private consultants; B. McRae, C. Waters, K. Briggs, C. Oakley, J. Baumann, K. Dockendorf, B. Ricks, J. McCargo, NC Wildlife Resources Commission; D. Caughlan, K. Baker, H. Barwick, B. Doby, D. Harrell, M. Abney, W. Foris, Duke Energy Co.; Eric Money, Duke University; J. Sykes, U.S. Army Corps of Engineers; J. Thompson, Christopher Newport University. Training or Professional Development: The project graduated one M.S. student (B. Galster-Bethke) and two Ph.D. students (M. Brey, L. Glass-Campbell) The project provides training opportunities for graduate and undergraduate student employees and volunteers, non-student employees and volunteers, post-docs, NCWRC biologists, Duke Energy Co. biologists, and staff scientists in the NC Divisions of Water Quality, Air Quality, Public Health and Marine Fisheries. TARGET AUDIENCES: Target audiences: Biologists and Staff Scientists in the NC Divisions of Water Quality, Air Quality, Public Health, and Marine Fisheries; NC Wildlife Resources Commission biologists; Duke Energy Co. Biologists; National Marine Fisheries Service and National Ocean Service scientists; NC sportfishing groups; Lake Norman Advisory Committee; NC Marine Fisheries Commission Northern Regional Advisory Committee; NC Cooperative Extension agents; graduate and undergraduate students; K-12 students; general public. Information resulting from our reservoir work is being used by the NCWRC to modify their reservoir fisheries management strategies. The NC Division of Water Quality is using our mercury study results to modify the sampling and monitoring strategies, and the NC Division of public health is using our results to modify how they develop mercury consumption advisories. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Preliminary estimates indicate that most mortality of white bass (both natural and fishing) occurs during the spawning run. Both white bass and white perch range widely around the lake and do not exhibit strong habitat preferences. Preliminary results indicate that coastal largemouth bass exhibit modest mortality rates and typically remain in the creek where they were tagged, but will temporarily leave creek habitats during episodes of hypoxia. Preliminary results indicate that largemouth bass displaced by angling tournaments show a wide range of movement responses, from staying in the creek where they are released, to returning within weeks to their original capture site within 1.5-4 weeks, sometimes traveling 9 km across the Sound to do so. Our analysis of striped bass summer mortality events in Lake Norman showed that two factors combine to differentiate years with kills from those without: formation of 3-8 m of extreme hypoxia in the metalimnion before oxygen concentration in the hypolimnion drops to lethal levels, and presence of coolwater forage fish in the hypolimnion. In the absence of such fish severe metalimnetic hypoxia does not cause mortality as striped bass avoid the hypolimnion. However, the introduction by striped bass anglers of alewife, a coolwater forage fish that occupies the hypolimnion, has caused major kills in every year with severe hypoxia since their introduction. Based on our lab experiments we developed a model using multiple bioindicators of recent growth that could explain 80% of the variability in growth among individual spot over the previous week. By applying this model to samples from fish collected in the Neuse River Estuary we found that spot growth was reduced about 50% following weeks of severe and frequent hypoxia, compared to growth after weeks of good water quality. Cumulative effects of hypoxia reduce spot growth over the summer by 6-18%. Fish size has a significant effect on Hg contamination independent of age and trophic level, and both the baseline level of contamination and rate of bioaccumulation can vary substantially among systems. The relationships we determined allow prediction of the sizes at which several common sportfish exceed EPA fish tissue Hg action levels; for some species, these levels are reached before, or shortly after, the fish reach legal harvest size. Fisheries managers and public health officials should work together to identify harvest regulation strategies that can minimize risk to anglers where feasible. Mercury concentration in largemouth bass eggs was positively correlated with concentrations in the female bass they came from. Because MeHg can have substantial negative effects on development early in life, these results have implications for selection of brood stock for hatchery production, and also suggest that environmental mercury contamination may be having negative effects on reproductive rates.

Publications

• Feiner, Z.S., Aday, D.D., and Rice, J.A. 2012. Phenotypic shifts in white perch life history strategy across stages of invasion. Biological Invasions 14(11): 2315-2329. DOI 10.1007/s10530-012-0231-z.

