Research
Our research philosophy is three-pronged. First, we study fisheries as ecosystems, using knowledge of fishes and their habitats to develop management-relevant approaches for sustaining fish production and biodiversity. Second, we research fisheries as human systems, acquiring information on fisheries stakeholders and their socioeconomic, cultural, and political environments to design management strategies that incorporate perspectives of diverse user groups. Finally, we study fisheries as coupled human and natural systems using innovative, interdisciplinary paradigms such as the metacoupling framework.
Projects
Linking local, regional, and global fisheries across an interconnected world
Fisheries are coupled human and natural systems (CHANS) important for human health and well-being. However, research approaches that consider human-nature interactions within as well as between adjacent and distant fisheries are scarce. As such, I am developing next-generation CHANS frameworks for understanding how fisheries – freshwater and marine – are locally, regionally, and globally connected with implications for food, nutrition, and livelihood security. This research is supported by Princeton University’s Dean For Research, Princeton Environmental Institute, Andlinger Center for Energy and the Environment, and the Office of the Provost and involves collaborative projects with the Stockholm Resilience Centre and the Potsdam Institute for Climate Impact Research.
Predicting effects of climate change on stream trout with implications for resilience-based management
The State of Michigan, USA, contains ecologically, socioeconomically valuable coldwater stream trout fisheries that are highly susceptible to climate change, habitat alteration, invasive species, and other stressors. Hence, there is a need for future management approaches that promote resilient stream ecosystems that absorb change amidst disturbances. Fisheries professionals in Michigan have responded to this need by designing a comprehensive management plan for stream Brook Trout (Salvelinus fontinalis), Brown Trout (Salmo trutta) and Rainbow Trout (Oncorhynchus mykiss) populations. To assist in developing this plan, I generated stream-specific and generalized (i.e., region-specific) models to forecast trout thermal habitat suitability in streams throughout Michigan from 2006 to 2056 under different predicted climate change scenarios. Projected stream temperature warming ranged from 0.1 to 3.8 °C in groundwater-dominated streams and 0.2–6.8 °C in surface runoff-dominated systems. Despite their generally lower accuracy in predicting exact stream temperatures, generalized models accurately projected trout thermal habitat suitability in 82% of groundwater-dominated streams (but only 54% of runoff-dominated systems). Hence, amid climate change and constraints in resource availability (e.g., time, money, personnel), generalized models are appropriate to forecast thermal conditions in groundwater-dominated streams in Michigan and inform region-level trout management strategies that are practical for coldwater fisheries managers, policy makers, and the public. On the other hand, relatively resource-intensive stream-specific models are best reserved for runoff-dominated systems containing high-priority fisheries resources (e.g. trophy individuals, endangered species) that will be directly impacted by projected stream warming.
Science to Action: decision-support to advance stream trout management in a changing climate
With funding from the USGS Science to Action Fellowship, I collaborated with Michigan fisheries professionals to coproduce a decision-support tool to facilitate fisheries management decision-making in 52 trout streams amid climatic changes. The tool ranked streams based on manager-defined stream criteria (e.g., current and projected 2056 temperature, groundwater contribution, trout relative abundance, watershed and riparian land cover), enabling fisheries professionals to make ecologically, socioeconomically robust management decisions that promote thermally resilient streams and populations of Brook Trout, Brown Trout, and Rainbow Trout. Stream ranking indicated that certain recreationally significant fisheries (e.g., Muskegon River) will experience warming that may cause them to become lower priorities for trout management. However, lesser-known fisheries (e.g., Davenport Creek) were projected to become more thermally suitable and important for trout management. With this information, managers can anticipate future thermal, hydrological, and biological conditions in streams and thereby make informed, resilience-based management decisions to sustain trout fisheries.
Developing precipitation- and groundwater-corrected stream temperature models to improve trout management amid climate change
Some models for predicting stream temperature have problematic flaws, such as assuming spatially uniform (inaccurate) air-stream temperature relationships or requiring measurement of expensive hydrometeorological drivers (e.g., solar radiation, convection) in a manner impractical for fisheries management. Hence, I developed an accurate, cost-effective, management-relevant approach for modeling effects of changes in air temperature, precipitation, and groundwater inputs on coldwater stream temperatures and trout survival and growth in Michigan, USA. Precipitation- and groundwater-corrected models were more accurate than air-stream temperature models for predicting stream temperatures. Projected stream warming intensified in proportion to simulated air temperature warming and was most extreme in surface runoff-dominated streams, given their limited groundwater-driven thermal buffering. However, groundwater-dominated streams will not invariably provide coldwater habitats for trout if groundwater temperatures increase or groundwater inputs decline due to reduced precipitation. Amid resource limitations, fisheries managers can use precipitation- and groundwater-corrected models to predict effects of climate change on trout survival and growth and take actions to facilitate their sustainability in riverine systems.
Fisheries as coupled human and natural systems
In collaboration with my Ph.D. advisors, Drs. William W. Taylor and Jianguo Liu, I applied the CHANS paradigm to global fisheries systems using emerging research methods such as the metacoupling and telecoupling frameworks. Although fisheries scientists have long known that fisheries have human and natural components, fisheries research has generally focused on better understanding either fisheries ecology or human dimensions in a specific place, rather than their interactions over distances. With increasing globalization, fisheries are becoming more globally connected via movements of fish products and fisheries finances, information, and stakeholders throughout the world. As such, there is a pressing need for systematic approaches to assess linkages among fisheries at international, national, regional, and local scales. Use of the metacoupling and telecoupling frameworks is a novel and insightful approach to evaluate socioeconomic and environmental interactions among fisheries. These frameworks highlight the systems, flows, agents, causes, effects, and complexities (e.g., feedbacks, legacy effects) of fisheries and provide a platform for socially and ecologically informed fisheries management and governance in a globalized world.
Understanding the ecological and social constraints to achieving sustainable fisheries resource policy and management
I work closely with Dr. William W. Taylor and fisheries faculty in universities throughout the United States on a multistate research project (United States Department of Agriculture, National Institute of Food and Agriculture, Project No. MICL04161, Multistate No. NC1189) focused on understanding the ecological and social constraints to achieving sustainable fisheries resource policy and management. We seek to create a collaborative, coupled human and natural systems research framework to assess the ecological and socioeconomic effects of climate change and invasive species on inland fisheries and aquatic resources, with emphasis on determining the social-ecological factors that influence the ways in which individuals and organizations respond to these stressors. Our first major project was a survey of state fisheries agency administrators and Agricultural Experiment Station directors in the United States to evaluate how they perceive and allocate resources toward fisheries management amid myriad fisheries sustainability threats.
In the footsteps of a heroine: honoring Janice Lee Fenske
In receiving the Janice Lee Fenske Memorial Award at the 2012 Midwest Fish and Wildlife Conference in Wichita, Kansas, I was recognized for my dedication to research, teaching, and outreach in fisheries conservation. Receiving this award before hundreds of fellow conservation professionals as a first-year M.S. student was an unforgettable experience that continually inspires me to strive for excellence in my career and life. As I learned more about Janice’s legacy prior to starting my Ph.D. at Michigan State University (MSU), I thought it would be fitting and beneficial for my career development to apply for an MSU fellowship honoring Janice. The Janice Lee Fenske Excellence in Fisheries Management Fellowship (Fenske Fellowship) provides financial support for a fisheries student to engage in a rich university-agency mentoring experience in fisheries management. Offered through the MSU Department of Fisheries and Wildlife, the Fenske Fellowship functions as a recruitment tool for incoming students interested in incorporating a fisheries management experience into their graduate research program. I was fortunate to receive the 2015-2016 Fenske Fellowship to assist with the design and completion of a human dimensions survey to evaluate the attitudes, behaviors, and demographics of Michigan’s inland trout anglers. Amazingly, Janice herself completed a similar survey some 35 years ago, offering a unique opportunity to compare historical and contemporary trout anglers and trout management programs. See Carlson 2016 (Fisheries) and Carlson and Zorn 2018 (Michigan DNR Report) for full details.