Progress 10/01/10 to 09/30/11

Outputs
OUTPUTS: Invasive species pose a substantial threat to established freshwater fish communities. We investigated the impact of several invasive species on reservoir food webs and sport fishes. A reservoir food web model was developed using Ecopath with EcoSim to evaluate effects of multiple species invasions on reservoir communities. Invasive white perch Morone americana populations were sampled in three reservoirs at different stages of invasion to evaluate their life history characteristics and population dynamics in relation to invasion stage. Similar characteristics, as well as other biotic and abiotic variables, were compared in reservoirs with high-density, stunted white perch populations vs. populations with low densities of large fish. We also examined diet overlap and the potential for resource competition between white perch and white bass Morone chrysops, a species that appears to be particularly impacted by white perch. Mercury bioaccumulation in fish is a major source of contamination for humans and wildlife, with significant health impacts. We used two independent datasets to validate the model we previously developed to predict mercury in fish. Additional work detailed the effect of fish size within species on mercury contamination, independent of age and trophic level. PARTICIPANTS: Individuals: J.A. Rice, D.D. Aday, W.G. Cope, R.J. Borski (PIs); D. Sackett, M. Brey, L. Glass, Z. Feiner, B. Galster (graduate students), S. Petre, B. Noffsinger, L. Snyder, B. Kornegay, A. Arrington, C. Williams, L. Garner, C. Andrews, S. Polland(hourly workers and technicians). Partner Organizations: NC Wildlife Resources Commission, NC Division of Water Quality, NC Division of Air Quality, Duke Energy Co., Duke University. Collaborators and Contacts: D. Aday, R. Borski, J. Hightower, Craig Sullivan, J. Buckel, NCSU Biology; C. Harms, NCSU College of Veterinary Medicine; G. Cope, D. Buchwalter, NCSU Env. and Molecular Toxicology; Mark Hale, Jeff Deberardinis, NC Division of Water Quality; R.L. Noble, H.C. Edwards, private consultants; B. McRae, C. Waters, K. Nelson, L. Dorsey, C. Oakley, J. Baumann, NC Wildlife Resources Commission; D. Caughlan, K. Baker, H. Barwick, B. Doby, D. Harrell, M. Abney, Duke Energy Co.; Eric Money, Duke University. Training or Professional Development: The project graduate one M.S. student (Z. Feiner) and one Ph.D. student (D. Sackett) The project provides training opportunities for graduate and undergraduate student employees and volunteers, post-docs, NCWRC biologists, Duke Energy Co. biologists, and staff scientists in the NC Divisions of Water Quality, Air Quality and Public Health. TARGET AUDIENCES: Target audiences: Biologists and Staff Scientists in the NC Divisions of Water Quality, Air Quality, Public Health, and Marine Fisheries; NC Wildlife Resources Commission biologists; National Marine Fisheries Service and National Ocean Service scientists; NC sportfishing groups; Lake Norman Advisory Committee; NC Cooperative Extension agents; graduate and undergraduate students. Information resulting from our reservoir work is being used by the NCWRC to modify their reservoir fisheries management strategies. The NC Division of Water Quality is using our mercury study results to modify the sampling and monitoring strategies, and the NC Division of public health is using our results to modify how they develop mercury consumption advisories. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Ecopath with EcoSim model simulations have demonstrated that impacts of multiple invasive species are nonadditive and often compensatory, and have also showed that order of invasion can alter their impacts on the native community. White perch exhibit shifts in life history strategy at different stages of invasion, consistent with life history theory, as well as broad diets and trophic position that appear to make them effective invaders. However, contrary to invasion theory, life history characteristics and abiotic variables do not explain why some white perch populations are abundant and stunted, while others are rare and large; growth appears to be density-dependent, and interactions with largemouth bass Micropterus salmoides at early life stages may drive abundance. White perch were more abundant and had wider diet breadth and trophic niche size than white bass across seasons, and also occupied lower trophic positions than white bass. However, diet analysis showed high overlap between juvenile white bass and all sizes of white perch. Thus, juvenile white bass may be susceptible to competition with white perch where resources are limited. These findings will provide insights for fisheries managers regarding the impacts of invasive species on reservoir communities and help identify management strategies (or lack thereof) for reducing the negative impacts of invasive species. Independent validation of our predictive model for mercury contamination in fish tissue confirmed the ability of the model to explain 80% of the variability in fish tissue Hg based on a few easily-obtained variables. This model will allow public health officials to identify waterbodies particularly likely to contain high-mercury fish, allowing them to efficiently target their monitoring efforts. Fish size has a significant effect on Hg contamination independent of age and trophic level, and both the baseline level of contamination and rate of bioaccumulation can vary substantially among systems. The relationships we determined allow prediction of the sizes at which several common sportfish exceed EPA fish tissue Hg action levels; for some species, these levels are reached before, or shortly after, the fish reach legal harvest size. Fisheries managers and public health officials should work together to identify harvest regulation strategies that can minimize risk to anglers where feasible.

Publications

• No publications reported this period