Otoliths as chemical tracers of fish environmental history
In this project I characterized environmental history of Walleye in Missouri River impoundments using otolith chemistry (i.e., trace element depositions in fish otoliths as compared to water column signatures). In particular, I reconstructed patterns in Walleye natal origins, movement, and inter-reservoir entrainment in response to a large flood in the Missouri River in 2011. My research demonstrated the utility of otolith chemistry for measuring habitat- and site-specific natal contributions and understanding Walleye movement and entrainment patterns during floods and normal hydrological conditions. In addition, my research provided a platform for subsequent otolith chemistry studies on natal origins and movements of other Missouri River sport fishes (e.g., Bluegill, Largemouth Bass, Smallmouth Bass, White Bass, Yellow Perch). Collectively, this research established otolith chemistry as a viable tool for sport fish management in Missouri River reservoirs, particularly in prioritizing areas for floodplain protection and rehabilitation, harvest regulations, stock enhancement, and other fisheries management activities.
Effects of historic flooding on fishes and aquatic habitats in a Missouri River delta
Riverine deltas are among the most biologically productive ecosystems on earth, yet the ecological effects of floods in deltas are poorly understood. Hence, in this project I examined impacts of historic flooding in 2011 on fish communities and aquatic habitats in the Lewis and Clark Delta, located in the Missouri River in South Dakota and Nebraska, USA. Although species richness and diversity declined in the six years preceding the flood, both metrics were similar to pre-flood levels after the disturbance, indicating short-term fish community resistance to the flood. The majority of fish species examined had greater relative abundance after the flood than before the disturbance regardless of age class (i.e., juvenile, adult), morphology (i.e., small-bodied, large-bodied), introduction history (i.e., introduced, native), or recreational importance (i.e., sport fish, non-recreational). However, the flood reduced relative abundance of juvenile Freshwater Drum and White Crappie and did not affect relative abundance of Emerald Shiner, Red Shiner, and Spotfin Shiner. Physical habitat alterations caused by the flood (e.g., decreased side channel and backwater frequency and width/area, increase sandbar abundance) had minimal effects on species richness and diversity of the Lewis and Clark Delta fish community. In contrast, an overall increase in relative abundance across species indicated that interspersed fluvial and slackwater habitats in the delta provided refuge from floodwaters during the disturbance. Illustrating the ecological effects and implications of a major flood, this study contributed to the nascent field of delta ecology and reinforced the importance of maintaining habitat connectivity in deltas during and after floods for fisheries conservation.
Brown trout growth in Minnesota streams as related to landscape and local factors
The Driftless Ecoregion of southeast Minnesota supports socioeconomically and recreationally valuable Brown Trout fisheries. This project, which culminated in an Honors Thesis from the University of Minnesota and a peer-reviewed journal article, helped increase understanding of spatial variability in individual Brown Trout growth among streams relative to landscape (i.e., watershed level) and local (i.e., reach-level) factors. In particular, I compared effects of drainage area on Brown Trout growth to the effects of local factors (i.e. thermal regime, riparian land cover, relative abundance) to provide managers with strategies for maximizing growth and the abundance of large individuals in southeast Minnesota streams. Age explained 63% of variation in growth and differed among streams for age-1 and age-2, but not age-3 Brown Trout. Model averaging indicated that growth of age-1 and age-2 individuals was positively related to drainage area and forested riparian area. Overall, this integrative landscape and local study advanced Brown Trout management by illustrating that systems with large watersheds and forested riparian zones are suitable for management strategies (e.g., harvest regulations, habitat restoration) to increase growth and abundance of large Brown Trout in southeast Minnesota streams.